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Why does light travel at the same speed when measured by a moving observer? [duplicate]

I know the hypothesis that the light speed is constant is retained by experiments. But is there any theory explaining why the light speed is constant no matter how an observer moves relative to light? ...
2k views

Why the speed of light in vacuum is same in all inertial reference frames? [duplicate]

If Cathy’s velocity toward Bill and away from Amy is v = 0.9c, Cathy finds, by making measurements in her reference frame, that the light from Bill approaches her at speed c, not at c + v = 1.9c. And ...
3k views

Nothing can travel faster than the speed of light. In what frame of reference? [duplicate]

Since frames of reference are arbitrary, I can define a frame of reference that moves backwards with a speed greater than $c$, then any static object in that frame of reference is already traveling ...
528 views

Why is the speed of light in vacuum constant? [duplicate]

Are there any proof of the speed of light in vacuum being constant? All I hear is that light in vacuum travels at a constant speed because that's an observation and that it fits in a coherent theory ...
301 views

The Speed of Light [duplicate]

I know that the speed of light is constant for some reason. But why is it that when shining light from a spacecraft that is moving at (almost) the speed of this light, the speed of this light wouldn'...
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Why light can't go faster then 300 000 km/s? What prevents it? [duplicate]

Why can't the speed of light be faster then approx 300 000 km/s? What prevents it?
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How can the speed of light be independent of the speed of the observer [duplicate]

First of all, I saw few similar questions here but most of them address the question of why, when I want to address a question of HOW. Also one question is addressing the same problem but I find it's ...
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Does the speed of light change? [duplicate]

I know that there is a similar questions, but I think mine is a bit different. I wonder if with the expansion of the universe the speed of light changes. It seems that the speed of light is very ...
155 views

Can we have a photon at rest? [duplicate]

Theoretically, Photons don't have rest mass but they behave as material particles in many cases. But is it possible to stop a photon without destroying it ie. Can we slow it down so much to make it ...
298 views

How can light have the same speed for all observers? [duplicate]

I'm a little confused on this. If you're travelling at, say, 10% of the speed of light then light is travelling at 3x10^8 ms^(-1) relative to you. If you're moving at 80% of the speed of light and ...
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Speed of light constant for all observers [duplicate]

General relativity has been proven many times over to be correct. In my meager understanding of things, they are all premised on the fact that the speed of light is constant to all observers. I would ...
117 views

Special Relativity Explanation [duplicate]

I'm in a relatively basic Physics class in university, and was reading the section in my textbook about The Principle of Relativity. It says: Einstein's Theory of Relativity ... added the ...
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What is the speed of light from a star moving towards a observer.? [duplicate]

We can say that in vacuum speed of light is constant. But if the star is moving with a certain velocity does it add that velocity to the velocity of photons emitted out of that star?