tag:theconversation.com,2011:/ca/topics/mass-21506/articlesMass – The Conversation2023-07-06T12:28:14Ztag:theconversation.com,2011:article/2088252023-07-06T12:28:14Z2023-07-06T12:28:14ZCan chatbots write inspirational and wise sermons?<figure><img src="https://images.theconversation.com/files/535891/original/file-20230705-22346-guktbb.jpg?ixlib=rb-1.1.0&rect=62%2C44%2C5892%2C3910&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">AI-created sermons have proved controversial for some religious leaders.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.co.uk/detail/news-photo/june-2023-bavaria-f%C3%BCrth-visitors-and-attendees-during-the-news-photo/1258555134?adppopup=true">Daniel Vogl/picture alliance via Getty Images</a></span></figcaption></figure><p>When several hundred Lutherans in Bavaria, Germany, attended a service on June 9, 2023, <a href="https://apnews.com/article/germany-church-protestants-chatgpt-ai-sermon-651f21c24cfb47e3122e987a7263d348">designed by ChatGPT</a>, the program not only selected hymns and prayers, but also composed and delivered a sermon, delivered by an avatar on a big screen. </p>
<p>Indeed, programs like ChatGPT, that can produce a sermon in seconds, might seem attractive to busy clergy. But several religious leaders, including rabbis serving Jewish congregations as well as Christian Protestant pastors, <a href="https://apnews.com/article/technology-artificial-intelligence-kentucky-religion-65822bf1c46de7630d3441e9ff4ff41a">have conflicting feelings</a> about utilizing chatbots in preparing sermons. </p>
<p>There may be several reasons for being cautious. From my perspective, as <a href="https://www.holycross.edu/academics/programs/religious-studies/faculty/joanne-pierce">a specialist in Catholic liturgy and ritual</a>, the most important critique has to do with true intent of preaching – to offer insight and inspiration on the human experience of faith.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/xmXghWi2lf8?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">More than 300 people attended an experimental Lutheran Protestant church service almost entirely generated by artificial intelligence in Germany on June 9, 2023. (AP video: Daniel Niemann)</span></figcaption>
</figure>
<h2>Historical practice</h2>
<p>In the early centuries of Christianity, <a href="https://www.newadvent.org/cathen/07443a.htm">preaching was largely reserved for bishops</a>, considered to be the successors to Jesus’ apostles. During the Middle Ages, priests were also allowed to preach, although their chief responsibility was to say the Mass – ritually consecrating the offerings of bread and wine – especially on Sundays. </p>
<p>In some religious orders, priests <a href="https://www.op.org/history/">became famous traveling preachers</a>, although much of the time they were preaching in other settings, not during Mass. <a href="https://brill.com/display/title/15499">The Franciscan</a> and <a href="https://exhibitions.lib.cam.ac.uk/dominicans/case/medieval-preachers-and-teachers/">Dominican</a> orders, for example, would send priests to preach on the streets and in city centers, traveling from town to town in fulfillment of this ministry. </p>
<p>During the next few centuries, preaching brief sermons or homilies became increasingly important during the celebration of Sunday Mass. The Second Vatican Council, convened in 1962, <a href="https://www.vaticannews.va/en/vatican-city/news/2022-10/vatican-ii-council-60th-anniversary-video-history-background.html">took a fresh look at all the church’s rituals</a> and stressed the role of preaching at worship, especially at Mass. </p>
<p>These principles have been <a href="https://www.vatican.va/roman_curia/congregations/ccdds/documents/rc_con_ccdds_doc_20140629_direttorio-omiletico_en.html#I._THE_HOMILY">reaffirmed in more recent documents</a> that guide Catholic preachers when writing a sermon. In essence, preaching was always believed to be a human activity grounded in faith. </p>
<h2>Insight and inspiration</h2>
<p>Preaching as a human activity has a special meaning for Catholics – and most Christians – because they believe that Jesus Christ is the incarnate Son of God, who <a href="https://www.vatican.va/archive/ENG0015/__P1J.HTM">came into human life to save all of humanity from their sins</a> and gave his <a href="https://www.biblegateway.com/passage/?search=Mark+16%3A15&version=NRSVCE">apostles the commandment to preach the gospel</a> about this “good news” to people of all nations. </p>
<p>In the decades since Vatican II ended in 1965, preaching in the Catholic tradition has been emphasized as a “<a href="https://www.vatican.va/archive/hist_councils/ii_vatican_council/documents/vat-ii_decree_19651207_presbyterorum-ordinis_en.html">primary duty</a>” of all priests. </p>
<p>The sermon is meant to <a href="https://www.vatican.va/roman_curia/congregations/ccdds/documents/rc_con_ccdds_doc_20140629_direttorio-omiletico_en.html#I._THE_HOMILY">inspire people</a> in their ordinary lives of faith. The preacher must spend time in preparing the sermon, but this does not just mean compiling theological quotes or doing research on the history of the Bible. </p>
<p>A good sermon is not just a classroom lecture. In fact, several contemporary popes have stressed that the language of sermons should avoid technical or obscure terminology. In 1975, Pope Paul VI wrote that the language of preaching should be “<a href="https://www.vatican.va/content/paul-vi/en/apost_exhortations/documents/hf_p-vi_exh_19751208_evangelii-nuntiandi.html">simple, clear, direct, well-adapted</a>” for the congregation in the pews. And in 2013, Pope Francis echoed these same words in his observation that “<a href="https://www.vatican.va/content/francesco/en/apost_exhortations/documents/papa-francesco_esortazione-ap_20131124_evangelii-gaudium.html#_ftn125%5D">simplicity has to do with the language we use</a>.”</p>
<p>But preaching is not just about offering pious mottoes or generic religious formulas. The preacher’s experience, insights and emotions all come into play when composing the homiletic text.</p>
<figure class="align-center ">
<img alt="Black and white photo of Billy Graham preaching to a packed audience. Graham stands at a lectern in front of many onlookers, with his hands raised above his head" src="https://images.theconversation.com/files/535893/original/file-20230705-26-esx3zq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/535893/original/file-20230705-26-esx3zq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=402&fit=crop&dpr=1 600w, https://images.theconversation.com/files/535893/original/file-20230705-26-esx3zq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=402&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/535893/original/file-20230705-26-esx3zq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=402&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/535893/original/file-20230705-26-esx3zq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=505&fit=crop&dpr=1 754w, https://images.theconversation.com/files/535893/original/file-20230705-26-esx3zq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=505&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/535893/original/file-20230705-26-esx3zq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=505&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Evangelist Billy Graham reached millions who were attracted by his charisma and preaching style.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.co.uk/detail/news-photo/evangelist-billy-graham-preaches-to-a-crowd-of-21-000-in-st-news-photo/515575744?adppopup=true">Bettmann / Contributor via Getty Images</a></span>
</figcaption>
</figure>
<p>The preacher is not simply offering good advice, but speaking out of personal reflection in a way that will inspire the members of the congregation, not just please them. It <a href="https://www.mccrimmons.com/shop/homilies/preaching-as-paying-attention--theological-reflection-in-the-pulpit/">must also be shaped</a> by an awareness of the needs and lived experience of the worshipping community in the pews. </p>
<h2>Use with caution</h2>
<p>In practice, chatbots might help clergy save time by finding sources and compiling relevant facts, but the results would need to be <a href="https://mashable.com/article/microsoft-bing-ai-chatbot-weird-scary-responses">checked for errors</a>. Chatbots have been known to <a href="https://www.theguardian.com/technology/2023/feb/09/ai-blunders-google-chatbot-chatgpt-cause-trouble-more-firms">make some factual blunders</a> or <a href="https://www.reuters.com/legal/transactional/lawyer-who-cited-cases-concocted-by-ai-asks-judge-spare-sanctions-2023-06-08/">invent sources completely</a>. </p>
<p>Above all, I believe chatbots, as of now, are not capable of preparing a text suitable for being offered as a sermon. From what we know about chatbots, <a href="https://theconversation.com/ai-isnt-close-to-becoming-sentient-the-real-danger-lies-in-how-easily-were-prone-to-anthropomorphize-it-200525">they cannot know</a> <a href="https://theconversation.com/it-takes-a-body-to-understand-the-world-why-chatgpt-and-other-language-ais-dont-know-what-theyre-saying-201280">what it means to be human</a>, to experience love or be inspired by a sacred text. </p>
<p>Perhaps Baptist pastor Hershael York, Dean of the School of Theology at The Southern Baptist Theological Seminary, has put it best. He has noted that the ultimate failure of a chatbot’s sermon lies in the fact that it “lacks a soul.” Without that empathetic consciousness, a chatbot-composed sermon cannot include genuine insights based on personal spiritual experience. And without that essential element of embodied human awareness, true preaching is simply not possible.</p><img src="https://counter.theconversation.com/content/208825/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Joanne M. Pierce does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Not quite, writes an expert on Christian worship. Chatbots do not have human experience of love – and, above all, they lack a soul.Joanne M. Pierce, Professor Emerita of Religious Studies, College of the Holy CrossLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1699402021-11-05T03:02:21Z2021-11-05T03:02:21ZCurious Kids: what is energy made of?<figure><img src="https://images.theconversation.com/files/430400/original/file-20211104-19-1eby6ie.jpg?ixlib=rb-1.1.0&rect=14%2C8%2C1982%2C1320&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/3d-rendering-abstract-energy-ball-fire-755829682">Jivacore / Shutterstock</a></span></figcaption></figure><blockquote>
<p>What is energy made of? — Ela, age 8, Melbourne </p>
</blockquote>
<p><a href="https://theconversation.com/au/topics/curious-kids-36782"><img src="https://images.theconversation.com/files/291898/original/file-20190911-190031-enlxbk.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=90&fit=crop&dpr=1" width="100%"></a></p>
<p>Hi Ela! What a great question! </p>
<p>For scientists, energy is not really a <em>thing</em> and so it isn’t made of something else, in the way a house is made of bricks.</p>
<p>Energy is more like a <em>capacity</em>. A capacity is an ability to <em>do</em> something. </p>
<h2>Energy and work</h2>
<p>Think of a musician: they have the capacity to play an instrument. A painter has the capacity to paint. </p>
<p>Energy is the capacity for something to <em>do work</em>.</p>
<p>Something does work when it exerts a force on another object, pushing the object to move in a particular direction. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/430401/original/file-20211104-14-8v9jk8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/430401/original/file-20211104-14-8v9jk8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/430401/original/file-20211104-14-8v9jk8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/430401/original/file-20211104-14-8v9jk8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/430401/original/file-20211104-14-8v9jk8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/430401/original/file-20211104-14-8v9jk8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/430401/original/file-20211104-14-8v9jk8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">When you hit a ball with a bat, the bat transfers some of its kinetic energy to the ball to change its speed and direction.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>What does that mean? Well, imagine someone throws a ball to you and you hit it with a bat. When the bat hits the ball, it changes the ball’s speed and direction. </p>
<p>Energy is the capacity the bat has to change the direction of the ball. When the bat is swinging, it can change the direction of any ball it hits. </p>
<p>When you swing the bat, you put energy stored in your muscles into it. The harder you swing, the more work the bat can do, so the more energy it carries.</p>
<h2>Types of energy</h2>
<p>There are many ways for something to do work, so there are different kinds of energy. </p>
<p>We have already encountered one: the swinging of the bat. This is called <em>kinetic energy</em>. It is the energy something has because it is moving. </p>
<p>Another kind of energy is <em>potential energy</em>. Potential energy is the capacity something has to do work because of its position in relation to other objects. </p>
<p>This means putting things in certain places gives them energy. </p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/430402/original/file-20211104-15-1vgzy1f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/430402/original/file-20211104-15-1vgzy1f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=899&fit=crop&dpr=1 600w, https://images.theconversation.com/files/430402/original/file-20211104-15-1vgzy1f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=899&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/430402/original/file-20211104-15-1vgzy1f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=899&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/430402/original/file-20211104-15-1vgzy1f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1130&fit=crop&dpr=1 754w, https://images.theconversation.com/files/430402/original/file-20211104-15-1vgzy1f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1130&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/430402/original/file-20211104-15-1vgzy1f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1130&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">If you balance a bucket of water on top of a door, you give it potential energy. When the door is opened, the bucket starts to move downwards, drenching the unlucky person who opened it.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Here’s a fun example: imagine putting a bucket of water on top of a door that is half open. When someone walks through the door, the bucket will fall on their head. </p>
<p>Because the bucket is on top of the door, it can fall. And when it falls, it can do some work. Not only will it soak whoever walks through the door, but it will also hit them on the head. </p>
<p>So the bucket has the capacity to do work just because it is put on top of the door, and not because it is moving. That capacity is the bucket’s potential energy. </p>
<h2>Einstein’s famous equation</h2>
<p>The famous physicist Albert Einstein made an equation about energy, which you may have seen before: <em>E</em> = <em>m</em> <em>c</em> ². </p>
<p>In this equation, the <em>E</em> is for energy, the <em>m</em> is for mass (which is roughly how much matter, or physical stuff, is in something), and <em>c</em> means the speed of light. </p>
<p>What the equation seems to say is that energy equals mass times some number. So then, isn’t energy made of something after all?</p>
<p>Not quite, because some things with no mass can still have energy. For example, light. We know it has energy because we catch light’s energy in solar panels, and turn it into electricity. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-how-do-solar-panels-work-123515">Curious Kids: how do solar panels work?</a>
</strong>
</em>
</p>
<hr>
<p>But light is <a href="https://theconversation.com/curious-kids-is-light-a-wave-or-a-particle-162514">made of tiny particles called photons</a>, and photons have no mass.</p>
<p>So, if energy were made of mass, then light would have no energy at all! That would make a mystery out of solar power. </p>
<p>As it turns out, even though light has no mass it does have something called <em>momentum</em>, which gives it a capacity to do work. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-is-light-a-wave-or-a-particle-162514">Curious Kids: is light a wave or a particle?</a>
</strong>
</em>
</p>
<hr>
<h2>Mass, energy and momentum</h2>
<p>There’s a more complicated version of Einstein’s equation that shows how energy is related to mass and momentum. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/430403/original/file-20211104-25-1muuzcb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/430403/original/file-20211104-25-1muuzcb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=250&fit=crop&dpr=1 600w, https://images.theconversation.com/files/430403/original/file-20211104-25-1muuzcb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=250&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/430403/original/file-20211104-25-1muuzcb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=250&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/430403/original/file-20211104-25-1muuzcb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=314&fit=crop&dpr=1 754w, https://images.theconversation.com/files/430403/original/file-20211104-25-1muuzcb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=314&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/430403/original/file-20211104-25-1muuzcb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=314&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Light is so fast it travels all the way from the Sun to Earth in just over 8 minutes.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>One important thing to know is that light moves very fast. Because the amount of energy in something depends on how much mass it has multiplied by the square of the speed of light, that means a little bit of matter carries a lot of energy!</p>
<p>Light travels almost 300 million metres in a single second, which means one kilogram of mass is equivalent to almost nine quintillion joules of energy! That’s a 9 with 18 zeroes after it: 9,000,000,000,000,000,000.</p>
<p>The trick is unleashing that capacity. That’s actually how nuclear bombs (and nuclear power) work: they unlock the energy captured in matter to produce an enormous effect.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/testing-the-theory-taking-einstein-to-primary-schools-9710">Testing the theory: taking Einstein to primary schools</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/169940/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sam Baron receives funding from the Australian Research Council. </span></em></p>Energy isn’t really made of anything else. It’s a kind of capacity to do thingsSam Baron, Associate professor, Australian Catholic UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1649032021-09-07T12:54:21Z2021-09-07T12:54:21ZWhy are planets round?<figure><img src="https://images.theconversation.com/files/413571/original/file-20210728-23-c5bsvh.jpg?ixlib=rb-1.1.0&rect=362%2C137%2C5018%2C3690&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Earth is round.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/boy-holding-up-a-large-globe-outdoors-royalty-free-image/1279305617?adppopup=true">Alistair Berg/DigitalVision via Getty Images</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
