Light emitting from an object moving near the speed of light.

  • #1

Main Question or Discussion Point

I am writing a storyline that has a battle scene that takes place in space. I was wondering, if one ship fires a small projectile at a speed nearing that of light, and it is emitting light, will the space ship it is being fired at be able to see the shot for more than a few milliseconds before it hit them?

Assuming that the ship firing is about a million (1.2million) miles away, and given that light travels about 186,000 miles in a second, there should be about a six second delay, but if the projectile is traveling .9 * (constant, the speed of light), for how long will it be detectable before impact?
 

Answers and Replies

  • #2
ghwellsjr
Science Advisor
Gold Member
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If the ships are 6 light years apart, then it will take 6/0.9=6.667 seconds for the projectile to make the trip, giving the target ship 666 milliseconds warning, assuming they can see the launch of the projectile. If you are thinking that they can only see the light being emitted by the projectile when it gets closer to them, then they will have proportionally less time. For example, if they cannot see it until it is halfway there, then they will have only 333 milliseconds.
 

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