tag:theconversation.com,2011:/au/topics/lightsabers-23337/articles
lightsabers – The Conversation
2017-12-14T11:16:56Z
tag:theconversation.com,2011:article/89102
2017-12-14T11:16:56Z
2017-12-14T11:16:56Z
Here’s how a real lightsaber would fare in a Star Wars-style lightning attack
<figure><img src="https://images.theconversation.com/files/199013/original/file-20171213-27572-pkh3rg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Watch out for that cloud, Rey!</span> <span class="attribution"><span class="source">Walt Disney Studios Motion Pictures / Lucasfilm Ltd. / Everett</span></span></figcaption></figure><p>With the latest film in the Star Wars saga hitting cinemas, it got me thinking about lightsabers – the iconic weapon of Jedi and Sith alike. Despite their name, these glowing blades would in fact be made of the stuff I research – a soup of charged particles called “plasma”. This is sometimes known as the “<a href="https://www.youtube.com/watch?v=_SoKuW1-Yf4">fourth state of matter</a>” in addition to solids, liquids and gases.</p>
<p>As I’ve <a href="https://theconversation.com/why-lightsabers-would-be-far-more-lethal-than-george-lucas-envisioned-55726">previously shown</a>, real-life lightsabers would theoretically be possible, though horrendously impractical and somewhat beyond our current technological capabilities. Essentially, glowing hot plasma could be shaped into a blade by using strong magnets in much the same way we do for current nuclear fusion reactor experiments.</p>
<p>The downside would be lightsaber battles. A fundamental plasma physics process called <a href="http://www.nasa.gov/content/goddard/science-of-magnetic-reconnection">magnetic reconnection</a> would be unavoidable when two blades got close enough to clash. The entire pattern of the magnetic field lines would change, explosively releasing all the hot plasma contained in both lightsabers. The likely result is that both you and your opponent would have body parts vaporised in a single clash.</p>
<p>Something of a disappointment. And so I wondered whether the lightsaber would be up to the task against a different form of attack from the films – lightning. The earlier films showed us that lightsabers seem to absorb or block “<a href="http://www.starwars.com/databank/force-lightning">force lightning</a>” attacks, but would the same happen for a lightsaber that obeys the laws of physics?</p>
<h2>Mysterious force</h2>
<p>Thunder and lightning have been the subject of speculation and scientific inquiry for at least 2,500 years. Ancient Greek philosopher <a href="https://en.wikipedia.org/wiki/Empedocles">Empedocles</a> thought that the sun’s rays hitting clouds caused fires which would quickly drive out air causing a noise, thunder, and a gleam, lightning. It wasn’t until some 2,000 years later that <a href="https://en.wikipedia.org/wiki/Electric_charge">the discovery of electric charges</a> started to reveal the true, but incredibly complex, nature of the phenomenon that scientists <a href="https://theconversation.com/thunderstorms-create-radioactivity-scientists-discover-87946">are still investigating to this day</a>.</p>
<p>Despite the fact that we still have a lot to learn about lightning and its many forms, there is a general consensus surrounding some of the basic concepts of how and why it occurs. The conditions in storm clouds lead to an updraft carrying light ice crystals which then collide with hail suspended in the clouds. These collisions result in static electric charges, which build up at the top and bottom of the cloud.</p>
<p>Thunder clouds are actually incredibly tall, around 10km, so the bottom of a cloud is actually closer to the ground than to the top of it. This means an electric field builds up in the air between the ground and the cloud. Normally, air, being a gas, is a pretty poor conductor of electricity – meaning currents aren’t able to flow through it. However, when the electric fields get large enough they can knock electrons off the air molecules, forming channels of plasma.</p>
<p>Plasmas, unlike gases, are great conductors of electricity – in fact, many laboratory plasmas are comparable with most metals in this regard. This is because plasmas contain loose electrons (negatively charged) and atoms that have lost electrons (positively charged). It’s the much lighter electrons which really allow electricity to flow within a plasma.</p>
<p>The flash of lightning occurs when a plasma channel connects the ground to the cloud, allowing huge currents to flow which superheat the air causing it to glow and emitting an audible shockwave or thunder. This all happens incredibly quickly though, typically lasting about 30 microseconds.</p>
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<p>But, if lightsabers are also made of plasma, that would make them fantastic conductors of electricity, too. Just like the lightning rods on buildings, a lightsaber would provide a low resistance path for electrical currents to flow to the ground – making them far more likely to be struck by lightning than anything in the surrounding area. </p>
<p>However, the easiest way for that current to flow to the ground after it hits the plasma blade would be to travel through your body, which is a fairly good conductor too. So a wielder of a real-life lightsaber would be prone to direct lightning hits and therefore subject to severe burns, burst blood vessels and potential cardiac arrest.</p>
<p>Given that in one of the <a href="https://www.youtube.com/watch?v=W4CB5SeBGkI">latest trailers</a> Rey is shown wielding a lightsaber during a rainstorm, I’m worried she might not survive to the end of the film.</p><img src="https://counter.theconversation.com/content/89102/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Martin Archer 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>
In Star Wars, ‘force lightning’ is a lethal weapon that can only be tackled with a lightsaber. But would it work in real life?
