Question about relativity theory

Originally posted by masterp

Originally posted by Anyndur
Hey, I was reading Einstein's relativity theory, but there's something that I read about lightspeed that seems to be, well, wrong.
The part where he says that the lightspeed is a constant, doesn't matter where it is, it will always be the same.
Look this hypothetical situation: if we could, somehow, put a light source to travel at 99% of the lightspeed, and them we could, somehow, watch this light while traveling at the same speed as the light source. Ok so far, according to Einstein, we would see the light at 300,000 km/s. But, at the same time, we have a person observing and measuring the speed of the light generated by the source traveling at 99% of the lightspeed, but he is standing still. There, he would see the source travelling at 99%, and, according to Einstein, the light generated by it would be at 100% the lightspeed. Well, that would be 1% for us who are watching at the same speed that the source. There, the lightspeed wouldn't be a constant.

I'm right with my thoughts? Share your opinions here please. Thanks.

Nope, you are wrong.

What Einstein actually said is that light is MEASURED 100% constant in different frames of reference. He did not say that light travels with constant speed.

So, if you are an observer standing still, watching a beam of light travelling at 99% of C, the images coming toward you, made of light, will travel with the speed of light.

In other words, you will watch the changes with the speed of light, but light will actually travel slower. So you will actually be able to see the light beam edge.

On the other hand, if you moved, let's say on the opposite direction, with speed C, you would not see anything, because light from the other beam would never catch you.

If you moved with speed less than C, let's say 95%, you would catch a glimse of the other beam, as if it was almost frozen in time, because light from the other beam would catch you slowly.

The tricky part lies in the concept of 'observing'. In order to observe something, a particle, let's say a photon, would have to travel from the source to you. When you observe a beam of light, you don't actually observe the beam of light, but the photon particles are accepted by your eye with a delay. These photon particles that got away from the light source travel at C, even if the light itself moves in less than C.

You are very wrong. The speed of light is constant in all reference frames.

If I am approaching you at the .999999C and you shine a light of photons at me. The velocity that Ill measure the lightwaves with is C....