tag:theconversation.com,2011:/us/topics/full-moon-33035/articlesFull moon – The Conversation2024-03-26T17:01:48Ztag:theconversation.com,2011:article/2266432024-03-26T17:01:48Z2024-03-26T17:01:48ZThe ‘worm moon’ once marked the spring return of earthworms – until global warming kicked in<figure><img src="https://images.theconversation.com/files/584414/original/file-20240326-16-7psmz6.jpg?ixlib=rb-1.1.0&rect=8%2C8%2C5982%2C3970&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption"></span> <span class="attribution"><span class="source">Darkfoxelixir / shutterstock</span></span></figcaption></figure><p>The worm moon has risen. The final full moon of winter in the northern hemisphere appeared on <a href="https://www.theguardian.com/news/gallery/2024/mar/25/a-volcanic-eruption-and-a-worm-moon-photos-of-the-day">March 25</a> and owes its name to <a href="https://www.nationalgeographic.co.uk/2019/02/full-moon-names-explained">Native Americans</a> who noted winter’s end by the trails of earthworms it illuminated on the newly thawed soil. </p>
<p>Common names of full moons generally come from seasonal animals, colours or crops: wolf moon, pink moon, harvest moon. But the worm moon may be losing its significance, as climate change leads to wetter summers and milder winters in much of the world. I’ve been an earthworm scientist for more than three decades, and, of late, I’m seeing signs of worms at the surface in months when they used to be inactive.</p>
<p>To track how the worm moon might be changing we can look at a particular earthworm species (<em>Lumbricus terrestris</em>, aka the dew worm, nightcrawler or lob worm) which is unusually easy to track. Also sometimes called the common earthworm, if you see a big worm in the garden, it’s likely to be this species. </p>
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<p><em>Do the seasons feel increasingly weird to you? You’re not alone. Climate change is distorting nature’s calendar, causing plants to flower early and animals to emerge at the wrong time.</em></p>
<p><em>This article is part of a series, <a href="https://theconversation.com/uk/topics/wild-seasons-152175?utm_source=InArticleTop&utm_medium=TCUK&utm_campaign=WS">Wild Seasons</a>, on how the seasons are changing – and what they may eventually look like.</em></p>
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<p>Most worms spend most of their lives underground, but the dew worm almost completely leaves its deep burrow, with tail tip left in, as it ventures on to the soil surface every night to feed on dead leaves. These worms also mate on the soil surface. They may be hermaphrodite (both male and female) but still need to exchange sperm with a partner – each fertilising the other.</p>
<p>Such activities usually take place under the cover of darkness to avoid birds and other potential daytime predators. However, the worms are restricted by soil conditions at the top of the burrow. They cannot surface if the soil is baked dry (in summer) or frozen (in winter). </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/584428/original/file-20240326-22-f8tpaz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Large worm in soil" src="https://images.theconversation.com/files/584428/original/file-20240326-22-f8tpaz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/584428/original/file-20240326-22-f8tpaz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/584428/original/file-20240326-22-f8tpaz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/584428/original/file-20240326-22-f8tpaz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/584428/original/file-20240326-22-f8tpaz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/584428/original/file-20240326-22-f8tpaz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/584428/original/file-20240326-22-f8tpaz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"><em>Lumbricus terrestris</em> is a large earthworm found across the world.</span>
<span class="attribution"><span class="source">D. Kucharski K. Kucharska / shutterstock</span></span>
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<p>In theory, the passing of winter would kickstart the surface activity (and therefore the worm moon). Yet if the winter isn’t that cold, we perhaps need to reconsider which moon should be termed the “worm moon”. Maybe a date earlier in the year would be better, or perhaps the term may cease to have any real meaning.</p>
<p>We can get a sense of how these earthworms can adapt to changing circumstances by looking at the northernmost populations, such as those in Finland, which are exposed to 24 hours of daylight in summer. These “white nights”, when the sky never gets dark, put additional stress on these worms as they cannot use darkness to hide from predators but must still feed and mate at the surface while conditions allow.</p>
<h2>Finland v Lancashire v Ohio</h2>
<p>A decade ago, colleagues and I set out to see if Finnish worms behaved any differently during the white night period to worms of the same species taken to Finland from lower latitudes. We <a href="https://www.sciencedirect.com/science/article/pii/S0038071714000248">compared native dew worms</a> from an area in south-west Finland at 60°N, with those from Lancashire in the UK (53°N) and Ohio in the US (40°N, more than 2,000km south of Finland), both of which have dark nights throughout the year.</p>
<p>We put these worms outdoors under ambient (white night) light in soil-filled drainpipes (1m deep) in a large, controlled temperature water bath (an old chest freezer with no lid). We looked at their feeding and mating, and, in parallel, repeated the experiment under darkened conditions at “night”. </p>
<p>In darkness, worms from all three origins were similarly very active in feeding and mating. </p>
<p>Under ambient conditions, the Finnish worms were generally the most active. They emerged earlier in the evening and ceased their activity later in the morning than those from the two more southerly populations. It seems the species had adapted to its conditions, with a normal reluctance to surface during daylight overtaken by a need to feed and mate.</p>
<p>Perhaps with warming soils, earthworms are becoming more active during traditionally colder or drier months. This will increase their effect on the soil – earthworms are ecosystem engineers and generally lead to increased soil fertility – which is generally positive, even if churning up the soil can lead to <a href="https://www.nature.com/articles/nclimate1692">further decomposition and greenhouse gas emissions</a>. </p>
<p>A worm moon and white nights would never normally appear in the same sentence. However, changes in the activities of worms as the global climate becomes less predictable means we may need to rethink at least one of our terms of reference that has marked time for hundreds or thousands of years. Enjoy the traditional worm moon while it lasts.</p><img src="https://counter.theconversation.com/content/226643/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kevin Richard Butt 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>The last full moon of winter can illuminate earthworms in newly-thawed soil.Kevin Richard Butt, Reader in Ecology, University of Central LancashireLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1612622021-05-21T20:13:41Z2021-05-21T20:13:41ZSupermoon! Red blood lunar eclipse! It’s all happening at once, but what does that mean?<figure><img src="https://images.theconversation.com/files/402165/original/file-20210521-15-mw9fey.jpg?ixlib=rb-1.1.0&rect=71%2C57%2C4685%2C2874&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A red blood moon is caused by sunlight passing through the Earth's atmosphere. </span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Lunar_eclipse_March_2007.jpg#/media/File:Lunar_eclipse_March_2007.jpg">U.S. Navy/Joshua Valcarcel/WikimediaCommons</a></span></figcaption></figure><p>The first lunar eclipse of 2021 is going to happen during the <a href="https://www.timeanddate.com/eclipse/">early hours of May 26</a>. But this is going to be an especially super lunar event, as it will be a supermoon, a lunar eclipse and a red blood moon all at once. So what does this all mean?</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/402166/original/file-20210521-19-1lzx779.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A comparison showing a larger moon and a smaller moon with a 12% difference in size." src="https://images.theconversation.com/files/402166/original/file-20210521-19-1lzx779.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/402166/original/file-20210521-19-1lzx779.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=364&fit=crop&dpr=1 600w, https://images.theconversation.com/files/402166/original/file-20210521-19-1lzx779.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=364&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/402166/original/file-20210521-19-1lzx779.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=364&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/402166/original/file-20210521-19-1lzx779.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=457&fit=crop&dpr=1 754w, https://images.theconversation.com/files/402166/original/file-20210521-19-1lzx779.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=457&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/402166/original/file-20210521-19-1lzx779.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=457&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 Moon appears 12% bigger when it is closest to Earth compared with its appearance when it’s farthest away.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Lunar_perigee_apogee.png#/media/File:Lunar_perigee_apogee.png">Tomruen/WikimediaCommons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
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</figure>
<h2>What’s a super moon?</h2>
<p>A <a href="https://earthsky.org/astronomy-essentials/what-is-a-supermoon">supermoon occurs</a> when a full or new moon coincides with the Moon’s closest approach to the Earth.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/402169/original/file-20210521-19-1upmozl.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="White lines showing the oblong shape of the moon's orbit." src="https://images.theconversation.com/files/402169/original/file-20210521-19-1upmozl.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/402169/original/file-20210521-19-1upmozl.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=522&fit=crop&dpr=1 600w, https://images.theconversation.com/files/402169/original/file-20210521-19-1upmozl.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=522&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/402169/original/file-20210521-19-1upmozl.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=522&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/402169/original/file-20210521-19-1upmozl.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=655&fit=crop&dpr=1 754w, https://images.theconversation.com/files/402169/original/file-20210521-19-1upmozl.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=655&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/402169/original/file-20210521-19-1upmozl.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=655&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 Moon’s orbit is not a perfect circle as it slowly rotates around Earth.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Moon_apsidal_precession.png#/media/File:Moon_apsidal_precession.png">Rfassbind/WikimediaCommons</a></span>
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</figure>
<p>The Moon’s orbit around Earth is not perfectly circular. This means the Moon’s distance from Earth varies as it goes around the planet. The closest point in the orbit, called the perigee, is roughly <a href="https://www.timeanddate.com/astronomy/moon/lunar-perigee-apogee.html">28,000 miles</a> closer to Earth than the farthest point of the orbit. A full moon that <a href="https://theconversation.com/supermoons-are-big-and-bright-but-not-as-rare-as-the-hype-would-suggest-68270">happens near the perigee is called a supermoon</a>.</p>
<p>So why is it super? The relatively close proximity of the Moon makes it seem a little bit bigger and brighter than usual, though the difference between a supermoon and a normal moon is usually hard to notice unless you’re looking at two pictures side by side.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/402173/original/file-20210521-15-1rocqcy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram showing the relative position of the Earth and Moon and how this corresponds with the phases of the Moon." src="https://images.theconversation.com/files/402173/original/file-20210521-15-1rocqcy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/402173/original/file-20210521-15-1rocqcy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=240&fit=crop&dpr=1 600w, https://images.theconversation.com/files/402173/original/file-20210521-15-1rocqcy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=240&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/402173/original/file-20210521-15-1rocqcy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=240&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/402173/original/file-20210521-15-1rocqcy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=302&fit=crop&dpr=1 754w, https://images.theconversation.com/files/402173/original/file-20210521-15-1rocqcy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=302&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/402173/original/file-20210521-15-1rocqcy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=302&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 phases of the Moon correspond to how much of the lit–up side you can see from Earth.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Moon_phases_en.jpg#/media/File:Moon_phases_en.jpg">Orion 8/WikimediaCommons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
