4

Have we tried in the past to run tests or do research to reach the speed of light ?

Taher
  • 1,057
  • 1
  • 12
  • 23
  • 1
    If single electrons and protons can't do it, it would be kind-of silly to try it with a rocket! – uhoh May 28 '18 at 13:01
  • 4
    @uhoh I think higher energetic CERN neutrinos aren't too far away from it :-) – peterh May 28 '18 at 13:44
  • Particle accelerators try to accelerate charged subatomic particles to as close to the speed of light as possible, as the comments above are alluding to. That makes this a question for [Physics.SE]. – kim holder May 28 '18 at 14:36
  • Yes, but we could write books about it. So your question is a bit too broad here. –  May 28 '18 at 15:08
  • @peterh the question is about accelerating things, not measuring their speed. Rockets are made of (roughly speaking) electrons, protons, and neutrons (and yes virtual stuff) and of those, two are charged and can be easily accelerated. Neutrons and neutrinos... not so much. – uhoh May 28 '18 at 16:05
  • @uhoh I dunno, sick a couple billionaires on it, they love building rockets. – corsiKa May 28 '18 at 16:09
  • 1
    @uhoh I am not a physicist, but as far I know, the acceleration itself is not a very well defined thing in the QFT. The accelerators are accelerating mainly protons or electrons, and then measure what is coming from their collisions. – peterh May 28 '18 at 16:11
  • 2
    @peterh Well acceleration is a very well defined thing in accelerator physics! Anyway, neutrinos only go faster than light in Italy, and then only before 2012. https://en.wikipedia.org/wiki/Faster-than-light_neutrino_anomaly and also BBC: Neutrino 'faster than light' scientist resigns and also Science: Once Again, Physicists Debunk Faster-Than-Light Neutrinos. – uhoh May 28 '18 at 16:16
  • 1
    @uhoh This comment tried to say only that a GeV order neutrino is quite close to $c$ in our reference frame. – peterh May 28 '18 at 16:30
  • 1
    @peterh oh I understand. I just like using any opportunity to reference the loose connection (wire, or fiber) that made some people take FTL neutrinos seriously, instead of hunting down the loose connection until they found it. – uhoh May 28 '18 at 16:33
  • 1
    From Wikipedia: "Since it is established that neutrinos possess mass, the speed of neutrinos of kinetic energies ranging from MeV to GeV should be slightly lower than the speed of light in accordance with special relativity. Existing measurements provided upper limits for deviations of approximately 10E−9, or a few parts per billion. Within the margin of error this is consistent with no deviation at all." – Uwe May 28 '18 at 19:18
  • 1
    @uhoh Ok-ok :-) But I didn't tought on that FTL thing, I've tought only for that a neutrino with the rest mass of some tenth $eV$, but with the energy of some tens $GeV$, is the most relativistic thing what we ever produced. – peterh Jun 03 '18 at 04:05
  • @peterh Yep that's very clear. I'll remove your username from the comment and repost. I just like the podcast. – uhoh Jun 03 '18 at 04:10
  • 1
    There's a humorous summary of the FTL neutrino debacle in the BBC podcast Can Anything Travel Faster Than Light? Discovery, The Curious Cases of Rutherford and Fry Episode 4 of 5 between about 07:15 and 13:40 involving someone not eating their underwear ;-) https://twitter.com/jimalkhalili/status/117160630527594496 – uhoh Jun 03 '18 at 04:11

1 Answers1

15

Not on macroscopic scale. The Special Relativity theory is fairly well understood and says it's impossible for any objects that possess rest mass, period. The closer you get to speed of light the more energy you need to accelerate, additional energy gets increasingly converted towards mass instead of velocity, so to actually reach it you would need infinite energy and your spacecraft would become infinitely heavy.

The observed non-massless object that was closest to speed of light, known as "Oh-my-god particle", reached 99.99999999999999999999951% of speed of light; it was a proton, and it had 48 joules of energy - equivalent to a baseball travelling at about 26 m/s (94 km/h; 58 mph). Its mass was therefore about $5.28×10^{−16} kg$ - normally, a proton at rest weighs $1.673×10^{−27} kg$ so, due to all that energy, its mass was 315,000,000,000 times higher than at rest - and yet it didn't reach speed of light.

So, we are fairly sure that no, achieving speed of light normally is not possible.

There exists a theoretical solution, a kind of hack that would allow travel faster than light, without actually breaking Special Relativity - while the craft would travel below speed of light, specific curving of space-time around it would allow that chunk of space to travel relative to surrounding space at an extra speed. This is the concept behind Alcubierre Drive. And it's a very nice idea except nobody has any shade of a clue how to curve space like that. Especially that while we can stretch it by placing a massive object, there's no known way to do the reverse: compress it.

What IS being researched is spacecraft that would get somewhere into range of a couple percent of light speed. And we have a draft of something that can work and might be created within our lifetimes: Breakthrough Starshot. It would be based on minuscule probes a couple centimeters big, equipped with solar sails and propelled by mighty ground-based lasers, to about 20% of speed of light, towards Proxima Centauri.

This is still only a concept, and there are still many unresolved problems about it (e.g. we don't have any means of the probe to communicate its findings back, no way to fit a radio good enough on it.) But the propulsion part is fully realistic.

Accelerating humans near speed of light though? Not anytime soon. Maybe if we get nuclear fusion under control we could begin thinking of fusion-based rocket engines that could get somewhere into the ballpark. Otherwise we'll have to tame anti-matter, which might allow reaching somewhat relevant speeds - except as of now, it's not only impossibly expensive, we simply don't have any means to harness its power output into a form of propulsion.

SF.
  • 54,970
  • 12
  • 174
  • 343