Naked Science Forum

On the Lighter Side => New Theories => Topic started by: AtomicX on 27/03/2018 18:59:04

Title: Gravitational shift or not?
Post by: AtomicX on 27/03/2018 18:59:04
Some days ago I had the idea that light frequency blueshifts as it leaves a gravitational field and that it redshifts as it enters it. But when i checked the internet, I saw that the opposite is supported to happen, it redshifts as it leaves a gravitational field and it blueshift as it enters it. This was a big surprise as it didn't make sense for me.

There are some reasons I thought the opposite and they don't seem bad at all.

First reason:
If gravity acts on an object moving in a straight line upwards, then it will decelerate and eventually it will accelerate downwards (It will never curve right or left). But as we know, a photon can't decelerate. Its nature gives it a constant speed. The only way for it seem like it's decelerating is for its frequency to constantly increase so it would cover smaller distances as time passes. So if it's inside a gravitational field, the only way to seem like it's decelerating is to increase it's frequency [Higher frequencies like red light move slower than lower frequencies like blue light].. What some theories tell us is that the frequency of the photon will not increase but it will get smaller meaning that it would accelerate. If that's the way then, why don't photons escape from a black hole as their phenomenal speed increases(frequency decrement). A logical explanation of mine to this is that photons instead, gain frequency inside a gravitational field and in black holes their wavelength becomes too small, or their frequency too big that it can't escape the black hole.

Second reason:
Black holes emit x-rays and gamma rays. How I can explain this is that long radio waves (high wavelength, very low frequency)may get emited from inside the black hole and when they finally get outside their wavelength is so small (high frequency) that they get the form of x-rays or g-rays. And also we know the smaller the black hole the more x-rays and g-rays are emited. So this might mean that more rays manage to escape from the black hole with high frequency

Last reason:
Neutron stars are often seen blue. This might be because of the strong gravity that acts on a photon that makes it gain frequency and shift towards blue.

So these were some reasons that support my opinion but of course I don't say that my assumption is correct and others are wrong, because i don't have any mathematical formulas either. But I would appreciate any answer that either considers my reasons or it totally rejects it.
Thanks!
Title: Re: Gravitational shift or not?
Post by: evan_au on 27/03/2018 21:59:39
You are quite right to say that photons don't change their speed (as seen by someone measuring it in their laboratory).

But observers do change their perception of time depending on where they are in a gravitational well.
- For someone in a deep gravitational well, their time goes more slowly. So they perceive the frequency of an incoming photon to be higher than someone outside the gravitational well. This is gravitational blueshift for incoming photons.
- Similarly, someone outside the gravitational well will have time pass more quickly than someone inside a gravitational well. So they perceive the frequency of the photons as lower. This is gravitational redshift for escaping photons.

Perhaps another way to look at this is from the viewpoint of photon energy:
- A photon has mass
- A photon gains energy as it falls into a gravitational well
- If a photon gains energy, its frequency is higher: This is gravitational blueshift for incoming photons.
- A photon loses energy as it climbs out of a gravitational well
- If a photon loses energy, its frequency is lower: This is gravitational redshift for escaping photons.
- If the gravitational well is very deep - deep enough to form a black hole, the photon loses so much energy as it climbs out of the gravitational well that its energy would become zero and its frequency would become zero. There is then nothing to detect, and light can't escape a black hole.
See: https://en.wikipedia.org/wiki/Gravitational_redshift

Quote
Neutron stars are often seen blue.
Neutron stars are extremely small, and often shrouded in the scattered remains of the star that exploded during their formation. Some of them also have a very hot accretion disk, as they consume matter from nearby stars.

They start with an incredibly high surface temperature, hot enough to emit X-Rays, so in that sense I guess you could say that their color is blue.
But this is due to the spectrum of black body radiation, rather than any gravitational effects.
See: https://en.wikipedia.org/wiki/Neutron_star#Mass_and_temperature

Edit: I added the purple text to clarify the confusion I caused below...
Title: Re: Gravitational shift or not?
Post by: timey on 28/03/2018 00:41:24
Evan - there is a misdemeanor in the logic presented here.

You say here below (example 1) that a photon gains energy as it falls into a gravitational well and that - If a photon gains energy, its frequency is higher.
- A photon gains energy as it falls into a gravitational well
- If a photon gains energy, its frequency is higher: This is gravitational blueshift for incoming photons.

But here you say (example 2) that - If the gravitational well is very deep - deep enough to form a black hole, the photon loses so much energy that its energy would become zero and its frequency would become zero.
- If the gravitational well is very deep - deep enough to form a black hole, the photon loses so much energy that its energy would become zero and its frequency would become zero.

Having already explained that:
- A photon loses energy as it climbs out of a gravitational well
- If a photon loses energy, its frequency is lower: This is gravitational redshift for escaping photons.

So which is it?
Does a photon falling into a gravtational well gain energy and frequency - (blueshift) as in example 1?
Or does a photon falling into a gravitational well lose energy and frequency - (redshift) as in example 2?
Title: Re: Gravitational shift or not?
Post by: Kryptid on 28/03/2018 00:54:32
Evan - there is a misdemeanor in the logic presented here.

You say here below (example 1) that a photon gains energy as it falls into a gravitational well and that - If a photon gains energy, its frequency is higher.
- A photon gains energy as it falls into a gravitational well
- If a photon gains energy, its frequency is higher: This is gravitational blueshift for incoming photons.

But here you say (example 2) that - If the gravitational well is very deep - deep enough to form a black hole, the photon loses so much energy that its energy would become zero and its frequency would become zero.
- If the gravitational well is very deep - deep enough to form a black hole, the photon loses so much energy that its energy would become zero and its frequency would become zero.

Having already explained that:
- A photon loses energy as it climbs out of a gravitational well
- If a photon loses energy, its frequency is lower: This is gravitational redshift for escaping photons.

So which is it?
Does a photon falling into a gravtational well gain energy and frequency - (blueshift) as in example 1?
Or does a photon falling into a gravitational well lose energy and frequency - (redshift) as in example 2?

He means that a photon trying to climb out of a gravity well is redshifted, whereas a photon falling into the well is blueshifted. Think of it as similar to throwing a ball up into the air. When it is moving away from the Earth (i.e. climbing against a gravity well), it slows down and loses energy. Once it stops, it reverses and starts travelling back towards the Earth (going into a gravity well), gaining speed and energy in the process.
Title: Re: Gravitational shift or not?
Post by: timey on 28/03/2018 01:11:31
How can he mean this
that a photon trying to climb out of a gravity well is redshifted, whereas a photon falling into the well is blueshifted.

If he said this:
- If the gravitational well is very deep - deep enough to form a black hole, the photon loses so much energy that its energy would become zero and its frequency would become zero.

???
Title: Re: Gravitational shift or not?
Post by: Kryptid on 28/03/2018 01:54:34
How can he mean this
that a photon trying to climb out of a gravity well is redshifted, whereas a photon falling into the well is blueshifted.

If he said this:
- If the gravitational well is very deep - deep enough to form a black hole, the photon loses so much energy that its energy would become zero and its frequency would become zero.

???

He was talking about a photon trying to climb out of a black hole's gravity well, hence why it loses energy. Take a look at what he said immediately before that statement:

Quote
- A photon loses energy as it climbs out of a gravitational well
- If a photon loses energy, its frequency is lower: This is gravitational redshift for escaping photons.
- If the gravitational well is very deep - deep enough to form a black hole, the photon loses so much energy that its energy would become zero and its frequency would become zero. There is then nothing to detect, and light can't escape a black hole.
Title: Re: Gravitational shift or not?
Post by: timey on 28/03/2018 02:14:27
Oh - ok, well if you put it like that, the photon is then climbing out of the blackhole, and the statement does make sense.

So would you then say that a photon that falls into a black hole gains energy as a symptom of being gravitationally shifted?
Title: Re: Gravitational shift or not?
Post by: timey on 28/03/2018 03:25:49
Anyway, my point was going to be that where Evan says this:

But observers do change their perception of time depending on where they are in a gravitational well.
- For someone in a deep gravitational well, their time goes more slowly. So they perceive the frequency of an incoming photon to be higher than someone outside the gravitational well. This is gravitational blueshift for incoming photons.
- Similarly, someone outside the gravitational well will have time pass more quickly than someone inside a gravitational well. So they perceive the frequency of the photons as lower. This is gravitational redshift for escaping photons.

...it suggests that gravitational blueshift and gravitational redshift are symptoms of the time measurement of the observer's position in the gravity potential.

Yet when Evan says this:
Perhaps another way to look at this is from the viewpoint of photon energy:
- A photon has mass
- A photon gains energy as it falls into a gravitational well
- If a photon gains energy, its frequency is higher: This is gravitational blueshift for incoming photons.
- A photon loses energy as it climbs out of a gravitational well
- If a photon loses energy, its frequency is lower: This is gravitational redshift for escaping photons.
- If the gravitational well is very deep - deep enough to form a black hole, the photon loses so much energy that its energy would become zero and its frequency would become zero. There is then nothing to detect, and light can't escape a black hole.

...it suggests that gravitational blueshift and gravitational redshift are symptoms of increased energy for blueshift, and decreased energy for redshift.

These 2 statements each state a differring reason for the same gravitational shift of light.

So Evan says a photon has mass, ie: energy mass.

