In Star Wars, there's some shots where Jedi deflect lasers with their lightsabers. I know there's a law that says you can't go faster then the speed of light and lasers are light, so what is the smallest change in physics to make it so that you can deflect the lasers? This is challenging because some lasers go slow (blasters) and others go fast (Life destroying moon that was badly named, even star energy sucking base was bigger). Also, the graphics seem good, meaning the light from the people was functioning like real-life light.


@Renan's answer makes sense to me, but if the bolts are plasma, then how do the lightsabers deflect the bolts?


closed as off-topic by We are Monica., Halfthawed, Ash, Cyn says make Monica whole, pluckedkiwi Aug 6 at 13:49

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  • $\begingroup$ There may be a follow-on question here about momentum of a blaster's plasma shot and where that goes when deflected, vs when it strikes the target and throws them backward. $\endgroup$ – Criggie Aug 4 at 7:25
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    $\begingroup$ The edit seems to put the question in the realm of "How does X works in Y universe", which is more of a scifi.SE question. You can ask multiple questions there to answer the several you're craming here. Moreover, the information is readily available on Internet. I suggest a closing for being OOT until there is an edit. $\endgroup$ – Nyakouai Aug 5 at 8:12
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    $\begingroup$ @Criggie It's a bit like when someone is short with a bullet in real life: they tend to go flying backwards. Except, that only happens when they notice that they've been shot. Hollywood has shown people being shot with bullets flying backwards so often that people in real life being shot with bullets automatically/unconsciously jump backwards, because that's what they expect to happen. The bullet itself doesn't deliver nearly enough concussive force for that, and often goes through the person instead of pushing them $\endgroup$ – Chronocidal Aug 5 at 9:44
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    $\begingroup$ The main problem is that you've mistaken starwars for science fiction. Hero uses magical sword to defeat the armies of evil lead by a black knight and a sorceror and rescues the princess? It is a fantasy story, with x-wings instead of dragons, etc etc. Why can the magical sword deflect magical arrows? Because it is magic, duh. $\endgroup$ – Starfish Prime Aug 5 at 11:00
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    $\begingroup$ I can't upvote this as long as the question, and especially the Title, use the word "laser". It's not only misleading, it's just plain wrong. Note that this MythBusters episode - Wikipedia, analysed the Star Wars films and measured the blaster bolts as travelling at only 210 km/h (130 miles / hour). That's far far slower than a laser, and relatively easy to track with the eye (e.g. tennis balls can be hit faster than that). $\endgroup$ – Ray Butterworth Aug 5 at 12:37

Allow me to challenge the premises:

  1. The shots that the Jedi deflect are not lasers. From the Wookiepedia::

A blaster, also called a gun, was any type of ranged weapon that fired bolts of intense plasma energy, often mistaken as lasers.

  1. The force is a great source of ***-pulls. Since the Jedi are able to see the future, if the plot requires, a Jedi might just position their light sword already knowing where the laser will hit.

Now let's assume that there is no challenge to the frame, and let's take your question to heart.

(...) what is the smallest change in physics to make it so that you can deflect the lasers?

Take a page from Terry Pratchett's Discworld. In The LastContinent, we find this gem:

Light travels slowly on the Disc and is slightly heavy, with a tendency to pile up against high mountain ranges. Research wizards have speculated that there is another, much speedier type of light which allows the slower light to be seen, but since this moves too fast to see they have been unable to find a use for it.

So there are two types of light. Jedi could then see the incoming laser through usage of the faster light, and thus move in time to score a home run with their laser bats.

  • $\begingroup$ And what will you do if I don't allow you to change the premises? $\endgroup$ – El El Aug 3 at 23:24
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    $\begingroup$ @El El, Renan is not changing the premises. He is only applying the actual premises that the "lasers" are not actually lasers. $\endgroup$ – Bilbo Baggins Aug 4 at 1:11
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    $\begingroup$ Pedanticism: "a priori" doesn't mean "prior knowledge", but knowledge consisting of ontological proofs. See this Wikipedia article for details about the various wildly inconsistent ways the word is used. $\endgroup$ – wizzwizz4 Aug 4 at 12:03
  • $\begingroup$ @wizzwizz4 if you have seen the future, then you have ontological knowledge of future events, no? $\endgroup$ – Renan Aug 4 at 14:17
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    $\begingroup$ @Renan Knowledge, yes, but empirical (a posteriori). $\endgroup$ – wizzwizz4 Aug 4 at 15:35

This doesn't require any changes in physics. You simply deflect the lasers by predicting where they will hit and interposing the lightsaber or other light deflecting tool in the path of travel. You don't need to move faster than the light. You just move faster than the people wielding the laser weapons, blocking where they aim rather than waiting until they fire.

This may or may not have been the solution in Star Wars. The SFF.SE site would be a better place to ask about that. Or why lightsabers deflect light. Lightsabers are a technology so advanced as to be indistinguishable from magic. So if you want more details related to that, you should specify more about how your magical technology works. Then we could try to explain why it worked that way. Or frame challenge that it wouldn't.


This is challenging because some lasers go slow (blasters) and others go fast (Life destroying moon that was badly named, even star energy sucking base was bigger)

I challenge that the Death Star beam goes slow. You have plenty of time to see the thing form and travel. It ostensibly goes much, much slower than the speed of light. I don't think it's mentioned to be a laser either. Ultimately it doesn't matter, the Death Star is a plot device, you can't deflect plot devices anyways.

Let's say you're not set on lightsabers[1] and blaster bolts being made of lasers, because the movies never mentions them being lasers. If you delve deep into the Expanded Universe, you'll find many rationalisations of what is most likely just 1970s Hollywood science (the Kessel run in 12 parsecs anyone?). But when taken at face value, what the movies show ain't lasers at all.

In some "science of videogames" thing on Star Wars and lightsabers, Michio Kaku explains how we could, with today's technology, build a lightsaber. Something about a ceramic blade engulfed in hot plasma. The caveat here is you'd need a small nuclear reactor to power it, and you have a solid ceramic blade that's isn't very sexy. Still, the idea of plasma is also common in the Star Wars EU to describe blaster shots. Therefore:

Everything is plasma

Plasma can be summarily described as an ionised state of matter. Plasma can generate a magnetic field.

If you consider a lightsaber is a plasma torch (with the blade shaped not by some physical ceramic tube but rather with the Force or some complicated space-age technology) and magnetised, and consider blaster bolts are magnetised bits of plasma, then it's magnets being repelled and that's just science.

It might also explain why lightsabers don't cut each other, because their magnetic fields don't allow them to pass through. And it also explains how some materials are impervious to lightsabers, since, as mentioned, some ceramics can sustain a whole lotta heat.

Okay but actually want to shoot real lasers too

What you're looking for here is refraction. Simply put, when light changes medium (going from air to water for instance), it turns slightly. You can observe this with a glass of water, and then moving your finger behind the glass. You'll see a lot of weird things happen to the image of your finger. That's light being refracted.

Now your lightsaber blade is a hot plasma. This is an inherently different medium from breathable air. A laser being made of light will be refracted, and appear to be deflected. Now I'm not sure you could deflect a laser back that way, but you can conceivably deflect them away from your person and that should be good enough.

Reaction time

As for being able to react in due time, as @Renan mentions Force-users seem to have the ability to feel the near future. It might be best illustrated in A New Hope when Luke deflects his first blasters from the training remote, explaining

I did feel something, I could almost see the remote.

It's not really clear how it works, but it evidently does work.

[1] In some languages, they're actually called lasersabers, but we can chalk it up to bad translation. Especially when the title translates to The Star War.

  • $\begingroup$ Actually, in the wookipedia page about the Death Stars beam of mass destruction, it's this: starwars.fandom.com/wiki/Superlaser $\endgroup$ – El El Aug 5 at 17:30
  • $\begingroup$ @ElEl Officially it's a "superlaser", and that entry is careful to not call it a regular laser. It probably knows it's way too slow (in the order of a fifth of the speed of light), you shouldn't be able to see it at all in vaccuum, and the way it combines into one big beam makes it closer to Captain Planet than an actual laser. But like I said it doesn't matter what it is, because you aren't going to deflect something with enough energy to destroy a planet with a lightsaber. It's just a cool weapon with a cool name. $\endgroup$ – AmiralPatate Aug 6 at 6:45

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