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</figure>
<h2>How does a lunar eclipse work?</h2>
<p>A lunar eclipse happens when the Earth’s shadow covers all or part of the Moon. This can only happen during a full moon, so first, it helps to understand what makes a full moon.</p>
<p>Like the Earth, half of the Moon is illuminated by the sun at any one time. A full moon happens when the Moon and the Sun are on opposite sides of the Earth. This allows you see the entire lit-up side, which looks like a round disc in the night sky.</p>
<p>If the Moon had a totally flat orbit, every full moon would be a lunar eclipse. But the Moon’s orbit is tilted by about <a href="http://hyperphysics.phy-astr.gsu.edu/hbase/Solar/lunecl.html">5 degrees relative to Earth’s orbit</a>. So, most of the time a full moon ends up a little above or below the shadow cast by the Earth. </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/402170/original/file-20210521-13-j8e7a1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram showing the orbits of the Earth and the moon and Earth's shadow." src="https://images.theconversation.com/files/402170/original/file-20210521-13-j8e7a1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/402170/original/file-20210521-13-j8e7a1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/402170/original/file-20210521-13-j8e7a1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/402170/original/file-20210521-13-j8e7a1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/402170/original/file-20210521-13-j8e7a1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/402170/original/file-20210521-13-j8e7a1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/402170/original/file-20210521-13-j8e7a1.jpg?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">A lunar eclipse occurs when the Moon passes through Earth’s shadow.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Geometry_of_a_Lunar_Eclipse.svg#/media/File:Geometry_of_a_Lunar_Eclipse.svg">Sagredo/WikimediaCommons</a></span>
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<p>But twice in each lunar orbit, the Moon is on the same horizontal plane as both the Earth and Sun. If this corresponds to a full moon, the Sun, the Earth and the Moon will form a straight line and the Moon will pass through the Earth’s shadow. This results in a <a href="https://svs.gsfc.nasa.gov/4158">total lunar eclipse</a>. </p>
<p>To see a lunar eclipse, you need to be on the night side of the Earth while the <a href="http://www.mreclipse.com/Special/LEprimer.html">Moon passes through the shadow</a>. The best place to see the eclipse on May 26, 2021, will be the middle of the Pacific Ocean, Australia, the East Coast of Asia and the West Coast of the Americas. It will be visible on the eastern half of the U.S., but only the very earliest stages before the Moon sets. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/402176/original/file-20210521-15-199f9vt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A red hued moon with a shadow on the top." src="https://images.theconversation.com/files/402176/original/file-20210521-15-199f9vt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/402176/original/file-20210521-15-199f9vt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=492&fit=crop&dpr=1 600w, https://images.theconversation.com/files/402176/original/file-20210521-15-199f9vt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=492&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/402176/original/file-20210521-15-199f9vt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=492&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/402176/original/file-20210521-15-199f9vt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=618&fit=crop&dpr=1 754w, https://images.theconversation.com/files/402176/original/file-20210521-15-199f9vt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=618&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/402176/original/file-20210521-15-199f9vt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=618&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 Earth’s atmosphere gives the Moon a blood-red glow during total lunar eclipses.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Eclipse_and_Super_blue_blood_moon_31.01.2018_DSCN9664.jpg#/media/File:Eclipse_and_Super_blue_blood_moon_31.01.2018_DSCN9664.jpg">Irvin Calicut/WikimediaCommons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>Why does the moon look red?</h2>
<p>When the Moon is completely covered by Earth’s shadow it will darken, but doesn’t go completely black. Instead, it takes on a red color, which is why total lunar eclipses are sometimes called red or blood moons. </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>Sunlight contains all colors of visible light. The particles of gas that make up Earth’s atmosphere are more likely to scatter blue wavelengths of light while redder wavelengths pass through. This is called <a href="http://hyperphysics.phy-astr.gsu.edu/hbase/atmos/blusky.html">Rayleigh scattering</a>, and it’s why the <a href="https://www.physicsclassroom.com/class/light/Lesson-2/Blue-Skies-and-Red-Sunsets">sky is blue and sunrises and sunsets are often red</a>. </p>
<p>In the case of a lunar eclipse, red light can pass through the Earth’s atmosphere and is refracted – or bent – toward the Moon, while blue light is filtered out. This leaves the moon with a <a href="https://www.timeanddate.com/eclipse/why-does-moon-look-red-lunar-eclipse.html">pale reddish hue during an eclipse</a>.</p>
<p>Hopefully you will be able to go see this super lunar eclipse. When you do, now you will know exactly what makes for such a special sight. </p>
<p><em>Portions of this story originally appeared in a <a href="https://theconversation.com/look-up-at-the-super-blue-blood-full-moon-jan-31-heres-what-youll-see-and-why-89738">previous article</a> published on Jan. 24, 2018.</em></p><img src="https://counter.theconversation.com/content/161262/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Shannon Schmoll receives funding from the Institute of Museum and Library Services and the National Science Foundation.</span></em></p>In the early morning of May 26, 2021, there will be a super blood-red lunar eclipse. The show will be spectacular and can all be explained by the orbits of the Earth and Moon.Shannon Schmoll, Director, Abrams Planetarium, Department of Physics and Astronomy, Michigan State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1597212021-04-26T10:41:18Z2021-04-26T10:41:18ZSupermoon: how an illusion makes the full Moon appear bigger than it really is<figure><img src="https://images.theconversation.com/files/397026/original/file-20210426-23-dhor35.jpg?ixlib=rb-1.1.0&rect=218%2C102%2C3566%2C2195&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/full-moon-sky-755632231">Shutterstock/Sergey Nivens</a></span></figcaption></figure><p>No matter where you are in the world, and no matter how light the skies are, the Moon is always there. Our <a href="https://theconversation.com/five-moon-myths-and-how-to-disprove-them-yourself-131165">only natural satellite</a> has inspired literature, art and science for thousands of years.</p>
<p>As the days lengthen in the northern hemisphere, it gets harder to spot some of the fainter stars in the sky. But our Moon is still there, and every few months we have a special sighting. </p>
<p>Not only is the Moon on 26 April a full Moon, it’s also what is known as a supermoon – and the first of the year. To understand why it is a supermoon, it’s important to understand a little more about why different parts of the Moon are lit up at different times of the month, and also a little more about the Moon’s orbit.</p>
<h2>Phases of the Moon</h2>
<p>The reason we see different proportions <a href="https://theconversation.com/to-the-moon-and-beyond-1-what-we-learned-from-landing-on-the-moon-and-why-we-stopped-going-119701">of the Moon</a> illuminated at different times of the month, or in different phases, is that the Moon is at different points in its orbit around Earth relative to the Sun. </p>
<p>When the Moon, the Earth and the Sun are all lined up together with the Earth between the Moon and Sun, sunlight shines on the whole lunar surface and is reflected back to Earth. On Earth, this is known as a full Moon. </p>
<p>When the Moon is between Earth and the Sun, no sunlight can reflect off its surface, and this is a new Moon. In between, only part of the Moon’s surface reflects sunlight, giving it different phases, as you can see in the diagram below.</p>
<figure class="align-center ">
<img alt="Diagram showing the moon's phases as it orbits Earth." src="https://images.theconversation.com/files/397029/original/file-20210426-17-oy57hu.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/397029/original/file-20210426-17-oy57hu.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=363&fit=crop&dpr=1 600w, https://images.theconversation.com/files/397029/original/file-20210426-17-oy57hu.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=363&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/397029/original/file-20210426-17-oy57hu.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=363&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/397029/original/file-20210426-17-oy57hu.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=456&fit=crop&dpr=1 754w, https://images.theconversation.com/files/397029/original/file-20210426-17-oy57hu.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=456&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/397029/original/file-20210426-17-oy57hu.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=456&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Phases of the moon.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-vector/moon-phases-moons-orbit-around-earth-120511270">Shutterstock/Redsapphire</a></span>
</figcaption>
</figure>
<p>What’s more, <a href="https://theconversation.com/how-did-the-moon-end-up-where-it-is-114930">the Moon’s orbit</a> around the Earth isn’t perfectly circular – it’s a very slightly squashed ellipse. This that means sometimes the Moon is closer to the Earth than at other times. The Moon’s closest approach to Earth is called its perigee, and a full Moon at or close to perigee is called a supermoon. </p>
<p>More technically, it’s also known as a perigee syzygy. The opposite phenomenon – when the full Moon is furthest away from Earth in its orbit – is called an apogee syzygy or micromoon. Obviously the supermoon is not a new phenomenon, but its name is quite new – the word doesn’t appear before the 1970s.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/five-moon-myths-and-how-to-disprove-them-yourself-131165">Five Moon myths – and how to disprove them yourself</a>
</strong>
</em>
</p>
<hr>
<p>Since the Moon is so big and bright compared to other objects in the night sky, it’s not hard to see on a clear night. To see the supermoon, the issues are working out when it rises and sets.</p>
<p>In the UK, the Moon rises in the east just before 7.30pm on Monday April 26 and sets in the west just after 6.00am on Tuesday April 27. It’ll be low in the sky, so try to get to a high place like a hill to see the supermoon. </p>
<p>If you don’t mind staying up late or getting up very early, look south around 4.40am. The Moon, Jupiter and Saturn will all be low in the sky and visible to the naked eye – a treat for early birds or night owls.</p>
<h2>The moon illusion</h2>
<p>There’s one catch to all this supermoon business. The Moon doesn’t actually look that much bigger in the sky compared to a normal full Moon. But it sometimes looks bigger when it’s closer to the horizon. Why is this, when its size in the sky doesn’t change very much when it orbits closer to Earth?</p>
<p>This is known as <a href="https://www.uww.edu/Documents/colleges/cls/Departments/Psychology/Mccread_Moon_Illusions.pdf">the Moon illusion</a>, and it really is an illusion. If you cover the Moon with your thumb, you’ll always be able to block it out, whether it looks tiny high up in the sky or whether it looks huge closer to the horizon. </p>
<figure class="align-center ">
