# Light speed changing

1. Feb 19, 2005

### Sariaht

They say it's so in this science illustrated. If it is so and lightspeed doubles in 2.000.000.000 years, will the sun become 4 times as warm (E = mc2) or what would really happen, would everything contain four times as much energy, would wood burn in blue flames? tell me what!

2. Feb 19, 2005

### Crosson

E = mc^2 specifically applies to the rest mass energy (the kind of energy that is released in a nuclear reaction).

If light speed is changing, even very slightly over the course of the universe's expansion, then the formula E = mc^2 is not quite right, just an approximation.

Remember conservation of energy, no matter what happens everything can't have "four times as much energy" out of nowhere.

In terms of what noticeable effects would occcur, colors would change. Light moving faster would make everything blue-er (shift away from red). The operation of the sun might be affected, but it would be speculative to guess because our current formulae don't account for a changing speed limit.

Black sholes would shrink, as light could escape from larger and larger masses.

Something like fire wouldn't change because that is a release of chemical potential energy, not rest mass energy.

3. Feb 19, 2005

### ZapperZ

Staff Emeritus
Light speed isn't "changing". This is NOT a done deal. In fact, there are more and newer experimental evidence that are throwing doubt into the original J.K. Webb results. So I wouldn't put all my money into this if I were betting.

Because of that, I don't think I want to entertain your "scenario" that clearly violates several conservation laws.

http://groups.yahoo.com/group/undernetphysics/message/1224

Zz.

4. Feb 20, 2005

### Sariaht

Perhaps it's not. But i thought, if m is s/c2 Then the energy is conserved.
Adding to this that G is proportional to c4 (which it also must be in case of conservation of energy) and that h is proportional to 1/c2 (if frequency is proportional to mass) and a is proportional with c2 which leads us to the conclusion that 1/s2 is proportional to c2 and that means that lightspeed wouldn't change at all, cool huh?

5. Feb 22, 2005

### rbj

there's even a more fundamental reason to reject this pop science snake oil (or cold fusion) even if "They say it's so in this science illustrated."

when we measure anything physical, we are actually measuring dimensionless quantities. when you measure a length with a tape measure or ruler, you are counting tick marks on that ruler. you are measuring the dimensionless ratio of the length you are measuring against the standard of length you are using.

it is true that some physicists have believed that there is a small change in the fine-structure constant, $$\alpha = \frac{e^2}{\hbar c 4 \pi \epsilon_0}$$ which is a dimensionless constant. for them to say that the speed of light is changing from that is to say that $c$ is changing relative to the standard $$\frac{e^2}{\hbar \epsilon_0}$$. but how do you know it is not the standard that has changed? the only meaningful physical quantities are dimensionless.

wikipedia is down right now, but when it comes up, you (i mean Sariaht) should look at the "Variable speed of light" article and the discussion page attached to it. also take a look at the "Planck units" article and the portion about the "Invariant scaling of nature". then follow the links to a couple of papers by Michael Duff about why claiming a change to a dimensionful quantity is not meaningful in and of itself.

r b-j

Last edited: Feb 22, 2005