Martin Archer, Space Plasma Physicist, Queen Mary University of London
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/55726
2016-04-04T11:24:19Z
2016-04-04T11:24:19Z
Why lightsabers would be far more lethal than George Lucas envisioned
<figure><img src="https://images.theconversation.com/files/116957/original/image-20160331-6126-1fronht.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">You may want to be careful with that, Darth!</span> <span class="attribution"><span class="source"> Kenny Louie/Flickr</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>Research is an unpredictable process. Sometimes you end up making a really cool discovery that you didn’t see coming. I recently uncovered a fundamental property of lightsabers (that’s right – the awesome weapons from Star Wars) while doing my regular plasma physics research. I found that, while it is in theory possible to build a lightsaber, it’s likely it would be the most dangerous weapon ever created – both for the perpetrator and the victim.</p>
<p>With <a href="https://theconversation.com/the-force-awakens-a-sugar-high-but-not-a-great-movie-49543">Star Wars: The Force Awakens</a> being released on DVD after breaking all kinds of records at the box office, I figured it was a good time to share the news. </p>
<p>Despite the name, it has been established in <a href="http://starwars.wikia.com/wiki/Lightsaber">Star Wars canon</a> that these ancient weapons of the Jedi are, in fact, not laser swords but blades of plasma. Plasma is often known as the “<a href="http://pluto.space.swri.edu/image/glossary/plasma.html">fourth state of matter</a>” in addition to the solids, liquid and gases that we’re all familiar with here on Earth. However, plasmas are by far the most common state of all visible matter in the universe (excluding the mysterious “dark matter” or “dark energy”) comprising some 99%.</p>
<p>The thing that makes plasmas different from the other states is that they are composed of electrically charged particles – loose electrons (negatively charged) and atoms that have lost electrons (positively charged), despite having no overall charge. Any moving electric charge, such as those inside a plasma, creates magnetic fields and can also be manipulated using magnetic or electric fields – unlike a neutral gas.</p>
<p>Magnetic fields are the key to containing the plasma in a blade, they can counteract the pressure of the hot plasma trying to expand into its surroundings. This is exactly one of the approaches that have been developed in trying to harness nuclear fusion power, in which atomic nuclei (atoms that have no electrons) collide to form a new nucleus while releasing huge amounts of energy.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/116952/original/image-20160331-9712-17tuxjp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/116952/original/image-20160331-9712-17tuxjp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=506&fit=crop&dpr=1 600w, https://images.theconversation.com/files/116952/original/image-20160331-9712-17tuxjp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=506&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/116952/original/image-20160331-9712-17tuxjp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=506&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/116952/original/image-20160331-9712-17tuxjp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=635&fit=crop&dpr=1 754w, https://images.theconversation.com/files/116952/original/image-20160331-9712-17tuxjp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=635&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/116952/original/image-20160331-9712-17tuxjp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=635&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Wendelstein X - a nuclear fusion reactor in Germany.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Wendelstein_7-X">Max Planck institute/wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Fusion requires incredible temperatures so that the positively charged atomic nucleii can overcome their tendency to repel each other. We create these hot plasmas in <a href="https://theconversation.com/for-decades-a-distant-dream-the-countdown-to-nuclear-fusion-may-have-finally-begun-17801">doughnut-shaped fusion reactors</a> (“tokamaks”) which use strong electromagnets in the reactor walls to keep this plasma at bay. The largest <a href="https://theconversation.com/nuclear-fusion-the-clean-power-that-will-take-decades-to-master-41356">of these such experimental reactors</a> will be <a href="https://www.iter.org/">ITER (International Thermonuclear Experimental Reactor)</a> construction of which will finish in 2019 and which aims to finally be able to produce more energy via fusion than is put in to create, sustain and control the plasma itself.</p>
<h2>Mysterious glow</h2>
