Relative Velocity Experiment - A Matter of Discussion

[Nugatory]

This is the most I know ridiculous impossibility, only idiot can believe in this. :)

You'd think so, wouldn't you? But experiment after experiment has shown that this really is the way the world works.

It might be a little bit less surprising if you know that the speed of light can be calculated from Maxwell's laws of electricity and and magnetism (google for "Maxwell's equations"). Now imagine me on Earth sending a light signal to someone on Mars. We're both sitting comfortably at rest at our desks in our homes on our respective planets, so it will be very hard to make a case that one of us is "really moving" and the other isn't - yet Mars is moving at many kilometers per second relative to earth. The signal leaves me traveling at speed $c$ relative to me, just as I expect from the laws of E&M. The only way it won't be traveling at speed $c$ when it reaches him is if the laws of E&M are different on Mars and on Earth - yet he is at moving at many kilometers per second relative to me.

So you get to take your choice: Either the laws of E&M change according to your motion; or everyone gets the same laws of E&M and therefore the same speed of light no matter how they're moving. Experiments have come down decisively on the side of "same speed of light".

As a historical note... this was THE great unsolved problem of physics between 1861 when Maxwell's equations were discovered, and 1905 when Einstein discovered relativity.

 

[ghwellsjr]

What do you mean by the one-way light-speed is contradictory to the axioms of SR? Einstein's second postulate (I assume that's what you mean by axiom) is that the unmeasurable one-way light-speed in any Inertial Reference Frame is equal to the two-way speed of light which is measured at c.

...I stay in place and there is the lightspeed, say from the sun, c relative to me.
Now I start to move with a speed v > 0, and the light reaches me still with the same speed c?

This is the most I know ridiculous impossibility, only idiot can believe in this. :)

I agree that what you said is ridiculous but that's not what Special Relativity says. Please re-read the quote of mine again and you should see how what you said is not what SR says.

If you still don't see the difference, please elaborate.

 

[CKH]

I stay in place and there is the lightspeed, say from the sun, c relative to me.
Now I start to move with a speed v > 0, and the light reaches me still with the same speed c?

This is the most I know ridiculous impossibility, only idiot can believe in this. :)

Well, it is experimentally true, so we are stuck with it. Einstein's explanation is that space and time depend on the movement of an observer in such a way that the measurement of c always gives the same value.

LET (Lorentz Ether Theory which is mathematically equivalent to SR) explains it a somewhat different way. LET analyzes propagation of waves (which comprise both light and matter) in a fixed medium called the ether. LET concludes that moving clocks actually run slower and moving meter sticks are shorter. This results in a measured constant speed for c by moving observers.

So the seemingly impossible happens because moving observers don't make that same measurements as an observer at rest with the source of light.

 

[nitsuj]

In fact the c = const in the relativity theory is a math trick only.
This is quite invisible in the equations, because there is always the compound: cdt, never the dt alone directly.
Therefore if the c changes, in any way, the SR interpretes this as the dt instead of the light speed changes (the relative simultaneity, ect.), and this gives the same equations, thus the results also.

I stay in place and there is the lightspeed, say from the sun, c relative to me.
Now I start to move with a speed v > 0, and the light reaches me still with the same speed c?

This is the most I know ridiculous impossibility, only idiot can believe in this. :)

lol...just when you thought you understood geometry, you realize in reality velocity is a crucial component. Physically more important than the shapes of things at a distance is the order of local "happenings".