A clock has mass. Lower one of two clocks into a gravity well and you will observe it to tick slower than the clock you kept with you*.  A clock ticking slower has a reduced frequency/energy.
(*the far away clock will confirm that the lower clock is ticking slower than your own)

Evan says that a photon gains energy as it falls into a gravitational well.

A clock raised above a gravitational mass will be observed to tick faster than the clock you kept with you on the ground*. A clock ticking faster has an increased frequency/energy.
(*the far away clock will confirm that the elevated clock is ticking faster than your own)

So where a photon is concerned, either it does not gain energy, or lose energy via changes in a gravitational field, and gravitational shifts are purely a measurement that is a consequence of clocks shifting in the gravity potential...
...Or the light is in fact gaining or losing energy as a result of changes in the gravitational field, and in that case, why does a clock gain energy in the weaker field where light loses energy, and lose energy in the stronger field where light gains energy?
Title: Re: Gravitational shift or not?
Post by: evan_au on 28/03/2018 10:06:08
Quote from: timey
A clock raised above a gravitational mass will be observed to tick faster...
why does a clock gain energy in the weaker field where light loses energy, and lose energy in the stronger field where light gains energy?
When a photon rises out of a gravitational well, the energy comes from the photon, and the photon loses energy.

The equivalent for a clock would be for the clock battery to power the lifting mechanism that lifts the clock out of the gravitational well (rather than assume some mysterious external agent who can lift and lower clocks).
- The clock battery gets weaker the higher it lifts
- Beyond a certain distance, the clock battery has no more power, and the clock can't get any higher.

But this is a very weak analogy, because our battery clocks are carefully designed to keep going at a constant rate regardless of how flat or full the battery is (the clock goes a bit bizarre just before it stops entirely).
Title: Re: Gravitational shift or not?
Post by: timey on 28/03/2018 14:14:41
OK - that analogy almost works. But when we raise a clock above the earth into the weaker field, and measure it, as NIST have done, the clock is not measured as it ascends, but is measured after it has been situated in the ascended position.
Therefore the action of the ascending motion is not relevant to the measurement of the elevated clock's tick rate.
There is a slight difference in centripetal motion between where the clock was on the ground and it's position of elevation, that will affect the tick rate of the clock.  But apart from this, there is no difference in 'motion' between the measurement of the clock when it was on the ground, and the measurement of the clock when it is in elevation.
If we ascended the clock at the speed of light, it's time would stop. This, of course is not possible.
But presumably, (just an interesting thought) if we ascended the clock at a certain speed that was accelerated at a particular rate, we could regulate the time of that clock, via speed control, to match the rate of the clock on the ground where we are observing from. (Leading, for me anyway, to a curiosity as to clock timings and escape velocity)
Title: Re: Gravitational shift or not?
Post by: timey on 28/03/2018 18:40:04
So to go back to the OP's original considerations here:

A logical explanation of mine to this is that photons instead, gain frequency inside a gravitational field and in black holes their wavelength becomes too small, or their frequency too big that it can't escape the black hole.

We have established that photon's will lose energy if they are escaping a blackhole here:

- A photon loses energy as it climbs out of a gravitational well

And this begs the question as to how much energy a blackholes radiation possessed before it escaped the black hole.

To say so, you will find descriptions of temperature versus entropy with regards to black holes via a google search, but as entropy is not entirely fully understood, your questions are intereseting.
If radiation escapes easier for smaller black holes than bigger black holes, this suggests that adding mass to a black hole does not increase it's temperature. And by all accounts, according to accepted physics, actually decreases the black holes temperature.

Since we are on New Theories, I will say that there is a possibility that the temperature of the black hole does increase with added mass, but that the increase in temperature is lesser than the increase in gravitational force (due to the added mass) that the radiation must escape in order to be observed by us. 
In this fashion, although the bigger black hole will be a slight bit hotter, it will apear cooler b/c the extra gravitational force due to the additional mass is causing less radiation to escape.
The temperature of a black hole is inversely proportional to it's mass.  I think that what I have just said would result in saying that the temperature increases would be proportional to the increases in mass, and the observed radiation would be inversely proportional to the increase in gravity.

Just a thought... anyway, @AtomicX good luck with your investigations...
Title: Re: Gravitational shift or not?
Post by: Colin2B on 28/03/2018 22:53:09
why does a clock gain energy in the weaker field where light loses energy, and lose energy in the stronger field where light gains energy?
It doesn’t, the problem is with the assumption below:

A clock ticking slower has a reduced frequency/energy....... A clock ticking faster has an increased frequency/energy.
Frequency is the number of events being timed divided by the time for the events to occur, so there is an inverse relationship between frequency and time. So if time is slower relative to another clock then the frequency will be greater ie blueshift.
For an atomic clock at a particular location, a fixed count n = 1s so f=n/1. You can see that f=n/1 will be the clock frequency at any location unless measured relative to a clock at another location - which will change the time the count n is divided by and hence the frequency, eg slower time greater frequency. So it is important to be clear which clock is your reference when making measurements.
Title: Re: Gravitational shift or not?
Post by: timey on 29/03/2018 01:18:41
My reference clock, when making these considerations, is 'always' the far away clock, that confirms that the clock where you are situated is ticking differently to the clock you are observing. (I did mention this in the post 7)

So - according to the far away clock, the clock that is elevated from the ground has a higher frequency than the clock on the ground.
A higher frequency is usually accompanied by a higher energy.
Yet - in the case of a photon departing the ground and being observed at the elevated clock - we know, (unless we are going to say that light does not change frequency between ground and elevated clock, b/c, as Evan posted in post 2, the faster ticking clock at elevation will record that the light arriving from below is a lower frequency than the slower ticking clock on the ground did, due to it's increased tick rate), that gravitationally shifted light loses energy climing out of a gravitational field.

And this is why I was saying:
Quote from: timey on Yesterday at 03:25:49
why does a clock gain energy in the weaker field where light loses energy, and lose energy in the stronger field where light gains energy?
Title: Re: Gravitational shift or not?
Post by: jeffreyH on 29/03/2018 05:51:10
You can calculate what other things may be doing at other points in space but it has to be with respect to your own proper time. You cannot be in more than one place at once. You can then use those measurements to compare with each other to build up a picture. The only independent reference is the speed of light in a vacuum. Unfortunately you can never tell how fast you are moving with respect to photons.
Title: Re: Gravitational shift or not?
Post by: evan_au on 29/03/2018 10:28:16
Quote from: timey
there is a possibility that the temperature of the black hole does increase with added mass
You seem to be describing two different temperatures of a black hole:
- The temperature of the event horizon, as described by Hawking radiation
- The temperature of the singularity, which is hidden behind the event horizon
- This is assuming that there is no accretion disk of infalling matter, which radiates heat, light and X-Rays

The event horizon of a black hole of the mass of the Sun has a temperature within a microKelvin of absolute zero. This is very cold.

In physics, if you compress matter, it gets hotter. As a wild extrapolation, if you compress matter into an infinitesimally small volume at the singularity of a black hole, the temperature should be astronomically high. But there are a few problems with this extrapolation:
- At a point at half the radius of the event horizon, the "escape velocity" is greater than c. So no light can escape from this point, or from points closer to the singularity.
- Spacetime inside the event horizon of a black hole is twisted in a bizarre way that makes it hard to compare with our familiar world
- The event horizon prevents us from knowing what goes on inside the event horizon.
- Even if we assume that we can assign a very high temperature to the singularity, it does not affect the location of the black hole, or it's effective temperature.
- High-frequency photons emitted by the singularity would have more mass than lower-frequency photons. This means that higher-frequency photons would lose more energy than low-frequency photons as they climb out of a gravitational well. Even if you doubled the temperature of the singularity (without changing its mass), the event horizon remains at exactly the same radius, and same temperature.

In my primitive understanding of Hawking radiation, it does not originate from the singularity, but from vacuum fluctuations in very close proximity to the event horizon itself.

See: https://en.wikipedia.org/wiki/Hawking_radiation
Title: Re: Gravitational shift or not?
Post by: timey on 29/03/2018 14:20:25
@jeffreyH The far away clock is a recognised concept in relativity with which to detect if 2 clocks that are in closer proximity to each other are ticking differently.

@evan_au Yes - there isn't that much known about black holes that isn't theoretical, where the theories can't quite cope with the concepts anyway. And some of what is known about black holes  doesn't fit with theory.  That's what makes black holes a really fun subject to discuss on New Theories. ;)
However, the OP has not returned, and I've got stuff to do anyway, so I'll leave you's to it.
Title: Re: Gravitational shift or not?
Post by: Colin2B on 30/03/2018 16:19:58
My reference clock, when making these considerations, is 'always' the far away clock, that confirms that the clock where you are situated is ticking differently to the clock you are observing. (I did mention this in the post 7)
I did notice that, and it doesn’t change my reply. The inverse relationship between frequency and time still holds, and also for any relationship with time in bottom line eg speed and acceleration/deceleration.
I appreciate your theory predicts a different arrangement and if this were  your thread I would not comment, but in this I am answering so the OP can understand what happens.