<img alt="A full moon above trees." src="https://images.theconversation.com/files/397025/original/file-20210426-23-1ijfrdk.jpg?ixlib=rb-1.1.0&rect=99%2C28%2C4608%2C3308&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/397025/original/file-20210426-23-1ijfrdk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=423&fit=crop&dpr=1 600w, https://images.theconversation.com/files/397025/original/file-20210426-23-1ijfrdk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=423&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/397025/original/file-20210426-23-1ijfrdk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=423&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/397025/original/file-20210426-23-1ijfrdk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=531&fit=crop&dpr=1 754w, https://images.theconversation.com/files/397025/original/file-20210426-23-1ijfrdk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=531&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/397025/original/file-20210426-23-1ijfrdk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=531&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The moon appears bigger when it’s near the horizon.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/supermoon-moon-great-sunset-view-big-501311485">Shutterstock/Paramonov Alexander</a></span>
</figcaption>
</figure>
<p>People have known about this optical illusion <a href="https://doi.org/10.1068%2Fp050377">for thousands of years</a>, but we still don’t completely understand how or why it comes about. </p>
<p>We do know it’s a psychological illusion, and probably at least partly due to the brain thinking that objects <a href="https://brill.com/view/journals/sv/20/1-2/article-p155_8.xml">near the horizon</a> must be closer to us. There are dozens of competing explanations, and most of them are to do with how our brains process information. </p>
<p>So although Monday’s supermoon might not objectively look much bigger in the sky, being low on the horizon could subjectively make it look much bigger to us anyway. Whatever the cause of the Moon illusion or the size of the Moon in the sky, here’s hoping for clear skies.</p><img src="https://counter.theconversation.com/content/159721/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Osnat Katz receives funding from the AHRC and Science Museum as part of her PhD. </span></em></p>April 26 is the first supermoon of the year.Osnat Katz, PhD Candidate in Space History, UCLLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1584122021-04-23T12:36:32Z2021-04-23T12:36:32ZThis supermoon has a twist – expect flooding, but a lunar cycle is masking effects of sea level rise<figure><img src="https://images.theconversation.com/files/394314/original/file-20210409-23-1ez8yna.jpg?ixlib=rb-1.1.0&rect=0%2C3%2C2507%2C1477&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">April's super full moon was known as the pink moon because it heralds the arrival of spring flowers.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/man-walks-along-the-huntington-beach-pier-as-a-sea-gull-news-photo/1130794137">Mark Rightmire/MediaNews Group/Orange County Register via Getty Images</a></span></figcaption></figure><p>Another “super full moon” is coming May 26, 2021, and coastal cities like Miami know that means one thing: a heightened risk of tidal flooding.</p>
<p>Exceptionally high tides are common when the moon is closest to the Earth, known as <a href="https://oceanservice.noaa.gov/education/tutorial_tides/tides06_variations.html">perigee</a>, and when it’s either full or new. In the case of what’s informally known as a super full moon, it’s both full and at perigee.</p>
<p>But something else is going on with the way the moon orbits the Earth that people should be aware of. It’s called the lunar nodal cycle, and it’s presently hiding a looming risk that can’t be ignored.</p>
<p>Right now, we’re in the phase of an 18.6-year lunar cycle that lessens the moon’s influence on the oceans. The result can make it seem like the coastal flooding risk has leveled off, and that can make sea level rise less obvious.</p>
<figure class="align-center ">
<img alt="Chart showing how the lunar nodal cycle can mask sea level rise" src="https://images.theconversation.com/files/393346/original/file-20210404-23-6jku7d.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/393346/original/file-20210404-23-6jku7d.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/393346/original/file-20210404-23-6jku7d.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/393346/original/file-20210404-23-6jku7d.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/393346/original/file-20210404-23-6jku7d.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=425&fit=crop&dpr=1 754w, https://images.theconversation.com/files/393346/original/file-20210404-23-6jku7d.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=425&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/393346/original/file-20210404-23-6jku7d.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=425&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">This simplified chart illustrates how the lunar nodal cycle suppresses and enhances the effects of sea level rise in Miami. The basic model assumes a constant linear increase of sea level, so it doesn’t capture the expected acceleration of sea level rise.</span>
<span class="attribution"><a class="source" href="https://twitter.com/BMcNoldy/status/1351630471487098881">Brian McNoldy</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>But communities shouldn’t get complacent. Global sea level is <a href="https://climate.nasa.gov/news/2680/new-study-finds-sea-level-rise-accelerating/">still rising with the warming planet</a>, and that 18.6-year cycle will soon be working against us.</p>
<p>I am an <a href="https://scholar.google.com/citations?user=CsAY3vUAAAAJ&hl=en">atmospheric scientist</a> at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science who keeps a close eye on sea level rise in Miami. Here’s what you need to know.</p>
<h2>What the moon has to do with coastal flooding</h2>
<p>The moon’s gravitational pull is the dominant reason we have tides on Earth. More specifically, Earth rotating beneath the moon once per day and the moon orbiting around Earth once per month are the big reasons that the ocean is constantly sloshing around.</p>
<p>In the simplest terms, the moon’s <a href="https://oceanservice.noaa.gov/education/tutorial_tides/tides03_gravity.html">gravitational pull</a> creates a bulge in the ocean water that is closest to it. There’s a similar bulge on the opposite side of the planet due to inertia of the water. As Earth rotates through these bulges, high tides appear in each coastal area <a href="https://oceanservice.noaa.gov/education/tutorial_tides/tides05_lunarday.html">every 12 hours and 25 minutes</a>. Some tides are <a href="https://www.youtube.com/watch?v=OP0cpXpw8yk">higher than others</a>, depending on geography.</p>
<p>The sun plays a role too: Earth’s rotation, as well as its elliptic orbit around the sun, generates tides that vary throughout the day and the year. But that impact is less than half of what the moon contributes.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1261617041926090752"}"></div></p>
<p>This gravitational tug-of-war on our water was discovered nearly 450 years ago, though it’s been happening for nearly four billion years. In short, the moon has very strong control over how we experience sea level. It doesn’t affect sea level rise, but it can hide or exaggerate it.</p>
<h2>So, what is the lunar nodal cycle?</h2>
<p>To begin, we need to think about orbits.</p>
<p>Earth orbits the sun in a certain plane – it’s called the ecliptic plane. Let’s imagine that plane being level for simplicity. Now picture the moon orbiting Earth. That orbit also lies on a plane, but it’s slightly tilted, about 5 degrees relative to the ecliptic plane.</p>
<p>That means that the moon’s orbital plane intersects Earth’s orbital plane at two points, called nodes.</p>
<figure class="align-center ">
<img alt="An illustration of the moon's path crossing the ecliptic plane" src="https://images.theconversation.com/files/393351/original/file-20210405-23-1b1r9fq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/393351/original/file-20210405-23-1b1r9fq.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=351&fit=crop&dpr=1 600w, https://images.theconversation.com/files/393351/original/file-20210405-23-1b1r9fq.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=351&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/393351/original/file-20210405-23-1b1r9fq.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=351&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/393351/original/file-20210405-23-1b1r9fq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=440&fit=crop&dpr=1 754w, https://images.theconversation.com/files/393351/original/file-20210405-23-1b1r9fq.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=440&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/393351/original/file-20210405-23-1b1r9fq.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=440&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The lunar nodes are the points where the moon’s path crosses the ecliptic, the plane of Earth’s orbit shown as the view of the sun from Earth over the span of a year.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Lunar_node#/media/File:Lunar_eclipse_diagram-en.svg">Wikimedia</a></span>
</figcaption>
</figure>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/394611/original/file-20210412-13-40jbdy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Illustration of the Earth and the ecliptic and orbital planes" src="https://images.theconversation.com/files/394611/original/file-20210412-13-40jbdy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/394611/original/file-20210412-13-40jbdy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/394611/original/file-20210412-13-40jbdy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/394611/original/file-20210412-13-40jbdy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/394611/original/file-20210412-13-40jbdy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/394611/original/file-20210412-13-40jbdy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/394611/original/file-20210412-13-40jbdy.jpg?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">Earth’s ecliptic and equatorial planes.</span>
<span class="attribution"><a class="source" href="https://solarsystem.nasa.gov/bosf/images/Celestial-Sphere-with-Ecliptic1.jpg">NASA</a></span>
</figcaption>
</figure>
<p>The moon’s orbital plane precesses, or wobbles, to a maximum and minimum of +/- 5 degrees <a href="https://pubs.geoscienceworld.org/gsa/geology/article-abstract/1/3/141/203356/Nodal-Tidal-Cycle-of-18-6-Yr-Its-Importance-in-Sea">over a period of about 18.6 years</a>. This natural cycle of orbits is called the <a href="https://doi.org/10.1029/2010JC006645">lunar nodal cycle</a>. When the lunar plane is more closely <a href="https://solarsystem.nasa.gov/bosf/images/Celestial-Sphere-with-Ecliptic1.jpg">aligned with the plane of Earth’s equator</a>, tides on Earth are exaggerated. Conversely, when the lunar plane tilts further away from the equatorial plane, tides on Earth are muted, relatively.</p>
<p>The lunar nodal cycle was <a href="https://doi.org/10.1098/rstl.1727.0064">first formally documented</a> in 1728 but has been known to keen astronomical observers for thousands of years.</p>
<h2>What effect does that have on sea level?</h2>
<p>The effect of the nodal cycle is gradual – it’s not anything that people would notice unless they pay ridiculously close attention to the precise movement of the moon and the tides for decades.</p>
<p>But when it comes to predictions of tides, dozens of astronomical factors are accounted for, including the lunar nodal cycle.</p>
<p>It’s worth being aware of this influence, and even taking advantage of it. During the most rapid downward phase of the lunar nodal cycle – like we’re in right now – we have a bit of a reprieve in the observed rate of sea level rise, all other things being equal.</p>
<figure class="align-center ">
<img alt="A man wearing flipflops steps onto a **flooded** sidewalk while leaving a hotel." src="https://images.theconversation.com/files/394315/original/file-20210409-17-1bow1k2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/394315/original/file-20210409-17-1bow1k2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/394315/original/file-20210409-17-1bow1k2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/394315/original/file-20210409-17-1bow1k2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/394315/original/file-20210409-17-1bow1k2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/394315/original/file-20210409-17-1bow1k2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/394315/original/file-20210409-17-1bow1k2.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">Street flooding has become a common problem during extremely high tides in Miami Beach.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/hotel-guest-steps-out-of-a-hotel-into-a-flooded-street-that-news-photo/490535700">Joe Raedle/Getty Images</a></span>
</figcaption>
</figure>
