Thread: Einstein's General Relativity and Gravitational Redshift .

Is the Gravitational Redshift really a proof for Einsteins General Relativity ?
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One of the last proofs of Einsteins General Theory of Relativity was the

Pound-Rebka experiment cf. http://en.wikipedia.org/wiki/Pound-Rebka_experiment


If take another look we can derive the Gravitational redshift without Einstein. Thus

it cannot in any case be considered a proof for Einstein.



The only facts we need to know is ;

1.The conservation of energy-matter.

2.The potential energy on earth PE=m*g*h (or that of a star G*M/r )

3.The energy of a photon E=h*f.

4.E=m*c^2. (or m=h*f/c^2)



There are no other theories or facts that we need to prove the

gravitational redshift.



To show this we make a thought experiment with Alice and Bob.


Alice and Bill have decided to do something dishonest.

They want to break the first law of physics that prohibits

perpetual motion machines.Alice goes to the bottom of a

mountain and Bill to the top.



Alice will then convert 1kg of water to a laser light and flash

it up to Bob .Bob will then convert this laser light back to

water and let it flow down the mountain.They will then sell the

energy of the flowing water on the black market .



This is obviously wrong.



The reason is that the potential energy of the water must be

subtracted from the energy Bill can get from the light rays.





The energy before must be equals the energy afterwards.



Thus ;




The energy recieved by Bob must be equal to the energy sent by Alice minus

the potential energy contained in the water .We will calculate this for just one

photon.



h*fo=h*fe-(h*fe/c/c)*g*h



This reduces to

fo=fe*(1-g*h/c/c)



This is exactly the result that Einstein obtained . The only difference is that

we have not used any assumptions other than those commonly quoted in

any introductory text book on physics.



For more details see http://uk.groups.yahoo.com/group/DynamicFT


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Sally,

I have two questions regarding your conclusion:

1. Do theoretical physicists regard this experiment as verifying General Relativity?

2. If so, why do you they disagree with you?

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Just curious,
Archie

My question is, if the experiment is about Alice and Bob, who the hell's Bill?

I'm not myself certain of the provenance of a thought experiment which involves "converting" water into laser light and back. You're essentially using a Star Trek-type transporter.

But let's go with it. You convert the 1Kg of water into light energy with 100% efficiency and beam it up the mountain, where it gets converted back with 100% efficiency, minus the energy it lost through redshift. And we get the result:

This is exactly the result that Einstein obtained . The only difference is that

we have not used any assumptions other than those commonly quoted in

any introductory text book on physics.

Perhaps that is because the assumptions commonly quoted in any introductory text book on physics involve knowledge of Einstein? Now, you converted water into energy and back again. Would that be via this equation? e = mc² by any chance? Now, who came up with that equation....... it's on the tip of my tongue.......

I'm only a Grade 10 science student. But what you said made alot of sense. Except for the part when you changed names but I did get your point.

The first thing you have to understand is that it was never considered proof but only evidence. When a theory predicts something and you check it and it turns out to be true then that is considered evidence which supports the theory.

The second thing you must understand is that according to Newton's theory of gravity, something only has potential energy if it has mass, so since photons do not have mass, Newton's theory does not predict gravitational redshift but Einstein's General theory of Relativity does predict it.

Proof plays a role in physics only in theory. But the real truth in physics relies not on proof but upon experimental evidence. There is no such thing as experimental proof. For example, John Stewart Bell proved that if there were hidden variables then a certain mathematical inequality must be obeyed in the correlations between the measurements in a certain type of experiment. These experiments were performed and the inquality was not obeyed. This provided experimental evidence that the idea of hidden variables was wrong and that the accepted understanding of Quantum physics was correct.