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Help me answer a question about light speed and relativity?
OK, so I want to race my spaceship against some photons, from point A to point B.
Ignoring the problems of energy and acceleration, my spaceship starts at point 'A' at 500,000,000mph.
You are holding the laser beam I will race against, also standing at point A.
We begin. From your perspective I am leaving at 500,000,000mph, and you measure the light as going 670,000,000mph. So, logically, you would assume the light is going 170,000,000mph faster than me.
In the spaceship, while going 500,000,000mph, I am still measuring the light as going 670,000,000mph. Common sense would expect me to think you are seeing this light going (500m+670m) 1,170,000,000mph.
So far I understand all this. This is where I get confused.
Assume there is a point C along our line.
I would expect the light to hit point C much faster than you would expect it.
SO, when does light hit this point (as observed from someone standing at point C)?
Thanks.
Also I am posting another relativity/light speed question, so please look for it =)
3 Answers
- Jeff in DallasLv 41 decade agoFavorite Answer
You are measuring things here based on time, which is not absolute under relativity.
The light would reach point B faster than. How many seconds faster depends on the observer.
This is called time dilation. Time will be different for you, the particle of light, and the observer. There is not one consistent measure of time between those three.
Observers at point A and C will measure things the same, they are both stationary and not moving RELATIVE to one another.
- 1 decade ago
But common sense is wrong. Haha. The light would reach point C faster than you because it genuinely is traveling faster than you. The idea that someone back at point A would measure the light at 1.17 billion mph is flawed. That would go against relativity.
- Anonymous1 decade ago
It hits point C quickly in your reference frame and takes a while in A's reference frame. The time you measure is different from the time that A measures. The distance to C that you measure is also different from the distance A measures.