<p>There are two ways plasmas can emit light. The first is by being incredibly hot. The sun, for instance, is a ball of hot plasmas whose heat source comes from the fusion taking place in its core. All hot objects emit electromagnetic radiation with specific wavelengths. Their perceived colour depends solely on their temperature, going from red for lower temperatures and blue for higher temperatures. This is likely the source of a lightsaber’s glow – if you want a really dangerous lightsaber, you need a blue one.</p>
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<figcaption><span class="caption">Lightsaber discovery.</span></figcaption>
</figure>
<p>The other way plasmas may glow is very similar to how a fluorescent bulb works. By running an electrical current through a plasma, electrons can collide with the positively-charged atoms (dubbed ions), which raises their energy. It’s similar to picking up a ball off the ground and putting it on one of many shelves – this raises the ball’s potential energy, whereby the shelves represent the energy levels of the ions. But nature is inherently lazy and will always strive to go back to the lowest possible state of energy. Eventually the ball will roll off of the shelf falling back to the ground. The ions do this by releasing their excess energy as light – which could create the lightsaber glow. This light will be of a specific colour depending on the composition of the plasma.</p>
<p>While lightsabers do seem feasible from a physics point of view, the power requirements for such a device would be immense, especially given that it needs to be contained within the small lightsaber hilt. Huge advances in technology would be required to make lightsabers a reality. But there’s an even bigger problem which would come about if you were to ever have a lightsaber duel like in the movies.</p>
<h2>Powerful magnetic effects</h2>
<p><a href="http://www.nasa.gov/content/goddard/science-of-magnetic-reconnection">Magnetic reconnection</a> is a fundamental plasma physics process which can occur when plasmas with different magnetic fields collide. As the magnetic fields of each plasma get close to each other, the entire pattern of magnetic field lines changes and everything realigns into a new magnetic configuration – releasing huge amounts of energy. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/116979/original/image-20160331-28459-d8vms0.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/116979/original/image-20160331-28459-d8vms0.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=436&fit=crop&dpr=1 600w, https://images.theconversation.com/files/116979/original/image-20160331-28459-d8vms0.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=436&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/116979/original/image-20160331-28459-d8vms0.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=436&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/116979/original/image-20160331-28459-d8vms0.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=548&fit=crop&dpr=1 754w, https://images.theconversation.com/files/116979/original/image-20160331-28459-d8vms0.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=548&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/116979/original/image-20160331-28459-d8vms0.gif?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=548&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Two plasmas (with magnetic fields coloured blue and red) move towards one another where they meet and they reconnect, changing their magnetic field lines.</span>
<span class="attribution"><span class="source">ChamouJacoN</span></span>
</figcaption>
</figure>
<p>This is what essentially fuels the aurora or northern lights – energy from the solar wind is released when these particles collide with plasma inside Earth’s magnetic field under a specific set of conditions.</p>
<p>It’s from our studies of the conditions under which reconnection can occur in space that I was able to realise the problem with lightsaber battles. When two plasma blades clash it is almost impossible to avoid magnetic reconnection, with the results being an explosive release of the plasma contained in both sabers. This would mean that, if you were in a lightsaber duel, both you and your opponent would have body parts vaporised in a single clash! </p>
<p>Perhaps the makers of the coming two Star Wars films should make a note … then again who knows how “The Force” really works?</p><img src="https://counter.theconversation.com/content/55726/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Martin Archer 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>
Warning: you’ll never watch a lightsaber duel in the same way again after you read this …
Martin Archer, Space Plasma Physicist, Queen Mary University of London
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/50812
2015-12-17T10:47:56Z
2015-12-17T10:47:56Z
Star Wars inspired me to become an astrophysicist – and I wasn’t disappointed