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<p>These are the years to implement <a href="https://theconversation.com/how-to-make-sure-bidens-infrastructure-plan-can-hold-up-to-climate-change-and-save-money-153869">infrastructure plans to protect coastal areas</a> against sea level rise. </p>
<p>Once we reach the bottom of the cycle around 2025 and start the upward phase, the lunar nodal cycle begins to contribute more and more to the perceived rate of sea level rise. During those years, the rate of sea level rise is effectively doubled in places like Miami. The impact varies from place to place since the rate of sea level rise and the details of the lunar nodal cycle’s contribution vary.</p>
<p>Like the “supermoon” in late April, the one on May 26 is a perigean full moon. Even with the lunar nodal cycle in its current phase, cities like Miami should expect some coastal flooding.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=504&fit=crop&dpr=1 754w, https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=504&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?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">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><strong><em>This story is part of <a href="https://theconversation.com/uk/topics/oceans-21-96784">Oceans 21</a></em></strong>
<br><em>Our series on the global ocean opened with <a href="https://oceans21.netlify.app/">five in depth profiles</a>. Look out for new articles on the state of our oceans in the lead up to the UN’s next climate conference, COP26. The series is brought to you by The Conversation’s international network.</em></p><img src="https://counter.theconversation.com/content/158412/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Brian McNoldy serves as a volunteer science advisor for Coastal Risk Consulting. </span></em></p>Sea level is still rising, and when that lunar cycle starts upward again, it will mean double trouble for places like Miami.Brian McNoldy, Senior Research Associate, University of MiamiLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1580612021-03-29T03:48:38Z2021-03-29T03:48:38ZWhy is the Moon bright? Is Easter a full moon? How long does a full moon last? Your Moon questions answered by an astronomer<figure><img src="https://images.theconversation.com/files/392135/original/file-20210329-19-14z8pkd.jpg?ixlib=rb-1.1.0&rect=0%2C44%2C3302%2C2282&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>If you stepped outside on the weekend and thought, “Gosh, the full moon looks nice tonight”, you are not alone. </p>
<p>According to Google Trends, Moon-related searches are up by more than 60% over the past week in Australia, led by Western Australia and Queensland. </p>
<p>Technically, the Moon is <a href="https://www.timeanddate.com/moon/phases/australia/sydney">currently</a> “waning gibbous” which means the moment of maximum fullness has passed, and it’s now starting to look smaller. But it’s still quite spectacular.</p>
<p>As someone teaching first-year astronomy at the moment, where much time is spent discussing the Moon, here are my answers to some of the most common recent Moon questions.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-big-is-the-moon-let-me-compare-118840">How big is the Moon? Let me compare ...</a>
</strong>
</em>
</p>
<hr>
<h2>1. A full moon is how many times brighter than a half moon?</h2>
<p>You might think a half moon (first quarter or last quarter, depending on where you are in the phases) is half as bright as the full moon. However, if you add up all the light being reflected from the Moon to us here on Earth, a half moon is a fair bit <em>less</em> than half as bright as the full moon. In fact, the full moon is <a href="https://skyandtelescope.org/astronomy-news/how-bright-moon-exactly/#:%7E:text=Yet%20the%20full%20Moon%20is,Earth's%20perspective%2C%20with%20few%20shadows.">roughly six times</a> brighter than the half moon.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/B22I9Z45yrM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>The main reason for this comes down to shadows. When the Moon is full, the Earth is between the Sun and the Moon. So when you look at the Moon rising in the evening, the Sun has just set, behind your back. </p>
<p>That means the side of the Moon facing Earth is fully illuminated. With the Sun at our backs, shadows cast by objects on the Moon are pointing <em>away</em> from us, hidden from view. So we see the maximum amount of the Moon lit up, nice and bright.</p>
<p>At half moon, however, the Sun is shining onto the Moon from one side so the craters, mountains, rocks and pebbles on the Moon all cast shadows. That reduces the amount of the Moon’s surface that’s lit up, so less light is reflected towards us than you’d otherwise expect. </p>
<p>Interestingly, the actual surface of the Moon isn’t that reflective. If the Moon and Venus were side by side and you <a href="https://apod.nasa.gov/apod/ap081204.html">zoomed in</a> to look at the surface brightness of a patch on Venus and compared it with the surface brightness of a patch on the Moon, you’d see the patch on <a href="https://www.reddit.com/r/space/comments/3vt50d/occultation_of_venus_by_the_moon_1272015_los/">Venus is brighter</a>. It’s more reflective because Venus has a lot of clouds that help reflect light back to Earth.</p>
<p>But because the Moon is closer to Earth, it looks bigger than Venus, so the total amount of light that is reflected back to us is bigger. When you look up at night, the Moon will seem much brighter than Venus.</p>
<p>There’s one extra reason the full moon is extra bright - and it’s called the <a href="https://en.wikipedia.org/wiki/Opposition_surge">opposition surge</a>. When the Moon is full (or almost full), the surface we see appears to be a little bit brighter than at all other times. </p>
<p>While the fact that shadows are hidden is part of the puzzle, that isn’t enough to explain all of the brightening of the Moon in the day or so around full moon. The “<a href="https://en.wikipedia.org/wiki/Opposition_surge">opposition surge</a>” is the final piece in the puzzle that makes the full moon so much brighter than the half moon. It’s something we see in all other rocky and icy objects in the Solar system, too.</p>
<h2>2. Why is the Moon bright?</h2>
<p>At the time of writing, we’re within 24 hours of full moon, so it looks big and bright in the sky. It looks so much bigger than everything else in the night sky because it’s near us, and so bright because it’s reflecting light from the Sun. </p>
<p>But the Moon is moving away from Earth at <a href="https://www.bbc.com/news/science-environment-12311119">almost 4cm per year</a>. In the olden days, it would have been even bigger and brighter. It would have been much closer to Earth if we’d been around when Earth was young. However, the Sun was a fair bit less luminous back then, so it’s hard to say exactly how bright the Moon would have been.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/392132/original/file-20210329-17-lx5eda.jpg?ixlib=rb-1.1.0&rect=8%2C8%2C5334%2C2603&q=45&auto=format&w=1000&fit=clip"><img alt="A full moon in the sky over a Queensland beach" src="https://images.theconversation.com/files/392132/original/file-20210329-17-lx5eda.jpg?ixlib=rb-1.1.0&rect=8%2C8%2C5334%2C2603&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/392132/original/file-20210329-17-lx5eda.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/392132/original/file-20210329-17-lx5eda.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/392132/original/file-20210329-17-lx5eda.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/392132/original/file-20210329-17-lx5eda.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=369&fit=crop&dpr=1 754w, https://images.theconversation.com/files/392132/original/file-20210329-17-lx5eda.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=369&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/392132/original/file-20210329-17-lx5eda.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=369&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">In the olden days, the Moon would have been closer to Earth than it is now.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>3. Is Easter a full Moon?</h2>
<p>No. Easter is the first Sunday after the first full moon after the March equinox. </p>
<p>The March equinox is the point in the year when the Sun crosses the Equator in the sky, passing from the southern hemisphere to the northern hemisphere. </p>
<p>To astronomers, this is the start of the northern hemisphere’s spring; for those of us in the southern hemisphere, it marks the start of astronomical autumn. The March equinox typically falls around March 21.</p>
<p>The time between two consecutive full moons is roughly 29.5 days. This means the date of Easter can move around quite a lot.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-all-the-super-buzz-about-the-supermoon-68480">Why all the super buzz about the supermoon?</a>
</strong>
</em>
</p>
<hr>
<h2>4. What is the worm Moon?</h2>
<p>This is a US thing. According to US <a href="https://www.usatoday.com/story/news/nation/2021/03/26/full-worm-moon-rise-sunday-evening-but-supermoon/6999775002/">reports</a>, the name might refer to <a href="https://edition.cnn.com/2021/03/28/world/worm-supermoon-march-2021-scn/index.html">earthworms</a> appearing in the soil as the weather warms in the northern hemisphere. It’s been reported this reflects detail from Native American knowledge systems.</p>
<p>It’s important we recognise traditional astronomy, but it’s worth noting this naming convention comes from Native American culture rather than <a href="http://www.aboriginalastronomy.com.au/">our own Indigenous cultures</a>.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-moon-plays-an-important-role-in-indigenous-culture-and-helped-win-a-battle-over-sea-rights-119081">The Moon plays an important role in Indigenous culture and helped win a battle over sea rights</a>
</strong>
</em>
</p>
<hr>
<h2>5. How long does a full moon last?</h2>
<p>Technically, the exact “moment” the Moon is fullest is the moment it is exactly opposite the Sun in the sky. That happens once every 29 days or so. It is the moment the Moon is most illuminated. </p>
<p>So how long does that last? In reality, it is a split second - the moment of maximum fullness is fleeting.</p>
<p>Either way, if you saw the full moon and thought it might be a nice night to go on a date, you probably have a couple of days left when the Moon will still look impressive and amazing in the sky.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/i-see-the-moon-introducing-our-nearest-neighbour-11499">I see the moon: introducing our nearest neighbour</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/158061/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jonti Horner 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>According to Google Trends, Moon-related searches are up by more than 60% over the past week in Australia. We asked an expert in astrophysics to answer your Moon questions.Jonti Horner, Professor (Astrophysics), University of Southern QueenslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1188402019-07-18T01:05:47Z2019-07-18T01:05:47ZHow big is the Moon? Let me compare …<figure><img src="https://images.theconversation.com/files/284040/original/file-20190715-173325-11n8cww.jpg?ixlib=rb-1.1.0&rect=183%2C115%2C1211%2C824&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The size of the Moon can be deceptive when viewed from Earth.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/ovi90/13196699704/">Flickr/Ovi Gherman</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span></figcaption></figure><p>Even though we can see the Moon shining brightly in the night sky – and sometimes in daylight – it’s hard to put into perspective just how large, and just how distant, our nearest neighbour actually is.</p>
<p>So just how big <em>is</em> the <a href="https://solarsystem.nasa.gov/moons/earths-moon/overview/">Moon</a>?</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/DMdhQsHbWTs?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The Moon passing in front of Earth, captured by the Earth Polychromatic Imaging Camera (EPIC), more than a million kilometres away from our planet.</span></figcaption>
</figure>
<p>That answer isn’t quite as straightforward as you might think. Like Earth, the Moon isn’t a perfect sphere. Instead, it’s slightly squashed (what we call an oblate sphereoid). This means the Moon’s diameter from pole to pole is less than the diameter measured at the equator.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-the-moon-is-such-a-cratered-place-118842">Why the Moon is such a cratered place</a>
</strong>
</em>
</p>
<hr>
<p>But the difference is small, just four kilometres. The equatorial diameter of <a href="https://nssdc.gsfc.nasa.gov/planetary/factsheet/moonfact.html">the Moon</a> is about 3,476km, while the polar diameter is 3,472km.</p>
<p>To see how big that is we need to compare it to something of a similar size, such as Australia.</p>
<h2>From coast to coast</h2>