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<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
<hr>
<blockquote>
<p><strong>Why are planets round? – Daniel B., La Crosse, Wisconsin</strong></p>
</blockquote>
<hr>
<p>The <a href="https://www.aps.org/publications/apsnews/200606/history.cfm">ancient Greeks proved</a> over 2,000 years ago that the Earth was round and figured out how big it was by using simple observations of the Sun. </p>
<p>But how do people know this today? When you drop anything, gravity causes it to fall directly toward the center of the Earth, at least until it hits the ground. <a href="https://plato.stanford.edu/entries/newton-principia/">Gravity</a> is a force that is caused by nearly everything that has mass. <a href="https://plato.stanford.edu/entries/newton-principia/">Mass</a> is a measure of how much material there is in anything. It could be in the form of rocks, water, metal, people – anything. Everything material has mass, and therefore everything causes gravity. Gravity always pulls toward the center of mass. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1171426852340207617"}"></div></p>
<p>The Earth and all planets are round because when the <a href="https://phys.org/news/2015-01-planets.html">planets formed</a>, they were composed of molten material – essentially very hot liquid. Since gravity always points toward the center of a mass, it squeezed the stuff the Earth is made of equally in all directions and formed a ball. When the Earth cooled down and became a solid, it was a round ball. If the Earth didn’t spin, then it would have been a perfectly round planet. Scientists call something that is perfectly round in all directions a “sphere.” </p>
<p>The gas cloud that the Earth was made from was slowly rotating in one direction around an axis. The top and bottom of this <a href="https://www.nationalgeographic.org/encyclopedia/axis/">axis are the north and south poles of Earth</a>.</p>
<p>Now, hold out your right hand. Point your thumb on your right hand straight up, and curl your fingers around the direction of rotation. Your thumb is pointing toward the North pole. The equator is defined as the plane, halfway between the North and South Poles. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/413592/original/file-20210728-15-1x6e081.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Three young girls playing on a playground carousel" src="https://images.theconversation.com/files/413592/original/file-20210728-15-1x6e081.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/413592/original/file-20210728-15-1x6e081.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/413592/original/file-20210728-15-1x6e081.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/413592/original/file-20210728-15-1x6e081.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/413592/original/file-20210728-15-1x6e081.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/413592/original/file-20210728-15-1x6e081.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/413592/original/file-20210728-15-1x6e081.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Centrifugal force in action on this carousel.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/kids-on-carousal-in-playground-royalty-free-image/82980840?adppopup=true">Todd Warnock/DigitalVision via Getty Images</a></span>
</figcaption>
</figure>
<p>If you ever played on a merry-go-round, you know that the spinning merry-go-round tends to throw you off. The faster it spins, the harder it is to stay on. This tendency to be flung off is called <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/centrifugal-force">centrifugal force</a> and pushes the mass on the equator outward. This makes the planet bulge at the equator.</p>
<p>The faster the spin, the more unround it becomes. Then, when it cools and hardens, it retains that shape. If a molten planet starts off spinning faster, it would be less round and have a bigger bulge. </p>
<p>The <a href="https://phys.org/news/2015-08-planet-saturn.html">planet Saturn</a> is very oblate – non-spherical – because it rotates very fast. Because of gravity, all planets are round, and because they rotate at different rates, some have fatter equators than their poles. So the shape of the planet and the speed and direction that it rotates depends on the initial condition of the material out of which it forms.</p>
<hr>
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<p class="fine-print"><em><span>James Webb is affiliated with American Astronomical Society -full member
Planetary society - member
National Space Society- member
Southern Cross Astronomical Society lifetime member</span></em></p>Gravity, mass and centrifugal force all contribute to the final shape of a planet.James Webb, Professor and Director, Stocker AstroScience Center for Physics; Stocker AstroScience Center, Florida International UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1631472021-06-28T12:14:21Z2021-06-28T12:14:21ZControversy over Communion in the Catholic Church goes back some 2,000 years<figure><img src="https://images.theconversation.com/files/408448/original/file-20210625-28-1uvawe2.jpg?ixlib=rb-1.1.0&rect=10%2C0%2C1011%2C676&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">When Pope John Paul II was beatified, Zimbabwe's ruler, Robert Mugabe, was in attendance and given Communion.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/zimbabwes-president-robert-mugabe-flanked-by-his-wife-grace-news-photo/457486158?adppopup=true.">Franco Origlia/Getty Images</a></span></figcaption></figure><p>The United States Conference of Catholic Bishops recently approved drafting a <a href="https://www.usccb.org/news/2021/united-states-conference-catholic-bishops-vote-write-document-meaning-eucharist-life">document on receiving Communion in the Catholic Church</a>. It will include a <a href="https://www.wsj.com/articles/catholic-bishops-debate-communion-for-biden-11623937299">section regarding standards</a> for politicians and public figures who support laws <a href="https://www.archstl.org/bishops-vote-to-draft-teaching-document-on-the-eucharist-6591">allowing abortion, euthanasia and other “moral evils</a>.” </p>
<p>The proposed document has already caused controversy. <a href="https://www.npr.org/2021/05/11/995796836/vatican-warns-u-s-bishops-about-denying-communion-to-supporters-of-abortion-righ">The Vatican</a> has warned against exclusively focusing on abortion and euthanasia and cautioned that the document could further <a href="https://www.nytimes.com/2021/06/18/us/targeting-biden-catholic-bishops-advance-controversial-communion-plan.html">divide U.S. Catholics</a>.</p>
<p>As a <a href="https://www.holycross.edu/academics/programs/religious-studies/faculty/mathew-schmalz">Catholic scholar of religion</a>, I would argue that battles over Communion are nothing new in the Catholic Church.</p>
<h2>The importance of Communion</h2>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/408417/original/file-20210625-23-9t0k7u.jpg?ixlib=rb-1.1.0&rect=47%2C0%2C2587%2C1690&q=45&auto=format&w=1000&fit=clip"><img alt="Archbishop Jose H. Gomez holds a Communion wafer during Mass at the Cathedral of Our Lady of the Angels in downtown Los Angeles in 2020." src="https://images.theconversation.com/files/408417/original/file-20210625-23-9t0k7u.jpg?ixlib=rb-1.1.0&rect=47%2C0%2C2587%2C1690&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/408417/original/file-20210625-23-9t0k7u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/408417/original/file-20210625-23-9t0k7u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/408417/original/file-20210625-23-9t0k7u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/408417/original/file-20210625-23-9t0k7u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/408417/original/file-20210625-23-9t0k7u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/408417/original/file-20210625-23-9t0k7u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The U.S. Conference of Catholic Bishops is debating which Catholics are worthy of receiving Communion.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/CatholicBishopsCommunionandPolitics/e0a310966abf4656bc4efd469229f175/photo?Query=United%20States%20Conference%20of%20Catholic%20Bishops%202021&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=4&currentItemNo=0">AP Photo/Damian Dovarganes, File</a></span>
</figcaption>
</figure>
<p>In the Catholic Church, the Communion service is one of seven rituals called <a href="https://www.vatican.va/archive/ENG0015/__P3E.HTM">sacraments</a> that have a primary significance. During this service, called <a href="https://www.usccb.org/offices/public-affairs/structure-and-meaning-mass">a Mass</a>, Catholics believe that the bread and wine, when specially blessed by a priest, become the body and blood of Jesus Christ. Ritually consuming this bread and wine is a special way to “commune,” or be united, with Jesus Christ. </p>
<p>Catholics call both the celebration of Mass and the blessed bread and wine <a href="https://denvercatholic.org/the-eucharist-throughout-history-a-timeline/">the Eucharist</a>, from the Greek word meaning “thanksgiving.” Receiving Communion can also be called receiving the Eucharist.</p>
<p>The Catholic Church teaches that <a href="https://www.americamagazine.org/faith/2019/10/30/explainer-when-can-someone-be-denied-eucharist">in order to receive Communion</a>, a person must not be <a href="https://www.vatican.va/archive/ENG0015/__P4D.HTM">conscious of a serious sin</a> – such as murder or adultery – that has not already been absolved through confession to a priest. </p>
<p>In early Christianity, rules about receiving Communion could be strict. Christians who were known to be guilty of serious sins were not supposed to receive Communion until they went through a process of reconciliation with a local bishop. In the <a href="http://cdn.theologicalstudies.net/16/16.4/16.4.1.pdf">Middle Ages</a>, very few Catholics actually received Communion at all, as many believed that they were unworthy to do so. </p>
<h2>The possibility of scandal</h2>
<p>In the 19th and 20th centuries, the Catholic Church <a href="https://www.ewtn.com/catholicism/library/decree-on-frequent--daily-reception-of-holy-communion-2174">encouraged a more frequent – even daily – reception of Communion</a>. </p>
<p>Still, one of the main concerns surrounding Communion is that someone publicly known to be committing serious sins would receive Communion. Such cases create “scandal.”</p>
<p>In the Catholic Church’s terminology, scandal is “<a href="https://www.vatican.va/archive/ENG0015/__P80.HTM">an attitude or behavior which leads another to do evil</a>.” So, someone who accepts Communion while at the same time publicly continuing in sinful behavior encourages others to continue to do the same as well. </p>
<p>When it comes to public policy, the compendium of Catholic doctrine, the Catholic Cathechism, <a href="https://www.vatican.va/archive/ENG0015/__P80.HTM">specifically states</a>, “they are guilty of scandal who establish laws or social structures leading to the decline of morals and the corruption of religious practice.”</p>
<h2>Denying Communion</h2>
<p>There is a history of the Catholic Church denying Communion to those participating in what is considered publicly sinful behavior.</p>
<p>One of the most famous examples is of <a href="https://www.britannica.com/biography/Saint-Ambrose">Ambrose</a>, bishop of Milan, who baptized the theologian Augustine of Hippo, who later became <a href="https://plato.stanford.edu/entries/augustine/">one of the most influential figures in Christian history</a>. Ambrose denied Communion to the Roman Emperor Theodosius in the fourth century. Enraged by the lynching of a leader of a Roman army garrison, Theodosius gave orders that led to a massacre in the port city of Thessalonica, which killed 7,000 citizens. <a href="https://www.newadvent.org/fathers/340951.htm">In a letter calling for Theodosius to take responsibility for his actions</a>, Ambrose wrote, “Are you ashamed, O Emperor?”</p>
<p>From 1208 to 1214, Pope Innocent III asked his bishops to place England and Wales under “<a href="http://magnacartaresearch.blogspot.com/2014/03/23-march-1208-interdict-is-laid-on.html#:%7E:text=On%2023%20March%201208%2C%20English,consecrated%20ground%20with%20religious%20ceremony.">interdict</a>,” or “prohibition,” which banned the performance of all sacraments – including the Eucharist – except for baptism and confession of the dying. The reason for this extreme act was said to be that King John had rejected Innocent III’s candidate for the important position of <a href="https://www.historic-uk.com/HistoryUK/HistoryofEngland/Archbishops-of-Canterbury/">archbishop of Canterbury</a>.</p>
<p>In the early 20th century, Irish bishops spoke against continuing acts of violence by Irish nationalists who opposed the <a href="https://www.bbc.co.uk/history/british/easterrising/aftermath/af06.shtml">Anglo-Irish treaty</a> of 1921, which established the Irish Free State and ended the Irish War of Independence. In <a href="http://catalogue.nli.ie/Record/vtls000514373#page/1/mode/1up">a letter</a> published on 22 October 1922, the <a href="https://www.jstor.org/stable/29742759?seq=36#metadata_info_tab_contents">Irish bishops</a> denied absolution and Communion to “irregulars” using violence against the “legitimate authority” of the government.</p>
<p>More recently, it was reported in 2011 that priests in <a href="https://www.theguardian.com/lifeandstyle/2011/may/28/malta-divorce-referendum">Malta were denying Communion to Catholics</a> who supported legalizing divorce. In the United States, presidential candidate John Kerry <a href="https://www.cbsnews.com/news/kerrys-communion-controversy/">was denied Communion in 2004</a>, reportedly for his support for abortion rights. The same issue saw Joseph Biden denied Communion in <a href="https://theconversation.com/why-joe-biden-was-denied-communion-at-a-church-126171">2019</a> by a church in South Carolina.</p>
<h2>Communion controversies</h2>
<p>At the same time, the Catholic Church has also been questioned for not denying Communion to Catholic public figures who have behaved sinfully.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/408421/original/file-20210625-28-ivnooy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Pope John Paul II, left, with Chilean President Gen. Augusto Pinochet in Santiago, Chile on April 1, 1987." src="https://images.theconversation.com/files/408421/original/file-20210625-28-ivnooy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/408421/original/file-20210625-28-ivnooy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/408421/original/file-20210625-28-ivnooy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/408421/original/file-20210625-28-ivnooy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/408421/original/file-20210625-28-ivnooy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=504&fit=crop&dpr=1 754w, https://images.theconversation.com/files/408421/original/file-20210625-28-ivnooy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=504&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/408421/original/file-20210625-28-ivnooy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=504&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Pope John Paul II gave Communion to military dictator Augusto Pinochet.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/CHILEPINOCHETOBIT/bdb7c8cb600b4fd8a4ba3b79d8ef61c1/photo?Query=pinochet%20john%20paul&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=2&currentItemNo=0">AP Photo/Pete Leabo</a></span>
</figcaption>
</figure>
<p>In <a href="https://www.upi.com/Archives/1987/04/11/Pope-avoids-confrontation-with-Pinochet/8894545112000/">his trip to Chile in 1987</a>, Pope John Paul II <a href="https://www.nytimes.com/1987/04/01/world/pope-on-latin-trip-attacks-pinochet-regime.html">criticized the military dictatorship</a> under the Army General Augusto Pinochet. Pinochet led a revolt that toppled the elected government. <a href="https://www.usip.org/publications/1990/05/truth-commission-chile-90">Thousands were tortured and executed</a> under his rule. But <a href="http://natcath.org/NCR_Online/archives2/2000b/060200/060200a.htm">the pope still gave Pinochet Communion</a>.</p>
<p>When Pope John Paul II was <a href="https://www.archbalt.org/holy-confusion-beatification-canonization-are-different/">beatified</a> – a crucial step in becoming named a saint – Zimbabwe’s ruler, <a href="https://www.bbc.com/news/world-africa-27519044">Robert Mugabe</a>, was in attendance. Among <a href="https://www.amnesty.org/en/latest/news/2019/09/robert-mugabe-1924-2019-a-liberator-turned-oppressor/">many human rights abuses</a>, Mugabe <a href="https://www.reuters.com/article/us-zimbabwe-mugabe-violence/mugabes-legacy-thousands-killed-in-rain-that-washes-away-the-chaff-idUSKCN1VR18H">sanctioned the killing of 20,000 people belonging to the Ndebele ethnic minority</a> who were loyal to his rival, <a href="https://www.washingtonpost.com/archive/local/1999/07/02/zimbabwe-nationalist-joshua-nkomo-dies-at-82/da22452e-4238-4f0d-9dbf-96a21eb7ee1c/">Joshua Nkomo</a>. Nonetheless, <a href="https://newrepublic.com/article/88416/robert-mugabe-vatican-catholic-pope-zimbabwe">Mugabe was allowed</a> to take Communion at the Vatican, in St. Peter’s Square. Some in the African Catholic media called this a “<a href="https://www.scross.co.za/2011/05/mugabe-the-scandal-factor/">scandal</a>.”</p>
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<h2>The path forward</h2>
<p>Pope Francis <a href="https://www.vatican.va/evangelii-gaudium/en/files/assets/basic-html/page40.html">has stated</a>: “The Eucharist, although it is the fullness of sacramental life, is not a prize for the perfect but a powerful medicine and nourishment for the weak.” And so one of the key issues that the United States Conference of Catholic Bishops’ proposed document will surely need to address is when human weakness becomes serious sin and scandal.</p>
<p>While the United States Conference of Catholic Bishops will issue guidelines for reception of Communion, it will be the task of individual bishops to decide how to put them into practice. And some Catholic bishops, notably Cardinal Wilton Gregory of Washington D.C., <a href="https://www.washingtonian.com/2021/06/21/washingtons-cardinal-wont-deny-biden-communion/">have said</a> they will not deny communion to President Biden in their jurisdictions.</p>
<p>At the present time, the Catholic Church in America is <a href="https://www.nytimes.com/2021/06/20/us/biden-abortion-catholic-church.html">highly polarized</a>. For his part, <a href="https://time.com/6074753/joe-biden-catholic-communion-abortion/">President Biden, who goes to Mass every week, has said</a> that he has no plan to change how he worships. In such a context, U.S. Catholic bishops will have to move forward very carefully. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/408420/original/file-20210625-21-wy6b49.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="In a Jan. 20, 2021 photo, President-elect Joe Biden and his wife, Jill Biden, attend Mass at the Cathedral of St. Matthew the Apostle during Inauguration Day ceremonies in Washington." src="https://images.theconversation.com/files/408420/original/file-20210625-21-wy6b49.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/408420/original/file-20210625-21-wy6b49.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/408420/original/file-20210625-21-wy6b49.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/408420/original/file-20210625-21-wy6b49.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/408420/original/file-20210625-21-wy6b49.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/408420/original/file-20210625-21-wy6b49.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/408420/original/file-20210625-21-wy6b49.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">President Biden is an observant Catholic who regularly attends Mass.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/BidenCatholicBishops/0f62214fa4ac438aa9fc13f6398b661c/photo?Query=biden%20AND%20communion&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=8&currentItemNo=1">AP Photo/Evan Vucci, File</a></span>
