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Author Topic: Does gravitational field increase energy of a photon?  (Read 15624 times)

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Offline MikeS

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Does gravitational field increase energy of a photon?
« Reply #50 on: 22/07/2011 17:06:59 »
Shrunk
I think this particular paper muddies the issue somewhat because he is primarily interested in experiments being carried out to verify that gravity bends light.  What he does not say in this paper is that space is curved.  By omitting to say that does not imply space is not curved, he was simply talking about something else.
The 1911 paper was written before Einstein developed general relativity and well before physicists began using "curved spacetime" language.

So what?  As I said, this particular paper just muddies the issue.
 

Offline yor_on

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Does gravitational field increase energy of a photon?
« Reply #51 on: 23/07/2011 09:57:54 »
Yes, it wasn't the best example PhysBang, I'm sorry, should have looked for a later paper. But what I understand him to say is that the photon/waves energy indeed will increase in our gravitational field, as defined from an observer on Earth. But also that it can be explained if you take into consideration gravity's influence on the different clocks rates, meaning that gravity influence all clocks, 'slowing them down', as defined from other 'frames of reference'. Making it essential to translate the energy observed at your local clock rate, to the 'clock rate' defined at the origin. If this now make sense? :)

"On the contrary, we must certainly define the time in K in such a way that the number of wave crests and troughs between S2 and S1 is independent of the absolute value of time: for the process under observation is by nature a stationary one. If we did not satisfy this condition, we should arrive at a definition of time such that by its application time would enter explicitly into the laws of nature, and this would certainly be unnatural and inappropriate."

And "“There are, however, two different types of such [non-inertial] motion; it may for instance be acceleration in a straight line, or circular motion with constant speed. In the first case the magnitude of the velocity vector changes but its direction remains constant, while in the second case the magnitude is constant but the direction changes. In each of these cases the motion is non-inertial, but there is a conceptual distinction to be made.” from "General Relativity", Lewis Ryder, Cambridge University Press (2009).

So Earth is not a inertial frame in General Relativity. Strictly defined it is only geodesics that can be defined such, as I understands it.

Speed Of Light. Hmm, just ignore the religious bit, I did. Can't understand why they have to mix religion with Relativity? For those wanting a better, but more mathematical, explanation of Einsteins 1911 paper try The Genesis of General Relativity.


To me it is the equivalence principle again, as applied from defining 'local time' as unvarying. Meaning that even though we find a 'different energy' in a gravitational field, if we take into consideration how different clocks act under gravity, we will see that the 'energy' we observe on Earth is compressed' by our gravity. If I on the other hand somehow was able to measure lights speed at earth using my 'space clock', outside of Earths gravity in a uniform motion (geodesic). I now would find it to have the 'wrong velocity', it would be slower than 'c' to according to my clock. That one is easier to understand though, than the fact that you locally, as on Earth, can find both 'c' and a higher 'energy' simultaneously, only depending on from what 'depth' inside the gravity well you measure it.

That one is harder to melt, and I got to admit that I'm not sure on how to see it. If I think of 'gravity' as some sort of energy, at least being able to translate its 'slope', as when you're falling, then I might say that the 'photon' too must gain energy in its 'fall' to Earth. And if it does, then it need to express itself, don't you agree? And as lights speed always will be 'c' locally, it can't really 'accelerate', but it can 'blue shift'. Which to us observing then will be a equivalence to accelerating, the 'photons energy' increasing as defined from us.

And it is also so that although we have experimented and tested the idea repeatedly with red shift, when it comes to this 'blue shift' I'm not as sure? The only one I know of is the Pound-Rebka Experiment? But I'm not sure I understand how they did it all together? "By vibrating the speaker cone the gamma ray source moved with varying speed, thus creating varying Doppler shifts. When the Doppler shift canceled out the gravitational blue shift, the receiving sample absorbed gamma rays and the number of gamma rays detected by the scintillation counter dropped accordingly." What do they mean there? That they moved the gamma ray source physically to cancel the Doppler shift?

How exactly?


