For a moment, assume that travel at/over the speed of light is possible, and we fire a laser in front of us, what happens to the light emitted from the laser?

Would the photons scatter, or would the light only move at light-speed (that is to say, without a visible source).

Edit: To add to this, I realise that the light would be doppler-shifted.

  • $\begingroup$ From the Help Center: Questions about physics of fictional worlds which are not sufficiently grounded in real physics are off topic here. This question is asking about a situation that is verboten with real physics. $\endgroup$
    – Kyle Kanos
    Aug 6, 2014 at 20:59
  • $\begingroup$ An edit : assume that at or near speed of light travel is possible. If this question seems wrong then Einstein shouldn't have asked it too. $\endgroup$ Aug 6, 2014 at 21:29
  • 1
    $\begingroup$ @AndresSalas, you've materially changed the question with your edit and, further, this edit makes the only answer given inappropriate. I consider this bad form and so I'm rolling back your edit. $\endgroup$ Aug 6, 2014 at 21:55
  • $\begingroup$ It is possible to move faster than the speed of light in a medium, so I'm not sure it's appropriate to flag this question as non-mainstream physics. In that case, as always, the speed of the light is independent of the speed of the source. $\endgroup$
    – benrg
    Aug 6, 2014 at 23:16
  • $\begingroup$ @benrg: non-mainstream covers fictional physics. Surely photons can exceed $c_m$ for media $m$, but it does not mean that spaceships/people can exceed $c$. $\endgroup$
    – Kyle Kanos
    Aug 6, 2014 at 23:28

1 Answer 1


For the observer traveling faster than the speed of light the light of the laser must appear to move away from him at the speed of light.

For the observer in the rest frame, the laser light travels slower than the person firing it.

I conclude that time is moving backwards for the guy with the laser...

But seriously - we are breaking laws of physics here. I think it should be anyone's guess what happens when you do that...


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