<p>The distance from <a href="https://www.freemaptools.com/how-far-is-it-between-perth_-australia-and-brisbane-qld_-australia.htm">Perth to Brisbane, as the crow flies, is 3,606km</a>. If you put Australia and the Moon side by side, they look to be roughly the same size.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/284051/original/file-20190715-173360-1nn1to4.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/284051/original/file-20190715-173360-1nn1to4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/284051/original/file-20190715-173360-1nn1to4.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=542&fit=crop&dpr=1 600w, https://images.theconversation.com/files/284051/original/file-20190715-173360-1nn1to4.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=542&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/284051/original/file-20190715-173360-1nn1to4.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=542&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/284051/original/file-20190715-173360-1nn1to4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=681&fit=crop&dpr=1 754w, https://images.theconversation.com/files/284051/original/file-20190715-173360-1nn1to4.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=681&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/284051/original/file-20190715-173360-1nn1to4.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=681&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 Moon vs Australia.</span>
<span class="attribution"><span class="source">NASA/Google Earth</span></span>
</figcaption>
</figure>
<p>But that’s just one way of looking at things. Although the Moon is about as wide as Australia, it is actually much bigger when you think in terms of surface area. It turns out the surface of the Moon is much larger than that of Australia.</p>
<p>The land area of Australia is some <a href="https://www.australia.gov.au/about-australia/our-country/the-australian-continent">7.69 million square kilometers</a>. By contrast, the surface area of the Moon is <a href="https://solarsystem.nasa.gov/moons/earths-moon/by-the-numbers/">37.94 million square kilometres</a>, close to five times the area of Australia. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/284052/original/file-20190715-173370-1n3nttf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/284052/original/file-20190715-173370-1n3nttf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/284052/original/file-20190715-173370-1n3nttf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=360&fit=crop&dpr=1 600w, https://images.theconversation.com/files/284052/original/file-20190715-173370-1n3nttf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=360&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/284052/original/file-20190715-173370-1n3nttf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=360&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/284052/original/file-20190715-173370-1n3nttf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=452&fit=crop&dpr=1 754w, https://images.theconversation.com/files/284052/original/file-20190715-173370-1n3nttf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=452&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/284052/original/file-20190715-173370-1n3nttf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=452&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 Moon rising above Uluru: You’d need five Australias to cover the land mass of the Moon.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/jurek_durczak/11466759956/">Flickr/jurek d Jerzy Durczak</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span>
</figcaption>
</figure>
<h2>How far is the Moon?</h2>
<p>Asking how far away is the Moon is another of those questions whose answer is more complicated than you might expect.</p>
<p>The Moon moves in an elliptical orbit around the Earth, which means its distance from our planet is constantly changing. That distance can vary by up to 50,000km during a single orbit, which is why the size of the Moon in our sky varies slightly from week to week.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/284236/original/file-20190716-173347-id8trq.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/284236/original/file-20190716-173347-id8trq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/284236/original/file-20190716-173347-id8trq.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=364&fit=crop&dpr=1 600w, https://images.theconversation.com/files/284236/original/file-20190716-173347-id8trq.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=364&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/284236/original/file-20190716-173347-id8trq.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=364&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/284236/original/file-20190716-173347-id8trq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=457&fit=crop&dpr=1 754w, https://images.theconversation.com/files/284236/original/file-20190716-173347-id8trq.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=457&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/284236/original/file-20190716-173347-id8trq.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=457&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Notice the difference in size? The Moon viewed from Earth at perigee (closest approach at 356,700km on October 26 2007) and apogee (farthest approach at 406,300km on April 3 2007).</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Lunar_perigee_apogee.png">Wikimedia/Tomruen</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>The Moon’s orbit is also influenced by every other object in the Solar System. Even when all of that is taken into account, the distance answer is still always changing, because the <a href="https://www.bbc.com/news/science-environment-12311119">Moon is gradually receding from the Earth</a> as a result of the tidal interaction between the two. </p>
<p>That last point is something we’ve been able to better study as a result of the Apollo missions. The astronauts who visited the Moon <a href="https://science.nasa.gov/science-news/science-at-nasa/2004/21jul_llr">placed an array of mirror reflectors on its surface</a>. Those reflectors are the continual target of lasers from the Earth. </p>
<p>By timing how long it takes for that laser light to travel to the Moon and back, scientists are able to measure the distance to the Moon with incredible precision, and to track the Moon’s recession from Earth. The result? The Moon is receding at a speed of 38mm per year – or just under 4 metres per century.</p>
<h2>Drive me to the Moon</h2>
<p>Having said all that, the average distance between the Moon and Earth is 384,402km. So let’s put that into context.</p>
<p>If I were to drive from Brisbane to Perth, following the <a href="https://goo.gl/maps/bZ62An1cBz9944zh6">fastest route suggested by Google</a>, I would cover 4,310km on my road trip. That journey, driving across the breadth of our country, would take around 46 hours.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/284231/original/file-20190716-173376-1mwkrmn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/284231/original/file-20190716-173376-1mwkrmn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/284231/original/file-20190716-173376-1mwkrmn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/284231/original/file-20190716-173376-1mwkrmn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/284231/original/file-20190716-173376-1mwkrmn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/284231/original/file-20190716-173376-1mwkrmn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/284231/original/file-20190716-173376-1mwkrmn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/284231/original/file-20190716-173376-1mwkrmn.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">The full Moon rising over the Perth Hills, in Western Australia, in 2016.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/135630555@N04/22823086188/">Paean Ng/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>If I wanted to clock up enough kilometres to say that I’d covered the distance between the Earth and the Moon, I’d have to make that trip more than 89 times. It would take five-and-a-half months of driving, non-stop, assuming I didn’t run into any traffic jams on the way.</p>
<p>Fortunately, the Apollo 11 astronauts weren’t restricted to Australian speed limits. The command module Columbia took just three days and four hours to reach lunar orbit following its launch on July 16 1969.</p>
<h2>An eclipse coincidence</h2>
<p>The equatorial diameter of the <a href="https://solarsystem.nasa.gov/solar-system/sun/by-the-numbers/">Sun</a> is almost 1.4 million kilometres, which is almost exactly 400 times the diameter of the Moon. </p>
<p>That ratio leads to one of astronomy’s most spectacular quirks – because the distance between the Earth and the Sun (149.6 million kilometres) is almost (but not quite) 400 times the distance between the Earth and the Moon.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explainer-what-is-a-solar-eclipse-33019">Explainer: what is a solar eclipse?</a>
</strong>
</em>
</p>
<hr>
<p>The result? The Moon and the Sun appear almost exactly the same size in Earth’s sky. As a result, when the Moon and the Sun line up perfectly, as seen from Earth, something wonderful happens – a total eclipse of the Sun.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/2lHb5ruGUyw?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The total solar eclipse seen from north Queensland in November 2012.</span></figcaption>
</figure>
<p>Sadly, such spectacular eclipses will eventually come to an end on Earth. Thanks to the Moon’s recession, it will one day be too distant to perfectly obscure the Sun. But that day will be a long time coming, with most estimates suggesting it will occur in something like 600 million years’ time.</p>
<h2>The moonwalkers</h2>
<p>While we’ve dispatched out robot envoys to the icy depths of the Solar System, the Moon remains the only other world on which humanity has walked.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/284252/original/file-20190716-173325-1pnn0bu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/284252/original/file-20190716-173325-1pnn0bu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/284252/original/file-20190716-173325-1pnn0bu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=619&fit=crop&dpr=1 600w, https://images.theconversation.com/files/284252/original/file-20190716-173325-1pnn0bu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=619&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/284252/original/file-20190716-173325-1pnn0bu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=619&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/284252/original/file-20190716-173325-1pnn0bu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=778&fit=crop&dpr=1 754w, https://images.theconversation.com/files/284252/original/file-20190716-173325-1pnn0bu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=778&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/284252/original/file-20190716-173325-1pnn0bu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=778&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Astronaut Buzz Aldrin was the second man to walk on the Moon and one of the few moonwalkers still alive today.</span>
<span class="attribution"><a class="source" href="https://solarsystem.nasa.gov/resources/840/apollo-11-buzz-aldrin/">NASA</a></span>
</figcaption>
</figure>
<p>Fifty years after that first adventure, the number of people to have walked on the Moon who are still alive is in sharp decline. <a href="https://solarsystem.nasa.gov/news/890/who-has-walked-on-the-moon/">Twelve people</a> have had that experience but, as of today, just four remain.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/five-ethical-questions-for-how-we-choose-to-use-the-moon-116801">Five ethical questions for how we choose to use the Moon</a>
</strong>
</em>
</p>
<hr>
