Relativity Postulate

[L-User]

I've recently been thinking about Einstein's Theory of Special Relativity (ie, trying to understand the theory and its implications). I don't have any formal training/education in physics, I'm just trying to understand the thoery based on the toolset I have. For the most part, I think I've got it.

 

But there is one thing troubling me, and it so happens to be one of the postulates to the theory. That is "The speed of light is constant." I'm wondering why the speed of light is constant, as in an explaination. I looked through about 20 pages in this forum, and didn't find the sort of explaination I'm looking for here. I have come across the following sorts of statements in my internet search for an answer, but they also aren't the sort of thing I'm looking for:

 

The speed of light is constant because that is what's observed.

An observation is just that: an observation. This doesn't help in my search for an explaination.

 

Because that's what is predicted by the Maxwell Equations.

Math is a great tool for describing a system, but doesn't, in itself, provide any explaination. So this doesn't really help either.

 

So if anybody has any knowledge as far as an explaination, it'd be greatly appreciated. Or even pointing me in the right direction. Or if an explaination is presently unknown, that would be good to know too.

[arkain101]

It is constant because it does not experience space or time.

 

It has a specific value because of something to do with maxwells equations.

 

-there is a minimum size of matter that can be measured (seen) If that size is smaller light doesnt come back. Like a mini black hole.

 

-there is a maximum of matter aswell and to reach that you need 0 energy (infinite)

 

It doesnt experience space or time because it does not act as it has mass.

 

It does not act as though it has mass because it is opposite to matter with mass, it is energy.

 

Thats all I got for now.

[Farsight]

L-User: the "speed of light" is constant because c is not a speed. It's not a speed because speed is distance over time, and time is not a fundamental component of the thing we call spacetime. What is fundamental is space, and it can only be quantified by distance. You can measure this distance by looking at some distance travelled by a photon. When you try to measure time to calculate distance / time = speed, what you're actually measuring is the distance travelled by the photons within your atoms/electrons, and brain, and clock. The constant you call c is how you relate the real Dimension of distance to the mathematical, subjective, imaginary dimension of time. Since these two dimensions are expressed in different units, you ascribe a dimensional conversion factor to c.

 

See this paper descibing A New Interpretation of Special Relativity:

 

A New Interpretation of Special Relativity

[arkain101]

Popular that is an interesting paper.

 

I had arrived at a similar concept in the earlier stages of my theory.

 

I moved from that theory though when I saw evidence that light traveled at C for two frames in non-intertial frames.

 

I do not know however that this data was correctly concluded.

 

If you know of any experimental data on one way trip light speed tests I'd be glad to see them.

[houserichichi]

If it's a philosophical answer you're looking for then the proper response is "we don't know anymore than we know why the electron's mass is what it is or any of the other fundamental constants". It just is and if it wasn't we wouldn't be here to wonder about it.

 

There might actually be an underlying reason why c has the value that it does but we have yet to discover it.

 

(please, someone correct me if I'm wrong)

[arkain101]

Yes that is a good point.

 

To answer that question is alike answering the question as to why the universe exists, and not only that, but exist like it does.

 

We just can't factually say why through science today.

 

On the other hand we can explain how.

[snark1100]

well, there is no particular reason why it must be a constant, but einstein found that if you were to postulate that it is, you get a very nice result, and a theory that correctly predicted the results of experiment and resolved a few problems.

[TheFaithfulStone]

Speed of light - Wikipedia, the free encyclopedia

 

That's a pretty good overview.

 

Maxwell's equations - Wikipedia, the free encyclopedia

 

Maxwell. Basically, Maxwell's equations work in every frame. No matter how fast you're going, you see c as being the same speed. If you are going 180,000 miles per second, you see light as going 186,000 miles per second faster than you, not 6,000.

 

When you chase that down, you end up with special relativity.

 

How do we know that Maxwell always works? Because we know that if there were a lumineferous aether, we wouldn't be stationary relative to it. But, yet, we would seem to be, given the results of the Michelson-Morley experiment and other's like it.

 

Simply put, we know by experimental observation that there is no "medium" in which light travels. Therefore, light is never in a particular frame of reference. Therefore, c is "frame invariant", or always the same. Therefore, the universe is one super-weird place.

 

TFS

[arkain101]

Super weird , or super perfect.

 

Imagine trying to live in a universe where your frame bent, time dilated, and your mass changed in your frame!

[LaurieAG]

Super weird , or super perfect.

 

Imagine trying to live in a universe where your frame bent, time dilated, and your mass changed in your frame!

 

Ha, arkain101, you could be talking about old age, how relative.

[Heresiarch]

well, there is no particular reason why it must be a constant, but einstein found that if you were to postulate that it is, you get a very nice result, and a theory that correctly predicted the results of experiment and resolved a few problems.

 

Actually, I keep coming across suggestions in news articles on cosmology that the speed of light is NOT constant, that light has been slowing down as time passes. Seems weird, but why assume constancy?

 

On a related topic, Whitehead came up with an alternative theory of relativity, but lost the battle to Einstein. Apparently part of Whitehead's argument was that rotary motion is NOT relative, which seems obvious. anybody know more about this?

[houserichichi]

Actually, I keep coming across suggestions in news articles on cosmology that the speed of light is NOT constant, that light has been slowing down as time passes. Seems weird, but why assume constancy?

 

As far as I can tell, whenever they say that light has "slown down" it's because it's not in a vacuum. Vacuums have nothing to interract with so photons travel at light speed. When in a medium, light is absorbed and emitted by all the little particles that it comes in contact with which takes time. That time, factored into the original speed of light, makes it appear as though light takes longer to get from point A to point B than it did were it in a strict vacuum. So it's only the apparent velocity of light that's actually slowing down. Between each little particle that light interacts with, it is still running strong and smooth at the constant speed we call "the speed of light".

 

If that's not what you're talking about then please disregard everything I've said, of course :naughty:

 

Addendum, most of the times the guys in the newspapers seem to have no idea what they're talking about to begin with anyway :doh:

[ughaibu]

If a vacuum is contentless, how is it measurable? Or how do concepts of distance and speed make sense in a vacuum?

[Heresiarch]

As far as I can tell, whenever they say that light has "slown down" it's because it's not in a vacuum. . . .

 

Addendum, most of the times the guys in the newspapers seem to have no idea what they're talking about to begin with anyway :naughty:

 

I know what you're saying--any medium that light passes through will slow it down. But I think there are cosmologists who say that the expansion of the universe itself over time actually slows down light, as if spacetime stretches, so that light has farther to go.

 

what about when the gravity of a body bends light--any affect on the speed of the light?

 

And you're right, popular reporting on science topics is dismal. We might have a new thread there . . . .

[Farsight]

I think some of you guys will be surprised at just how weird the world really is. And horrified at just how simple it all is.

[Heresiarch]

I think some of you guys will be surprised at just how weird the world really is. And horrified at just how simple it all is.

 

The suspense is killing me. Please explain it to us lunkheads.

[Farsight]

See TIME EXPLAINED and ENERGY EXPLAINED and MONEY EXPLAINED, and look out for MASS EXPLAINED later this week. Teatime, gotta go.