<figure><img src="https://images.theconversation.com/files/106252/original/image-20151216-25618-19vf3az.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">© 2014 Lucasfilm Ltd. & TM</span></span></figcaption></figure><p>For nearly 40 years, the phrase “a long time ago in a galaxy far, far away” has resonated in popular culture – forever linked to the iconic opening credits of <a href="https://theconversation.com/uk/topics/star-wars">Star Wars</a>. When I watched the movie for the first time in 1978, at the tender age of ten, I was instantly entranced by its visions of alien worlds, lightsaber battles and the mysterious <a href="https://theconversation.com/how-star-wars-music-lets-us-feel-the-force-49337">Force</a> that “binds the galaxy together”. </p>
<p>Star Wars wasn’t the only reason I became an astrophysicist, but it certainly played its part. And so here I find myself four decades later, surveying 13 billion years of cosmic history and mapping events that really did happen a long time ago, in galaxies far, far away.</p>
<p>So how does the real universe compare with what we see on the silver screen? It would be easy to unpick all those places where the science in Star Wars doesn’t hang together, but then few sci-fi and fantasy films would fare well under that kind of forensic analysis. </p>
<p>But “the science of Star Wars” can be considered in a different light if we regard the films simply as fuel for our imaginations, inviting a host of “what if?” questions. Could you really <a href="https://theconversation.com/how-to-build-a-real-lightsaber-51000">build a lightsaber</a>? Could the <a href="https://theconversation.com/theres-more-than-one-way-to-destroy-a-death-star-disrupt-the-system-for-a-start-38238">Death Star</a> actually destroy a planet? Could you use a tractor beam to capture a spaceship? While most such questions flatly can be answered “no”, a little speculation can introduce audiences to some remarkable recent developments in real science.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/106278/original/image-20151216-25606-1x59kw1.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/106278/original/image-20151216-25606-1x59kw1.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/106278/original/image-20151216-25606-1x59kw1.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/106278/original/image-20151216-25606-1x59kw1.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/106278/original/image-20151216-25606-1x59kw1.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/106278/original/image-20151216-25606-1x59kw1.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/106278/original/image-20151216-25606-1x59kw1.png?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">
<figcaption>
<span class="caption">Future weapons?</span>
<span class="attribution"><span class="source">Lucasfilm</span></span>
</figcaption>
</figure>
<p>Take the question of hyperspace travel, for example. In sci-fi, travelling between the stars needs this convenient plot device because space is really, really big. Even the nearest star to the Sun is more than four light years away (one light year being the distance that light travels in one year, about 10 million million kilometres). Yet according to Albert Einstein’s theory of relativity – which a century ago revolutionised our understanding of space, time and gravity – nothing can travel faster than light. So does this immediately render the Millennium Falcon’s hyperspace jumps complete fantasy?</p>
<p>Let’s consider the other great 20th century revolution, quantum physics. This is what shapes our understanding of the atomic and sub-atomic world. On these scales the universe is “fuzzy”: the laws of physics are governed by uncertainty and randomness and have no respect for Einstein’s cosmic speed limit, with physicists now able to <a href="https://theconversation.com/teleportation-just-got-easier-but-not-for-you-unfortunately-17060">“teleport” sub-atomic particles</a> instantaneously across their laboratories. </p>
<p>For a century, we have striven to unify gravity and quantum physics with (so far, at least) only limited success. But some theories of quantum gravity suppose that on the very tiniest scales space is “<a href="https://theconversation.com/the-universes-resolution-limit-why-we-may-never-have-a-perfect-view-of-distant-galaxies-50993">foamy</a>” due to the fuzziness of the quantum world. It has been suggested that quantum foam may be permeated by “wormholes” that bridge the vast distances of interstellar space. Perhaps this could provide the key to the Falcon’s hyperspace flights.