Question about gravitational redshift

[Rolando]

 

If you are unable to do the maths, how can you say that a description does not match the mathematics? You can only rely on your "gut feeling". And that is obviously misleading you. So you have to learn not to trust it.

 

I have no problem with the math at the level that this requires. I would have if it would require handling tensors.

[Mordred]

This link is fairly straightforward

 

https://www.aapt.org/doorway/tgrutalks/Ashby/ashbyGRworkshop.pdf

[xyzt]

 

One of them, I can see as representative of the model Einstein used in 1911. If it is claimed to be a description of GR, this is severely misleading.

Einstein's view from 1911 is not GR. You can stop beating this particular strawman.

 

 

 

I came to this forum because I noticed deficiencies in both of the ways in which GR is commonly

presented

 

There are no such "deficiencies". The only deficiency is in your understanding.

Edited April 14, 2015 by xyzt

[Rolando]

 

And the equation is identical for both descriptions.

 

The equation is identical, and my question really concerns only one of the descriptions, namely that given in the book by Atkins, which I referred to as alternative (1).

 

In this alternative, the phenomenon is explained through the behaviour of atoms that emit radiation of lower frequency the deeper they are located in a potential well, while the frequency of the radiation does not change on its way to a different height. Time is dilated in gravitational wells, and this is an effect of the curvature of space-time. My question was: why is the light itself not affected by this curvature?

Edited April 14, 2015 by Rolando

[Strange]

In this alternative, the phenomenon is explained through the behaviour of atoms that emit radiation of lower frequency the deeper they are located in a potential well, while the frequency of the radiation does not change on its way to a different height. Time is dilated in gravitational wells, and this is an effect of the curvature of space-time. My question was: why is the light itself not affected by this curvature?

 

There is a difference in frequency. You can either describe this in terms of energy lost by the photon (i.e. the light "being affected buy the curvature" as you put it) OR in terms of the atoms emitting light at a different frequency. These are the same thing.

Edited April 14, 2015 by Strange

[Rolando]

This link is fairly straightforward

 

https://www.aapt.org/doorway/tgrutalks/Ashby/ashbyGRworkshop.pdf

 

This is indeed fairly straightforward, but it involves much more than required here, and it does not answer my question.

[xyzt]

 

while the frequency of the radiation does not change on its way to a different height. Time is dilated in gravitational wells, and this is an effect of the curvature of space-time.

You keep repeating this false claim, several of us have debunked your claim. The radiation is received at a frequency lower than the value at which it was emitted.

 

 

 

My question was: why is the light itself not affected by this curvature?

 

 

You keep repeating this other false claim, light frequency is affected the same way as any other em radiation. I have shown you the exact equations that account for the gravitational redshift.

[Rolando]

 

There is a difference in frequency. You can either describe this in terms of energy lost by the photon (i.e. the light "being affected buy the curvature" as you put it) OR in terms of the atoms emitting light at a different frequency. These are the same thing.

 

In alternative (1), this is described in terms of the atoms emitting the radiation. My particular question concerns this alternative alone.

You keep repeating this false claim, several of us have debunked your claim. The radiation is received at a frequency lower than the value at which it was emitted.

 

 

You keep repeating this other false claim, light frequency is affected the same way as any other em radiation. I have shown you the exact equations that account for the gravitational redshift.

 

You talk as if it was me who had made these claims. I only retell what Atkins and many others claim.

Edited April 14, 2015 by Rolando

[Strange]

 

In alternative (1), this is described in terms of the atoms emitting the radiation. My particular question concerns this alternative alone.

 

Then your question makes no sense. If you are considering the difference to be due to the atoms emitting the photons at a different frequency then that is the explanantion of the redshift that you have chosen.

 

OR you could choose the alternative, where the redshift is described as being due to the effects on the photon.

 

You can't choose both.

[xyzt]

 

In alternative (1), this is described in terms of the atoms emitting the radiation. My particular question concerns this alternative alone.

 

You talk as if it was me who had made these claims.

You are making these false claims. And you do it repeatedly, despite the fact that several of us have corrected you.

[Strange]

In alternative (1), this is described in terms of the atoms emitting the radiation. My particular question concerns this alternative alone.

 

To give a more concrete example. We could describe the difference in height between me and my brother in two ways: (1) he is 6 inches taller than me or (2) I am 6 inches shorter than him. You seem to be saying that if he is 6 inches taller and I am 6 inches shorter then the height difference must be 12 inches. And this is obviously wrong, therefore I don't have a brother.

 

You see: it makes no sense.

[Rolando]

 

Then your question makes no sense. If you are considering the difference to be due to the atoms emitting the photons at a different frequency then that is the explanantion of the redshift that you have chosen.