<p>Vast as the Moon is, those 12 moonwalkers barely scratched the surface. Hopefully, in the coming years, we will return, to inspire a whole new generation and to continue humanity’s in-person exploration of our nearest celestial neighbour.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/284248/original/file-20190716-173351-17qv15a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/284248/original/file-20190716-173351-17qv15a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/284248/original/file-20190716-173351-17qv15a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=255&fit=crop&dpr=1 600w, https://images.theconversation.com/files/284248/original/file-20190716-173351-17qv15a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=255&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/284248/original/file-20190716-173351-17qv15a.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=255&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/284248/original/file-20190716-173351-17qv15a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=320&fit=crop&dpr=1 754w, https://images.theconversation.com/files/284248/original/file-20190716-173351-17qv15a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=320&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/284248/original/file-20190716-173351-17qv15a.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=320&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 Moon over the Sydney Opera House.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/paulcarmona/15332847519/">Flickr/Paul Carmon</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure><img src="https://counter.theconversation.com/content/118840/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jonti Horner 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>Just 12 people have walked on the Moon and they’ll know better than anyone just how big (or small) the place is. But we can make some comparisons with things on Earth to get a measure of the Moon.Jonti Horner, Professor (Astrophysics), University of Southern QueenslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1053712018-12-11T23:30:28Z2018-12-11T23:30:28ZCurious Kids: How does the Moon, being so far away, affect the tides on Earth?<figure><img src="https://images.theconversation.com/files/244951/original/file-20181111-116841-10bxw8f.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C4224%2C3168&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">When the sea level rises to its highest point, we call that high tide. When it falls to its lowest point, that's called low tide.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/bpinzini/4811517787/in/photolist-8kbhBe-t6Wqu-V9E4Rj-bwPoqJ-oY6DQ2-poSVN-8HEPDt-8zzY37-dgfS7Y-5ZWhDN-ooeRhw-oFjni7-drDheu-pgUnWK-7Efezw-WjLGdD-hGrGu4-2cMqEer-cLPprS-275aF2W-4LApJD-o9n4S1-P5NfW-Y9UcXm-oBbG-5a5jJr-VJTPAi-4RMFK7-8zwUKg-nFiY7-o9Fk99-39kKrk-dDYxAm-9pjmWu-qeQwN6-6p9dyV-dNkyY6-23gFUAK-kEBNt4-dNbvbU-NgC4KX-rg8Pyu-4T846v-5jZTGg-fEBa7u-nXAhnv-4r9o1w-7PHt5p-hfyc7-8zwNNn">Flickr/bpinzini</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</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. You can send your question to curiouskids@theconversation.edu.au. You might also like the podcast <a href="http://www.abc.net.au/kidslisten/imagine-this/">Imagine This</a>, a co-production between ABC KIDS listen and The Conversation, based on Curious Kids.</em> </p>
<hr>
<blockquote>
<p><strong>How does the Moon, being so far away, affect the tides on Earth? – Lachie, age 8, Doreen, Melbourne.</strong></p>
</blockquote>
<hr>
<p>Great question Lachie!</p>
<p>The short answer is that the Moon’s gravity pulls the oceans (and us) towards it. Even though the Moon is so far away, it is large enough that its force of gravity is strong enough to do that.</p>
<p>But before we get into how the Moon affects tides, let’s look at what tides are.</p>
<p>Tides are the rise and fall of water level in the oceans (and lakes, and even in your cup of water, but they’re very small). </p>
<p>When the sea level rises to its highest point, we call that high tide. When it falls to its lowest point, that’s called low tide.</p>
<p>The rise and fall of the tides is known as the tide cycle. If there’s one high tide and one low tide a day, like you would see if you went on holiday to Perth, it’s called a diurnal tide cycle. If there are two high tides and two low tides, like you see in Victoria, it’s called a semi-diurnal tide cycle. </p>
<p>The Moon has the most effect on the tides, but it’s not the only factor that affects them. The Sun and the Earth can also affect the tides. We’ll start with the Moon. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-are-there-living-things-on-different-galaxies-98562">Curious Kids: Are there living things on different galaxies?</a>
</strong>
</em>
</p>
<hr>
<h2>Tides and the Moon</h2>
<p>The Moon affects the tides because of gravity. You will have noticed that every time you jump, you always land back on the ground. This is because the Earth’s gravity is pulling you back down. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/244956/original/file-20181111-116841-1euc09g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/244956/original/file-20181111-116841-1euc09g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/244956/original/file-20181111-116841-1euc09g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=424&fit=crop&dpr=1 600w, https://images.theconversation.com/files/244956/original/file-20181111-116841-1euc09g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=424&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/244956/original/file-20181111-116841-1euc09g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=424&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/244956/original/file-20181111-116841-1euc09g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=533&fit=crop&dpr=1 754w, https://images.theconversation.com/files/244956/original/file-20181111-116841-1euc09g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=533&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/244956/original/file-20181111-116841-1euc09g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=533&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 Earth’s spinning means that another high tide occurs on the opposite side of the Earth to the Moon.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>The Moon has gravity of its own, which pulls the oceans (and us) towards it. The Moon’s gravitational pull on us is much weaker than Earth’s, so we don’t really notice it, but we can see the Moon’s effect on the liquid water of the oceans. The oceans are pulled towards the Moon’s gravity slightly, causing a bulge or high tide on the side of the Earth closest to the Moon. </p>
<h2>The Earth’s effect</h2>
<p>If the Moon causes a high tide on one side of the Earth, what causes the high tide on the other side?</p>
<p>The Earth is spinning, which is why we have night and day. The Earth’s spinning means that another high tide occurs on the opposite side of the Earth to the Moon. </p>
<p>These two high tides draw water away from the rest of the oceans, causing two low tides between the high tides. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/4UZxzyOVJ8Q?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Why do we have tides? - Forces of Nature with Brian Cox: Episode 2 - BBC One.</span></figcaption>
</figure>
<h2>The Sun</h2>
<p>The Sun, just like the Moon and the Earth, also has its own gravity which can affect the tides. Although the Sun is much larger than the Moon and has more gravity, it’s also much further away, meaning its pull on the tides is less than half as strong as the Moon’s. </p>
<p>It still does have an effect, though. When the Sun and Moon are in line with the Earth (when a full moon or new moon occur), their combined gravity cause very high tides (and very low tides), known as “spring tides.”</p>
<p>When the Sun and Moon are at right angles to each other (during a waxing or waning moon), the Sun helps to cancel out the pull of gravity from the Moon, causing lower high tides and higher than average low tides, known as “neap tides”. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/244955/original/file-20181111-37973-1i6ogp8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/244955/original/file-20181111-37973-1i6ogp8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/244955/original/file-20181111-37973-1i6ogp8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/244955/original/file-20181111-37973-1i6ogp8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/244955/original/file-20181111-37973-1i6ogp8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/244955/original/file-20181111-37973-1i6ogp8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/244955/original/file-20181111-37973-1i6ogp8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/244955/original/file-20181111-37973-1i6ogp8.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">Lunar and Solar tides diagram.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>So the Moon affects the tides because of gravity, but gravity from the Sun and the spinning of the Earth also change how the tides behave.</p>
<p>Best wishes,</p>
<p>Mark Hemer.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-is-there-anything-hotter-than-the-sun-105748">Curious Kids: Is there anything hotter than the Sun?</a>
</strong>
</em>
</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/105371/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mark Hemer receives funding from the National Environmental Science Program Earth Systems and Climate Change Hub, and the Australian Renewable Energy Agency.</span></em></p>The Moon has gravity of its own, which pulls the oceans (and us) towards it.Mark Hemer, Senior Research Scientist, Oceans and Atmosphere, CSIROLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1015242018-09-24T06:25:04Z2018-09-24T06:25:04ZIt’s better light, not worse behaviour, that explains crimes on a full Moon<figure><img src="https://images.theconversation.com/files/237651/original/file-20180924-129844-hy0pa7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">When people know it's a full moon, they tend to use it to explain all sorts of human behaviour. </span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/x9TZjFdvr0Y">Todd Diemer/Unsplash</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>It’s a full Moon on September 25. </p>
<p>If past months have been anything to go by, this will be accompanied by a round of public chat about how this affects human behaviour – claims of more hospital admissions and arrests, to crazy antics in children. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"948657284024070144"}"></div></p>
<p>Beliefs in the Moon’s behavioural effects are <a href="https://theconversation.com/mondays-medical-myth-hospitals-get-busier-on-full-moons-5383">not new</a> and date back to ancient times. But what evidence is there that the Moon has an impact on behaviour?</p>
<p>As a criminologist, I look at evidence related to arrests and behaviour linked with criminal activity. </p>
<p>The only explanation I can see that links criminology with Moon phases is just about the practicalities of being a criminal: when it’s a full Moon, there’s more light. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/five-reasons-india-china-and-other-nations-plan-to-travel-to-the-moon-87589">Five reasons India, China and other nations plan to travel to the Moon</a>
</strong>
</em>
</p>
<hr>
<p>While somewhat dated, one of the most significant studies looking at Moon phases and linking this with behaviour is a 1985 <a href="http://psycnet.apa.org/record/1985-19152-001">meta-analysis</a> – a study of the findings of 37 published and unpublished studies. The paper concludes it is not sound to infer that people behave any more – or less – strangely between Moon phases. The authors write:</p>
<blockquote>
<p>Alleged relations between phases of the moon and behavior can be traced to inappropriate analyses […] and a willingness to accept any departure from chance as evidence of a lunar effect. </p>
</blockquote>
<p>Two more recent studies have looked at links between criminal activity and phases of the Moon. </p>
<p>A <a href="https://www.sciencedirect.com/science/article/pii/S0010440X09000030">study published in 2009</a> looked at more than 23,000 cases of aggravated assaults that took place in Germany between 1999 and 2005. The authors found no correlation between battery and the various lunar phases. </p>
<p>A <a href="https://link.springer.com/article/10.1007/s12103-016-9351-9">study reported in 2016</a> was careful to make a distinction between indoor and outdoor crime committed in 13 US states and the District of Columbia in 2014.</p>
<p>The authors found no link between lunar phases and total crime or indoor crime. </p>
<p>But they did find the intensity of moonlight to have a substantive positive effect on outdoor criminal activity. As moon illumination increased, they saw an escalation in criminal activity.</p>
<p>One explanation for this finding is what is referred to as the “illumination hypothesis” – suggesting that criminals like enough light to ply their trade, but not so much as to increase their chance of apprehension. </p>
<p>It may also be that there is greater movement of people during lighter nights, thus providing a bigger pool of victims. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/confirmation-bias-a-psychological-phenomenon-that-helps-explain-why-pundits-got-it-wrong-68781">Confirmation bias: A psychological phenomenon that helps explain why pundits got it wrong</a>
</strong>
</em>
</p>
<hr>
<p>Why do some people still cling to the belief that the Moon causes criminal or other antisocial behaviour? The answer most likely lies in human cognition and our tendency to focus on that which we expect or predict to be true.</p>
<p>During an expected lunar event – such as a full or super Moon – we expect that there will be a change in behaviour so we pay more attention when we see it. In the area of cognitive psychology this is known as <a href="https://theconversation.com/confirmation-bias-a-psychological-phenomenon-that-helps-explain-why-pundits-got-it-wrong-68781">confirmation bias</a>.</p>