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/106279/original/image-20151216-25600-1rf6mdu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/106279/original/image-20151216-25600-1rf6mdu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=455&fit=crop&dpr=1 600w, https://images.theconversation.com/files/106279/original/image-20151216-25600-1rf6mdu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=455&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/106279/original/image-20151216-25600-1rf6mdu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=455&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/106279/original/image-20151216-25600-1rf6mdu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=571&fit=crop&dpr=1 754w, https://images.theconversation.com/files/106279/original/image-20151216-25600-1rf6mdu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=571&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/106279/original/image-20151216-25600-1rf6mdu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=571&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">If we could travel through wormholes, who knows what we’d find on the other side.</span>
<span class="attribution"><span class="source">© 2014 Lucasfilm Ltd. & TM</span></span>
</figcaption>
</figure>
<p>Unfortunately, however, quantum wormholes are almost unimaginably small, so it’s not clear how a spaceship could pass through one. That’s where movies such as <a href="https://theconversation.com/uk/topics/star-wars">Star Wars</a> (and, for that matter, Christopher Nolan’s <a href="https://theconversation.com/interstellar-gives-a-spectacular-view-of-hard-science-33991">Interstellar</a> – featuring an artificial wormhole found near Saturn) have to call upon a major dose of scientific licence. </p>
<p>But this doesn’t necessarily lead us to a scientific dead end: <a href="https://theconversation.com/the-search-for-dark-matter-and-dark-energy-just-got-interesting-46422">dark energy</a> – the exotic substance that cosmologists believe is driving the accelerated expansion of the universe – could have just the right properties to “blow up” a wormhole and hold it open.</p>
<p>Alas, we’re not even sure yet what dark energy is, far less ready to harness it for building hyperspace drives. But the innate strangeness of our real universe, from teleporting photons to dark matter, means that we shouldn’t completely rule out developing Star Wars-like technology in our distant future. And if it could happen in our future, in a universe of a 100 billion galaxies maybe it already has happened somewhere out there, long, long ago … </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/106281/original/image-20151216-25610-1bd3rkr.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/106281/original/image-20151216-25610-1bd3rkr.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/106281/original/image-20151216-25610-1bd3rkr.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/106281/original/image-20151216-25610-1bd3rkr.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/106281/original/image-20151216-25610-1bd3rkr.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/106281/original/image-20151216-25610-1bd3rkr.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/106281/original/image-20151216-25610-1bd3rkr.png?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">
<figcaption>
<span class="caption">Distant worlds.</span>
<span class="attribution"><span class="source">© 2014 Lucasfilm Ltd. & TM</span></span>
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<p>Arguably the most dramatic astronomical discoveries of the past few decades have come in the search for planets orbiting other stars. In 1978, when the first Star Wars film was released, most astronomers would have agreed these so-called <a href="https://theconversation.com/uk/topics/exoplanets">exoplanets</a> should exist. But it would take nearly 20 years before they were detected. Fast forward to 2015 and we’ve found thousands of them, and are closing in on the “holy grail”: an earth-like planet orbiting a sun-like star at a distance where liquid water could exist. We have even found a “Tatooine”: the roughly Saturn-sized <a href="http://www.space.com/12963-tatooine-planet-2-suns-star-wars-kepler-16b.html">Kepler 16b</a> orbiting a twin-star system in the constellation of Cygnus.</p>
<p>Could Kepler 16b be the home to Banthas, Jawas and the occasional Jedi knight? Probably not: with a likely surface temperature of minus 100, the ice planet Hoth is perhaps a better match. But as Episode VII fires the imaginations of a whole new generation of fans (and maybe a few budding astrophysicists) I look forward to falling under the Star Wars spell once more – content in the knowledge that the real universe is much richer, more surprising and just plain weirder than anything we will see on the screen.</p><img src="https://counter.theconversation.com/content/50812/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Martin Hendry receives funding from receives research funding from the Science and Technology Facilities Council.
</span></em></p>
Four decades later, I find myself surveying 13 billion years of cosmic history and mapping events that really did happen a long time ago in galaxies far, far away.