 

OR you could choose the alternative, where the redshift is described as being due to the effects on the photon.

 

You can't choose both.

 

If the difference is due to the atoms emitting the photons at a different frequency, there must be a reason for this. In GR, this reason lies in the geometry. Then it does make sense to ask why the photons are not affected by this geometry on their way.

 

As for the alternative, I understand myself that it fails to account for time dilation, (which was absent in Einstein's model of 1911).

 

I agree that one cannot choose both.

Edited April 15, 2015 by Rolando

[Strange]

I agree that one cannot choose both.

 

This is not true as you previously said: "then it does make sense to ask why the photons are not affected by this geometry on their way".

 

It doesn't make sense to ask that if you are choosing to use a different description of what is happening.

 

You can choose one description or the other, not both. Because they are both describing the same thing. Sheesh.

[Rolando]

 

This is not true as you previously said: "then it does make sense to ask why the photons are not affected by this geometry on their way".

 

It doesn't make sense to ask that if you are choosing to use a different description of what is happening.

 

You can choose one description or the other, not both. Because they are both describing the same thing. Sheesh.

 

I do not quite understand what you are trying to tell. It is true that the question of why the photons are not affected by the geometry on their way makes sense only within alternative (1). The other alternative is not involved here.

Edited April 15, 2015 by Rolando

[Mordred]

Still wrong you must look at the problem of time dilation in terms of 4d geometry change. Here is a key line.

 

"In studying relativity, one must be willing to adopt different points of view--that is, different reference frames. The physical phenomena

dont change, but our description of them does change."

 

Another key line the equivalence principle. Gravitational potential is the same as an inertial frame.

 

this tells you gravitational redshift is the same as Doppler redshift. Change in gravitational potential is exactly the same as a change in inertia.

 

The workshop clearly shows BOTH time dilation and Frequency change. Not one or the other.

 

EVERY example and article we posted shows BOTH. Not one or the other.

 

The metrics are there, look at the geometry change due to relativity.

 

The speed of light is constant, invariant. As the time dilation change occurs the frequency of light (energy) also changes. Energy is also an observed property . Inertial mass. Photons have no rest mass but via its frequency can gain inertial mass.

 

Relativity has three simultaneous effects. Length contraction, time dilation, and change in inertial mass. These CANNOT be separated from each other in real world applications. We can merely model each seperately. However we must keep in mind they are a combined and inseparable effect.

same with time dilation and Frequency change

 

This is shown in the first pages of the workshop, look at the graphs and rocket

A couple of key aspects to study in further detail.

 

Proper time and coordinate time and Lorentz boost

 

Take this one step further the cosmological redshift. In this case the frequency change is due to a change in geometry (expansion). Time dilation is also a change in geometry. The two are related.

When you get deep enough into the math, you realize Doppler, gravitational redshift and cosmological redshift are all the same. The difference between them us which coordinate change is occurring and what causes the coordinate change. Frequency and particle interactions are also described by geometry.

( if you truly want to understand nearly EVERY formula used in physics, study differential geometry). Makes it incredibly easier to understand the most technical of papers. This includes Symmetry in particle physics and string theory for that matter

Edited April 15, 2015 by Mordred

[Strange]

It is true that the question of why the photons are not affected by the geometry on their way makes sense only within alternative (1).

 

Of course it doesn't make sense: you have chosen the description where the effect is caused by the atom emitting a different frequency. If you choose that description then that is the explanation.

 

If you chose the alternative explanation then there is no change to the atom.

 

And just to be clear: neither of these are "true". They are just alternative explanations of what we observe. They are both equally wrong.

 

 

I do not quite understand what you are trying to tell.

 

And that is the problem.

Edited April 15, 2015 by Strange

[swansont]

I do have a sufficient understanding of what these two descriptions are about, and the math is not the problem at this level.

 

I do not argue about the maths, and you are right in that I have just to accept what the experts say when it becomes more advanced. I argue about the descriptions. To me, they cannot be simply different views of the same model. One of them, I can see as representative of the model Einstein used in 1911. If it is claimed to be a description of GR, this is severely misleading. The other one is adequate to GR, but it rises my question.

If the math is the same, the difference is in interpretation.

 

Anything published in 1911 was still under development. 1915 is widely considered to be when GR was "born"

[Rolando]

And that is the problem.

 

In order to obtain empirical adequacy, the following holds:

 

If you have chosen description (1), where the effect is caused by the atom emitting a different frequency, ... the photons are not affected by the geometry.

 

If you have chosen description (2), where the effect is caused by the photons loosing energy, then ... the clocks are not affected.

 

For ... , you can substitute either

1) then,

2) then it remains a mystery why,

3) then it is necessary to assume that,

but you cannot choose

4) then this choice is the explanation for why

if you strive for being taken seriously.