</figcaption>
</figure><img src="https://counter.theconversation.com/content/163147/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mathew Schmalz is a political independent.</span></em></p>Biden is not the first public figure to whom the Catholic Church wants to deny Communion. Over the centuries, the Church has often come under criticism for either denying or giving Communion.Mathew Schmalz, Professor of Religious Studies, College of the Holy CrossLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1626872021-06-18T12:21:25Z2021-06-18T12:21:25ZCern: how we’re probing the universe’s origins using record precision measurements<figure><img src="https://images.theconversation.com/files/407198/original/file-20210618-18-1h7sua8.jpg?ixlib=rb-1.1.0&rect=0%2C35%2C5973%2C3898&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Cern has measure a tiny mass difference by colliding huge amounts of particles.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/fragmentation-highenergy-collisions-between-atomic-subatomic-1443036710">Jurik Peter/Shutterstock</a></span></figcaption></figure><p>What happened at the beginning of the universe, in the very first moments? The truth is, we don’t really know because it takes huge amounts of energy and precision to recreate and understand the cosmos on such short timescales in the lab. But scientists at the Large Hadron Collider (LHC) at CERN, Switzerland aren’t giving up. </p>
<p>Now our <a href="https://home.cern/news/news/physics/lhcb-measures-tiny-mass-difference-between-particles">LHCb experiment</a> has measured one of the smallest difference in mass between two particles ever, which will allow us to discover much more about our enigmatic cosmic origins. </p>
<p>The Standard Model of particle physics describes <a href="https://theconversation.com/explainer-what-are-fundamental-particles-38339">the fundamental particles</a> which make up the universe, and the forces that act between them. The elementary particles include quarks, of which there are six – up, down, strange, charm, top and bottom. Similarly there are six “leptons” which include the electron, a heavier cousin called the muon, and the still heavier tau, each of which has an associated neutrino. There are also “antimatter partners” of all quarks and leptons which are identical particles apart from an opposite charge. </p>
<p>The Standard Model is experimentally verified to an incredible degree of accuracy but has some significant shortcomings. 13.8 billion years ago, the universe was created in the Big Bang. The theory suggests this event should have produced equal amounts of matter and “antimatter”. Yet today, the universe <a href="https://theconversation.com/explainer-what-is-antimatter-53414">is almost entirely made up of matter</a>. And that’s lucky, because antimatter and matter annihilate in a flash of energy when they meet.</p>
<p>One of the biggest open questions in physics today is why is there more matter than antimatter. Were there processes at play in the early universe that favoured matter over antimatter? To get closer to the answer, we have studied a process where matter transforms into antimatter and vice versa. </p>
<p>Quarks are bound together to form particles called baryons – including the protons and neutrons that make up the atomic nucleus – or mesons, which consist of quark-antiquark pairs. Mesons with zero electric charge continually undergo a phenomenon called mixing by which they spontaneously change into their antimatter particle, and vice versa. In this process, the quark turns into an anti-quark and the anti-quark turns into a quark.</p>
<p>It can do this because of quantum mechanics, which <a href="https://theconversation.com/physicists-prove-quantum-spookiness-and-start-chasing-schrodingers-cat-48190">governs the universe</a> on the tiniest of scales. According to this counter-intuitive theory, particles can be in many different states at the same time, essentially being a mix of many different particles – a feature called superposition. It is only when you measure its state that it “picks” one of them. A type of meson called D0, for example, which contains charm quarks, is in a superposition of two normal matter particles called D1 and D2. The rate at which the D0 meson turns into its anti-particle and back again, an oscillation, depends on the difference in masses of D1 and D2. </p>
<h2>Tiny masses</h2>
<p>It is difficult to measure mixing in D0 mesons, but <a href="https://www.desy.de/f/seminar/Staric.pdf">it was done</a> for the first time in 2007. However, until now, nobody has reliably measured the mass difference between D1 and D2 that determines how quickly the D0 oscillates into its antiparticle. </p>
<figure class="align-center ">
<img alt="Figure of the D1 and D2 meson." src="https://images.theconversation.com/files/407197/original/file-20210618-24-1844qru.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/407197/original/file-20210618-24-1844qru.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=333&fit=crop&dpr=1 600w, https://images.theconversation.com/files/407197/original/file-20210618-24-1844qru.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=333&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/407197/original/file-20210618-24-1844qru.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=333&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/407197/original/file-20210618-24-1844qru.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=419&fit=crop&dpr=1 754w, https://images.theconversation.com/files/407197/original/file-20210618-24-1844qru.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=419&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/407197/original/file-20210618-24-1844qru.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=419&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The D1 and D2 mesons, which are a manifestation of the quantum superposition of the D0 particle and its antiparticle.</span>
<span class="attribution"><span class="source">Cern</span></span>
</figcaption>
</figure>
<p>Our latest discovery, <a href="https://home.cern/news/news/physics/lhcb-measures-tiny-mass-difference-between-particles">announced at the Charm conference</a>, changes this. We measured a parameter that corresponds to a mass difference of 6.4x10<sup>-6</sup> electron Volts (a measure of energy) or 10<sup>-38</sup> grams – one of the smallest mass differences between two particles ever measured.</p>
<p>We then calculated that the oscillation between the D0 and its antimatter partner takes around 630 picoseconds (1 ps = 1 millionth millionth of a second). This may seem fast, but the D0 meson doesn’t live long – it isn’t stable in the lab and falls apart (decays) into other particles after only 0.4 picoseconds. So it will typically disappear long before this oscillation occurs, posing a serious experimental challenge. </p>
<p>The key is precision. We know from theory that these oscillations follow the path of a a familiar type of wave (sinusoidal). Measuring the start of the wave very precisely, we can infer its full period as we know its shape. The measurement therefore had to reach record precision on several fronts. This is made possible by the unprecedented amount of charm particles produced at the LHC. </p>
<p>But why is this important? To understand why the universe produced less antimatter than matter we need to learn more about the asymmetry in the production of the two, a process known as CP-violation. It has already been shown that some unstable particles decay in a different way to their corresponding antimatter particle. This may have contributed <a href="https://theconversation.com/cern-study-sheds-light-on-one-of-physics-biggest-mysteries-why-theres-more-matter-than-antimatter-113947">to the abundance of matter in the universe</a> – with <a href="https://www.nobelprize.org/prizes/physics/2008/kobayashi/lecture/">previous discoveries</a> of it leading to Nobel Prizes.</p>
<p>We also want to find CP-violation in the process of mixing. If we start with millions of D0 particles and millions of D0 antiparticles, will we end up with more D0 normal matter particles after some time? Knowing the oscillation rate is a key step towards this goal. While we did not find an asymmetry this time, our result and further precision measurements can help us find it in the future. </p>
<p>Next year, the LHC will switch on after a long shut down and the new upgraded LHCb detector will take much more data, boosting the sensitivity of these measurements further. Meanwhile, theoretical physicists are working on new calculations to interpret this result. The LHCb physics programme will also be complemented by the <a href="https://www.belle2.org">Belle-II experiment</a> in Japan. These are exciting prospects for investigating matter-antimatter asymmetry and the oscillations of mesons.</p>
<p>While we cannot yet completely solve the mysteries of the universe, our latest discovery has put the next piece in the puzzle. The new upgraded LHCb detector will open the door to an era of precision measurements that have the potential to uncover yet unknown phenomena – and perhaps physics beyond the Standard Model.</p><img src="https://counter.theconversation.com/content/162687/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Martha Hilton receives funding from STFC (Science Technology Facilities Council). </span></em></p><p class="fine-print"><em><span>Nathan Jurik received funding from the STFC (Science Technology Facilities Council).</span></em></p><p class="fine-print"><em><span>Sascha Stahl does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Record precision measurements at Cern may help explain why the universe has more matter than antimatter.Martha Hilton, PhD candidate in Particle Physics, University of ManchesterNathan Jurik, Research Fellow of Particle Physics, Syracuse UniversitySascha Stahl, Research staff at CERN, CERNLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1533642021-02-01T13:09:54Z2021-02-01T13:09:54ZCould a human enter a black hole to study it?<figure><img src="https://images.theconversation.com/files/381286/original/file-20210129-19-1ly38eg.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A person falling into a black hole and being stretched while approaching the black hole's horizon.</span> <span class="attribution"><span class="source">Leo Rodriguez and Shanshan Rodriguez</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>.</em></p>
<hr>
<blockquote>
<p><strong>Could a human enter a black hole to study it? – Pulkeet, age 12, Bahadurgarh, Haryana, India</strong></p>
</blockquote>
<hr>
<p>To solve the mysteries of black holes, a human should just venture into one. However, there is a rather complicated catch: A human can do this only if the respective black hole is supermassive and isolated, and if the person entering the black hole does not expect to report the findings to anyone in the entire universe. </p>
<p>We are <a href="https://www.grinnell.edu/user/rodriguezl">both</a> <a href="https://www.grinnell.edu/user/rodriguezs">physicists</a> who study black holes, albeit from a very safe distance. Black holes are <a href="https://doi.org/10.1093/mnras/stx1959">among the most abundant astrophysical objects in our universe</a>. These intriguing objects appear to be an essential ingredient in the <a href="https://link.springer.com/chapter/10.1007%2F978-3-642-39596-3_8">evolution of the universe</a>, from the Big Bang till present day. They probably had an <a href="https://doi.org/10.1093/mnras/stz2161">impact on the formation of human life in our own galaxy</a>. </p>
<h2>Two types of black holes</h2>
<p>The universe is littered with a <a href="https://www.washingtonpost.com/science/2019/11/29/scientists-find-monster-black-hole-so-big-they-didnt-think-it-was-possible/">vast zoo of different types of black holes</a>. </p>
<p>They can vary by size and be electrically charged, the same way electrons or protons are in atoms. Some black holes actually spin. There are two types of black holes that are relevant to our discussion. The first does not rotate, is electrically neutral – that is, not positively or negatively charged – and has the mass of our Sun. The second type is a supermassive black hole, with a mass of millions to even billions times greater than that of our Sun. </p>
<p>Besides the mass difference between these two types of black holes, what also differentiates them is the distance from their center to their “event horizon” – a measure called radial distance. The event horizon of a black hole is the point of no return. Anything that passes this point will be swallowed by the black hole and forever vanish from our known universe. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/379201/original/file-20210118-13-1j8ys1.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/379201/original/file-20210118-13-1j8ys1.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/379201/original/file-20210118-13-1j8ys1.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=598&fit=crop&dpr=1 600w, https://images.theconversation.com/files/379201/original/file-20210118-13-1j8ys1.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=598&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/379201/original/file-20210118-13-1j8ys1.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=598&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/379201/original/file-20210118-13-1j8ys1.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=752&fit=crop&dpr=1 754w, https://images.theconversation.com/files/379201/original/file-20210118-13-1j8ys1.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=752&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/379201/original/file-20210118-13-1j8ys1.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=752&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The distance from a black hole’s center of mass to where gravity’s pull is too strong to overcome is called the event horizon.</span>
<span class="attribution"><span class="source">Leo and Shanshan</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>At the event horizon, the black hole’s gravity is so powerful that no amount of mechanical force can overcome or counteract it. <a href="https://doi.org/10.1088/2053-2571/ab06bd">Even light</a>, the fastest-moving thing in our universe, cannot escape – hence the term “black hole.”</p>
<p>The radial size of the event horizon depends on the mass of the respective black hole and is key for a person to survive falling into one. For a black hole with a mass of our Sun (one solar mass), the event horizon will have a radius of just under 2 miles. </p>
<p>The supermassive black hole at the center of our Milky Way galaxy, by contrast, has a mass of roughly 4 million solar masses, and it has an event horizon with a radius of 7.3 million miles or 17 solar radii. </p>
<p>Thus, someone falling into a stellar-size black hole will get much, much closer to the black hole’s center before passing the event horizon, as opposed to falling into a supermassive black hole. </p>
<p>This implies, due to the closeness of the black hole’s center, that the black hole’s pull on a person will differ by a factor of 1,000 billion times between head and toe, depending on which is leading the free fall. In other words, if the person is falling feet first, as they approach the event horizon of a stellar mass black hole, the gravitational pull on their feet will be exponentially larger compared to the black hole’s tug on their head. </p>
<p>The person would experience spaghettification, and most likely not survive being stretched into a long, thin noodlelike shape.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/379434/original/file-20210119-21-1lb26xu.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/379434/original/file-20210119-21-1lb26xu.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/379434/original/file-20210119-21-1lb26xu.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=383&fit=crop&dpr=1 600w, https://images.theconversation.com/files/379434/original/file-20210119-21-1lb26xu.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=383&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/379434/original/file-20210119-21-1lb26xu.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=383&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/379434/original/file-20210119-21-1lb26xu.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=482&fit=crop&dpr=1 754w, https://images.theconversation.com/files/379434/original/file-20210119-21-1lb26xu.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=482&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/379434/original/file-20210119-21-1lb26xu.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=482&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">As the person approaches the event horizon of a a Sun-size black hole, the vast difference in gravitational pull between the inidvidual’s head and toes causes the person to stretch into a very long noodle, hence the term ‘spaghettification’.</span>
<span class="attribution"><span class="source">Leo and Shanshan Rodriguez</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Now, a person falling into a supermassive black hole would reach the event horizon much farther from the the central source of gravitational pull, which means that the difference in gravitational pull between head and toe is nearly zero. Thus, the person would pass through the event horizon unaffected, not be stretched into a long, thin noodle, survive and float painlessly past the black hole’s horizon.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/379435/original/file-20210119-24-1w07b7a.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/379435/original/file-20210119-24-1w07b7a.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/379435/original/file-20210119-24-1w07b7a.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=566&fit=crop&dpr=1 600w, https://images.theconversation.com/files/379435/original/file-20210119-24-1w07b7a.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=566&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/379435/original/file-20210119-24-1w07b7a.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=566&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/379435/original/file-20210119-24-1w07b7a.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=711&fit=crop&dpr=1 754w, https://images.theconversation.com/files/379435/original/file-20210119-24-1w07b7a.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=711&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/379435/original/file-20210119-24-1w07b7a.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=711&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A person falling into a supermassive black hole would likely survive.</span>
<span class="attribution"><span class="source">Leo and Shanshan Rodriguez</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Other considerations</h2>