So - according to the far away clock, the clock that is elevated from the ground has a higher frequency than the clock on the ground.
A higher frequency is usually accompanied by a higher energy.
Ok, just to be clear:
We have a clock F = far away
We have a clock A = above ground
We have a clock G = on the ground
If F measures the tick rate of clock G, relative to its own clock, it will find G to be redshifted ie lower frequency.
If G is then raised to A it will still be redshifted relative to F, but less so than when at G, so it will appear to have increased in frequency - blueshifted.
This exactly the same for a source of photons located at G measured from F and moved to A. The photon frequencies behave in exactly the same way as the clocks.
This is all very understandable, time dilation and hence frequency shift are dependent on the difference in gravitational potential between the source and receiver, and in this case the GP between G & F is greater that that between A & F. The measured energy of photons is not dependent on height but dependent on difference in GP.
Title: Re: Gravitational shift or not?
Post by: jeffreyH on 30/03/2018 19:40:34
@jeffreyH The far away clock is a recognised concept in relativity with which to detect if 2 clocks that are in closer proximity to each other are ticking differently.

@evan_au Yes - there isn't that much known about black holes that isn't theoretical, where the theories can't quite cope with the concepts anyway. And some of what is known about black holes  doesn't fit with theory.  That's what makes black holes a really fun subject to discuss on New Theories. ;)
However, the OP has not returned, and I've got stuff to do anyway, so I'll leave you's to it.

How are you going to determine the rate of your far away clock? I mean physically and not just abstractly.
Title: Re: Gravitational shift or not?
Post by: timey on 31/03/2018 01:13:44
@Colin2B You said
quote
"Ok, just to be clear:
We have a clock F = far away
We have a clock A = above ground
We have a clock G = on the ground
If F measures the tick rate of clock G, relative to its own clock, it will find G to be redshifted ie lower frequency.
If G is then raised to A it will still be redshifted relative to F, but less so than when at G, so it will appear to have increased in frequency - blueshifted."

Absolutely.

quote
"This exactly the same for a source of photons located at G measured from F and moved to A"

Absolutely...it is the same for a 'source' of photons

quote
"The photon frequencies behave in exactly the same way as the clocks."

Wrong!
Have a 'source' release a photon at G, and A will observe that photon to be redshifted, F will observe that photon to be further redshifted.  Move the 'source' from G to A, and F will observe the 'source' releasing a photon at A, as blushifted compared to the photon the 'source' released at G.


@jefferyH
you said:
quote
"How are you going to determine the rate of your far away clock? I mean physically and not just abstractly."

In the same way that NIST does.  They measured a clock on the ground with a far away clock, and, after they jacked the clock up a metre elevation, they measured it again with the far away clock.
Same with the NIST motion related experiment.  They measured the clock when it was at rest with the far away clock, and then they measure the clock in relative motion with the far away clock.
Not too hard to concieve that an experiment at NIST with 2 clocks, 1 on the ground, and 1 at a metre elevation could be measured simultaniously by the far away clock.
I believe the GPS works on the same kind of principle, only vastly more complicated, where the central computer is acting in some sense in the role of the far away clock.
Title: Re: Gravitational shift or not?
Post by: Colin2B on 31/03/2018 18:47:15
@Colin2B You said
quote
"The photon frequencies behave in exactly the same way as the clocks."

Wrong!
Have a 'source' release a photon at G, and A will observe that photon to be redshifted, F will observe that photon to be further redshifted.  Move the 'source' from G to A, and F will observe the 'source' releasing a photon at A, as blushifted compared to the photon the 'source' released at G.
No, correct. Your above description is exactly the same as the way clocks tick rates are measured relative to the far away clock. By the way you missed out a bit - when moved to A, G the photons are still redshifted when measured by F, but less so, hence blue shift.
If you take time to work out what happens to clock ticks you will see it is exactly the same as for photon frequencies.

They measured a clock on the ground with a far away clock, and, after they jacked the clock up a metre elevation, they measured it again with the far away clock.
Ok, I can see where your mistake is.
If you read the NIST 2010 experiment you will see there were only 2 clocks, the jacked up clock and the fixed, lower (ground) clock. They used the lower (ground) clock as the reference from which to compare the jacked up clock, the write up is very clear on this.
It is impossible for them to have used a far away clock as they do not have access to one. The clock would need to be far away from any gravitational field, eg aboard Voyager.

If you include errors like this in your paper you will never get endorsement.
Title: Re: Gravitational shift or not?
Post by: jeffreyH on 31/03/2018 19:46:24
@timey You may benefit from reading the following.
https://www.amazon.co.uk/Illustrated-Guide-Relativity-Tatsu-Takeuchi/dp/0521141001
 
Title: Re: Gravitational shift or not?
Post by: evan_au on 01/04/2018 06:26:19
Quote from: timey
Not too hard to conceive that an experiment at NIST with 2 clocks, 1 on the ground, and 1 at a metre elevation could be measured simultaneously by the far away clock
On the Earth's surface, or in Low Earth Orbit (LEO), we can use the GPS satellites to have a common time reference.
- Note that although the GPS satellites are well above the Earth's surface, they are pre-adjusted before launch so that when they are in the intended orbit, they will keep time as if they were on the ground.

However, this time reference is not usable for satellites which are farther away.
- It has been suggested that we could use the periodic pulses from far away neutron stars to produce a common time reference that can be used reliably by space probes near our Solar System (eg Voyager and New Horizons).
- It's not very easy, since neutron stars can have sudden changes in frequency due to "starquakes". But as long as you are monitoring at least 10 neutron stars, a starquake on 1 or 2 can be recognized and taken into account.
- Despite these neutron stars being far away compared to our Solar System, they are still within our galaxy, and still within our galaxy's gravitational well.
- Ironically, each of these rotating neutron stars are actually deep inside their own gravitational well.

So it takes more than just distance to make a clock a "far" reference, outside a gravitational well.
Title: Re: Gravitational shift or not?
Post by: Colin2B on 01/04/2018 22:42:23
Interesting thought @evan_au as to whether an astronomical feature could be used as a far away clock. As you say, most would be in a gravitational well.
Until we find one, the concept will remain a calculation tool.
Title: Re: Gravitational shift or not?
Post by: timey on 02/04/2018 19:03:44
Why does the far away clock need to be far away? The far away clock is a calculation tool, and only needs to be 'at' a differing gravity potential from the clock/clocks it is measuring.

@evan_au - there is indeed in existence a proposal to use observation of neutron stars as a means of detecting gravitational waves via changes in signal via changes in time, as well as a plan to utilise a satellite system of precision clocks for the same purpose. (I'll see if I can find links to these proposals.)

@jeffreyH - I very much doubt that book will say anything different to the many other books I've read on relativity including Einstein's own papers.

@Colin2B -
Quote Evan
" - For someone in a deep gravitational well, their time goes more slowly. So they perceive the frequency of an incoming photon to be higher than someone outside the gravitational well. This is gravitational blueshift for incoming photons.
- Similarly, someone outside the gravitational well will have time pass more quickly than someone inside a gravitational well. So they perceive the frequency of the photons as lower. This is gravitational redshift for escaping photons."

So here it is being said that light is perceived to change frequency due to the difference in tick rate.

So the clock at G (ground) observes a photon to be a certain frequency. The clock at A (elevated from ground) observes the same photon arriving at A's position to be a lower frequency, ie: redshifted.  And clock F (situated 1 metre elevation from A) observes that same photon arriving at F's position to be a lower frequency, ie: further redshifted, than A did.
That is what occurs for photons.

Quote Colin
" Ok, just to be clear: 
We have a clock F = far away
We have a clock A = above ground
We have a clock G = on the ground
If F measures the tick rate of clock G, relative to its own clock, it will find G to be redshifted ie lower frequency. 
If G is then raised to A it will still be redshifted relative to F, but less so than when at G, so it will appear to have increased in frequency - blueshifted."

How can you possibly state that the clock is changing frequency in the gp the same as the photon? Clearly a photon is becoming redshifted the further it gets from the ground, and a clock is becoming blueshifted the further it gets from the ground.

Now we can look at
Quote Evan
" Perhaps another way to look at this is from the viewpoint of photon energy:
- A photon has mass
- A photon gains energy as it falls into a gravitational well
- If a photon gains energy, its frequency is higher: This is gravitational blueshift for incoming photons.
- A photon loses energy as it climbs out of a gravitational well
- If a photon loses energy, its frequency is lower: This is gravitational redshift for escaping photons."

So this is the part that I am trying to bring to your attention.
If gravitational redshift and blueshift for a photon is due to being measured by a clock that is ticking faster or slower, then what's all this about light losing or gaining energy?
Are we saying that the light changes frequency/energy in the changing gp, 'AND' that clocks will measure the frequency of that light differently when they tick at different rates?
Title: Re: Gravitational shift or not?
Post by: alancalverd on 02/04/2018 19:43:43
A photon has mass
Bad starting point. What is the mass of a photon? It's easy to get confused when you start dividing by zero.

But that is of no consequence. You can skip the introduction and just note that in moving from a high to a low gravitational potential a photon must gain kinetic energy, and since its speed is constant, its frequency must increase. Which is exactly observed.

Quote
How can you possibly state that the clock is changing frequency in the gp the same as the photon? Clearly a photon is becoming redshifted the further it gets from the ground, and a clock is becoming blueshifted the further it gets from the ground.
It all depends on the relative position of the observer to the source. From the point of view F, Colin has raised the source of G therefore increased its gp and reduced its redshift relative to F. The photon's redshift likewise depends only on the gp difference between source and F. The redshift of the photon does not increase with distance, but with gp difference between source and observer. If you raise the photon source from G to A it will have the same redshift as the clocks at A when observed from F.
Title: Re: Gravitational shift or not?
Post by: jeffreyH on 02/04/2018 20:58:34
Think of it this way. The photon never changes. When it starts its journey it is being measured by a time dilated clock. So the frequency appears high. As the photon moves out of the gravity well the clocks are getting faster so that they record lower and lower frequencies. If you don't understand time dilation properly then you can get into all sorts of trouble.
Title: Re: Gravitational shift or not?
Post by: timey on 02/04/2018 21:04:46
@alancalverd, I did not say that photons have mass, that was Evan, whom I quoted. He is talking about photon energy/mass.

Also, I have clearly stated the relative positions of the observers.

So - you agree with me that a photon released at G, when arriving at A is redshifted from A's perspective, and when arriving at F is further redshifted from F's perspective.

And that a clock at G is redshifted from the perspective of A, and further redshifted from the perspective of F.  But if we move the clock from G and place it at A, the clock will be blueshifted as compared to when it was at G from A, F and G's perspective, and blueshifted further if we move the clock to F, from F and A and G's perspective.

Can you confirm that we are agreed upon the above?
Title: Re: Gravitational shift or not?
Post by: timey on 02/04/2018 21:09:19
Think of it this way. The photon never changes. When it starts its journey it is being measured by a time dilated clock. So the frequency appears high. As the photon moves out of the gravity well the clocks are getting faster so that they record lower and lower frequencies. If you don't understand time dilation properly then you can get into all sorts of trouble.

So you are saying that light itself does not gain or lose energy, and it only looks that way b/c of the clocks.
(Edit: Where it may be considered that stating this as the case puts you on shaky ground with regards to the remit of GR, in that GR requires that light change energy and frequency in order to remain travelling at the constant speed of light.)

So do the clocks lose or gain energy in order that their frequency is changed?
Title: Re: Gravitational shift or not?
Post by: Colin2B on 02/04/2018 22:58:52
Why does the far away clock need to be far away? The far away clock is a calculation tool, and only needs to be 'at' a differing gravity potential from the clock/clocks it is measuring.
In your example F cannot be at any differing gravitational potential, it has to be further away from M than either G or A.
A far away clock/observer is usually assumed to be at infinity - away from any influence of M.

By stating that the jacked up clock in the NIST experiment was measured by a far away clock you are misquoting what happened. The reference clock was the fixed ground clock, the jacked up clock was higher and hence showed blueshift. Don't confuse this with a reduction in redshift in your G, A, F scenario.
Title: Re: Gravitational shift or not?
Post by: timey on 02/04/2018 23:21:26
I know what the concept of far away clock is usually used for, but the concept works just fine when stating the clock to be closer, and as a third entity, is a useful means of showing the difference between 2 or more clocks it observes, and gives us the opportunity to talk about time dilation as observed by a third clock.

What NIST did, or did not do doesn't really affect the discussion as laid out in posts 26 & 27.

Quote Colin
" The reference clock was the fixed ground clock, the jacked up clock was higher and hence showed blueshift. Don't confuse this with a reduction in redshift in your G, A, F scenario."

My G, A, F scenario of clocks is no different. A reduction in redshift actually being blueshift. The reference clock observes the higher clock to be blueshifted, just the same as clock F and clock A observes clock G, when clock G was moved to clock A's position, as blueshifted compared to when clock G was on the ground.
(Edit: And if we say there was 2 clocks on the ground and clock G(a) was moved to A's position, clock G(b) left on ground also observes clock G(a) to be blueshifted.)
Title: Re: Gravitational shift or not?
Post by: alancalverd on 03/04/2018 06:50:06
@alancalverd, I did not say that photons have mass, that was Evan, whom I quoted. He is talking about photon energy/mass.
an uncharacteristic solecism, best not repeated.

Quote
So - you agree with me that a photon released at G, when arriving at A is redshifted from A's perspective, and when arriving at F is further redshifted from F's perspective.

And that a clock at G is redshifted from the perspective of A, and further redshifted from the perspective of F. 
These two experiments are identical and therefore give identical results.

Quote
But if we move the clock from G and place it at A, the clock will be blueshifted as compared to when it was at G from A, F and G's perspective, and blueshifted further if we move the clock to F, from F and A and G's perspective.

Can you confirm that we are agreed upon the above?
Yes. You have placed the source at a higher gravitational potential so it will appear blue (or less red) shifted to all observers.
Title: Re: Gravitational shift or not?
Post by: timey on 03/04/2018 07:15:03
So - as I have been saying for last 3 years, a photon shifts  oppositly to a clock in the gravity potential!

Glad we've got that sorted out.

So - what about what Jeff says in post 25?  He is saying that photons do not shift in the gp, and that they only appear shifted as a symptom of clocks being time dilated.

Do you share this viewpoint @alancalverd ?
Title: Re: Gravitational shift or not?
Post by: Colin2B on 03/04/2018 11:18:37
So - as I have been saying for last 3 years, a photon shifts  oppositly to a clock in the gravity potential!

Glad we've got that sorted out.

Do you share this viewpoint Alan?
I don’t see how you conclude that. Alan is saying same as me, photons sources and clocks behave same when measured from another location.
If i have time i’ll do you an example to show what happens.

What NIST did, or did not do doesn't really affect the discussion as laid out in posts 26 & 27.
But it does make a difference, see below

And if we say there was 2 clocks on the ground and clock G(a) was moved to A's position, clock G(b) left on ground also observes clock G(a) to be blueshifted.
Yes, but G(b) observes A to be always blueshifted, which differs from your original G, A, F scenario where reference F sees a redshift for both A and G. Also what you describe here for clocks is exactly the same for photon sources - there is no difference, they are not opposite.
Title: Re: Gravitational shift or not?
Post by: timey on 03/04/2018 11:28:58
Yes @Colin2B. Photon 'sources' behave the same way as clocks, but the photons themselves behave oppositely.

The particulars of how NIST measured their clocks is relevant.  But with regards to this discussion, we can manage just fine talking about clocks G, A, and F.

Photons 'do not' behave the same as clocks in the gravity potential.
Remember that when we moved clock G to A, that A observes the clock as blueshifted compared to when it observed clock G on the ground...
So if a photon behaves the same as a clock, then a photon released at G will be observed by A as blueshifted, when it arrives at A...
BUT a photon released at G and observed by A will be REDSHIFTED Colin, won't it?
Title: Re: Gravitational shift or not?
Post by: jeffreyH on 03/04/2018 14:26:16
If you view the photons as not changing it makes it more apparent WHY both photons and clocks combine to show the effects of shift. I was trying to make it easier for you to understand.
Title: Re: Gravitational shift or not?
Post by: jeffreyH on 03/04/2018 14:30:06
In a strong gravitational field we can treat that field like a medium though which the photons are traveling. Like any other medium it will affect the passage of light. Except that it is a directional medium. Red shift out and blue shift in. This is the whole basis for the equivalence of inertial and gravitational mass.
Title: Re: Gravitational shift or not?
Post by: guest45734 on 03/04/2018 14:48:57
Black holes emit x-rays and gamma rays

I think I am correct in stating Black holes emit x rays and gamma rays from the event horizon. Nothing escapes a blackhole once it has passed the event horizon, except perhaps hawking radiation.

Quasars emit x rays and gamma rays. Speculating once a blackhole has lost enough mass/energy due to hawking radiation can it become a quasar or supernovae? Big Bang?

With all the talk on time dilation, no one has mentioned distance foreshortening and muon lifetimes which is interesting, would it be inappropriate to discuss this on this thread.
Title: Re: Gravitational shift or not?
Post by: timey on 03/04/2018 15:27:34
If you view the photons as not changing it makes it more apparent WHY both photons and clocks combine to show the effects of shift. I was trying to make it easier for you to understand.
Again, Jeff, I have studied relativity for 10 years +. You don't need to make it easier for me to understand. My purpose here is to have a discussion 'about' relativity, rather than a lesson 'in' relativity.

So yes, as per my reposting of that discussion below...
Think of it this way. The photon never changes. When it starts its journey it is being measured by a time dilated clock. So the frequency appears high. As the photon moves out of the gravity well the clocks are getting faster so that they record lower and lower frequencies. If you don't understand time dilation properly then you can get into all sorts of trouble.

So you are saying that light itself does not gain or lose energy, and it only looks that way b/c of the clocks.
(Edit: Where it may be considered that stating this as the case puts you on shaky ground with regards to the remit of GR, in that GR requires that light change energy and frequency in order to remain travelling at the constant speed of light.)

So, (edited) looking at clocks, is there a possibilty that the clocks lose or gain energy in order that their frequency is changed?
Title: Re: Gravitational shift or not?
Post by: jeffreyH on 03/04/2018 16:44:45
I give up.
Title: Re: Gravitational shift or not?
Post by: timey on 03/04/2018 17:26:11
You give up? :(

This is how they answer at physics stack exchange:
https://physics.stackexchange.com/questions/172854/do-photons-lose-energy-due-to-gravitational-redshift-if-so-where-does-the-lost

" According to this paper, "On the Interpretation of the Redshift in a Static Gravitational Field", the answer I give below is a common but misleading interpretation.

The classical phenomenon of the redshift of light in a static gravitational potential, usually called the gravitational redshift, is described in the literature essentially in two ways: on the one hand the phenomenon is explained through the behaviour of clocks which run the faster the higher they are located in the potential, whereas the energy and frequency of the propagating photon do not change with height. The light thus appears to be redshifted relative to the frequency of the clock. On the other hand the phenomenon is alternatively discussed (even in some authoritative texts) in terms of an energy loss of a photon as it overcomes the gravitational attraction of the massive body. This second approach operates with notions such as the “gravitational mass” or the “potential energy” of a photon and we assert that it is misleading.

Do photons lose energy due to gravitational redshift?

More precisely, the redshift is how the loss of energy is manifest.

For a massive particle moving radially away from a (Newtonian) gravitational source, kinetic energy is 'traded' for gravitational potential energy. Since the KE is proportional to the speed squared, the loss of KE is manifest as reduced speed.

Since the speed of a photon is always cc, it might seem that photons would not lose energy propagating away from a gravitational source. However, as Einstein demonstrated with a simple thought experiment, if photons did not lose energy, we could in principle build a perpetual motion machine. From page 119 of "A first course in general relativity"'
Title: Re: Gravitational shift or not?
Post by: alancalverd on 03/04/2018 18:44:44
So - as I have been saying for last 3 years, a photon shifts  oppositly to a clock in the gravity potential!
No. The observed shift depends only on the difference in gravitational potential; between the source and the observer. It is exactly the same for all sources, as I said but you refuse to accept.
 
Quote
So - what about what Jeff says in post 25?  He is saying that photons do not shift in the gp, and that they only appear shifted as a symptom of clocks being time dilated.Do you share this viewpoint @alancalverd ?
It is the same phenomenon., differently expressed. The fractional change in observed clock frequency is the same as the fractional change in photon energy fore a given difference in gravitational potential because the laws of physics are the same for everyone and everything, everywhere.
Title: Re: Gravitational shift or not?
Post by: timey on 03/04/2018 19:46:41
Wtf @alancalverd ? Yes I do accept that  "The observed shift depends only on the difference in gravitational potential; between the source and the observer. It is exactly the same for all sources".

But the photons (NOT the source of the photons) the photons, ie: electro magnetic radiation, REDSHIFTS (as observed by observer in the higher potential, really don't know why I have to include this, it's obvious, and also the first thing one learns about relativity) as it moves away from a gravitational mass, and a clock, or a photon source BLUESHIFTS (as observed by the blah, blah) when placed in the higher potential)
And a photon IS shifted oppositely to a photon source/clock in the gravity potential.

You say that is the same phenomenon, differently expressed.
Yes, as shown in the physics exchange quote/link in post 39.

However, given that you say that physics is the same for everyone everywhere, it hardly seems possible that light would deem to 'have' a constant energy in one description, yet would deem to gain or lose energy in the other description.

Light/electro magnetic radiation cannot be doing both.

(BTW, my sister and I are looking after grandma Joan, who is 103 years age, for few days. She's great, a real trooper. 103, fancy that aye!)
Title: Re: Gravitational shift or not?
Post by: jeffreyH on 03/04/2018 20:07:21
Well as I said already. I give up.
Title: Re: Gravitational shift or not?
Post by: timey on 03/04/2018 20:23:40
Well as I said already. I give up.

Yes - well that is very boring of you.
Title: Re: Gravitational shift or not?
Post by: alancalverd on 03/04/2018 23:03:55
I'm with Jeffrey. You are incorrigible. Perhaps Grandma Joan will persuade you of the error of your thinking - give her my best wishes.
Title: Re: Gravitational shift or not?
Post by: Colin2B on 03/04/2018 23:11:31
OK, one last try, then I’m with Jeff & Alan

Photons 'do not' behave the same as clocks in the gravity potential.
Remember that when we moved clock G to A, that A observes the clock as blueshifted compared to when it observed clock G on the ground...
So if a photon behaves the same as a clock, then a photon released at G will be observed by A as blueshifted, when it arrives at A...
BUT a photon released at G and observed by A will be REDSHIFTED Colin, won't it?
We are in danger here of not comparing like with like. To move a clock is the equivalent of moving a source, in this case a source of ticks, so let’s clarify.

We have a clock H = highest, above A (I want to avoid ‘far away’ as it has a specific meaning)
We have a clock A = above ground
We have a clock G = on the ground

Let’s say for easy numbers clock H is 2x faster than A which is 2x faster than G, so H is 4 times faster than G.

Clock G thinks it is running at 1s/s but we want to know what H measures it as. So G sets off a light which flashes once every tick =1/second, which we let run for say 20 flashes. H sees those 20 flashes but, because it is running 4x faster, 80s have passed thus the ticks released at G are measured at H as tick rate = 20/80 = 0.25ticks/s ie redshift.
Similarly A measures G as 0.5ticks/s ie redshift, but less so than H measures G.
Also H sees A as 0.5ticks/s. So if G moves to A, H will see it as having same redshift as A.
This is exactly the same behaviour as photons and photon sources.

The point about where the reference clock is in the NIST experiment is that a clock at ground level will always see clocks, sources or photons from above it as blueshifted, unless the clock or source is lowered towards it.

For the benefit of the OP it is also important to note that we can set up G, A and H at any height above the ground and as long as the ratio of Gravitational Potential (GP) between them remains the same we will get the same result. In other words these shifts depend only on difference in GP and not directly on height or distance.




Title: Re: Gravitational shift or not?
Post by: timey on 03/04/2018 23:33:25
I'm with Jeffrey. You are incorrigible. Perhaps Grandma Joan will persuade you of the error of your thinking - give her my best wishes.

Well I'm with @evan_au
- A photon loses energy as it climbs out of a gravitational well
- If a photon loses energy, its frequency is lower: This is gravitational redshift for escaping photons.
...and with them's that are over at physics stack exchange:
https://physics.stackexchange.com/questions/172854/do-photons-lose-energy-due-to-gravitational-redshift-if-so-where-does-the-lost

Honestly Alan, sometimes I wonder if you purchased your physics degree off that dodgy dude round back of Kings Cross station (chuckle)
(For the benefit of OP who might not be used to mine and Alan's banter, that was a joke)

And while I'm at it, you know how sometimes a person can have more than one profile? Well there have been times when I have, just very briefly, wondered if you actually are Jeff, lol.

I will most certainly shout your best wishes to Joan. She's a tad hard of hearing, doesn't get about too much anymore, but loves her food, and is excellent company for short times between long sleeps.

Very good evening to you, don't know why, absolutely no reason for it, but I'm in a f'ing brilliant mood tonight.
Title: Re: Gravitational shift or not?
Post by: timey on 04/04/2018 00:22:03
@Colin2B I don't know why you have to complicate the matter. Einstein himself said that light (not a light source) loses energy climbing out of a gravitational well. If the light has lost energy, it is redshifted.

So imagine now a light source placed on ground producing a continuous stream of photons that are escaping the gravitational well.
Place 10 clocks at 1 metre elevation apart in the gravity potential, and at each elevation the clock there will tick faster than the clock below. ie: blueshifted.
So at each position of elevation in the gravity potential the clock at that position is blueshifted, and at each position of elevation in the gravity potential, when the light arrives there, the light is redshifted.

Now tell me that light that is escaping a gravitational well behaves the same as a clock placed at elevation in the gravity potential of a gravity well.  I double, triple, dare you. (Chuckle)

However, what I really want to discuss is the fact that the elevated clocks are ticking faster, and that this affects the measurement of the observation of the arriving light. And I want to discuss this in relation to how this affects the fact of light losing energy when climbing out of a gravity well.
Title: Re: Gravitational shift or not?
Post by: alancalverd on 04/04/2018 08:23:57

Well I'm with @evan_au
- A photon loses energy as it climbs out of a gravitational well
- If a photon loses energy, its frequency is lower: This is gravitational redshift for escaping photons.

...Alan, sometimes I wonder if you purchased your physics degree off that dodgy dude round back of Kings Cross station (chuckle)

Exactly the point. Kings Cross being the lowest potential point on the route, the train that leaves KX uses a lot of energy to get to Cambridge.

The train that leaves from Stevenage only uses half as much energy to get here, so on arrival it's blueshifted compared with the KX train.

The dodgy degree I got from the bloke  in Cambridge market has a genuine Cantab attached. I think it was from Carlsberg Export (only the best at High Table), but it was an official seal. 
Title: Re: Gravitational shift or not?
Post by: timey on 04/04/2018 09:00:28
Alan, surely no matter if you are travelling from Kings Cross, or Stevenage, your sharp eye would be checking the clock at every station, noting that each is running faster than the last, and you will be scratching your head as to how much energy your train has actually lost?

I didn't know they sold degrees in Cambridge Market.  Good to hear Kings Cross doesn't have the monopoly, and a genuine cantab to boot. Sounds like you've 'probably' got the best degree in the world (or was that Heineken?)
Title: Re: Gravitational shift or not?
Post by: alancalverd on 04/04/2018 13:06:44
Alan, surely no matter if you are travelling from Kings Cross, or Stevenage, your sharp eye would be checking the clock at every station, noting that each is running faster than the last, and you will be scratching your head as to how much energy your train has actually lost?

