# Is it possible to go faster than the speed of light in vacuum?

If it is possible for particles to go faster than the speed of light in certain events, would it be possible to create a situation in which the barrier of the speed of light can be crossed?

• But it isn't, so no. – Jon Custer Jan 5 '16 at 16:22
• Particles can only go faster than the speed of light in a medium. Light is slowed down in optically dense media, but it might happen that high-energy particles move faster than that (Cherenkov effect). – ahemmetter Jun 15 '18 at 7:19

No. According to Special Relativity, speed of light is the maximum speed at which anything can travel through free space. And there are no known violations of Relativity.

• Dark energy violates dominant energy condition and is in agreement with observations. – Mikey Mike Jan 5 '16 at 16:27

If you had a magic rocket with unlimited fuel, and if your body could withstand any acceleration, then there would be no lower bound to how quickly you could get from one place to another in your own proper time. You could travel from here to another galaxy and back in a matter of minutes, but...

...if you sent a powerful radio message to that galaxy before you took off, you would never be able to catch up to it, and...

...when you returned, you would find that millions of years had passed on Earth while you were away.

• There actually are minimum times: in order to reach a high enough speed, you need to carry a rocket producing a lot of energy, which may create a black hole eventually. – fffred Jan 5 '16 at 17:35
• That is false. Even if your body could handle any acceleration, you wouldn't be abe to travel faster than light and light takes more than "a matter of minutes" to travel between galaxies. – thermomagnetic condensed boson Jan 5 '16 at 17:49
• @no_choice99, I did not say you could travel faster than light. In fact, I explicitly said that you would not be able to catch up to a light beam (radio signal) that was making the same trip. I explicitly said that millions of years would elapse on Earth while you made the trip. But your subjective experience of the trip could, in theory, only seem to take a few minutes. – Solomon Slow Jan 5 '16 at 18:36
• @fffred, :-) Obviously I wasn't thinking out all of the details. I guess it's risky when you start a hypothetical with, "Assuming we could do the impossible,..." There's also a little detail of radiation exposure (if that's the right word for it) as you and your magic rocket collided with the occasional stray hydrogen atom out in the intergalactic medium. – Solomon Slow Jan 5 '16 at 18:38
• @jameslarge in this case could you edit your post and replace subjective time by proper time? Else I can't remove my downvote. – thermomagnetic condensed boson Jan 5 '16 at 19:01

No, it's not possible. All objects slow down their systems with time by a factor of $\frac{1}{\sqrt{1 - \frac{v^2}{c^2}}}$ and contract in length by a factor of $\frac{1}{\sqrt{1 - \frac{v^2}{c^2}}}$ in their direction of motion. If you exert a constant force on a particle with mass, as it gets closer to the speed of light, its time dilation and length contraction keep getting bigger so it can never quite reach the speed of light.