Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Can you see inside a space ship moving at the speed of light?

  1. Nov 1, 2013 #1
    Lets pretend I am in a space ship and I am moving at the speed of light. There is a light bulb at the center of the ship. I understand that velocities don't simply add together, and the formula is v[itex]_{3}[/itex]=[itex]\frac{v_{1}+v_{2}}{1+\frac{v_{1}v_{2}}{c_{2}}}[/itex]. So the light would not be moving in your frame of reference. So if you look behind you, you would see darkness. But if you look in front of you, you could not see the light reflect off of the front walls of the ship, but couldn't you see the light that started in front of you? because that light would simply go toward you. I think if you looked behind you, you would see darkness. If you looked in front of you, you would see constant light. What do you think?
  2. jcsd
  3. Nov 1, 2013 #2


    User Avatar

    Staff: Mentor

    That's like saying "Let's pretend that there is an odd number that can be evenly divided by two..."; you'll be able to derive all sorts of strange and wonderful results, but they'll all be bogus because the premise itself is bogus.

    In particular, the addition of velocity formula you're trying to use is derived from assumptions that are inconsistent with any observer moving at the speed of light, so if you try using it in your "let's pretend" scenario, the results of the calculation will be bogus.
    Last edited: Nov 1, 2013
  4. Nov 1, 2013 #3

    D H

    User Avatar
    Staff Emeritus
    Science Advisor

    A spaceship cannot move at the speed of light. You essentially are asking "what do the laws of physics say will happen if we violate the laws of physics?"

    It's a nonsense question.
  5. Nov 1, 2013 #4
    As I understand it, if you were moving at the speed of light you would not see anything at all because time would literally stop for you.
  6. Nov 1, 2013 #5


    User Avatar
    Science Advisor

    The whole point of "relativity" is that speed is always relative to some other reference. If you were in a space ship moving, relative to me, at any speed less than the speed of light, you would see nothing at all different. Relative to the space ship you are motionless.
  7. Nov 1, 2013 #6


    User Avatar

    Staff: Mentor

    Not only is that not right, but it's also not the result that you get if you try setting your speed equal to the speed of light in the various equations of relativity.

    One way of seeing this: Right now you are moving at 99.99999999% of the speed of light relative to some observer somewhere in the universe. Are you experiencing even the least little bit of "time slowing down"?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook