Is the speed of light today same as the speed of light billions of years ago????

Question

Cant we find this using the lights reaching us due to gamma bursts which takes place billons of miles from earth and whos rays reach us after billion of years after the stars have born....

Answer 1

Yes, and according to Einstein it is constant...regardless of time, place or circumstance.

Answer 2

Well... the jury is out. There is another 'constant' called alpha which is the fine structure constant. Alpha is the inverse of the speed of light. Problem is - they are both supposed to be constants and yet, scientists have recently (2001) measured an increase in alpha over the last 12 billion years. Since 'c' is the inverse of alpha... it necessarily would change the speed of light as well. The first responder was correct in that if this is true - it would throw a monkey wrench into Einsteins theory of relativity but it would clear up questions like why the temp of the universe is near constant.

By the way, I just saw your other comments below the question... actually we can't simply use the light reaching us as evidence. One reason is: The light may have travelled at many speeds to get here - calculating the 'average' speed does not insure that it did not vary.

Answer 3

You asked an excellent question. Physicsts have long been pondering questions like yours, but they ask a more general question, which is: is the "Laws of Physics" the same for all time and everywhere?"

Of course, currently we do not know a definitive answer to this question. For most practical purposes, physicsts assume the answer is "Yes". But there are String Theorists today who have proposed (with good reasons) that the Big Bang itself may have been the result of the "Laws of Physics" making a big change, and that prior to the Big Bang, our Universe wasa very different Universe (it was actually microscopic - no bigger than the size of an atom, and the laws of physics it had was completely different.) For whatever reason, the Universe spontaneously changed, and the new laws of physics that took over initiated a tremendous expansion of 3 spatial dimensions. And over the last 14.7 billion years since the Big Bang, the laws of physics most probably have undergone very minute changes.

As for finding the light that traveled from the other side of the Universe and from a very distant past, that alone would not tell us if the speed had changed, and also the gamma ray bursts were from hundreds of millions of years after the Big Bang, so very unlikely to have had a different speed than today. BTW, those gamma ray burst were from super massive blackholes that are currently inside the core of every observable galaxy. So quasars are the precursor to the galaxies we see today.

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Sorry, I just want to respond to some of the answers above:

(1) if the speed of light did change over time, this does NOT alter Einstein theory of Special Relativity one iota. Because his theory assumes only that the speed of light is constant for all reference frames in constant motion. It never assumed that the speed of light had to be constant for ALL times. So whatever speed it was several billion years ago, Special Relativity would have applied equally. So no money wrench there.

Answer 4

This is a really intriguing question. The speed of light is set to be constant, but the universe is expanding so there is more space/time for light to travel through. The distances however are unimportant. Lorentz contractions correct for the changes in distance.

Answer 5

How can the speed of light be the same ? There was no vehicle then? Speed of light coming from a static object and that the same erupting from a Boeing 747 cannot be the same. Velocity of the aircraft will be the differential.

Answer 6

just a thought:

The speed of light must be able to be altered for black holes can trap light so whats to say that other factors cannot harbor the speed?

Gravity? X-Rays? Bad Television? (j/k)
I'm certain in a controlled enviornment, the speed of light is constant I'm just saying that other factors should be considered before assuming thats it is constant in the "enviornment".

Answer 7

Yes, the speed of light is a constant.

Answer 8

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Answer 9

Common sense, speed of light will never change.

Answer 10

Scientists aren't sure. Here's what it says on wikipedia. I saw an article somewhere recently about this and there is evidence that it may not be constant.

Answer 11

yes i think that it will not change over billions of years because we have the relation frequency*wavelenth = speed of light