# Why is the speed of light 186,000 miles per second?

1. Apr 5, 2015

### thejun

Why is the speed of light 186,000 miles per second? Is that how fast the ether will allow it to travel? and if that is the case, if the edge of the universe; the edge to which the universe is speeding up, would the ether out there let light travel at higher or lower speeds? Which to me means that light is 186,000 miles per second in our are of the universe?

2. Apr 5, 2015

What ether?

3. Apr 5, 2015

### thejun

the ether that all particles travel through, what gets there momentum, and probably their spin

4. Apr 5, 2015

### rootone

'Ether' is a very wrong term to use to describe space in modern physics.
It is a term used for a long discarded idea, in which space is a substance through which light propagates in a way similar way to sound propagating through air.
Transmission of light (or any electromagnetism) in a vacuum is very different, but it does have a fixed speed 'c', and this has been verified repeatedly in different ways.

Why 'c' has that particular value is unknown, it just does.
According to special relativity 'c' is constant for all points in space, if it wasn't then SR wouldn't work, but clearly it does work.

Last edited: Apr 5, 2015
5. Apr 5, 2015

### thejun

let me start with a simpler question.
Why does light go at 186,000 miles per second. Why not 196,000, or 296,000.
What makes it travel at 186,000 miles per second?

6. Apr 5, 2015

### rootone

We don't know why it has that particular value any more than we know why Pi has a particular value.
It just does, it has been experimentally confirmed repeatedly, c is not a theory.

Last edited: Apr 5, 2015
7. Apr 5, 2015

### thejun

Hence, the ether, and you don't know if Pi has a particular value... the answer "it just does", sounds religious to me... Physics is theory, just wondering what people are theorizing...

8. Apr 5, 2015

### rootone

The existence of Ether has been proven wrong experimentally.
http://en.wikipedia.org/wiki/Michelson–Morley_experiment
and also other experiments.
Aether theories are not consistent with what is actually observed.
Special relativity IS consistent with what is actually observed (repeatedly)

Observations, measurements, are facts, not a religion.

Last edited: Apr 5, 2015
9. Apr 5, 2015

### phinds

In addition to no ether that light travels in, there is no edge to the universe. You would do well to study some very basic cosmology.

10. Apr 5, 2015

### thejun

im not talking about measurements. how do you smash to protons together to get the higgs? the higgs is way more massive than the the 2 protons, no matter how much energy you throw at it... if you cant answer why the speed of light is c, and you don't have any theories, than just say I don't know, and let somebody else theorize the question..
thanks for talking with me though!!!

11. Apr 5, 2015

### rootone

Protons colliding at near light speed apparently IS able to produce a particle with a rest mass in the range where the Higgs particle was predicted to be.
That's what the LHC run1 set out to look for, that predicted particle (amongst other things), and they found it.

Last edited: Apr 5, 2015
12. Apr 5, 2015

### bahamagreen

I believe current thinking is that the ether theory and relativity theory make identical predictions so they appear experimentally indistinguishable, the only difference being that the ether theory assumes of all possible inertial frame of reference there is one unique frame at absolute rest (which can never be experimentally identified from the others) and relativity theory assumes there is no such unique absolute frame of rest.

thejun, I think the best explanation about c comes from Minkowski's famous "valiant piece of chalk" address, but it is not easy going; here is a step by step walk through that paper... Minkowski.

13. Apr 5, 2015

### Drakkith

Staff Emeritus
It travels that fast because free space has very specific values for the electric and magnetic constants: http://en.wikipedia.org/wiki/Speed_of_light#Propagation_of_light

Now, if you were to ask why those values are what they are, then the only answer we can give is that "we don't know".

Take it as "we don't know" instead. There are plenty of fundamental constants and rules which have no underlying explanation. That's the nature of science. You always have something which isn't currently explained.

14. Apr 8, 2015

### quincy harman

Pi is the ratio of a circles diameter by the circumference. In other words it's how many times you can fit the diameter in the circumference of any given circle.

15. Apr 8, 2015

### Greg Bernhardt

Last edited: May 7, 2017
16. Apr 8, 2015

### rootone

Yes that's right, and that ratio is a universal constant, having the same value for all circles.
The same can be said of 'c', it is similarly a universal constant
We know what the value of PI is and we know what the value of C is, to a very high degree of precision.

The OP asked why 'c' has the value it does, and the fact is that we don't know, just as we don't know why Pi has the value it has.
All we do know in both cases is that they are universal constants, and knowing their value is extremely useful.

The situation with Pi is exactly analogous to that of 'c', and there are several other such universal constants.
We know what the value of the constant is, but we don't know why they have the values they do.
Universal constants such as these are observed facts, not a consequence of any theory.
As such they simply are what they are and we can make use of them without the neccessity of an underlying explanation for them.

Last edited: Apr 8, 2015
17. Apr 8, 2015

### phinds

Were you making a point with that statement or did you think we didn't know that?

18. Apr 8, 2015

### quincy harman

well he said we don't know why the value of pi is pi. so I didn't know if he knew. lol

19. Apr 8, 2015

### rootone

That's right, we don't know why Pi has the value it has.
We can measure it, and we calculate it to many decimal places,
but that doesn't explain why the value Pi is what it is.

20. Apr 8, 2015

### wabbit

But is the question about c ? In natural units c=1, there's no mystery in that. The number we get is an effect of our choice of units it seems to me, is there more to it than that?