Martin Hendry, Professor of Gravitational Astrophysics and Cosmology, University of Glasgow
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/51000
2015-12-10T15:48:57Z
2015-12-10T15:48:57Z
How to build a real lightsaber
<figure><img src="https://images.theconversation.com/files/105290/original/image-20151210-7467-yqhtzr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">David James/Lucasfilm </span></span></figcaption></figure><p>As even casual Star Wars fans will know, lightsabers are probably the coolest weapon ever to make an appearance on the big screen. Lightsaber fights are so elegant that they are almost hypnotic and, even though not all of us might have a strong enough flow of Force running through our veins, a lightsaber in the right hand is by far the deadliest weapon to be found in the universe. </p>
<p>The idea behind a lightsaber is simple genius: a light-weight and immensely powerful tool that uses a blade of energy to not only slice up disciples of the Dark Side in a single blow but also act as an effective shield against laser blasts. So why don’t we have working lightsabers in real life? Surely physicists must be smart enough (and big enough Star Wars fans) to be able to produce one of these incredible objects.</p>
<p>The obvious way of building a lightsaber would be to use a laser, which can be seen as a particularly bright and directional burst of light. But even though laser technology is continuously striding towards more efficient and practical machines, we are still miles away from a working lightsaber. Let’s see why.</p>
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<p>The first challenge is making the blade of your lightsaber an acceptable size, let’s say around three feet or so. To do this, you would have to make the laser beam come to a stop at a certain point. This won’t be easy since light has a rather strong natural tendency to <a href="http://www.physicsclassroom.com/mmedia/waves/em.cfm">keep travelling</a> if it doesn’t encounter any obstacles. </p>
<p>One solution could be to place a small mirror at the tip of the blade. But can you imagine how embarrassing it would be to show up in the battlefield with a lightsaber surrounded by a whole supporting structure for a tiny mirror at its end? Apart from being really fragile, such a blade wouldn’t be able to hurt anyone.</p>
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<img alt="" src="https://images.theconversation.com/files/105291/original/image-20151210-7442-dr37bk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/105291/original/image-20151210-7442-dr37bk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=251&fit=crop&dpr=1 600w, https://images.theconversation.com/files/105291/original/image-20151210-7442-dr37bk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=251&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/105291/original/image-20151210-7442-dr37bk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=251&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/105291/original/image-20151210-7442-dr37bk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=316&fit=crop&dpr=1 754w, https://images.theconversation.com/files/105291/original/image-20151210-7442-dr37bk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=316&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/105291/original/image-20151210-7442-dr37bk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=316&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Passing the baton. Where the baton is actually a deadly laser weapon.</span>
<span class="attribution"><span class="source">Lucasfilm</span></span>
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<p>The second problem is that the blade will need a lot of power to be able to slice through materials. Welding lasers used in industry can do that but they typically require <a href="http://www.glassonweb.com/articles/article/20/">several kilowatts of power</a>. The power supply for these lasers is huge and would certainly not fit in the tiny hilt of a lightsaber. Plus you would need a considerable cooling mechanism if you didn’t want the hilt to become incandescent and to melt your hand.</p>
<p>Besides these more practical points, the amazing effects of lightsaber fights would be unfeasible. Two laser-based lightsabers would never clash against each other. They would simply pass through one another with no effect. What’s more, a laser focuses light in one direction so sharply that you <a href="http://physics.stackexchange.com/questions/20259/what-makes-some-laser-beams-visible-and-other-laser-beams-invisible">can’t see it</a> unless you look directly down its axis. This is the reason why lasers used in clubs need smoke or fog to be seen. The smoke particles act as tiny scatterers that spray the laser light and make the beams visible.</p>
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<p>But all is not lost. No one ever said a lightsaber had to be based on laser technology. An alternative exists already in the form of plasma. Plasma is effectively gas so hot that its atoms are broken into their more fundamental components, namely electrons and nuclei. They can be generated by applying powerful electrical discharges to a gas (lightning is an example) and are able to sustain searing hot temperatures as high as millions of degrees Celsius.</p>
<p>Most interestingly, hot plasmas tend to emit different colours depending on the gas they are made of. For example, a neon light is nothing but a tube filled with neon gas in a plasma state. The green lightsabers of Jedi knights could be made of chlorine plasma, which emits predominantly green light, while the red lightsabers of the Sith villains could be made of helium, which mostly emits in the red-to-violet <a href="http://www.plasma.de/en/glossary/glossary-entry-486.html">region of the spectrum.</a></p>
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<span class="caption">Anyone got a light?</span>
<span class="attribution"><span class="source">Lucasfilm</span></span>
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<p>How might a plasma lightsaber work in practice? A small but powerful power supply hidden in the hilt could be attached to a long and tiny filament that carries the electrical discharge and puffs some gas around it. When you turn it on, the filament would become incandescent and the gas around it would turn into plasma, emitting its colour in every direction. The searing heat of the plasma would instantaneously melt any object it touches, cutting cleanly like a blade.</p>
<p>You might still have an issue or two in making everything compact (where are you going to store the gas to be continuously puffed out of the filament?) and sturdy enough to resist a blow from another lightsaber, but it’s a good start. After all, the Galactic Empire wasn’t built in a day.</p><img src="https://counter.theconversation.com/content/51000/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Gianluca Sarri receives funding from the Engineering and Physical Sciences research Council, UK. </span></em></p>
It’s not easy – but we are moving in the right direction.
Gianluca Sarri, Lecturer at the School of Mathematics and Physics , Queen's University Belfast
Licensed as Creative Commons – attribution, no derivatives.