<p>Most black holes that we observe in the universe are surrounded by very hot disks of material, mostly comprising gas and dust or other objects like stars and planets that got too close to the horizon and fell into the black hole. These disks are called accretion disks and are very hot and turbulent. They are most certainly not hospitable and would make traveling into the black hole extremely dangerous. </p>
<p>To enter one safely, you would need to find a supermassive black hole that is completely isolated and not feeding on surrounding material, gas and or even stars. </p>
<p>Now, if a person found an isolated supermassive black hole suitable for scientific study and decided to venture in, everything observed or measured of the black hole interior would be confined within the black hole’s event horizon.</p>
<p>Keeping in mind that nothing can escape the gravitational pull beyond the event horizon, the in-falling person would not be able to send any information about their findings back out beyond this horizon. Their journey and findings would be lost to the rest of the entire universe for all time. But they would enjoy the adventure, for as long as they survived … maybe ….</p>
<hr>
<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>. Please tell us your name, age and the city where you live.</em></p>
<p><em>And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.</em></p><img src="https://counter.theconversation.com/content/153364/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>If you are a sci-fi junkie you’ve probably wondered what would happen if you were unlucky enough to fall into a black hole. How well you’d fare all depends on the type of black hole.Leo Rodriguez, Assistant Professor of Physics, Grinnell CollegeShanshan Rodriguez, Assistant Professor of Physics, Grinnell CollegeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1536852021-01-20T22:22:36Z2021-01-20T22:22:36ZSt. Matthew’s Cathedral, where Biden attended pre-inauguration Mass, has long been a place where politics and faith meet<figure><img src="https://images.theconversation.com/files/379800/original/file-20210120-23-vs9z6n.jpg?ixlib=rb-1.1.0&rect=0%2C8%2C5571%2C3700&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Joe and Jill Biden attend Mass at St. Matthew the Apostle before the inauguration.</span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/BidenInauguration/65c4c4e4a1a34b07bd3373acec9b3b13/photo?Query=Matthew%20AND%20Biden&mediaType=photo&sortBy=arrivaldatetime:desc&dateRange=Anytime&totalCount=101&currentItemNo=11">AP Photo/Evan Vucci</a></span></figcaption></figure><p>Prior to being sworn in as the 46th president of the United States – and only the second Catholic to hold the post – Joe Biden attended Mass.</p>
<p>Accompanied by his wife, Jill Biden, and now-Vice President Kamala Harris and her husband, Doug Emhoff, he occupied the front pew of <a href="https://www.caravaggio.org/the-calling-of-saint-mathew.jsp">the Cathedral of St. Matthew the Apostle</a>, known as St. Matthew’s Cathedral. It isn’t Washington’s largest Catholic church, but it has long been a place where politics and faith meet – making it a fitting venue to start the day’s proceedings.</p>
<p><a href="https://www.stmatthewscathedral.org/about/history">Established in 1840</a>, St. Matthew’s is named for <a href="https://www.catholic.org/saints/saint.php?saint_id=84">the tax collector</a> called by Jesus to be one of the Twelve Apostles. The Cathedral is a short walk from the White House and government buildings. Fittingly for the District of Columbia cathedral that carries his name, Matthew is recognized as the <a href="https://www.stmatthewscathedral.org/about/saint-matthew">patron saint of civil servants</a>. </p>
<p>But if tourists to Washington visit a Catholic church at all, they probably go to the much larger <a href="https://www.nationalshrine.org/">Basilica of the Shrine of the Immaculate Conception</a>. A shrine is a site for visitors and pilgrims.</p>
<p>A cathedral, meanwhile, serves as a home church for <a href="https://adw.org/">a Catholic diocese</a> or archdiocese. </p>
<p>But St. Matthew’s – first in its original building and now in its newer 1913 structure – has been a downtown parish far longer than it has been a cathedral. Washington <a href="https://adw.org/about-us/who-we-are/historic-moments/75th-anniversary/">became an archdiocese only in 1939</a>. </p>
<p>In fact, Roman Catholics were a negligible presence in the city until the mid-20th century and the election of John F. Kennedy, the first Catholic U.S. president. </p>
<p>And it was Kennedy’s 1963 funeral that cast history’s spotlight on St. Matthew’s for the first time.</p>
<figure class="align-center ">
<img alt="John F. Kennedy Jr. salutes as the casket of his father, the late President John F. Kennedy, is carried from St. Matthew's Cathedral in Washington, DC." src="https://images.theconversation.com/files/379803/original/file-20210120-17-14xxlx5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/379803/original/file-20210120-17-14xxlx5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/379803/original/file-20210120-17-14xxlx5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/379803/original/file-20210120-17-14xxlx5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/379803/original/file-20210120-17-14xxlx5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/379803/original/file-20210120-17-14xxlx5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/379803/original/file-20210120-17-14xxlx5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">John F. Kennedy Jr. salutes as his father’s casket is carried from St. Matthew’s Cathedral.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/john-f-kennedy-jr-who-turns-three-today-salutes-as-the-news-photo/517330220?adppopup=true">Bettmann via Getty images</a></span>
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<p>As Kennedy’s remains were carried from the cathedral to later be <a href="https://www.jfklibrary.org/learn/about-jfk/life-of-john-f-kennedy/fast-facts-john-f-kennedy/president-kennedys-grave-in-arlington-national-cemetery">interred at Arlington National Cemetery</a>, 3-year-old John F. Kennedy Jr. offered a salute captured in an <a href="https://www.politico.com/blogs/politico-now/2013/11/story-behind-the-salute-178248">iconic photograph</a>.</p>
<p>The spot near the altar in St. Matthew’s where Kennedy’s body lay as Boston’s Cardinal Richard Cushing offered his <a href="https://www.youtube.com/watch?v=kPXSwoTcL0g">funeral Mass</a> on Nov. 25, 1963, is marked by <a href="https://www.stmatthewscathedral.org/about/history">an inlay</a> that designates it as the spot where “President Kennedy” rested. Using Kennedy’s civic title rather than his baptismal name is an unusual touch for a Catholic church. But it is a reminder that St. Matthew’s sits where church and state meet.</p>
<p>[<em>Like what you’ve read? Want more?</em> <a href="https://theconversation.com/us/newsletters/the-daily-3?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=likethis">Sign up for The Conversation’s daily newsletter</a>.]</p>
<p>St. Matthew’s was the funeral site for <a href="https://news.google.com/newspapers?id=7RssAAAAIBAJ&pg=3481%2C4039763">Sen. Joseph McCarthy</a>, too, as well as President Jimmy Carter’s national security adviser, <a href="https://www.voanews.com/episode/zbigniew-brzezinskis-funeral-service-friday-washington-3754136">Zbigniew Brzezinski</a>. Each year, St. Matthew’s is the site of the <a href="https://www.johncarrollsociety.org/membership/the-red-mass">Red Mass</a> that marks the opening of a Supreme Court term. A nonpartisan crossroads of Catholic faith and American politics, St. Matthew’s today also is notable as the seat of the <a href="https://adw.org/about-us/who-we-are/cardinal-gregory/">first African American cardinal, Wilton Gregory</a>.</p>
<p>Perhaps St. Matthew’s is best <a href="https://ctu.edu/faculty/steven-millies/">appreciated the way I knew it</a>. Like many Catholics who have worked in downtown Washington, D.C., I looked upon St. Matthew’s as a quiet refuge for prayer and reflection in the middle of a workday. Joe Biden is among those Catholics working and living in the neighborhood. His prayers for the nation at St. Matthew’s add to the cathedral’s deep history, and the nation’s second Catholic president will feel that history all around him.</p>
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<p class="fine-print"><em><span>Steven P. Millies does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>St. Matthew is the patron saint of civil servants – making the Washington, D.C., church bearing his name a fitting venue for presidents, both past and present.Steven P. Millies, Professor of Public Theology and Director of The Bernardin Center, Catholic Theological UnionLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1177132019-07-28T12:30:51Z2019-07-28T12:30:51ZRedefining the kilogram means redefining how we measure wealth<figure><img src="https://images.theconversation.com/files/277236/original/file-20190530-69063-16j0i2o.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5183%2C3444&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">In May 2019, the measure of a kilogram was changed. This has implications for how we measure wealth.</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Between November 2008 and October 2014, an additional $85 billion was created on an almost-monthly basis by the United States Federal Reserve Bank. As a result, <a href="https://money.cnn.com/2018/07/31/investing/stocks-market-federal-reserve-qe/index.html">the total amount of newly created electronic cash</a> used to purchase government bonds in that period is estimated to be $4.5 trillion. </p>
<p>On World Metrology Day 2019, <a href="https://futurism.com/the-byte/redefined-kilogram">the kilogram was fundamentally redefined</a>. It has now become a number whose value is defined by <a href="https://www.vox.com/science-and-health/2018/11/14/18072368/kilogram-kibble-redefine-weight-science">the energetics of a hoard of photons</a>. Accordingly, those same electromagnetic phenomena that created $4.5 trillion in electronic cash are also now controlling our traditional understanding of wealth itself.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/284117/original/file-20190715-173329-1i4ifxp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/284117/original/file-20190715-173329-1i4ifxp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/284117/original/file-20190715-173329-1i4ifxp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/284117/original/file-20190715-173329-1i4ifxp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/284117/original/file-20190715-173329-1i4ifxp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/284117/original/file-20190715-173329-1i4ifxp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/284117/original/file-20190715-173329-1i4ifxp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/284117/original/file-20190715-173329-1i4ifxp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Martin J.T. Milton, the head of the International Bureau of Weights and Measures, holds a replica of the International Prototype Kilogram in Sèvres, near Paris, in October 2018.</span>
<span class="attribution"><span class="source">Christophe Ena/AP Photo</span></span>
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<p>I have been teaching and writing about coherent systems of units and their importance for accurate characterization of heat and mass transfer processes in food-processing operations. My work also examines the effective utilization of units in the trading and processing of agricultural commodities. For example, conversions between mass and volume dictate <a href="https://www.agric.gov.ab.ca/app19/calc/crop/bushel2tonne.jsp">price returns</a> and <a href="https://www.canada.ca/en/health-canada/services/understanding-food-labels/serving-size.html">nutrient content</a> in many sectors of our food supply chains.</p>
<h2>Gold standards</h2>
<p>Up until 1931, the value of a British pound was defined by its ability to be exchanged for 0.235849 ounces of gold. Likewise, until 1971, a U.S. dollar was valued at 0.028571 ounces of gold. To some economists, the U.S. government’s decision to abandon the <a href="https://doi.org/10.1177%2F0032329218823648">gold standard</a> was licence for the dollar to claim values divorced from traditional measures of wealth. </p>
<p>Freed from the obligation to redeem a given number of dollars against a specific mass of an immutable metal, the Federal Reserve was able to tweak currency flows to hit its desired liquidity targets. The outcome of six years of <a href="https://doi.org/10.1111/j.1468-0297.2012.02551.x">quantitative easing</a> was a global economy that landed softly from the financial crisis of 2008, but at the price of a <a href="https://doi.org/10.1080/13563467.2015.1041478">greater concentration of wealth for those already wealthy</a>.</p>
<p>The change in the kilogram that occurred on May 20th, 2019, eliminated another long-held standard, which will also have global ramifications: <a href="https://doi.org/10.1088/1681-7575/ab0013">a redefinition of the very mass of gold</a>.</p>
<h2>Standard purpose</h2>
<p>The need for fixed and legitimate standards has been a longstanding trade issue. Some 2,800 years ago, <a href="https://www.bible.com/bible/100/AMO.8.5.NASB">Amos decried the prevalence of shrunken bushels and inflated shekels in the trading of cereals</a> in Jerusalem.</p>
<p>But it was in post-revolutionary France where <a href="https://archive.org/details/lesystmemtri00bigo/page/n10">measurement standards were defined for trading on a global scale</a>. When the new government devised the metre as the standard for length, it was conceived as a fraction of the Earth’s circumference. In defining a unit for mass, the kilogram was assigned as the mass of water contained within a volume governed by that standard of length.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/284131/original/file-20190715-173355-uulya4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/284131/original/file-20190715-173355-uulya4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/284131/original/file-20190715-173355-uulya4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=875&fit=crop&dpr=1 600w, https://images.theconversation.com/files/284131/original/file-20190715-173355-uulya4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=875&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/284131/original/file-20190715-173355-uulya4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=875&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/284131/original/file-20190715-173355-uulya4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1099&fit=crop&dpr=1 754w, https://images.theconversation.com/files/284131/original/file-20190715-173355-uulya4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1099&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/284131/original/file-20190715-173355-uulya4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1099&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">One of six temporary prototypes made in 1793 by the French Temporary Commission on Weights and Measures. Originally called the ‘grave,’ the name was changed to ‘kilogram’ in 1795. The prototype is in the collection of the U.S. National Institute of Standards and Technology Museum in Bethesda, Md.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Grave_kilogram_standard_1793.jpg">U.S. National Institute of Standards and Technology Museum</a></span>
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<p>To ensure that all traders adhered to these new standards of length and mass, prototypes of the metre and the kilogram were fabricated - the first, ironically enough, by the former king’s royal jeweller. These prototypes were made of precious metal, not because of its value, but because of its inertness. </p>
<p>They were retained under lock and key, but were periodically available for standardization and correction of more widely available secondary standards of length and mass. Although new physical versions of the prototype metre and kilogram were produced in 1889, these physical standards endured because no better standards were available. As a result, the physical kilogram lasted for more than 200 years.</p>
<h2>Scientific standards</h2>
<p>With advances in science, additional standards were appended to the kilogram and metre. We now have <a href="https://doi.org/10.1088/0026-1394/31/6/011">seven standards</a> from which everything that we know about our universe is defined and quantified. This includes how many pecks of wheat we get for a pound of gold. Yes, I did write pecks and pounds. Despite our southern neighbour’s stolid indifference to Canada’s metrication, their standard for mass, a physical pound, was eliminated as early as 1893.</p>
<p>Just as new measurement technologies brought <a href="https://www.history.com/this-day-in-history/galileo-is-convicted-of-heresy">Galileo into conflict with accepted cosmological standards</a>, advanced techniques revealed deficiencies in the standards in use. So in 1960, <a href="https://doi.org/10.1139/p61-088">the prototype metre was abandoned</a>. </p>
<p>If size did matter, it was measured against standards regulated by the properties of light, specifically a defined number of wavelengths of an orange line emitted when the noble gas krypton was electrically excited. The prototype metre thus became a quaint historical artefact.</p>
<p>The <a href="https://doi.org/10.1088/1681-7575/ab0013">prototype kilogram</a> was then left as the only tangible standard of the scientific and social upheaval that flowed from the ideas of Thomas Jefferson, John Adams and Benjamin Franklin.</p>
<p>As we advance well into the 21st century, the lifetime of this <a href="https://www.bipm.org/en/measurement-units/faqs.html">one remaining tangible standard has just expired</a>.</p>
<p>It was recognized for a number of years that gentle polishing and environmental pollution had been incrementally <a href="https://doi.org/10.1088%2F0026-1394%2F33%2F6%2F1">changing the mass of the prototype kilogram</a>. The simple solution of replacing the old prototype kilogram with a new one is no longer tenable in an age of enlightenment where the ideas of <a href="https://doi-org.uml.idm.oclc.org/10.1098/rspb.1967.0069">John Dalton</a>, <a href="https://doi.org/10.1007/s00016-002-8363-7">Max Planck</a> and <a href="https://plato.stanford.edu/entries/statphys-Boltzmann/">Ludwig Boltzmann</a> dictate a new fiat.</p>
<p>In the future, <a href="https://doi.org/10.1088%2F1681-7575%2Faa966c">mass will no longer be mass</a> as tangibly defined throughout history. A select group with access to sophisticated equipment will tweak the number that now defines mass as they see fit, or “<a href="https://www.nytimes.com/2018/11/16/science/kilogram-physics-measurement.html">conjure [it] on demand</a>.”</p>
<p>From this point onwards, it matters not what <a href="https://doi.org/10.1111/johs.12139">mass of Franklin D Roosevelt’s confiscated gold</a> exists in Fort Knox; the same electrons that create the Federal Reserve’s wealth now govern our very definition of the gold’s existence.</p>