No. As the station clock is always at the same gravitational potential as my watch, there will be no difference in tick rate.
Title: Re: Gravitational shift or not?
Post by: timey on 04/04/2018 15:28:02
Well we'd better invoke the far away clock then.
Title: Re: Gravitational shift or not?
Post by: alancalverd on 04/04/2018 20:15:13
By all means. Seen from Cambridge, the KX clock will be ticking slower than the STV  clock, which will be ticking slower than the CAM clock. And the 21 cm hydrogen line photon from a lamp at KX will have a greater red shift than one emitted from STV. Exactly as observed in laboratories and observatories, and predicted by general relativity,  for the last several years.
Title: Re: Gravitational shift or not?
Post by: guest45734 on 04/04/2018 20:38:10
don't know why you have to complicate the matter. Einstein himself said that light (not a light source) loses energy climbing out of a gravitational well. If the light has lost energy, it is redshifted.

Why not consider space to be flowing towards mass (gravity), or expanding in between masses/galaxies (Dark energy). What is the obsession with gravity wells and acceleration in 4 D space time. Why not add additional dimensions ?D space time.
Title: Re: Gravitational shift or not?
Post by: alancalverd on 04/04/2018 21:43:50
1. KISS

2. Facts.
Title: Re: Gravitational shift or not?
Post by: timey on 04/04/2018 23:48:43
By all means. Seen from Cambridge, the KX clock will be ticking slower than the STV  clock, which will be ticking slower than the CAM clock. And the 21 cm hydrogen line photon from a lamp at KX will have a greater red shift than one emitted from STV. Exactly as observed in laboratories and observatories, and predicted by general relativity,  for the last several years.

Yes exactly!
So the train (light) travelling from KX, to CAM, via STV, is losing energy.  At each station the train is observed as redshifted according to the blueshifted clock at that station, by remit of measuring the train's (light's) frequency via the faster ticking clock.

So - is the redshifted train losing energy, or is the redshifted train's energy constant?
Title: Re: Gravitational shift or not?
Post by: alancalverd on 05/04/2018 07:05:14
Redshift = less energy.

And just to get ahead of your next posting: the energy loss equals the gravitational potential difference between the source (KX) and the observer (STV or CAM).  An identical train starting from STV would have less redshift on arrival at CAM because it started with the same amount of fuel but further up the track.

Actually it's a crap analogy as the line is almost horizontal. Think of the Snowdon mountain railway starting from Llanberis (LL) and seen from Halfway (HW) and the top (SN) , compared with one that starts at HW.
Title: Re: Gravitational shift or not?
Post by: timey on 05/04/2018 10:08:10
Yes " the energy loss equals the gravitational potential difference between the source (KX) and the observer (STV or CAM)", but the blueshifted clocks at the stations are also equal to the gravitational potential difference.  But note that the redshift of the light (train) is 'measured' via the clock at the station.

As things stand, we are now making a double usage of a singular gravitational potential difference.  That is like saying 1+1=1. 
If you can accept this as fact Alan, then we can start talking in terms of special relativity and flat space..
Title: Re: Gravitational shift or not?
Post by: alancalverd on 05/04/2018 15:47:05
Yes " the energy loss equals the gravitational potential difference between the source (KX) and the observer (STV or CAM)", but the blueshifted clocks at the stations are also equal to the gravitational potential difference.  But note that the redshift of the light (train) is 'measured' via the clock at the station.

as is the redshift of the clock at the lower potential, when seen from the higher potential. It doesn't matter whether you send me a photon, a train, or a carrier pigeon: if you are at a lower gp than me, it will be redshifted on arrival compared with a carrier pigeon born in Cambridge. 
Title: Re: Gravitational shift or not?
Post by: guest45734 on 05/04/2018 17:12:42
1. KISS

2. Facts.

1 KISS: it is easy to envisage at the noddy level space as membrane being absorbed by mass/flowing towards it, and in the absence of mass space expanding. This gives a noddy level understanding of gravity and dark energy, it also helps when viewing red/blue shift near gravity wells if the 3 dimensional medium the light is oscillating through is moving.

2 FACTS: Space time can be said to be the multi dimensional framework within which we locate events and describe the relationships between them in terms of space and time. The concept of space time follows from the observation that the speed of light is invariant. The equations of GR describe gravity as simply geometry which is altered in the presence of mass. Space time can be warped, twisted curved, and have gravitational waves. We observe distant galaxies and stars lensed by the geometry and curvature of space time.

How and why spacetime curvature isn't considered in relativity. BUT for a noddy level appreciation of space time if space is assumed to be a multidimensional membrane or sheet that contracts as it moves towards mass and expands in the absence of mass. I find it helps to explain time dilation, and Muon lifetimes, and many other effects of space time, including Gravitational lensing, and frame dragging for example. If you add to this the general statement that quantum fluctuations are the cause of the expansion and contraction of the membrane of space, and possibly include an additional dimension to explain the effects of non locality and entanglement. Then I suspect you have a basic idea of the Hows and Whys of space time.  One does not need to focus on the type of quantum fluctuation when dealing in generalities such as I have stated here. The theoretical virtual graviton is a spin 2 boson, which is a quantum fluctuation.

Red shift and blue shift of photons is easy to explain using the flowing space concept. I trying to help apologies
Title: Re: Gravitational shift or not?
Post by: alancalverd on 05/04/2018 17:54:32
If it's simpler than everyday relativity, let's see the calculation! Use 14 keV photons falling about 22 meters in earth's surface gravity.
Title: Re: Gravitational shift or not?
Post by: timey on 05/04/2018 18:00:20
Yes " the energy loss equals the gravitational potential difference between the source (KX) and the observer (STV or CAM)", but the blueshifted clocks at the stations are also equal to the gravitational potential difference.  But note that the redshift of the light (train) is 'measured' via the clock at the station.

as is the redshift of the clock at the lower potential, when seen from the higher potential. It doesn't matter whether you send me a photon, a train, or a carrier pigeon: if you are at a lower gp than me, it will be redshifted on arrival compared with a carrier pigeon born in Cambridge. 

Yes - we already established this.
But - if the light is measured as redshifted by the blueshifted clock, then as Jeff pointed out earlier, the light will not be losing energy in the higher potential, and it is only because the clock is ticking faster that the light is measured as redshifted.

You cannot state the light as redshifted due to being measured by a blueshifted clock in addition to stating that the light changes frequency due to losing energy.  Not if you are describing the measure of both instances as occurring due to the difference in gravity potential between source and receiver. In doing so you are using 2 helpings of the difference in gravity potential.
Title: Re: Gravitational shift or not?
Post by: alancalverd on 05/04/2018 20:57:24
Light is redshifted in comparison with a photon generated by the same process at the receiver. Whether you calculate the redshift by considering kinetic energy loss, or time dilatation as measured by identical clocks,  you get the same answer, because the only difference between the source and the receiver is their gravitational potential difference.

If this were not so, you could generate free energy.

I have said, umpteen times, that a = b. Why do you  accuse me of saying that a = 2b?
Title: Re: Gravitational shift or not?
Post by: jeffreyH on 06/04/2018 00:35:14
@timey Try actually studying Alan's answer above and its implications. It gets right to the point.
Title: Re: Gravitational shift or not?
Post by: timey on 06/04/2018 02:08:27
Light is redshifted in comparison with a photon generated by the same process at the receiver. Whether you calculate the redshift by considering kinetic energy loss, or time dilatation as measured by identical clocks,  you get the same answer

Of course you get the same answer if you calculate via kinetic energy loss, or alternatively calculate via time dilation as measured by identical clocks...

However it does not escape my notice that time dilation and kinetic energy loss are phenomenon that are both occurring simultaniously. Therefore if you calculate only via kinetic energy loss, or only via time dilation, then 'one' is negating half of the story...leading to a special relativity conversation, but never mind.

Let's change tack...
This is interesting:

If this were not so, you could generate free energy.

Can you describe your understanding of why "if this were not so, you could generate free energy" ?
Title: Re: Gravitational shift or not?
Post by: Colin2B on 06/04/2018 08:37:15
However it does not escape my notice that time dilation and kinetic energy loss are phenomenon that are both occurring simultaniously. Therefore if you calculate only via kinetic energy loss, or only via time dilation, then 'one' is negating half of the story...leading to a special relativity conversation, but never mind.
They would only be ‘negating’ if one was working in opposition to the other, which they are not. They are different sides of the same coin.
Remember that any measure of energy will involve time in the equation, if time changes so does energy, it all works together.

I hadn't intended to reply to your earlier reply to me as i seemed to be on a hiding for nothing, but i cant help feeling this is part of your confusion regarding clocks and photons working in opposite directions.


Let's change tack...
This is interesting:

If this were not so, you could generate free energy.

Can you describe your understanding of why "if this were not so, you could generate free energy" ?
You provided the textbook explanation in your link https://physics.stackexchange.com/questions/172854/do-photons-lose-energy-due-to-gravitational-redshift-if-so-where-does-the-lost
Not sure Alan would say anything that differs.


Anyway, here for reference, whether you choose to read it or not, is my reply to your earlier post which I had decided not to post.

@Colin2B I don't know why you have to complicate the matter.
I haven’t complicated anything, just explaining how the measurements are made.