And here is Gravitational Potential Energy.
==

Hmm :)

How about this, the equivalence principle states that all accelerations is equal to 'gravity'. If that is true then all invariant mass should be equivalent to an acceleration. So one gravity on Earth is then a measure of a 'speed'. And when it comes to speeding 'towards' that 'photon', it must blue shift. If it didn't Doppler would be wrong. And that one we have tested repeatedly to be correct, on and off earth.

Strange, it took me some time to see it. I will blame it on Inertia. 
« Last Edit: 23/07/2011 10:41:30 by yor_on »
 

Offline Mr. Data

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Does gravitational field increase energy of a photon?
« Reply #52 on: 28/07/2011 18:10:51 »
It might be assumed that high gravitational area's of spacetime contribute energy to systems. There is even a relationship which states that the density of matter depends on the gravitational field, given as

ρ = ▲φ

When we talk about the density of things, we are really talking about the energy density. It is even known in relativity that the spacetime curvature stores energy, and we also know that the electromagnetic field can also store energy, so why shouldn't a dynamical part of a field contribute to the local energy of a particle?

note ▲ is the d'Alembertian

 

Offline Mr. Data

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Does gravitational field increase energy of a photon?
« Reply #53 on: 28/07/2011 18:33:10 »
I've been considering a personal theory based on ρ = ▲φ. I know personal theories rely on using the other subforum which is why I won't post anything here on the technicalities, but I will quickly tell you a basic: If the equation is taken as true, then matter depends on gravitational fields - or rather, the entire density of an object relies on graviational fields. This density is in respect to mass, which means it would not contribute an energy exactly to a photon, unless a photons energy is changed in relative respect to an inertial environment.
 

Offline simplified

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Does gravitational field increase energy of a photon?
« Reply #54 on: 30/07/2011 07:31:04 »
If MikeS wants to use not local meters and seconds,then he should use this formula:
                  E=hν•√(c/c')
c'-speed of the photon relatively of not local observer
                              :P
« Last Edit: 30/07/2011 07:46:58 by simplified »
 

Offline MikeS

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Does gravitational field increase energy of a photon?
« Reply #55 on: 31/07/2011 07:28:36 »
If MikeS wants to use not local meters and seconds,then he should use this formula:
                  E=hν•√(c/c')
c'-speed of the photon relatively of not local observer
                              :P

Russian humour?
 

Offline simplified

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Does gravitational field increase energy of a photon?
« Reply #56 on: 31/07/2011 16:07:39 »
If MikeS wants to use not local meters and seconds,then he should use this formula:
                  E=hν•√(c/c')
c'-speed of the photon relatively of not local observer
                              :P

Russian humour?
Unchanging frequency of wave is changed per second of changed time.If you can understand this,then you can use normal formula. :)
 

Offline MikeS

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Does gravitational field increase energy of a photon?
« Reply #57 on: 01/09/2011 07:37:07 »
"An object in free-fall is in actuality inertial, but as it approaches the planetary object the time scale stretches at an accelerated rate, giving the appearance that it is accelerating towards the planetary object when, in fact, the falling body really isn't accelerating at all. This is why an accelerometer in free-fall doesn't register any acceleration; there isn't any."
http://en.wikipedia.org/wiki/Equivalence_principle

This is why a photon does not gain energy 'falling'within a gravitational field.  A free falling accelerator proves it.
 

Offline simplified

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Does gravitational field increase energy of a photon?
« Reply #58 on: 01/09/2011 13:22:27 »
"An object in free-fall is in actuality inertial, but as it approaches the planetary object the time scale stretches at an accelerated rate, giving the appearance that it is accelerating towards the planetary object when, in fact, the falling body really isn't accelerating at all. This is why an accelerometer in free-fall doesn't register any acceleration; there isn't any."
http://en.wikipedia.org/wiki/Equivalence_principle

This is why a photon does not gain energy 'falling'within a gravitational field.  A free falling accelerator proves it.
Then show right formula of energy of photon in gravitational field. ;D
 

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Does gravitational field increase energy of a photon?
« Reply #58 on: 01/09/2011 13:22:27 »

 

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