It is no explanation and not even an acceptable excuse.

 

You can choose one description or the other, not both. Because they are both describing the same thing. Sheesh.

 

You can choose one description or the other, not both, but they do not describe the same thing.

This is so embarassingly simple to see.

 

Take a clock that flashes in intervals of one second.

Place it on a body whose gravitation is strong enough to cause a redshift z = 1 when looked at from your safe distance.

Alternative 1) tells you that you will see the flashes arriving in intervals of two seconds.

Alternative 2) tells you that you will see the flashes arriving in intervals of one second.

[xyzt]

 

In order to obtain empirical adequacy, the following holds:

 

If you have chosen description (1), where the effect is caused by the atom emitting a different frequency, ... the photons are not affected by the geometry.

 

If you have chosen description (2), where the effect is caused by the photons loosing energy, then ... the clocks are not affected.

 

It is not clear how you consistently manage to get things wrong:

 

1. In the frame of the emitter (atom) the frequency does not change

2. In the frame of the receiver, the frequency is detected as being either blue or red shifted, depending on the gravitational potential difference (difference in the Schwarzschild radial coordinate).

3. All em radiation (light included) is affected the same way.

 

Take a break from posting while you try to learn the above.

[Strange]

 

In order to obtain empirical adequacy, the following holds:

 

If you have chosen description (1), where the effect is caused by the atom emitting a different frequency, ... the photons are not affected by the geometry.

 

If you have chosen description (2), where the effect is caused by the photons loosing energy, then ... the clocks are not affected.

 

Correct.

 

For ... , you can substitute either

1) then,

2) then it remains a mystery why,

3) then it is necessary to assume that,

but you cannot choose

4) then this choice is the explanation for why

if you strive for being taken seriously.

It is no explanation and not even an acceptable excuse.

 

I have no idea what that is supposed to mean.

You can choose one description or the other, not both, but they do not describe the same thing.

This is so embarassingly simple to see.

 

They obviously do describe the same thing: the underlying theory.

 

Take a clock that flashes in intervals of one second.

Place it on a body whose gravitation is strong enough to cause a redshift z = 1 when looked at from your safe distance.

Alternative 1) tells you that you will see the flashes arriving in intervals of two seconds.

Alternative 2) tells you that you will see the flashes arriving in intervals of one second.

 

Nonsense. Because explanation 2 is about photons not about ticking cloks and so is not applicable to this case.

 

This is the problem when people who are ignorant of the theory try and extend analogies beyond where they can be applied. Next you will be telling us that the "rubber sheet" analogy proves GR wrong:

[Rolando]

If the math is the same, the difference is in interpretation.

 

Anything published in 1911 was still under development. 1915 is widely considered to be when GR was "born"

 

As you can see from my response to Strange, the difference between the descriptions is not just in the interpretation.

By telling the year 1911, I ment to tell precicely what you said.

[Strange]

As you can see from my response to Strange, the difference between the descriptions is not just in the interpretation.

 

The interpretation is the ONLY difference. They both describe the same thing from different points of view.

[imatfaal]

!

Moderator Note

 

OK - this is getting silly. The thread no longer seems to be asking legitimate questions in a search for understanding but promoting alternative hypotheses at odds to current ideas and without reference to the technical and non-technical responses given

 

Moved to Speculations - please take a moment to read the rules of the Speculations forum. Do not respond to this moderation

 

[Rolando]

It is not clear how you consistently manage to get things wrong:

 

1. In the frame of the emitter (atom) the frequency does not change

2. In the frame of the receiver, the frequency is detected as being either blue or red shifted, depending on the gravitational potential difference (difference in the Schwarzschild radial coordinate).

3. All em radiation (light included) is affected the same way.

 

I am in full agreement with what you say here. This is all stuff that I assumed to be sufficiently well known to all who follow this topic. I cant see what you mean to be wrong.

 

The interpretation is the ONLY difference. They both describe the same thing from different points of view.

 

Alternative 1) tells you that you will see the flashes arriving in intervals of two seconds.

Alternative 2) tells you that you will see the flashes arriving in intervals of one second.

 

Interpretation only? Same thing from different points of view?

[xyzt]

 

I am in full agreement with what you say here. This is all stuff that I assumed to be sufficiently well known to all who follow this topic. I cant see what you mean to be wrong.

This is not what you have been saying. If you do not realize what you are saying then this is an even bigger problem. See below:

 

 

 

Alternative 1) tells you that you will see the flashes arriving in intervals of two seconds.

Alternative 2) tells you that you will see the flashes arriving in intervals of one second.

 

Actually , in BOTH 1 AND 2, the flashes are received at the SAME interval. The above is just ONE of your many distortions of basic physics.

Edited April 15, 2015 by xyzt