Place 10 clocks at 1 metre elevation apart in the gravity potential, and at each elevation the clock there will tick faster than the clock below. ie: blueshifted.
So at each position of elevation in the gravity potential the clock at that position is blueshifted, and at each position of elevation in the gravity potential, when the light arrives there, the light is redshifted.
However, i see you are still confusing how the measurements are made.
Blueshift/redshift are only meaningful when related to a specific reference clock and you are using 2 reference clocks above.
“10 clocks at 1 metre elevation apart in the gravity potential, and at each elevation the clock there will tick faster than the clock below. ie: blueshifted.” - here you are comparing each stationary clock with the one below.
“when the light arrives there, the light is redshifted” - only when observed by a clock above the photon source.
You are using different reference clocks and getting different answers, surprise, surprise.

Now tell me that light that is escaping a gravitational well behaves the same as a clock placed at elevation in the gravity potential of a gravity well.  I double, triple, dare you. (Chuckle)
As I have already explained, you are not comparing like with like.

However, what I really want to discuss is the fact that the elevated clocks are ticking faster, and that this affects the measurement of the observation of the arriving light.
which is what I have explained. Just do the same calculations I used for clocks G, A & H, using photon frequencies instead of the light flashes.
Lets say photon source at G emits frequency of 600THz. Clock at H is running 4x faster than clock G so will measure the photon frequency as 600\4 THz ie redshifted. H will measure photons from A as 600\2 THz ie still redshifted but less than G.
Move source G to A and H will measure 600\2 THz ie redshifted but less so = blueshift.
Now compare this with what I described for clocks and you will see they are the same.
However, make G your reference clock and it will see A & F as blueshifted and if H is lowered to A, G will still see blueshift, but less so = redshift.

Title: Re: Gravitational shift or not?
Post by: evan_au on 06/04/2018 13:39:32
Quote from: timey
So at each position of elevation in the gravity potential the clock at that position is blueshifted, and at each position of elevation in the gravity potential, when the light arrives there, the light is redshifted.
- This description assumes that "redshift" or blueshift" is an absolute thing. It is not, it is a relative thing, so you always need to say "redshifted compared to (some reference point)".
- This description is also confusing clocks and light. Now there are some visible-light trapped ion clocks that can do both functions at once, and might avoid this source of confusion.

I think the scenario you are trying to present is:
- A light beam is emitted by a trapped ion source from the lowest clock. When viewed by a higher clock with the same type of trapped ion source, the lower clock will be seen to be emitting photons with a lower frequency (red-shifted), and will be emitting ticks more slowly than the "local" (higher) trapped ion clock.
- Conversely, assume that a light beam is emitted by a trapped ion source from the higher clock. When viewed by the lower clock with the same type of trapped ion source, the higher clock will be seen to be emitting photons with a higher frequency (blue-shifted), and will be emitting ticks more rapidly than the "local" (lower) trapped ion clock.
- The clock ticks are shifted by the same percentage amount, and in the same direction as the visible light frequency shift from the same trapped-ion clock.
- No matter where your local clock is located (high or low in the gravitational well), it will seem to be keeping perfect time, and will be neither redshifted nor blueshifted compared to other trapped ion clocks at the same altitude.

Quote from: disinterested
Quasars emit x rays and gamma rays. Speculating once a blackhole has lost enough mass/energy due to hawking radiation can it become a quasar or supernovae?
It is true that if a hypothetical micro-black hole did evaporate, it would go off like a massive nuclear device, emitting large amounts of energy for its last few microseconds.
But this level of peak power level from a micro black hole is nothing compared to the peak power output of a supernova or a quasar.
See: https://en.wikipedia.org/wiki/Micro_black_hole

Another difference is in the duration of the emission:
- Supernovae emit huge amounts of energy for weeks, after which they fade away over a period of months. At its peak, it may equal the brightness of the whole galaxy in all directions.
- Quasars emit huge amounts of energy continuously for years. If it is pointing in our direction, it will outshine the whole galaxy continuously.

They have very different sources of energy, have black holes of very different masses, and are visible over very different distances:
- A hypothetical micro-black hole (weighing as much as a small mountain) would release the mass-energy of a small mountain via Hawking radiation in its last seconds of life. This might be detectable if it were nearby in our spiral arm of our galaxy (we haven't any confirmed detections yet).
- A core collapse supernova (weighing, say, 10 solar masses) would release a mass-energy greater than the Earth, lighting up the debris field for weeks. This is visible from another galaxy cluster. At its center would be a black hole weighing a few times the mass of the Sun, which would emit very little Hawking radiation, but which could pull in a small accretion disk from the debris of the explosion.
- A quasar is formed from the supermassive black hole (weighing perhaps millions to a billion times the mass of the Sun), which is actively drawing in gas, dust and stars from the dense accumulation of matter at the core of a galaxy. This forms a very hot accretion disk, accelerating matter to perhaps 30% of c before it enters the event horizon. A small fraction of this matter and energy is funneled into a "polar jet" of matter emitted at almost the speed of light away from the black hole. If that polar jet happens to be facing towards Earth, we can see it >80% of the way across the observable universe.
See: https://en.wikipedia.org/wiki/Quasar
Title: Re: Gravitational shift or not?
Post by: alancalverd on 06/04/2018 21:21:04
To compress Colin's patient explanation to one equation

up ≠ down

specifically

up = − down
Title: Re: Gravitational shift or not?
Post by: timey on 07/04/2018 00:01:58
They would only be ‘negating’ if one was working in opposition to the other, which they are not. They are different sides of the same coin.
Remember that any measure of energy will involve time in the equation, if time changes so does energy, it all works together.

Yes I agree.  However, if one makes a calculation of it all working together, including changes in energy as per the difference in gravity potential between source and receiver, and also including changes in time as per the difference in gravity potential between source and receiver... Then within the calculation, one has used the fact of the difference in gravity potential between source and receiver twice, when the physicality of the difference only occurs once.

“10 clocks at 1 metre elevation apart in the gravity potential, and at each elevation the clock there will tick faster than the clock below. ie: blueshifted.” - here you are comparing each stationary clock with the onebelow.
“when the light (from light source on ground) arrives there, the light is redshifted” - only when observed by a clock above the photon source.
You are using different reference clocks and getting different answers, surprise, surprise.

Can we please consider 'how' we are observing the signal from the clock?
So - going back to the light source that stays on the ground - each clock (observer) above observes that light (electromagnetic radiation) only when it arrives in the reference frame of that observer.  So - in this scenario we are always using the clock above as the reference frame.
Now going back to the clocks. Let's also use the clock above as the reference frame.
So - just to set the scene, the 1st clock is on the ground, and observes the light at a certain frequency.  The 2nd clock observes the 1st clock as ticking slower (redshifted). The 3rd clock observes the 2nd clock as ticking slower than itself, and it also observes the clock on the ground as being further redshifted (as it will the light arriving from the light source on ground).  So the clock and the light source are behaving the same.  Move the light source up to clock 2's position, and clock 3 will observe the light arriving from the light source as less redshifted, as per bueshifted in comparison to the observation of that light when it was arriving from the ground position.
Now we look at the electromagnetic radiation, where we are now making a distinction between the radiation itself and it's source

Example 1: The source of this radiation is being affected in the gravity potential. We just established this above by measuring the differences with a 3rd clock.  The 3rd clock observes that there is less redshift (ie:blueshift) if the light source is moved to clock 2's position.

Exmple 2: The radiation itself is being affected in the gravity potential, we just established this. The 3rd clock observes this radiation as being more redshifted (ie: redshifted) than the 2nd clock did when the radiation arrives there.

Example 3: The clock behaves the same as a light source.  We just established this above. When the light source was moved from ground to clock 2's position, the 3rd clock observed the arriving radiation as less redshifted (ie: blueshifted), as is clock 2 in comparison to clock 1, according to clock 3.

So here I have given specifics from the 3rd clocks perspective where:
A light source or a clock elevated in the gravity potential are observed to be "less redshifted (ie: blueshifted)
And:
Electromagnetic radiation escaping upwards in the gravity potential is observed by clock 3 to be "more redshifted (ie: redshifted)" than clock 2 is.

Therefore electromagnetic radiation shifts oppositely in the higher gravity potential than a clock or light source does.
Now we are back to the phenomenon of measuring the frequency loss of the electromagnetic radiation via the increased tick rate of the clock, versus measuring the frequency loss of the electromagnetic radiation via the loss of kinetic energy.

Where, these both being two sides of the same coin, if 'each' are seperately calculated as per the difference in gravity potential between source and receiver, this constitutes using the difference in gravity potential between source and receiver twice in the calculation, where the phenomenon of difference is only occurring once.

OK let's work backwards through that, as I have feeling you may complain about example 2, in that I have had to refer back to clock 2 in order to make description. Of course we could just phone observer with clock 2 and ask him what frequency he is observing, but this question does rather depend on what frequency the observer at clock 2 is perceiving his clock to have. He thinks that his clock is ticking normally (same frequency as he would observe if he where on the ground) and that clock 1 on the ground is ticking slower than normal.  Fortunately clock 3, who also observes his clock ticking normally, can see that there is a difference between clock 1 and clock 2, so it follows that his clock will be subject to same phenomenon, he can see by how much clock 1 is slower than 2, and by how much his clock is faster than 2, and calculates the difference between his clock and the clock 1 on ground via the difference in gravity potential between source and himself, the receiver.
OK, so now he calculates for the frequency of the electromagnetic radiation.  He can, on the basis that the clocks are ticking faster via the difference in gravity potential between source and receiver, say that he is measuring the light via a faster tick rate as compared to the rate that he observes clock 1 to be ticking at, remembering that he has established that both his clock, being clock 3, and clock 2 are indeed running faster than clock 1...  Or he might calculate that the electromagnetic radiation is losing frequency b/c it is losing kinetic energy while escaping into the higher gravity potential, where this kinetic energy loss calculation also directly corresponds to the difference in gravity potential between source and receiver.