<p>[ <em><a href="https://theconversation.com/ca/newsletters?utm_source=TCCA&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=expertise">Expertise in your inbox. Sign up for The Conversation’s newsletter and get a digest of academic takes on today’s news, every day.</a></em> ]</p><img src="https://counter.theconversation.com/content/117713/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Martin Scanlon receives funding from NSERC Canada. He is a member of the Board of Directors of AACCI - Cereals & Grains Association. </span></em></p>Measurement and standards are at the heart of how we trade commodities and measure wealth. So what happens now that the planet’s most critical standard has been completely overhauled?Martin Scanlon, Dean, Faculty of Agricultural and Food Sciences, University of ManitobaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1175382019-05-28T11:10:42Z2019-05-28T11:10:42ZCurious Kids: how long has gravity existed?<figure><img src="https://images.theconversation.com/files/276775/original/file-20190528-42600-gdbw65.jpg?ixlib=rb-1.1.0&rect=23%2C0%2C2346%2C1476&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Gravity helps stars to form. </span> <span class="attribution"><a class="source" href="http://www.esa.int/spaceinimages/Images/2017/02/Star_formation_on_filaments_in_RCW106">UNIMAP / L. Piazzo, La Sapienza – Università di Roma; E. Schisano / G. Li Causi, IAPS/INAF, Italy</a>, <a class="license" href="http://artlibre.org/licence/lal/en">FAL</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p><em><a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a> is a series by <a href="https://theconversation.com/uk">The Conversation</a>, which gives children of all ages the chance to have their questions about the world answered by experts. All questions are welcome: you or an adult can send them – along with your name, age and town or city where you live – to curiouskids@theconversation.com. We won’t be able to answer every question, but we’ll do our best.</em></p>
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<p><em><strong>How long has gravity existed? - Aine, aged 13, Edinburgh, UK.</strong></em></p>
<p>Gravity is <a href="https://www.esa.int/kids/en/learn/Earth/Natural_disasters/What_Is_Gravity">a force</a> between two masses, so gravity exists wherever there is mass. To discover when gravity started to exist, we need to understand what mass is, and when it started to exist. </p>
<p>Let’s dive right in: “mass” is what we use to measure how much “matter” there is. Scientists use <a href="http://www.chem4kids.com/files/matter_intro.html">the term “matter”</a> to describe stuff like stars, planets, oceans, rocks, molecules, atoms, particles like electrons and protons that make up atoms, and even the particles that make up electrons and protons.</p>
<p>Very nearly everything you encounter in everyday life counts as “matter”: a book, a glass of water, a bird – anything you might also call “stuff”. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-is-everything-really-made-of-molecules-109145">Curious Kids: is everything really made of molecules?</a>
</strong>
</em>
</p>
<hr>
<p>There are <a href="https://theconversation.com/curious-kids-is-everything-really-made-of-molecules-109145">some exceptions</a>: for example, neither light nor sound is matter, nor are feelings. Light can even travel through completely empty space, where there’s no matter at all. </p>
<p>If a feather and a football are both made of matter, you might wonder why they’re so different. Well, a football has much more matter than a feather, so we’d say its “mass” is higher. </p>
<p>On the other hand, a kilogram of feathers and a kilogram of iron have the same mass because they weigh the same – even though the feathers take up a lot more space. </p>
<p>If you could count every particle in your body, then you could add up all of their masses and you would have a measure of your own mass. </p>
<h2>Mass, weight and gravity</h2>
<p>Of course, that isn’t how we actually measure masses in real life. Here on Earth, we measure mass via weight. Mass and weight are not quite the same thing, but they are related. </p>
<p>If you took a scale to the moon and weighed yourself on it, the number it showed would be smaller than when you weighed yourself on the Earth – even though your mass is still the same, your weight would change. This is because the scale you use is actually not measuring your mass directly, but rather the gravitational force your mass is feeling from the Earth, or the moon.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/276778/original/file-20190528-42556-4yguri.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/276778/original/file-20190528-42556-4yguri.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=576&fit=crop&dpr=1 600w, https://images.theconversation.com/files/276778/original/file-20190528-42556-4yguri.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=576&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/276778/original/file-20190528-42556-4yguri.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=576&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/276778/original/file-20190528-42556-4yguri.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=724&fit=crop&dpr=1 754w, https://images.theconversation.com/files/276778/original/file-20190528-42556-4yguri.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=724&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/276778/original/file-20190528-42556-4yguri.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=724&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">You weigh less on the moon.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/sites/default/files/thumbnails/image/apollo08_earthrise.jpg">NASA.</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>How strong gravity is <a href="https://www.esa.int/kids/en/learn/Earth/Natural_disasters/What_Is_Gravity">depends on</a> the mass of both objects, as well as the distance between them. Because the Earth has a lot more mass than the moon, the force of gravity you experience on Earth is stronger. That’s why you weigh more on Earth than on the moon. </p>
<h2>A cosmic creation</h2>
<p>So, when did mass first appear? Based on our best understanding of the physics of the universe, the first mass was created in the form of tiny particles (a LOT of them) right after the beginning of the universe itself, about <a href="https://www.esa.int/kids/en/learn/Our_Universe/Story_of_the_Universe/The_Big_Bang">13.7 billion years ago</a>.</p>
<p>The creation of matter happened so fast after the creation of the universe that you could fit more than a million of those instants in the time it takes to blink an eye. And from that moment, gravity was at work, pulling matter together, gathering atoms and molecules into dense clouds that eventually formed stars and galaxies and planets.</p>
<p>Of course, there are <a href="https://physics.info/newton-first/">many forces</a> in nature, and gravity is only one of them. The other forces work on matter too, so there has always been a cosmic dance between the different forces in the universe, which makes it look how it does. </p>
<p>Gravity might be the force that we’re all most familiar with because we all have felt it since the moment we were born, but actually compared to many of the other forces it’s not especially strong. </p>
<p>But since gravity is found anywhere there is mass, it’s basically everywhere, at all times. </p>
<p>The same gravity that keeps you on the ground here on Earth also holds the Earth together, holds the Earth in orbit around the sun, and holds the sun in orbit around the rest of the galaxy. </p>
<p>Gravity has existed for as long as the universe has, and it will keep existing, for as long as we do, and beyond. </p>
<hr>
<p><em>More <a href="https://theconversation.com/topics/curious-kids-36782?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">Curious Kids</a> articles, written by academic experts:</em></p>
<ul>
<li><p><em><a href="https://theconversation.com/curious-kids-why-do-we-lose-our-baby-teeth-111911?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">Why do we lose our baby teeth? - Jack, age 8.</a></em></p></li>
<li><p><em><a href="https://theconversation.com/curious-kids-why-do-pets-have-dark-eyes-while-humans-have-mostly-white-eyes-115391?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">Our guinea pigs have dark eyes. Why do we have white eyes? - Rhoswen, aged three, Bristol, UK.</a></em></p></li>
<li><p><em><a href="https://theconversation.com/curious-kids-how-was-the-earth-made-112067?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CuriousKidsUK">How was the Earth made? - Audrey, age 5.</a></em></p></li>
</ul><img src="https://counter.theconversation.com/content/117538/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Brooke Simmons has previously received funding from the National Aeronautics and Space Administration (NASA) to research galaxies, which are mentioned in this article. </span></em></p>Gravity exists because the universe is full of ‘stuff’ – here’s how it came to be.Brooke Simmons, Lecturer in Astrophysics, Lancaster UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1172552019-05-19T19:37:23Z2019-05-19T19:37:23ZThe way we define kilograms, metres and seconds changes today<figure><img src="https://images.theconversation.com/files/275076/original/file-20190517-69189-f6415j.jpg?ixlib=rb-1.1.0&rect=149%2C177%2C4932%2C3148&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A new standard defines the kilogram from today.</span> <span class="attribution"><span class="source">Shutterstock/Piotr Wytrazek </span></span></figcaption></figure><p>We measure stuff all the time – how long, how heavy, how hot, and so on – because we need to for things such as trade, health and knowledge. But making sure our measurements compare apples with apples has been a challenge: how to know if my kilogram weight or metre length is the same as yours.</p>
<p>Attempts have been made to define the units of measurement over the years. But today – <a href="http://www.worldmetrologyday.org/">International Metrology Day</a> – sees the <a href="https://www.bipm.org/en/measurement-units/rev-si/">complete revision</a> of those standards come into play.</p>
<p>You won’t notice anything – you will not be heavier or lighter than yesterday – because the transition has been made to be seamless. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explainer-what-is-mass-49299">Explainer: what is mass?</a>
</strong>
</em>
</p>
<hr>
<p>Just the definitions of the seven base units of the <a href="https://www.bipm.org/en/measurement-units/">SI</a> (Système International d'Unités, or the International System of Units) are now completely different from yesterday.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/275067/original/file-20190517-69174-kx7jf6.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/275067/original/file-20190517-69174-kx7jf6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/275067/original/file-20190517-69174-kx7jf6.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/275067/original/file-20190517-69174-kx7jf6.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/275067/original/file-20190517-69174-kx7jf6.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/275067/original/file-20190517-69174-kx7jf6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/275067/original/file-20190517-69174-kx7jf6.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/275067/original/file-20190517-69174-kx7jf6.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">New definitions of the (SI) standards for the kilogram (kg), metre (m), second (s), ampere (A), kelvin (K), mole (mol) and candela (cd).</span>
<span class="attribution"><a class="source" href="https://www.bipm.org/en/si-download-area/graphics-files.html#">BIPM</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>How we used to measure</h2>
<p>Humans have always been able to count, but as we evolved we quickly moved to measuring lengths, weights and time.</p>
<p>The Egyptian Pharaohs caused pyramids to be built based on the length of the royal forearm, known as the Royal Cubit. This was kept and promulgated by engineer priests who maintained the standard under pain of death.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/274858/original/file-20190516-69195-1v3habt.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/274858/original/file-20190516-69195-1v3habt.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/274858/original/file-20190516-69195-1v3habt.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=312&fit=crop&dpr=1 600w, https://images.theconversation.com/files/274858/original/file-20190516-69195-1v3habt.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=312&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/274858/original/file-20190516-69195-1v3habt.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=312&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/274858/original/file-20190516-69195-1v3habt.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=393&fit=crop&dpr=1 754w, https://images.theconversation.com/files/274858/original/file-20190516-69195-1v3habt.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=393&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/274858/original/file-20190516-69195-1v3habt.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=393&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Metrology in action – weighing the souls of the dead and the Egyptian Royal Cubit (the black rod).</span>
<span class="attribution"><span class="source">Brynn Hibbert</span></span>
</figcaption>
</figure>
<p>But the cubit wasn’t a fixed unit over time – it was about half a metre, plus or minus a few tens of millimetres by today’s measure. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/written-in-stone-the-worlds-first-trigonometry-revealed-in-an-ancient-babylonian-tablet-81472">Written in stone: the world's first trigonometry revealed in an ancient Babylonian tablet</a>
</strong>
</em>
</p>
<hr>
<p>The first suggestion of a universal set of decimal measures was made by John Wilkins, in 1668, then Secretary of the Royal Society in London. </p>
<p>The impetus for doing something practical came with the French Revolution. It was the French who defined the first standards of length and mass, with two platinum standards representing the metre and the kilogram on June 22, 1799, in the Archives de la République in Paris.</p>
<h2>Agreed standards</h2>
<p>Scientists backed the idea, the German mathematician Carl Friedrich Gauss being particularly keen. Representatives of 17 nations came together to create the International System of Units by signing the <a href="https://www.bipm.org/en/worldwide-metrology/metre-convention/">Metre Convention treaty</a> on May 20, 1875.</p>
<p>France, whose street cred had taken a battering in the Franco-Prussian war and was not the scientific power it once was, offered a beaten-up chateau in the Forest of Saint-Cloud as an international home for the new system.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/274859/original/file-20190516-69174-1pddybz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/274859/original/file-20190516-69174-1pddybz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/274859/original/file-20190516-69174-1pddybz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=448&fit=crop&dpr=1 600w, https://images.theconversation.com/files/274859/original/file-20190516-69174-1pddybz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=448&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/274859/original/file-20190516-69174-1pddybz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=448&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/274859/original/file-20190516-69174-1pddybz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=563&fit=crop&dpr=1 754w, https://images.theconversation.com/files/274859/original/file-20190516-69174-1pddybz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=563&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/274859/original/file-20190516-69174-1pddybz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=563&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">BIPM, home of the SI.</span>
<span class="attribution"><span class="source">Brynn Hibbert (2012)</span></span>
</figcaption>
</figure>
<p>The Pavilion de Breteuil still houses the Bureau International de Poids et Mesures (<a href="https://www.bipm.org/en/about-us/">BIPM</a>), where resides the International Prototype of the Kilogram (henceforth the Big K) in two safes and three glass bell jars.</p>
<p>The Big K is a polished block of platinum-iridium used to define the kilogram, against which all kilogram weights are ultimately measured. (The original has only been weighed three times against a number of near-identical copies.)</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/275220/original/file-20190517-69178-rnekh0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/275220/original/file-20190517-69178-rnekh0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/275220/original/file-20190517-69178-rnekh0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=745&fit=crop&dpr=1 600w, https://images.theconversation.com/files/275220/original/file-20190517-69178-rnekh0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=745&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/275220/original/file-20190517-69178-rnekh0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=745&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/275220/original/file-20190517-69178-rnekh0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=937&fit=crop&dpr=1 754w, https://images.theconversation.com/files/275220/original/file-20190517-69178-rnekh0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=937&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/275220/original/file-20190517-69178-rnekh0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=937&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">International prototype of the kilogram (the Big K).</span>
<span class="attribution"><span class="source">Photograph courtesy of the BIPM</span></span>
</figcaption>
</figure>
<p>The British, who had been prominent in the discussions and had provided the platinum-iridium kilogram, refused to sign the Treaty until 1884. </p>
<p>Even then the new system was only used by scientists, with everyday life being measured in traditional Imperial units such as pounds and ounces, feet and inches. </p>
<p>The United States signed the Treaty on the day, but then never actually implemented it, hanging on to its own version of the British Imperial system, which it still mostly uses today.</p>
<p>The US may have rued that decision in 1999, however, when the Mars Climate Orbiter (<a href="https://www.jpl.nasa.gov/missions/mars-climate-orbiter/">MCO</a>) went missing in action. The <a href="https://llis.nasa.gov/llis_lib/pdf/1009464main1_0641-mr.pdf">report into the incident</a>, quaintly called a “mishap” (which cost US$193.1 million in 1999), said:</p>
<blockquote>
<p>[…] the root cause for the loss of the MCO spacecraft was the failure to use metric units in the coding of a ground software file, “Small Forces”, used in trajectory models.</p>
</blockquote>
<p>Essentially the spacecraft was lost in the atmosphere of Mars as it entered orbit lower than planned. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/275038/original/file-20190516-69189-6ha4gc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/275038/original/file-20190516-69189-6ha4gc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/275038/original/file-20190516-69189-6ha4gc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=545&fit=crop&dpr=1 600w, https://images.theconversation.com/files/275038/original/file-20190516-69189-6ha4gc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=545&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/275038/original/file-20190516-69189-6ha4gc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=545&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/275038/original/file-20190516-69189-6ha4gc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=685&fit=crop&dpr=1 754w, https://images.theconversation.com/files/275038/original/file-20190516-69189-6ha4gc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=685&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/275038/original/file-20190516-69189-6ha4gc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=685&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Lost on Mars: An investigation found the Mars Climate Orbiter likely burned up in the atmosphere of the red planet due to a clash of metrics.</span>
