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The speed of light Is influenced by the strength of the gravitational field where the measurement is made,the fields encountered in the region of the Solar system have only a tiny effect but close to Neutron stars and black holes the effect is considerable. I believe that I read an article awhile back about a woman stopping light in cold sodium and then restarting it again with a shot of laser. If this is true, light is certainly not a constant as Einstein stated. That leads me to question the validity of E=MC2. Thanks for your comments. Joe L. Ogan
Is the speed of light constant?
Did Einstein assume that the speed of light is constant when he devised the formula E=mc˛? If the speed of light is not constant does this cast doubt on the formula E=mc˛? Is it possible that Einstein was just looking for the largest number he could find to justify his opinion that there is a lot of energy in any mass?
Looked up your reference Farsight and saw this "This is already true in special relativity: if you measure the speed of light in an accelerating reference frame, the answer will, in general, differ from c." How, relative what?
As I understands it the speed of light is invariant, meaning that from any frame it will be measured as having the exact same speed relative that frame of reference in a vacuum? To say that a accelerating system would present a different answer when measuring light-speed seems to imply that motion then exists as some sort of 'instants'?
What I would ecpect from measuring inside an accelerating frame is that to a far observer 'at rest versus both origins (Earth)' the light would increase its frequency, nothing more? And that when measuring it inside that accelerating frame the light still would come out as being at 'c', as tested by letting it meet a sink, either inside that frame, or reflected from something 'being still' relative the accelerated frame, like a 'unmoving' mirror hanging in space relative our rocket.
Am I wrong there?
Did you mean me Lightarrow?
Yes Farsight, that's one way of expressing it... Or you can state it like this.No matter where you measure it, under any circumstance, will that light speed differ relative the guy measuring it. That makes this frame 'invariant' to that guy, no matter where he is. All other frames will differ, depending on speed/velocity and mass, but not the 'intrinsic one' belonging to the guy measuring, if I got it right that is?
So in a way you have an 'invariant frame' in SpaceTime, even though your relations with all other frames differ, if you see how I think of it That is also the frame creating our 'arrow in time' I think. But, even if you look at it that way you will still find it hard to understand how all those different 'frames of reference' in terms of time dilation and contraction can be experienced simultaneously by you seamlessly, never 'coming apart'.