<p>But other questions remain, including why any behavioural effects must be inherently negative? Even if there was a direct effect, explanations as to why acts of kindness and altruism do not increase or decrease during Moon phases are conspicuously absent. </p>
<p>It is likely that we just assume the folklore is true, and believe that we become the werewolf and not the sheep.</p><img src="https://counter.theconversation.com/content/101524/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Wayne Petherick 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>The ‘illumination hypothesis’ – suggests that criminals like enough light to ply their trade, but not so much as to increase their chance of apprehension.Wayne Petherick, Associate professor of criminology, Bond UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/897382018-01-24T11:40:34Z2018-01-24T11:40:34ZLook up at the super blue blood full moon Jan. 31 – here’s what you’ll see and why<figure><img src="https://images.theconversation.com/files/203104/original/file-20180123-33560-1wukgov.jpg?ixlib=rb-1.1.0&rect=137%2C0%2C1269%2C864&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">As long as clouds don't get in the way, the view should be spectacular.</span> <span class="attribution"><a class="source" href="https://images.nasa.gov/details-GSFC_20171208_Archive_e001982.html">NASA Goddard</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p><a href="https://www.timeanddate.com/astronomy/moon/blue-moon.html">During the early hours of Jan. 31</a>, there will be a full moon, a total lunar eclipse, a blue moon and a supermoon – all at the same time. None of these things is really all that unusual by itself. What is rare is that they’re happening all together on one day.</p>
<h2>What makes the moon look full?</h2>
<p>Like the Earth, half the moon is illuminated by the sun at any one time. The <a href="https://highered.mheducation.com/olcweb/cgi/pluginpop.cgi?it=swf::800::600::/sites/dl/free/0072482621/78778/Lunar_Nav.swf::Lunar%20Phases%20Interactive">moon orbits around the Earth</a> and as a result we see different amounts of the lit-up side.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/203083/original/file-20180123-33535-18ufglr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/203083/original/file-20180123-33535-18ufglr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/203083/original/file-20180123-33535-18ufglr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=240&fit=crop&dpr=1 600w, https://images.theconversation.com/files/203083/original/file-20180123-33535-18ufglr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=240&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/203083/original/file-20180123-33535-18ufglr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=240&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/203083/original/file-20180123-33535-18ufglr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=302&fit=crop&dpr=1 754w, https://images.theconversation.com/files/203083/original/file-20180123-33535-18ufglr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=302&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/203083/original/file-20180123-33535-18ufglr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=302&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 phases of the moon visible from Earth are related to its revolution around our planet.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Moon_phases_en.jpg">Orion 8</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>A full moon is when we see its entire lit-up side. This occurs every 29.5 days, when the moon is directly opposite the sun relative to the Earth. Jan. 31 will be our <a href="http://www.moonconnection.com/moon-january-2018.phtml">next full moon in the lunar cycle</a>. </p>
<h2>What’s a lunar eclipse?</h2>
<p>The moon’s orbit is tilted by about 5 degrees relative to the Earth’s orbit. So, most of the time the moon ends up a little above or below the path Earth follows as it revolves around the sun. But twice in each lunar cycle, the moon does <a href="http://hyperphysics.phy-astr.gsu.edu/hbase/Solar/lunecl.html">cross into our planet’s orbital plane</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/203111/original/file-20180123-33571-lpjctf.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/203111/original/file-20180123-33571-lpjctf.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/203111/original/file-20180123-33571-lpjctf.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=299&fit=crop&dpr=1 600w, https://images.theconversation.com/files/203111/original/file-20180123-33571-lpjctf.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=299&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/203111/original/file-20180123-33571-lpjctf.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=299&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/203111/original/file-20180123-33571-lpjctf.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=376&fit=crop&dpr=1 754w, https://images.theconversation.com/files/203111/original/file-20180123-33571-lpjctf.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=376&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/203111/original/file-20180123-33571-lpjctf.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=376&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 lunar eclipse happens when the moon is completely in the Earth’s shadow.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Solar_lunar_eclipse_diagram.png">Tomruen</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>If that crossing corresponds to a full moon, the moon will pass into the Earth’s shadow, resulting in <a href="http://www.mreclipse.com/Special/LEprimer.html">a total lunar eclipse</a>. Since the moon needs to be behind the Earth, relative to the sun, a lunar eclipse can only happen on a full moon.</p>
<p>To see the phenomenon, you need to be on the night side of the Earth; <a href="https://eclipse.gsfc.nasa.gov/LEplot/LEplot2001/LE2018Jan31T.pdf">this eclipse will be visible mostly</a> in Asia, Australia, the Pacific and North America. But don’t worry if you miss it, lunar eclipses happen on average a couple times a year. The next one visible in North America <a href="https://eclipse.gsfc.nasa.gov/LEplot/LEplot2001/LE2019Jan21T.pdf">will be on Jan. 21, 2019</a>.</p>
<h2>A blue moon that looks red</h2>
<p>When a lunar eclipse happens, the moon appears to darken as it moves into the Earth’s shadow called the umbra. When the moon is all the way in shadow it doesn’t go completely dark; instead, it looks red due to a <a href="http://hyperphysics.phy-astr.gsu.edu/hbase/atmos/blusky.html">process called Rayleigh scattering</a>. The gas molecules of Earth’s atmosphere scatter bluer wavelengths of light from the sun, while redder wavelengths pass straight through.</p>
<p>This is why we have <a href="http://www.physicsclassroom.com/class/light/Lesson-2/Blue-Skies-and-Red-Sunsets">blue skies and red sunrises and sunsets</a>. When the sun is high in the sky, red light passes straight through to the ground while blue light is scattered in every direction, making it more likely to hit your eye when you look around. <a href="https://www.atoptics.co.uk/atoptics/sunsets.htm">During a sunset</a>, the angle of the sun is lower in the sky and that red light instead passes directly into your eyes while the blue light is scattered away from your line of sight. </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/203107/original/file-20180123-33560-r0cofb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/203107/original/file-20180123-33560-r0cofb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/203107/original/file-20180123-33560-r0cofb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=654&fit=crop&dpr=1 600w, https://images.theconversation.com/files/203107/original/file-20180123-33560-r0cofb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=654&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/203107/original/file-20180123-33560-r0cofb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=654&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/203107/original/file-20180123-33560-r0cofb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=822&fit=crop&dpr=1 754w, https://images.theconversation.com/files/203107/original/file-20180123-33560-r0cofb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=822&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/203107/original/file-20180123-33560-r0cofb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=822&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 super blood moon tinted red by scattered light.</span>
<span class="attribution"><a class="source" href="https://images.nasa.gov/details-GSFC_20171208_Archive_e000601.html">GSFC</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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</figure>
<p>In the case of a lunar eclipse, the sunlight that makes it around Earth passes through our atmosphere and is refracted toward the moon. Blue light is filtered out, leaving the moon <a href="https://www.timeanddate.com/eclipse/why-does-moon-look-red-lunar-eclipse.html">looking reddish during an eclipse</a>.</p>
<p>On top of it all, the Jan. 31 full moon is also a considered a blue moon. There are two different definitions of blue moon. The first is any time a second full moon occurs in a single month. Since there are 29.5 days between two full moons, we usually only end up with one per month. With most months longer than 29.5 days, it occasionally works out that we have two full moons. We already had one on the first of this month and our second will be Jan. 31, making it a blue moon. With this definition our next blue moon is in March, leaving February with no full moon this year.</p>
<p>The second definition of a blue moon states it’s the <a href="https://www.timeanddate.com/astronomy/moon/blue-moon.html">third moon in a season</a> in which there are four moons, which <a href="https://www.space.com/16776-blue-moon-explained-infographic.html">happens about every 2.7 years</a>. We’ll only have three this winter, so the Jan. 31 full moon won’t be blue by this definition. Stargazers will need to wait until May 18, 2019, for a blue moon that fits this older, original definition.</p>
<h2>A supersized supermoon</h2>
<p>Finally, to add the cherry on top, this will also <a href="https://theconversation.com/supermoons-are-big-and-bright-but-not-as-rare-as-the-hype-would-suggest-68270">be a supermoon</a>. The moon’s orbit is not perfectly circular, meaning its distance from Earth varies as it goes through one cycle. The closest point in its orbit is called the perigee. A full moon that happens near perigee is <a href="https://www.space.com/38940-supermoon-facts.html">called a supermoon</a> by some. </p>
<p>This happened with our full moon earlier this month on Jan. 1 and will again on Jan. 31.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/203086/original/file-20180123-33557-n72zr9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/203086/original/file-20180123-33557-n72zr9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/203086/original/file-20180123-33557-n72zr9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=599&fit=crop&dpr=1 600w, https://images.theconversation.com/files/203086/original/file-20180123-33557-n72zr9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=599&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/203086/original/file-20180123-33557-n72zr9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=599&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/203086/original/file-20180123-33557-n72zr9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=752&fit=crop&dpr=1 754w, https://images.theconversation.com/files/203086/original/file-20180123-33557-n72zr9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=752&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/203086/original/file-20180123-33557-n72zr9.jpg?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">Appearance of an ‘average’ moon versus a supermoon.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Supermoon_comparison.jpg">Marcoaliaslama</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Its proximity makes it seem a little bit bigger and brighter than usual, but that’s the extent of its effects on Earth. The distinction is usually hard to notice unless you’re looking at two pictures side by side.</p>