<span class="attribution"><a class="source" href="https://www.jpl.nasa.gov/missions/mars-climate-orbiter/">NASA/JPL</a></span>
</figcaption>
</figure>
<h2>The new SI definitions</h2>
<p>So why the change today? The main problems with the previous definitions were, in the case of the <a href="https://www.bipm.org/en/bipm/mass/ipk/">kilogram</a>, they were not stable and, for the unit of electric current, the ampere, could not be realised.</p>
<p>And from weighings against official copies, we think the Big K was slowly losing mass.</p>
<p>All the units are now defined in a common way using what the BIPM calls the “<a href="https://www.bipm.org/en/measurement-units/rev-si/explicit-constant.html">explicit constant</a>” formulation. </p>
<p>The idea is that we take a universal constant – for example, the speed of light in a vacuum – and from now on fix its numerical value at our best-measured value, without uncertainty.</p>
<p>Reality is fixed, the number is fixed, and so the units are now defined.</p>
<p>We therefore needed to find seven constants and make sure all measurements are consistent, within measurement uncertainty, and then start the countdown to today. (All the technical details are <a href="https://www.bipm.org/en/measurement-units/rev-si/">available here</a>.)</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/275072/original/file-20190517-69195-odf7rf.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/275072/original/file-20190517-69195-odf7rf.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/275072/original/file-20190517-69195-odf7rf.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/275072/original/file-20190517-69195-odf7rf.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/275072/original/file-20190517-69195-odf7rf.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/275072/original/file-20190517-69195-odf7rf.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/275072/original/file-20190517-69195-odf7rf.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/275072/original/file-20190517-69195-odf7rf.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The seven unites are now defined by universal constants such as the speed of light <em>c</em> for the metre.</span>
<span class="attribution"><a class="source" href="https://www.bipm.org/en/si-download-area/graphics-files.html">BIPM</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Australia had a hand in fashioning the roundest macroscopic object on the Earth, a silicon sphere used to measure the <a href="https://www.nist.gov/si-redefinition/meet-constants">Avogadro constant</a>, the number of entities in a fixed amount of substance. This now defines the SI unit, mole, used largely in chemistry. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/274862/original/file-20190516-69195-1wqx8z5.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/274862/original/file-20190516-69195-1wqx8z5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/274862/original/file-20190516-69195-1wqx8z5.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=448&fit=crop&dpr=1 600w, https://images.theconversation.com/files/274862/original/file-20190516-69195-1wqx8z5.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=448&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/274862/original/file-20190516-69195-1wqx8z5.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=448&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/274862/original/file-20190516-69195-1wqx8z5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=563&fit=crop&dpr=1 754w, https://images.theconversation.com/files/274862/original/file-20190516-69195-1wqx8z5.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=563&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/274862/original/file-20190516-69195-1wqx8z5.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=563&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Walter Giardini of the National Measurement Institute Australia holding a silicon sphere as part of the Avogadro project.</span>
<span class="attribution"><span class="source">Brynn Hibbert</span></span>
</figcaption>
</figure>
<h2>From standard to artefact</h2>
<p>What of the Big K – the standard kilogram? Today it becomes an object of great historical significance that can be weighed and its mass will have measurement uncertainty. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/its-not-so-easy-to-gain-the-true-measure-of-things-92741">It's not so easy to gain the true measure of things</a>
</strong>
</em>
</p>
<hr>
<p>From today the kilogram is defined using the Planck constant, something that doesn’t change from quantum physics.</p>
<p>The challenge now though is to explain these new definitions to people – especially non-scientists – so they understand. Comparing a kilogram to a metal block is easy.</p>
<p>Technically a kilogram (kg) is <a href="https://www.bipm.org/en/CGPM/db/26/1/">now defined</a>:</p>
<blockquote>
<p>[…] by taking the fixed numerical value of the Planck constant <em>h</em> to be 6.626 070 15 × 10<sup>–34</sup> when expressed in the unit J s, which is equal to kg m<sup>2</sup> s<sup>–1</sup>, where the metre and the second are defined in terms of <em>c</em> and Δν<sub>Cs</sub>. </p>
</blockquote>
<p>Try explaining that to someone!</p>
<hr>
<p><em>Update: the phrase “tens of centimetres” was changed to “tens of millimetres” at the request of the author.</em></p><img src="https://counter.theconversation.com/content/117255/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Brynn Hibbert receives funding from ARC, International Union of Pure and Applied Chemistry (IUPAC). He is Past President of the Royal Society of New South Wales, Past Chair of the Analytical Division of IUPAC and present Secretary of the IUPAC Interdivisional Committee on Terminology Nomenclature and Symbols (ICTNS).</span></em></p>Today marks one of the biggest shake-ups in the history of measurement. But the new standards on how we define units of mass, length, time and so on are not easy to explain.David Brynn Hibbert, Emeritus Professor of Analytical Chemistry, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1119062019-04-08T10:43:48Z2019-04-08T10:43:48ZCatholic missionaries are evangelizing on college campuses and trying to bring back the ‘nones’<figure><img src="https://images.theconversation.com/files/267652/original/file-20190404-123413-134u2ho.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A group of millennials are working to bring Catholic religious practice to American college campuses.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/bostoncatholic/13987189808">Roman Catholic Archdiocese of Boston </a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>More than 20% of all adults and over a third of millennials in the United States are not affiliated with a religion. <a href="http://www.pewforum.org/2012/10/09/nones-on-the-rise/">For at least a decade</a>, this number <a href="https://www.prri.org/wp-content/uploads/2016/09/PRRI-RNS-Unaffiliated-Report.pdf">has been on the rise</a>. </p>
<p>Sexual abuse by clergy and a poor response by the church hierarchy has led many young Catholics to <a href="https://www.washingtonpost.com/news/acts-of-faith/wp/2018/08/19/wasted-our-lives-catholic-sex-abuse-scandals-again-prompt-a-crisis-of-faith/?utm_term=.2299cfcaa4d7">lose trust</a> in their religious institution. Some 36% of those without religious affiliation report having grown up <a href="http://religiondispatches.org/is-the-rise-of-nones-actually-the-decline-of-catholics">Catholic</a>. </p>
<p>But countering this trend is a movement led by millennials who are devoted to <a href="https://global.oup.com/academic/product/millennial-missionaries-9780190875961?cc=us&lang=en&">bringing Catholicism back</a> on college campuses – with a modern flair. </p>
<h2>Missionaries on campus</h2>
<p>I have spent the the last seven years <a href="https://global.oup.com/academic/product/millennial-missionaries-9780190875961?cc=us&lang=en&">researching</a> these young adults. These millennials are Catholic, and being Catholic is more central to their identity than <a href="https://global.oup.com/academic/product/young-catholic-america-9780199341078?cc=us&lang=en&">many of their peers</a>. </p>
<p>These missionaries follow church teachings with an adherence more common with the baby boomers and the <a href="https://www.thebalancecareers.com/workplace-characteristics-silent-generation-2164692">Silent Generation</a>. They attend Mass every week, go to Confession frequently, memorize Latin prayers and are devoted to saints. As college campus missionaries, they spend their days inviting college students to be similarly committed to Catholicism. </p>
<p>Though a minority among the millennial-generation Catholics, they are <a href="https://global.oup.com/academic/product/millennial-missionaries-9780190875961?cc=us&lang=en&#">part of a movement</a> that has been running parallel to mainstream U.S. Catholicism for just over 20 years. </p>
<p>Known as the <a href="https://www.focus.org/">Fellowship of Catholic University Students, or FOCUS</a>, the movement started in 1998 when two male and two female college graduates began working as Catholic missionaries at Benedictine College and the University of Northern Colorado. As students, they had seen the <a href="https://news.gallup.com/poll/232226/church-attendance-among-catholics-resumes-downward-slide.aspx">decline in Catholic practice among their peers</a> and wanted to promote an attractive version of Catholicism. </p>
<p>Following the example of <a href="https://www.uncpress.org/book/9780807858738/bill-bright-and-campus-crusade-for-christ/">Protestant groups like Cru</a> and <a href="https://nyupress.org/9781479818136/playing-for-god/">Athletes in Action</a>, FOCUS began holding Bible studies on campuses. They trained increasing numbers of missionaries to build friendships with college students. As missionaries worked to make Catholicism look relevant to college students, FOCUS established itself as a religiously affiliated outreach program.</p>
<p>Over the course of the next two decades, <a href="https://www.baylorpress.com/9781481308717/the-resilience-of-religion-in-american-higher-education/">FOCUS grew rapidly</a>. At first, it was through word of mouth between bishops and priests. Gradually, as more college students attended FOCUS events and began participating in Catholic ritual life, campus ministries on private, Catholic and public universities and campuses began to request a FOCUS team. </p>
<h2>Who are these missionaries?</h2>
<p>FOCUS partners with Catholic centers on campuses and recruits college students to become missionaries after graduation. Each missionary spends two years on a campus, working with students, promoting Catholicism. Many of the college students that missionaries reach out to describe themselves as <a href="https://books.google.com/books?id=D895CwAAQBAJ&printsec=frontcover#v=onepage&q&f=false">“spiritual but not religious,”</a> or a “none.” </p>
<p>The missionaries are much like any other middle-class young adult in the U.S.: They live on their iPhones, drink craft beer, buy pumpkin spice lattes and love March Madness. Some even have tattoos, often with quotes from saints. </p>
<p>They go through much the same relationship issues as other young adults. I interviewed over 50 missionaries about their experiences. Over cups of coffee or while jogging, they shared with me their struggles with depression and alcohol abuse. They also shared the pain of losing intimate friendships.</p>
<p>What sets them apart, however, is that <a href="https://news.gallup.com/poll/232226/church-attendance-among-catholics-resumes-downward-slide.aspx">unlike most other millennials</a>, they find answers to life’s struggles in being Catholic. And they want others to know that as well. </p>
<p>One missionary, for example, told me, “I have seen change in my life” since becoming more Catholic in college. Another said it was hard for him to watch college students suffer with anxiety. “I just know,” he told me, “their lives could be better with Catholicism.”</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/267653/original/file-20190404-123395-11rtmqz.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/267653/original/file-20190404-123395-11rtmqz.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=901&fit=crop&dpr=1 600w, https://images.theconversation.com/files/267653/original/file-20190404-123395-11rtmqz.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=901&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/267653/original/file-20190404-123395-11rtmqz.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=901&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/267653/original/file-20190404-123395-11rtmqz.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1133&fit=crop&dpr=1 754w, https://images.theconversation.com/files/267653/original/file-20190404-123395-11rtmqz.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1133&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/267653/original/file-20190404-123395-11rtmqz.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1133&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Altar servers at SEEK 2013.</span>
<span class="attribution"><span class="source">Katherine Dugan</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>They present Catholicism as relevant and “cool.” I heard stories about missionaries hosting foam parties and black-light parties – flashy dance parties that are popular on college campuses. </p>
<p>One missionary told me how she trained for a popular test of physical strength called a Tough Mudder with some college students. Another explained how he used games of pickup basketball to make friends with college students. They also planned gender-segregated camping trips and tailgate parties before sporting events. </p>
<p>In addition to these typical college campus events, these Catholics invited students to prayer, Bible study and to attend Mass. </p>
<h2>Growth amid concerns</h2>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/267655/original/file-20190404-123405-j73lsd.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/267655/original/file-20190404-123405-j73lsd.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/267655/original/file-20190404-123405-j73lsd.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/267655/original/file-20190404-123405-j73lsd.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/267655/original/file-20190404-123405-j73lsd.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/267655/original/file-20190404-123405-j73lsd.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/267655/original/file-20190404-123405-j73lsd.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Students at a leadership summit in 2014.</span>
<span class="attribution"><span class="source">Katherine Dugan</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>A media report from March 2018 <a href="https://www.ncronline.org/news/people/focus-promises-fight-generation-college-campuses">described the fast growth of FOCUS in just two decades</a> into an organization with 660 missionaries on 137 campuses. That year the organization was spread across 38 U.S. states and at four international locations. In my own work, I watched a campus program in the Midwest grow from nothing to a group of 20 students within the first year. </p>
<p>This year, in perhaps the largest five-day gathering, called <a href="http://www.seek2019.com/">SEEK2019</a>, some <a href="http://cnstopstories.com/2019/01/08/young-adults-embrace-opportunity-to-deepen-their-faith-at-seek2019">17,000 Catholics</a>, which included college students and other young adults, met in Indianapolis. </p>
<p>But critics have also pointed out serious concerns with how FOCUS works. There is a <a href="https://www.ncronline.org/news/people/focus-promises-fight-generation-college-campuses">lack of racial diversity</a> among missionaries, who mostly belong to the white middle- and upper-class.</p>
<p>In informal conversations with campus ministers, I have heard concerns about a lack of formal pastoral training given to missionaries. FOCUS missionaries receive just four to six weeks of training over the summer. Their attention to making Catholicism attractive through friendship with “nones” and other college students has also made them inattentive to Catholicism’s emphasis on social justice. On a large, public campus, I observed a program close down because of disagreements between the campus ministry and the FOCUS over how to best reach college students. </p>
<p>Nonetheless, at a time when young Catholics are moving away from their faith, the role of missionary organizations such as FOCUS is worth noticing.</p><img src="https://counter.theconversation.com/content/111906/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Katherine Dugan does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Many young Catholics are moving away from their faith and joining the growing number of the religiously unaffiliated. The missionary group FOCUS is evangelizing on campuses, though there are concerns.Katherine Dugan, Assistant Professor of Religion, Springfield CollegeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1068382018-11-14T18:06:46Z2018-11-14T18:06:46ZThe kilogram is being redefined – a physicist explains<figure><img src="https://images.theconversation.com/files/245563/original/file-20181114-194500-gn0w70.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/old-white-vintage-kitchen-scale-brass-1040010754">Stefan Rotter/Shutterstock</a></span></figcaption></figure><p>How much is a kilogram? 1,000 grams. 2.20462 pounds. Or 0.0685 slugs based on the old Imperial gravitational system. But where does this amount actually come from and how can everyone be sure they are using the same measurement?</p>
<p>Since 1889, countries who are members of the <a href="https://www.bipm.org/en/worldwide-metrology/cgpm/">General Conference on Weights and Measures</a> have agreed to use a standard block of metal – kept near Paris – to define the kilogram. But although the modern block is stored in a highly controlled environment, its weight can change by tiny amounts as wear and tear causes it to lose mass and dirt causes it to increase. To address this problem, scientists around the world have spent nearly two decades discussing how the kilogram could instead be defined in relation to constant measurements of nature. And now they have finally reached a decision.</p>
<p>The <a href="https://books.google.nl/books?id=FufDNJHvgFEC&pg=RA1-PA278&lpg=RA1-PA278&dq=18841+grains+grave&source=bl&ots=B8Aenskenh&sig=zanQ-d8GXWWN3q6bG2YBbh9bZOM&hl=en&sa=X&ved=0ahUKEwjy0-C5rr7MAhWBLMAKHcG2AhwQ6AEIKTAD#v=onepage&q=%22nom%20generique%20de%20grave%22&f=false">first kilogram</a> (originally called a grave) was defined in 1793 by a commission of the French Academy of Sciences, who wanted a better standard than the fixed amounts of grain that had traditionally been used. The commission decided that the new measure would be the mass of one cubic decimetre of distilled water at 4°C (the temperature at which water has its highest density under standard conditions). This had the advantage in that most properly equipped labs would be able to reproduce this standard. Subsequently, a prototype of this mass was cast in brass. </p>
