Do we know with absolute certainty that the speed of light has always been a constant?

Question

Is it a proven fact that the speed of light has always traveled at the same speed as it does today since the beginning.

If possible, please list your source.

Answer 1

We know of no reason why it should be otherwise.

Why do people that base their life around faith always demand "proof" of things that don't fit their worldview? There's no "proof" Jesus was anything other than some guy who thought he was god.

Answer 2

No.

A much better question is this: Do you have any evidence to support the idea that the speed of light has ever been anything different?  Or are you just trying to jump to ignorant conclusions because they support your personal ideology and you're close minded to anything else?

Without evidence to support an idea (like the idea that the speed of light isn't constant) then you've got nothing.  Yes, it's *possible* that the speed of light was once different, but without any evidence of it, it would be rather ignorant to believe it.  It's *possible* that someone has placed a new Lamborghini in my driveway as a present for me, and I'll be a happy camper next time I go outside.

Science does not deal in absolute certainty, science deals in conclusions supported by evidence.  Any intelligent, reasonable person would do the same.

Answer 3

no

Answer 4

What force would make it travel faster?  Determine that factor and you have a reason to question it.  Otherwise, it's a constant...and good luck proving its not.

Answer 5

it is the uneversal speed limit,nothing travles faster and it remains at a constant speed of 186,282.40mps(in a vacume)and einstein proved this.but it changes when going thru a medium,but just a little.

Answer 6

The speed of light actually changes depending on the medium the light is passing through.  The speed of light in water is different from the speed of light in a vacuum or through a window (SiO2).  "For example, typical glass has a refractive index of 1.5, which means that in glass, light travels at 1 / 1.5 = 0.67 times the speed of light in a vacuum."

Now is the speed of light in a vacuum constant?  Yup,  the speed of light is constant by definition.  It is defined as 299 792 458 m/s.  That's a definition.

Now you can ask a couple of other questions:

1.)  Has the length of a meter always been a constant?

2.)  Has the amount of time in a second always been the same?

I guess so, but what was the universe like in the first fraction of a second after the big bang is really anyone's guess.  It's beyond our experience and we can only conjecture about it.

Answer 7

We can never know anything with "certainty".  We can know than all scientific observations so far, can be explained without assuming a changable speed of light (in vacuum).  Untill somebody sees something that can be explained only by assuming a changable speed of light, there is no reason to bring in that extra complication .

Answer 8

the speed of light is constant. the light does not go on forever hough. light can be reflected, transmited, and absorbed. light travels in a straight line until reflected of a surface. light can be slightly bent by being transmitted through transparent objects. particles like dust and gas fumes absorb light by taking in heat. thats why a flashlight's light does not go on forever.

Answer 9

yes, if it has, it will be...

Answer 10

If this were a genuine scientific query, I'd give you a thoughtful answer.  As it is just a lame attempt at self-justifying what you've already concluded about the world*, I' won't bother.

*For the interested, just look at his profile.

Answer 11

yes

sick christian slipknot on your myspace page.

Answer 12

Interesting.  I was struck by the tone of this question as apparently were others.  Absolute certainty has NO place in science.  Those who offer it or look for it should go  elsewhere.  Perhaps religion or intense therapy.

I would say it is a foolish question, but its not, its just sad.

Sad someone just doesn't get it, sad that someone is looking for absolutes.  No doubt they will be found.  The truth SEEMS to be that the world is 1) without absolute truths or 2) if it has them they are too complicated for us to understand.  The way the world is, by either design, chance or necessity, is that there are no truths of absolute certainty for a questioning mind.  Other minds need not apply.

Proof is evidence sufficient to convince.  Since for ANY given question, there are people who already ARE convinced (and hence need NO data or logical argument to be so) and  those who are convinced (absolutely) otherwise (and hence no amout of data will convince them of their error), then we must (rationally) conclude that the concept of absolute truth belongs in the realm of fantasy. philosophy and the thought police.