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Light speed

  1. Feb 20, 2009 #1


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    So let me first off say i probably have no idea what im talking about. I am simply a junior in high school whos only knowledge of physics is that of what i try to research on my own time. I really do like it though.

    But it is my understanding that light speed is a consistent rate and no matter how fast you are moving you can not increase the speed of light.

    So here is the question:

    If you were in a spaceship moving at 99.5% the speed of light from left to right and you turn on a light inside the cabin which made the light travel left to right. Would you be able to see the light go across the room in a like slow mode manner due to your speed is so close to that of light or would it be instant due to time relativity? or do i just not have a clue what i'm talking about?

    (ps this is not homework)
  2. jcsd
  3. Feb 20, 2009 #2
    All observers will always measure light at c, regardless of their speed. Both the people on your ship and people that are stationary relative to it (Earth), would measure the light moving at the normal speed of light. It would be due to time dilation, and length contraction.
  4. Feb 20, 2009 #3
  5. Feb 20, 2009 #4
    It turns out that you'll measure the light to travel at c anyway, and so will someone standing outside the ship who is considered motionless. The reason is that you register, say, 1 tick on your clock and the motionless guy registers, say, 500 ticks. Read up on it, you need to learn about how waves (like sound) behave and about the Lorentz transformations.
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