<p>Unfortunately, this definition of mass depended upon another variable measurement, the metre. At this point, the metre was only provisionally defined as part of the distance from the North Pole to the equator. Once the value of the metre and the temperature of water at its densest were more accurately defined, the kilogram also had to be replaced. And a new prototype was cast in platinum to represent this mass. </p>
<p>Eventually, this was replaced with the international prototype kilogram (IKP) used today, cast from a mixture of platinum and iridium to make it very hard and prevent it reacting with oxygen. The IPK and six copies are kept by the International Bureau of Weights and Measures in the Pavillon de Breteuil, Saint-Cloud, near Paris in France to act as a reference to measure against. Copies of the IPK are transported across the world to ensure all participating countries use the same standard.</p>
<p>But even the modern IPK can gradually change in mass. Radically, the answer from the International Bureau of Weights and Measures is to overhaul the definitions of a kilogram, as well as all the other basic units of measurement used in science (known as SI units, from the French for international system).</p>
<p>Instead of measuring the kilogram against a block stored in a vault, we can define it based on precise values of constants of nature. Agreeing a definition has taken a long time because we needed to be able to measure these constants to <a href="https://www.bipm.org/utils/en/pdf/BIPM-strategic-plan-2018.pdf">exacting standards</a> with an uncertainty of 30 parts per billion (meaning the measurements are accurate to 0.00000003 of a unit).</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/245568/original/file-20181114-194506-hgutu7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/245568/original/file-20181114-194506-hgutu7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/245568/original/file-20181114-194506-hgutu7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/245568/original/file-20181114-194506-hgutu7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/245568/original/file-20181114-194506-hgutu7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/245568/original/file-20181114-194506-hgutu7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/245568/original/file-20181114-194506-hgutu7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A copy of the international prototype kilogram.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Prototype_kilogram_replica.JPG">Japs88/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Scientists have actually already done this for time and length. A second is no longer a fraction of the time it takes the Earth to revolve, which can change as the globe speeds up or slows down. Instead, a second is <a href="https://www.scientificamerican.com/article/how-does-one-arrive-at-th/">now defined</a> by the time it takes for a certain amount of energy to be released as radiation from atoms of Caesium-133. Specifically, <a href="https://www.bipm.org/en/publications/si-brochure/second.html">one second equals</a> 9,192,631,770 transitions in the hyperfine ground state levels of Caesium-133. This is the same no matter when or where it is measured.</p>
<p>Scientists were then able to <a href="https://www.bipm.org/metrology/length/units.html">redefine the metre</a> in relation to the second and another natural constant, the speed of light in a vacuum (c), which scientists have calculated as 299,792,458 metres per second. So one metre is now the length travelled by light in 1/c seconds.</p>
<p>The new definition of the kilogram uses a measurement from another fixed value from nature, <a href="http://astronomy.swin.edu.au/cosmos/P/Planck%27s+Constant">Planck’s constant</a> (h), which will be defined as 6.62607015×10<sup>−34</sup> joule seconds. Planck’s constant can be found by dividing the amount of energy a particle of light or “photon” carries by its electromagnetic frequency.</p>
<p>The constant is usually measured in joule seconds but this can also be expressed as kilogram square metres per second. We know what a second and a metre is from the other definitions. So by adding these measurements, along with an exact knowledge of Planck’s constant, we can get a new, very precise definition of the kilogram. </p>
<h2>Other units</h2>
<p>Part of the reason creating the new definition has taken so long is because scientists have had to create <a href="https://www.scientificamerican.com/article/the-kilogram-may-be-redefined/">very precise devices</a> to measure Planck’s constant with a high enough degree of accuracy. The method has also been controversial because it will break the link that the kilogram has to other base SI units, particularly <a href="https://physics.nist.gov/cuu/Units/mole.html">the mole</a>, which measures the amount of a substance in terms of the number of particles it’s made from. Some scientists have proposed <a href="http://iopscience.iop.org/article/10.1088/0026-1394/49/4/487/">alternative methods</a> as a result.</p>
<p>But following a symbolic vote, the new definition of the kilogram will be used by the International Bureau of Weights and Measures and national measurement institutes around the world, along with <a href="https://www.bipm.org/utils/en/pdf/CGPM/Convocation-2018.pdf#page=30">new definitions</a> of several other base SI units, the mole, the kelvin (temperature) and the ampere (current).</p>
<p>For most people, everyday life will carry on as normal despite the redefinitions. One standard bag of sugar will contain as much sugar as it ever did. But some of these changes, for example to the kelvin, will mean <a href="https://www.bipm.org/wg/CCT/TG-SI/Allowed/Documents/Report_to_CIPM_2.pdf">practical advantages</a> for scientists making very precise measurements. And to answer the question “how much is a kilogram”, we will no longer have to compare blocks of platinum or worry about scratching them.</p><img src="https://counter.theconversation.com/content/106838/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kevin Pimbblet receives funding from STFC and the Royal Astronomical Society. </span></em></p>The international prototype kilogram keeps changing weight so scientists have come up with a new way to calculate.Kevin Pimbblet, Senior Lecturer in Physics, University of HullLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/910062018-03-11T19:52:57Z2018-03-11T19:52:57ZCurious Kids: Why aren’t birds pulled down by gravity while they’re flying?<figure><img src="https://images.theconversation.com/files/204995/original/file-20180206-14067-a0uzox.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Marcella Cheng/The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span></figcaption></figure><p><em>This is an article from <a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a>, a series for children. The Conversation is asking kids to send in questions they’d like an expert to answer. All questions are welcome – serious, weird or wacky!</em> </p>
<hr>
<blockquote>
<p><strong>Why aren’t birds pulled down by the force of gravity while they’re flying? – Claudia, age 7, Canberra.</strong></p>
</blockquote>
<p>This is a great question, and funnily enough there is a recent <a href="http://www.smh.com.au/environment/animals/dead-goose-falls-from-sky-and-knocks-out-us-hunter-20180204-h0toy1.html">news story out</a> which helps answer it.</p>
<p>In the United States, a dead goose weighing over 5kg fell from the sky. This poor goose shows us that flying birds can fall from the sky under the force of gravity, just like everything with mass.</p>
<p>The larger the mass (or how much something weighs), the larger the force of gravity. This goose fell from the sky because it was killed while flying. The other geese flying with it did not fall because they were doing a few important things to fight the effects of gravity.</p>
<p>To stay up, the bird must overcome gravity with a force called “lift”. Lift is a very active force, made by moving the wing at speed through air. It causes the bird to rise upwards, as shown in the picture below.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/205026/original/file-20180206-14093-foowre.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/205026/original/file-20180206-14093-foowre.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/205026/original/file-20180206-14093-foowre.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/205026/original/file-20180206-14093-foowre.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/205026/original/file-20180206-14093-foowre.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/205026/original/file-20180206-14093-foowre.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/205026/original/file-20180206-14093-foowre.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/205026/original/file-20180206-14093-foowre.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">As the air is pushed down, this pushes the wing (and the bird attached to it) upwards.</span>
<span class="attribution"><span class="source">Marcella Cheng/The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>To create lift, the bird holds the front part of its wing slightly higher than the back part. As the air passes over the wing, (from front to back), the air underneath is pushed downwards. This pushes the wing (and bird) upwards. A bird’s wings are just the right shape to build this upward force.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-do-so-many-animals-seem-to-have-pink-ears-when-their-bodies-are-all-different-colours-83878">Curious Kids: Why do so many animals seem to have pink ears, when their bodies are all different colours?</a>
</strong>
</em>
</p>
<hr>
<p>Birds of different shapes and sizes have wings that provide the perfect amount of lift for their needs. The Australian pelican is one of the largest flying birds, weighing almost 7kg - that’s about as much as two bricks! A pelican’s wings need to be very big to create enough lift to overcome gravity. They also need to move very fast for take off. That’s why large birds like pelicans typically have to run a long way before flying. </p>
<p>Here’s a video showing how difficult take off can be for a pelican.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/P5f6qOMhIH0?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">A pelican slowly takes off while an amused friend watches.</span></figcaption>
</figure>
<p>Large flying birds can also create lift using patches of warm air that form, for example, over hot rocky ground. Hot air rises and that means birds can spread their wings over these patches and get a free lift.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-dont-cats-wear-shoes-75308">Curious Kids: Why don’t cats wear shoes?</a>
</strong>
</em>
</p>
<hr>
<p>Smaller birds also need to create enough lift to be able to fly. That’s why so many birds are light compared to animals of similar sizes. For example, a fully grown zebra finch bird is about the same size as a house mouse but weighs just 12g, while the mouse weighs around 19g. </p>
<p>Birds also have hollow bones with lots of air spaces inside them. If you break open a chicken bone the next time you have chicken for dinner, you will see this for yourself. </p>
<hr>
<p><em>Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to us. You can:</em></p>
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<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p><em>Please tell us your name, age and which city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! We won’t be able to answer every question but we will do our best.</em></p><img src="https://counter.theconversation.com/content/91006/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Simon Griffith receives funding from the Australian Research Council. </span></em></p>To stay up, the bird must overcome gravity with a force called ‘lift’.Simon Griffith, Professor of Avian Behavioural Ecology, Macquarie UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/803112017-09-19T19:41:02Z2017-09-19T19:41:02ZCurious Kids: Why is the Earth round?<figure><img src="https://images.theconversation.com/files/180163/original/file-20170728-23788-1z0m3og.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The mass of the Earth is big enough that the gravitational force it creates can pull the hard shape of ice, rock and metal into a sphere.</span> <span class="attribution"><a class="source" href="https://www.nasa.gov/feature/goddard/2017/new-night-lights-maps-open-up-possible-real-time-applications">NASA Earth Observatory images by Joshua Stevens, using Suomi NPP VIIRS data from Miguel Román, NASA's Goddard Space Flight Center</a></span></figcaption></figure><p><em>This is an article from <a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a>, a series for children. The Conversation is asking kids to send in questions they’d like an expert to answer. All questions are welcome – serious, weird or wacky!</em> </p>
<hr>
<blockquote>
<p><strong>Why is the Earth round? – Zoe, age 3, Sydney.</strong></p>
</blockquote>
<p>Thank you, Zoe, for your great question. Asking questions like this is a really important part of being a scientist.</p>
<p>Imagine the Earth pulling everything it is made up of, all of its mass, towards its centre. This happens evenly all over the Earth, causing it to take on a round shape. Let me explain what I mean by that.</p>
<p>To understand why the Earth is round we need to look at two things - mass and gravity. </p>
<p>Every single thing in the universe has mass - from the biggest star to a tiny grain of sand. People, too, have mass. The more big and dense something is, the more mass it has. So an elephant would have more mass than a mouse, for example.</p>
<h2>More mass means more gravity</h2>
<p>While you might not be able to see it, all objects with mass are actually being pulled towards each other by a force called gravity. The bigger the mass of something, the stronger its pull.</p>
<p>Have you ever wondered why if you drop something, it falls towards the Earth and not up into the sky? Or the reason why we’re all stuck to the ground? </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/180458/original/file-20170801-2341-1tvg9xi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/180458/original/file-20170801-2341-1tvg9xi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/180458/original/file-20170801-2341-1tvg9xi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/180458/original/file-20170801-2341-1tvg9xi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/180458/original/file-20170801-2341-1tvg9xi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/180458/original/file-20170801-2341-1tvg9xi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/180458/original/file-20170801-2341-1tvg9xi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/180458/original/file-20170801-2341-1tvg9xi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">From the moment water is flung upwards, gravity is working to pull it back down.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/davidwithacamera/32520273400/in/photolist-RxGUhY-9itKGb-axJt8E-AtYxsD-5gh6L2-4rpofz-h6FC2E-81VdTs-jSQ2xp-ogD97x-sugELC-e3Az52-3HDYJE-qicgYj-o1Ac7w-4YUs1Y-UoCRJQ-dAhboR-TKivXi-TKeb8X-BGhh5f-SgeSqp-Wag2jn-TGiTJy-ef63pa-akvk22-GLiQb-6LzFvm-VUsdJb-qnzpeB-W6NZLy-fJ1kig-qE9EDw-VBJiNu-VUsF8d-oW6oWb-W6PfRJ-frCJ1-jzDbYy-gHFxcE-5u7hZZ-hUq4nj-dMmz2n-6fHHFc-9bWN4e-Ba9949-ehrQ4j-UYHBH4-ebPnWn-dfKHb1">David Simmonds/flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>That’s because of gravity. Because the mass of the Earth is so much bigger than the mass of people (or spoons, or vases, or water), we’re all strongly pulled towards it, which is why it feels like we’re stuck to the earth’s surface.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-what-plants-could-grow-in-the-goldilocks-zone-of-space-76918">Curious Kids: What plants could grow in the Goldilocks zone of space?</a>
</strong>
</em>
</p>
<hr>
<h2>Not everything in space is round</h2>
<p>Part of what makes a planet a planet is its round shape. But most things in space are not perfectly round at all! In fact, some things are very lumpy. The reason for this is the way planets are made.</p>
<p>Planets are made of rock, ice, and gas. Before becoming a planet, the rocky and icy parts are small lumps, no bigger than sand grains, moving around the young Sun.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/180451/original/file-20170801-22140-1sorxcu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/180451/original/file-20170801-22140-1sorxcu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/180451/original/file-20170801-22140-1sorxcu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=281&fit=crop&dpr=1 600w, https://images.theconversation.com/files/180451/original/file-20170801-22140-1sorxcu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=281&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/180451/original/file-20170801-22140-1sorxcu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=281&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/180451/original/file-20170801-22140-1sorxcu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=353&fit=crop&dpr=1 754w, https://images.theconversation.com/files/180451/original/file-20170801-22140-1sorxcu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=353&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/180451/original/file-20170801-22140-1sorxcu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=353&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An accretion disk, made from gas rock and ice, similar to the one that formed our Solar system billions of years ago.</span>
<span class="attribution"><a class="source" href="https://exoplanets.nasa.gov/news/239/8-planets-that-make-you-think-star-wars-is-real/">NASA/JPL-Caltech</a></span>
</figcaption>
</figure>
<p>Over millions of years, gravity pulled the small rocky and icy parts towards each other until they started to stick together. Eventually these small parts grew from the size of sand into the size of mountains.</p>
<p>These mountains of rock and ice are fluffy, like giant dirty snowballs. So the small mass - and weak gravity - of the whole mountain is unable to overcome the hard shape of the rock and ice lumps to become round. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-do-stars-twinkle-81188">Curious Kids: Why do stars twinkle?</a>
</strong>
</em>
</p>
<hr>
<p>Fluffy mountains like these got swept together billions of years ago to make the planets we recognise today. But some of them are still minor objects in the Solar system. These bits of leftover planet-building material, called asteroids and comets, have very lumpy shapes. Some are shaped like potatoes and others like eggs.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/180447/original/file-20170801-22136-15k0b50.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/180447/original/file-20170801-22136-15k0b50.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/180447/original/file-20170801-22136-15k0b50.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=470&fit=crop&dpr=1 600w, https://images.theconversation.com/files/180447/original/file-20170801-22136-15k0b50.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=470&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/180447/original/file-20170801-22136-15k0b50.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=470&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/180447/original/file-20170801-22136-15k0b50.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=590&fit=crop&dpr=1 754w, https://images.theconversation.com/files/180447/original/file-20170801-22136-15k0b50.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=590&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/180447/original/file-20170801-22136-15k0b50.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=590&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A comparison of asteroid sizes, including Ceres and Vesta, the two largest objects in the asteroid belt.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Asteroid_size_comparison.jpg">NASA/ESA/STScI</a></span>
</figcaption>
</figure>
<p>The largest of these minor bodies, such as Ceres and Pluto, have enough gravity to look round like a planet. They are called dwarf planets. Some, like Haumea, spin very fast, giving them an stretched shape, like this:</p>
<iframe src="https://giphy.com/embed/3oEhmHt60uQY4Y4mLC" width="100%" height="480" frameborder="0" class="giphy-embed" allowfullscreen=""></iframe>
<p><a href="https://giphy.com/gifs/3oEhmHt60uQY4Y4mLC"></a></p>
<hr>
<p><em>Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to us. You can:</em></p>
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<p class="fine-print"><em><span>Jonathan P. Marshall does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Imagine the Earth pulling everything it is made up of, all of its mass, towards its centre. This happens evenly all over the Earth, causing it to take on a round shape.Jonathan P. Marshall, Vice Chancellor's Post-doctoral Research Fellow, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/492992015-11-11T19:21:13Z2015-11-11T19:21:13ZExplainer: what is mass?<figure><img src="https://images.theconversation.com/files/101632/original/image-20151111-9396-18hihtf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">You can feel the weight of an object on Earth because of its mass. But what is mass?</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/jeremybrooks/3785305675/">Flickr/Jeremy Brooks </a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>When it comes to electrons, Higgs bosons or photons, they don’t have much going for them. They possess spin, charge, mass and … that’s about it.</p>
<p>Sometimes they only carry a vanishing amount of some of these features at that. So the mass of a particle is an important property to understand, because it goes to the root of fundamental particle physics.</p>
<p>What is mass then, in the sense of its physical meaning? Why do some particles have mass and others don’t? And you may not think this would be important, but the biggest question is: why do particles have mass at all?</p>
<p>To answer those questions, and go well beyond what Albert Einstein knew about mass, let’s dive into particle physics and general relativity. </p>
<h2>The measure of it</h2>
<p>A professor once told me that the best definition of a physical property is its way of measurement. Following this definition, let’s see how we measure mass.</p>
<p>When you step on a scale, like it or not, it registers your weight. This is because the Earth attracts you with the gravitational force. The force between you and the Earth exists because both you and the Earth have mass.</p>
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<span class="caption">Your weight is a based on your mass on Earth.</span>
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<p>If you stepped on the same scale on the moon it would register a fraction of your weight on Earth. About one sixth, to be precise. (There has never been a more effective diet plan: lose 83% of your body weight just by flying to the moon.)</p>
<p>Your moon weight is less because the mass of the moon is less than Earth’s mass, and the gravitational force between the moon and you is proportional to the mass of the moon (<em>M</em>) and your mass (<em>m</em>). This is given by the formula <em>F = GMm/(R<sup>2</sup>)</em> where <em>R</em> is the radius of the moon and <em>G</em> is called Newton’s gravitational constant. </p>
<p>Mass is the charge of the gravitational interaction and without it no gravitational force exists. Physicists refer to this manifestation of mass as gravitational mass. </p>
<p>When you open a door, you have to push it with a force, otherwise the door won’t move. This is because the door has mass manifested as inertia, that is, it counteracts you to change the state of its motion.</p>
<p><a href="http://www.livescience.com/46560-newton-second-law.html">Newton’s second law</a> says that the force you need to change the state of motion of an object is proportional to its inertial mass (<em>F = ma</em>). It’s easier to push a light door than a heavy one with the same acceleration. </p>
<h2>Mass unified</h2>
<p>Einstein connected gravitational and inertial mass via his gravitational equivalence principle. The equivalence principle simply says that gravitational and inertial mass are one and the same thing.</p>
<p>This simple statement, however, coupled with the mathematical idea that the equations of physics <a href="https://theconversation.com/from-newton-to-einstein-the-origins-of-general-relativity-50013">should not depend</a> on the reference frame, leads very far. A main consequence of the equivalence principle are Einstein’s gravitational equations. These equations specify how mass curves space and warps time. </p>
<p>The meaning of Einstein’s gravitational equations is simple: mass warps space-time and curved space-time moves mass around. If you have ever seen a coin spiralling down a funnel shaped wishing well, you know what I’m talking about.</p>
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<p>According to Einstein’s geometric picture of gravity, the Earth orbits around the sun because the latter creates a funnel shaped gravitational well in the fabric of space-time and Earth rotates in it just as the coin rotates in the wishing well.</p>
<p>If the sun had no mass, the gravitational well around it wouldn’t exist and Earth would fly straight away. If Earth had no mass, it wouldn’t feel the curvature of the well and would fly away in a straight line. That’s general relativity in a funnel shaped nut-shell.</p>
<p>Einstein knew all this and much more. After all, he wrote the books on relativity – both on special and general. He figured out how mass is connected to gravity and energy.</p>
<p>The first relation is encapsulated by his gravitational field equations, and the second is the widely known <a href="http://science.howstuffworks.com/science-vs-myth/everyday-myths/einstein-formula.htm"><em>E = mc<sup>2</sup></em></a>. Unfortunately, he never had a chance to learn WHY anything has the property of mass. </p>
<h2>There’s more to mass</h2>
<p>Modern fundamental particle physics gave us the answer in 2012 when the <a href="https://theconversation.com/au/topics/higgs-boson">Higgs boson</a> was finally <a href="https://theconversation.com/cern-discovers-a-higgs-like-particle-let-the-party-and-head-scratching-begin-8036">discovered</a>.</p>
<p>The question is fairly important because, as we saw earlier, without mass there’s no gravity. Or is there? Well, actually, there is.</p>
<p>Take a photon, for example. A photon is the quintessence of masslessness. According to our present understanding, one of the deepest fundamental laws of particle physics, called gauge symmetry, prevents any force carrier particles, including photons, from acquiring even the tiniest of mass.</p>
<p>Yet, a photon is attracted by the sun. Observations clearly show that light from a galaxy far far away, positioned exactly behind the sun, can be observed on either side of the sun. The fact that the sun’s gravitational field bends light was used to prove that general relativity was correct in 1919.</p>
<p>Light interacts with gravitational fields because of <em>E = mc<sup>2</sup></em>. This equation tells us that, from the gravitational perspective, energy and mass are equivalent. A photon carries a tiny bit of energy, so it is slightly attracted by the sun. </p>
<p>The fact that energy gravitates is important, because the bulk of mass around us is, in fact, energy. All the visible parts of galaxies and stars are known to be made mostly of hydrogen, which is just protons and electrons.</p>
<p>Earth is made of many different atoms, but those are just made of nucleons (protons and neutrons) and electrons. Electrons are 2,000 times lighter than nucleons, so they bring much less to the table in terms of mass. And remarkably, most of the mass of protons and neutrons is energy stored in glue.</p>
<p>Glue (or gluon, in scientific terms) is the stuff that keeps protons and neutrons together. It is the carrier of the strong force. Binding energy stored in gluons makes up most of the mass of protons, neutrons, hydrogen and any atom for that matter.</p>
<h2>The role of the Higgs boson</h2>
<p>We could stop here, because we’ve understood the origin of most of the visible mass in the universe. Einstein didn’t know where the mass of macroscopic objects came from, but particle physics revealed this late in the 20th century.</p>
<p>There is, however, one more twist in the story. Perhaps the most amazing one. If Einstein had known about it, he would certainly have loved it.</p>
<p>It is the role of the Higgs boson in generating mass. The <a href="https://theconversation.com/explainer-the-higgs-boson-particle-280">Higgs boson</a>, which is the excitation of the Higgs field, is what provides mass at the fundamental level: it lends mass to the elementary particles.</p>
<p>The Higgs story began with a serious problem in particle physics. By the late 20th century it was evident that gauge symmetries, mentioned earlier, are fundamental laws and they forbid any mass of force carriers.</p>
<p>Yet in 1983 massive force carries, the <a href="http://cern-discoveries.web.cern.ch/cern-discoveries/courier/heavylight/heavylight.html">W and Z bosons</a>, were discovered by the Large Electron-Positron (<a href="http://home.cern/about/accelerators/large-electron-positron-collider">LEP</a>) (the predecessor of the Large Hadron Collider (<a href="http://home.cern/topics/large-hadron-collider">LHC</a>)).</p>
<p>This was a serious conundrum: one of the most fundamental laws of nature, gauge invariance was at stake. Giving up gauge invariance would have meant starting particle physics over from scratch.</p>
<p>Amazingly, smart theorists figured out a way to have their cake and eat it too! They introduced the Higgs mechanism, which allows us to preserve gauge symmetries at the fundamental level but break them such that in our particular universe massive W and Z particles are still possible.</p>
<p>This incredible trick won Sheldon Glashow, Abdus Salam, and Steven Weinberg the <a href="http://www.nobelprize.org/nobel_prizes/physics/laureates/1979/">1979 Nobel Prize in Physics</a>. Besides force carriers, the Higgs mechanism also lends mass to fundamental matter particles, explaining why electrons, neutrinos or quarks have mass.</p>
<p>The contribution of fundamental electron, quark or neutrino mass, however, is negligible compared to the mass generated by glue around us. So does this mean that the Higgs is negligible at the atomic level?</p>
<p>The answer is no! Without the Higgs boson, electrons would have no mass and all atoms would fall apart. Neutrons would not decay, so even atomic nuclei would look very different. Altogether, the universe would be a very-very different place, lacking galaxies, stars and planets. </p>
<h2>And then came the dark stuff</h2>
<p>So, now we know everything about mass, right? Unfortunately not. Only 5% of the mass in the whole universe comes from ordinary matter (the mass of which is understood).</p>
<p>Nearly 70% of the mass of the universe comes from <a href="http://www.space.com/20929-dark-energy.html">dark energy</a> and about 25% from <a href="http://www.space.com/20930-dark-matter.html">dark matter</a>. </p>
<p>Not only do we not have a clue about what kind of mass that is, we don’t even know what the dark sector is composed of. So stay tuned because the story of mass continues, well into the millennium.</p><img src="https://counter.theconversation.com/content/49299/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Csaba Balazs receives funding from the Australian Research Council. </span></em></p>We talk about mass all the time but what is it that actually gives an object mass? And why do some things have mass and others have no mass at all?Csaba Balazs, Associate Professor in Physics, Monash UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/490252015-10-15T04:13:25Z2015-10-15T04:13:25ZBenefits of knowing more about neutrinos which pass through our bodies unnoticed<figure><img src="https://images.theconversation.com/files/98365/original/image-20151014-12654-1q4usks.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Neutrinos, we're looking for you! Japan's Super-Kamiokande detector.</span> <span class="attribution"><span class="source">Kamioka Observatory, ICRR (Institute for Cosmic Ray Research), The University of Tokyo</span></span></figcaption></figure><p>The observation that <a href="http://www.nobelprize.org/nobel_prizes/physics/laureates/2015/">neutrinos</a> have mass, which led to the 2015 Nobel Prize for Physics being awarded jointly to Japan’s Takaaki Kajita Japan and Canada’s Arthur McDonald, is important for two key reasons. First, it provides a deeper knowledge of the fundamental tenets of nature. Second, as with any discovery, it comes with innovation in science and technology. </p>
<p>While we know of the existence of neutrinos, not much is known about them. Neutrinos exist in huge numbers in the universe. That is why understanding neutrinos is directly relevant to our knowledge of the universe. </p>
<p>Now that it has been established that neutrinos have <a href="http://www.sciencedaily.com/releases/2015/10/151006083633.htm">mass</a>, we have a key to better understanding how mass is distributed in the universe. Neutrinos may also contribute to understanding why the universe is continuously expanding. </p>
<p>It sits on the similar scale as the discovery of the <a href="http://www.nobelprize.org/nobel_prizes/physics/laureates/2013/">Higgs boson</a> at the <a href="http://home.web.cern.ch/topics/large-hadron-collider">Large Hadron Collider</a> at European Organisation for Nuclear Research (<a href="http://home.web.cern.ch/about">CERN</a>), and the future discoveries expected from the <a href="http://www.ska.ac.za/about/project.php">Square Kilometre Array</a> (SKA) project. </p>
<p>Any discovery in experimental science is the result of titanic efforts to overcome technological difficulties and challenges. When the neutrino was first <a href="http://www.pbs.org/wnet/hawking/strange/html/neutrinos.html">postulated</a> in 1930, many thought that it would be mission impossible to detect them, let alone to study its properties – such as its mass.</p>
<p>The relentless need to understand nature better forces scientists to innovate with which to push the boundaries of science and technology. The efforts exerted to demonstrate that neutrinos contain mass have bolstered science and technology in <a href="http://www.cbc.ca/news/technology/canadian-s-nobel-prize-in-physics-highlights-why-basic-science-matters-1.3262835">Canada</a> and <a href="http://www.gmanetwork.com/news/lite/story/539768">Japan</a>. South Africa’s <a href="http://mg.co.za/article/2013-11-27-sa-will-feel-economic-benefits-of-ska-says-director-general">support</a> of projects at CERN, the SKA and other efforts already have a similar effect.</p>
<p>Boosting science and technology via large scientific projects brings the added value of human capacity development in high technology that South Africa is in so much need of.</p>
<h2>What are neutrinos?</h2>
<p>Before answering this question we need to backtrack a bit. Matter is made of <a href="http://education.jlab.org/atomtour/">atoms</a>. Atoms are made of positively charged <a href="http://dictionary.reference.com/browse/nuclei">nuclei</a> and negatively charged <a href="http://dictionary.reference.com/browse/electron">electrons</a> travelling very fast around the nuclei. </p>
<p>The electro-magnetic force holds the electrons in orbit around the nuclei because opposite electric charges attract each other. Nuclei are very heavy compared to electrons and are composed of protons and neutrons. </p>
<p>Neutrinos can be thought of cousins of the electrons, only neutral. Neutrinos share some of the properties of the electrons – for instance, the spin. There is one type of neutrino coupled to the electron, which is called electron neutrino. The electron has an anti-particle, the positron, which has positive electric charge. There is also an electron anti-neutrino.</p>
<p>In nature there are other charged particles that are similar to the electron, which are called muons and taus. These are heavier than the electron. The muons and taus also have two other types of neutrinos respectively. In total we are aware of three types of neutrinos (electron, muon, and tau) and their anti-particles.</p>
<h2>Why are neutrinos elusive?</h2>
<p>Neutrinos do not have electric charge. Therefore, they do not get repelled or attracted to other charged particles in nature. They interact very weakly with matter so they very rarely leave a trace. </p>
<p>Vast amounts of neutrinos <a href="http://timeblimp.com/?page_id=1033">pass through us</a> every day, but we do not feel them because neutrinos hardly ever interact with the atoms that make up our bodies.</p>
<p>Most of the neutrinos that pass through earth come from the sun and are produced by nuclear fusion. These are called solar neutrinos. The other neutrinos are produced as a result of the collision of cosmic particles with the Earth’s atmosphere. These are called atmospheric neutrinos.</p>
<h2>How can we tell that neutrinos have mass?</h2>
<p>There are three types of neutrinos. If neutrinos were massless then they would travel forever unencumbered. If neutrinos have mass then, as they travel, they gradually “disappear” to become a different type of neutrino. </p>
<p>This is referred to as neutrino oscillation and it is a quantum mechanical effect. </p>
<p>For instance, the Sun creates electron neutrinos. By the time neutrinos reach Earth we only observe about one-third of the emitted neutrinos. The remaining two-thirds of the electron neutrinos becomes muon and tau neutrinos. Through this process, it is directly demonstrated that neutrinos have mass.</p>
<h2>Decades of research pay off</h2>
<p>Neutrinos were put forward in 1930 as a means to explain missing energy from a certain type of nuclear reactions. It was not until 1956 that neutrinos were detected unequivocally in laboratory conditions, for which a <a href="http://www.nobelprize.org/nobel_prizes/physics/laureates/1995/press.html">Nobel Prize in Physics</a> was awarded in 1995. </p>
<p>Scientists from all over the world have not stopped investigating the nature of these elusive particles. Neutrinos were known to be neutral and assumed to be massless. It was not until the late 1990s and early 2000s that experimental techniques became available in order to elucidate if neutrinos have mass. </p>
<p>The latter signifies a major discovery in physics, leading to a Nobel Prize in Physics in 2015. The fact of the matter is that to date we do not really know how neutrinos acquire mass. Unravelling this mystery may lead to other groundbreaking discoveries.</p><img src="https://counter.theconversation.com/content/49025/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Bruce Mellado receives funding from the DST, the NRF, Wits research office.</span></em></p>The Nobel Prize-winning research on neutrinos is expected to push the boundaries of science and technology.Bruce Mellado, Professor of Physics, University of the WitwatersrandLicensed as Creative Commons – attribution, no derivatives.