<p>There are long traditions of giving <a href="https://www.timeanddate.com/astronomy/moon/full-moon-names.html">different moons names</a>. This being a bigger, brighter, reddish-looking blue moon, perhaps we should call the next full moon the super purple moon. The moon will not actually appear purple, nor will have it a cape – but <a href="https://www.nasa.gov/sites/default/files/thumbnails/image/lunar_eclipse_01182018a.png">Jan. 31 is a great time</a> to gaze up and enjoy the night sky.</p><img src="https://counter.theconversation.com/content/89738/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Shannon Schmoll 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>A bunch of uncommon things all happening at the same time mean this full moon will have some special attributes.Shannon Schmoll, Director, Abrams Planetarium, Department of Physics and Astronomy, Michigan State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/682702016-11-08T20:53:15Z2016-11-08T20:53:15ZSupermoons are big and bright, but not as rare as the hype would suggest<figure><img src="https://images.theconversation.com/files/145081/original/image-20161108-16730-qa8ndt.jpg?ixlib=rb-1.1.0&rect=527%2C217%2C4229%2C2716&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Enjoy the full moon's glow.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/91467128@N08/14694185668">mstollenwerk</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span></figcaption></figure><p>As an observational astronomer who teaches students about the behavior of the moon, I’m thankful for anything that inspires people to go out and look at the sky. For me it’s second nature to pay attention to the moon; when my son was born, I would take him out at night to observe with me, and one of his very first words was “moon.”</p>
<p>But I have mixed feelings about what’s being billed as the upcoming “super-supermoon.” Many astronomers do not like using the term because reports overhype the factors that make certain full moons unusual. Most of what you’ve likely read has probably misled you about what you can expect to see on Nov. 14 and just how rare this event is. Beautiful, yes. Worth looking up for, definitely. Once in a lifetime… that’s a bit overblown.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/144941/original/image-20161107-4718-1y7vtow.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/144941/original/image-20161107-4718-1y7vtow.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/144941/original/image-20161107-4718-1y7vtow.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=240&fit=crop&dpr=1 600w, https://images.theconversation.com/files/144941/original/image-20161107-4718-1y7vtow.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=240&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/144941/original/image-20161107-4718-1y7vtow.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=240&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/144941/original/image-20161107-4718-1y7vtow.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=302&fit=crop&dpr=1 754w, https://images.theconversation.com/files/144941/original/image-20161107-4718-1y7vtow.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=302&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/144941/original/image-20161107-4718-1y7vtow.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=302&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 moon’s phases as it revolves around the Earth.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Moon_phases_en.jpg">Orion 8</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>The moon’s cyclical phases</h2>
<p>Just about everyone is familiar with the moon’s changing appearance as it goes through its phases from crescent, to half-illuminated (first quarter), to gibbous, to full, and then back through gibbous, to half-illuminated (third quarter), to crescent, to new.</p>
<p>This pattern occurs because the moon orbits the Earth. When the moon is between the Earth and sun, it’s a new moon, and you don’t see it that day. When the moon is on the opposite side of the Earth from the sun we get a full moon as the sun’s light illuminates almost its entire face. The complete sequence of phases takes about the same amount of time as it does for the moon to orbit the Earth once – just about a month. </p>
<p>As the moon makes its monthly trip around our planet, it travels on an elliptical, not circular, path. Every object in the solar system orbits like this, including the Earth around the sun; over the course of the year, the Earth is sometimes closer to the sun and sometimes more distant. Same for the moon – sometimes it’s closer to us and sometimes farther away.</p>
<p>The changes are proportionally not large; at “perigee” (the closest it gets to the Earth) the moon’s approximately 10 percent closer to the Earth than at “apogee” (most distant point on its orbit). Over the year, the moon’s distance from Earth <a href="http://nssdc.gsfc.nasa.gov/planetary/factsheet/moonfact.html">varies from around 222,000 to 253,000 miles</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/144944/original/image-20161107-4711-1rrj2jf.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/144944/original/image-20161107-4711-1rrj2jf.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/144944/original/image-20161107-4711-1rrj2jf.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=522&fit=crop&dpr=1 600w, https://images.theconversation.com/files/144944/original/image-20161107-4711-1rrj2jf.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=522&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/144944/original/image-20161107-4711-1rrj2jf.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=522&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/144944/original/image-20161107-4711-1rrj2jf.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=655&fit=crop&dpr=1 754w, https://images.theconversation.com/files/144944/original/image-20161107-4711-1rrj2jf.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=655&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/144944/original/image-20161107-4711-1rrj2jf.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=655&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 moon’s orbit is elliptical and changes over time.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Moon_apsidal_precession.png">Rfassbind</a></span>
</figcaption>
</figure>
<p><a href="https://eclipse.gsfc.nasa.gov/SEhelp/moonorbit.html">The time it takes the moon</a> to go from perigee to perigee (about 27.3 days) is shorter than the time it takes to go through a complete set of phases (about 29.5 days). Because these timescales are different, the phase at which perigee occurs varies. Sometimes perigee occurs when the moon is full, but it is just as likely for perigee to occur when the moon is in the first quarter phase, or any other. Whichever phase the moon is in when it’s at perigee will be the one that looks largest to us here on Earth for that month.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/145075/original/image-20161108-16718-1ncist6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/145075/original/image-20161108-16718-1ncist6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/145075/original/image-20161108-16718-1ncist6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/145075/original/image-20161108-16718-1ncist6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/145075/original/image-20161108-16718-1ncist6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/145075/original/image-20161108-16718-1ncist6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/145075/original/image-20161108-16718-1ncist6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/145075/original/image-20161108-16718-1ncist6.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">Two full moons as seen from Earth: at perigee on the left, at apogee on the right.</span>
<span class="attribution"><a class="source" href="http://apod.nasa.gov/apod/ap140908.html">Catalin Paduraru</a></span>
</figcaption>
</figure>
<p>At perigee, the moon can appear <a href="https://science.nasa.gov/news-articles/2016-ends-with-three-supermoons">14 percent larger and 30 percent brighter</a> than an apogee full moon. But this is complicated by the fact that our eyes play tricks on us and convince us the <a href="http://www.skyandtelescope.com/observing/moon-illusion-confusion11252015/">moon looks larger when it is near the horizon</a> than when it is higher in the sky. Every full moon will look big and bright whether it happens at perigee or apogee.</p>
<h2>So what’s a supermoon?</h2>
<p>The first time I heard the phrase “supermoon” was in 2011, and someone had to explain the suddenly in vogue term to me. People were using it to describe the full moon that happened to occur within an hour of perigee in March of that year. The moon’s perigee distance also varies a bit, and March 2011 was the moon’s closest perigee of that year.</p>
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<a href="https://images.theconversation.com/files/144952/original/image-20161107-4683-17xsos7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/144952/original/image-20161107-4683-17xsos7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/144952/original/image-20161107-4683-17xsos7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=849&fit=crop&dpr=1 600w, https://images.theconversation.com/files/144952/original/image-20161107-4683-17xsos7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=849&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/144952/original/image-20161107-4683-17xsos7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=849&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/144952/original/image-20161107-4683-17xsos7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1067&fit=crop&dpr=1 754w, https://images.theconversation.com/files/144952/original/image-20161107-4683-17xsos7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1067&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/144952/original/image-20161107-4683-17xsos7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1067&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 2013 supermoon as seen from Ireland.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/johnfinn/9125026108">John Finn</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>This was a somewhat rare event – a full moon occurring not just at perigee, but at the closest perigee of the year. But many people got the impression that this was an exceedingly unusual event, and rushed to see and capture images of this supposedly ultra-rare moon. Depending on how closely you require the full moon to occur to perigee in order to call it a supermoon, though, these events happen at least roughly once a year, and often more frequently.</p>
<p>Which brings us to this month’s much ballyhooed “super-supermoon.” News stories are hyping the upcoming full moon as a once-in-a-lifetime viewing opportunity. It’s true that the Nov. 14 full moon is the <a href="http://www.astronomy.com/observing/news/2016/11/theres-super-hype-for-this-months-super-moon">closest since 1948</a>, and the next time the full moon will be closer is in 2034.</p>
<p>But this month’s full moon is only 0.02 percent closer – a mere 41 miles! – than the March 2011 supermoon. These tiny distances make no noticeable difference in the moon’s appearance. </p>
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<a href="https://images.theconversation.com/files/144949/original/image-20161107-4694-1f5evl6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/144949/original/image-20161107-4694-1f5evl6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/144949/original/image-20161107-4694-1f5evl6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=533&fit=crop&dpr=1 600w, https://images.theconversation.com/files/144949/original/image-20161107-4694-1f5evl6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=533&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/144949/original/image-20161107-4694-1f5evl6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=533&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/144949/original/image-20161107-4694-1f5evl6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=670&fit=crop&dpr=1 754w, https://images.theconversation.com/files/144949/original/image-20161107-4694-1f5evl6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=670&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/144949/original/image-20161107-4694-1f5evl6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=670&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Get out there and enjoy this supermoon!</span>
<span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Missouri-Daily-LIfe/26c430a53589446ea7ccd3368553f4be/1/0">AP Photo/Charlie Riedel</a></span>
</figcaption>
</figure>
<p>Please do go out and observe the November full moon. If you are good with photography, try to document that the moon does appear larger than the other months this year. Just be aware you’ll have other virtually equivalent opportunities to do so pretty much every year for the rest of your life. So don’t worry if you miss it. You can catch the supermoon next time around.</p><img src="https://counter.theconversation.com/content/68270/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Christopher Palma 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>Full moons are good reason to look up – and the one on Nov. 14 is no exception. But here’s why you likely won’t see something shockingly different from other full moons you’ve observed over the years.Christopher Palma, Senior Lecturer and Associate Department Head for Undergraduate Programs in Astronomy & Astrophysics, Penn StateLicensed as Creative Commons – attribution, no derivatives.