Where again I have given the perspective from the 3rd clock, and again we are looking at two sides of the same coin that are occurring simultaneously. If each are calculated as per the difference in gravity potential between source and receiver, this constitutes using the difference in gravity potential between source and receiver twice in the calculation.

You said:
Remember that any measure of energy will involve time in the equation, if time changes so does energy, it all works together.

If the difference in gravity potential between source and receiver is being used twice in the calculation, it is little wonder that general relativity gives twice the curvature of Newton.

Einstein has said that light must change energy, b/c if it didn't then we could generate free energy.  Presumably (correct me if I am wrong) this is b/c if light didn't change energy then the energy change would be occurring for the clock, and physics states that it doesn't. (don't see why it can't be energy changes for both myself, but that's my story and I'll keep that on my thread).

@evan_au , just read your post, think I've addressed the points you mention in the post above answering Colin. Enjoyed the points on Black holes and quasars.
Title: Re: Gravitational shift or not?
Post by: Colin2B on 07/04/2018 06:43:46
Yes I agree.  However, if one makes a calculation of it all working together, including changes in energy as per the difference in gravity potential between source and receiver, and also including changes in time as per the difference in gravity potential between source and receiver... Then within the calculation, one has used the fact of the difference in gravity potential between source and receiver twice, when the physicality of the difference only occurs once.
Can you provide a worked example of a calculation which uses GP twice?

Remember that any measure of energy will involve time in the equation, if time changes so does energy, it all works together.
If the difference in gravity potential between source and receiver is being used twice in the calculation, it is little wonder that general relativity gives twice the curvature of Newton.
But it isn’t used twice in any of the calculations.
Take simple example E = hf, it is fairly obvious that if time varies then E will vary (in inverse proportion). Single calculation.

However, I don’t mind what you use in your own theory, I won’t challenge it.

@evan_au , just read your post, think I've addressed the points you mention in the post above answering Colin.
Alan, Evan and myself have said the same thing, the points don’t need to be ‘addressed’.
Again, I don’t mind what you use in your own theory, I won’t challenge it.
Title: Re: Gravitational shift or not?
Post by: alancalverd on 07/04/2018 08:08:10
A light source or a clock elevated in the gravity potential are observed to be "less redshifted (ie: blueshifted)
No. blueshift is in the opposite direction to redshift. The comparison is always and only with the receiver reference. Forget clocks, think about pianos. If you are on the moon and there are two pianos playing C, one on the ground and one in low earth orbit, you will hear Bb and B respectively, but never C#.

This may be the basis of your misunderstanding. Remember every measurement is made relative to the local clock/Mossbauer linesource/piano/whatever.
Title: Re: Gravitational shift or not?
Post by: timey on 07/04/2018 21:09:27
Oops Alan, you seem to have committed the cardinal sin of forum quoting in that you have forgotten to include the rest of the paragraph in your quote. I have added the rest of the paragraph back in in inverted coma's...

"So here I have given specifics from the 3rd clocks perspective where:"
A light source or a clock elevated in the gravity potential are observed to be "less redshifted (ie: blueshifted)
"And:
Electromagnetic radiation escaping upwards in the gravity potential is observed by clock 3 to be "more redshifted (ie: redshifted)" than clock 2 below is measuring of the light".
No. blueshift is in the opposite direction to redshift. The comparison is always and only with the receiver reference. Forget clocks, think about pianos. If you are on the moon and there are two pianos playing C, one on the ground and one in low earth orbit, you will hear Bb and B respectively, but never C#.

This may be the basis of your misunderstanding. Remember every measurement is made relative to the local clock/Mossbauer linesource/piano/whatever.


Now that I have added in the rest of the paragraph, your post is somewhat superfluous.

Yes " blueshift is in the opposite direction to redshift." and electromagnetic radiation shifts oppositely to a light source or clock in both the up and the down directions of the gravity potential.
Title: Re: Gravitational shift or not?
Post by: alancalverd on 07/04/2018 22:20:53
Rubbish.
Title: Re: Gravitational shift or not?
Post by: timey on 07/04/2018 23:57:11
Rubbish.
So - according to you it is rubbish that electromagnetic radiation shifts oppositely to how a clock or light source shifts in the up direction, or the down direction.
So if they both shift the same way in the same direction then:

Clock 3 (that is above clock 2, that is above clock 1 on the gound) will observe the electromagnetic radiation that is escaping a gravitational well from a light source on the ground as blueshifted, just as clock 3 observes clock 2 to be less redshifted, ie: blueshifted, as compared to clock 3's observation of clock 1 on the ground.  And clock 2 will observe electromagnetic radiation escaping a gravitational well from a light source on the ground to be blueshifted, just as clock 2 would observe clock 1, when clock 1 is elevated to clock 2's position, to be less redshifted, ie: blueshifted, as compared to when clock 1 was on the ground.

Now the shift of clocks and the shift of electromagnetic radiation are shifting the same in the up direction.  Electromagnetic radiation is blueshifting at higher positions in the gravity potential just like clocks are observed to do.

But that is not what clock 3 observes in real life Alan. Clock 3 will observe clock 2 as less redshifted (ie:blueshifted) than it observes clock 1 to be, and it observes electromagnetic radiation from light source on ground as more redshifted, (ie: reshifted) than clock 2 will observe that light to be.

Yes, you can say that it is b/c the clock is ticking faster that the electromagnetic radiation is measured as having a lower frequency, but this requires that one say that the electromagnetic radiation is 'not' losing kinetic energy as it escapes the field.

I have made a reply to Colin's post which I am posting below that I think you should read.  Apart from that, you have asked me in the past to 'not put words in your mouth'.  I now ask you to please not partially quote my posts in a manner that negates to include the very point you then berate me over as a misunderstanding. In this instance I had 'clearly' indicated the receiver reference, this being clock 3.
Title: Re: Gravitational shift or not?
Post by: timey on 07/04/2018 23:59:37
Alan, Evan and myself have said the same thing, the points don’t need to be ‘addressed’.

I don't know why it is that you guys seem to get so defensive. I didn't mean that the points 'needed' to be addressed.  I just said that I had addressed them, as in evan_au had included the fact that a person with their clock perceives their clock to be ticking normally, and I had already mentioned that, and other things he said, in the post I was posting.

Colin, you ask:
Can you provide a worked example of a calculation which uses GP twice?

The GR equations 'are' using a double dollop of the difference in gravity potential, in that they are accounting for time being faster in the higher gravity potential, via the difference in gravity potential between source and receiver, and they are accounting for the frequency change due to kinetic energy loss for light via the difference in gravity potential between source and receiver.

Jeff says here that:
Think of it this way. The photon never changes. When it starts its journey it is being measured by a time dilated clock. So the frequency appears high. As the photon moves out of the gravity well the clocks are getting faster so that they record lower and lower frequencies. If you don't understand time dilation properly then you can get into all sorts of trouble.

If the shift of the photon (escaping from source on ground) is measured by remit of the amount by which the faster ticking (elevated) clock is ticking, then if we 'correct' the elevated clock to tick as the ground clock ticks, according to Jeff's post, and Evan's post 1, the photon has not changed energy.
Why? B/c the amount by which the clock is ticking faster corresponds to the difference in gravity potential between source and receiver.

If the shift of the escaping photon is measured by remit of kinetic energy loss, the change in frequency observed of that light in the higher potential 'cannot' be due to the measuring by the faster ticking clock.
Why?  B/c the frequency change due to the kinetic energy loss corresponds to the difference in gravity potential between source and receiver.

GR equation then distorts the geometry of space via time on the left side, and states this as equal to energy considerations on the right.  Which is all very well, but it leaves us with this:

https://en.m.wikipedia.org/wiki/Cosmological_constant_problem

And although the calculation for the redshift of light escaping a gravitational well due to kinetic energy loss is equal to the calculation for the blueshift of clocks in the higher gravity potential, both kinetic energy loss and clocks ticking faster, as part and parcel of a mathematical spacetime structure, are occurring simultaniously.
So if there is an energy change in the escaping electromagnetic radiation, then it is not as Jeff said, and photons do change energy/frequency due to kinetic energy loss, but we also have experimental proof that clocks do tick faster in the higher potential, so the measurement of the redshift in the higher potential, by the faster ticking clock, must "also" be a factor...
(none of the above has bog all to do with my theory, but...)

In which case, as a matter of conversation, the only logical conclusion that I can see is that the calculation of the observed redshift of the electromagnetic radiation by the faster ticking clock is half times the difference in gravity potential between source and receiver... And that the observation of a faster ticking clock is half times the difference in gravity potential between source and receiver.
But to be clear, that is just my opinion.
Title: Re: Gravitational shift or not?
Post by: alancalverd on 08/04/2018 07:30:13
PLEASE, for you own sanity, note that "less redshifted" is not the same as "blueshifted". I was looking forward to flying with you in the summer, but if you  don't appreciate the difference between "less left"  and "right", or "less climb" and "dive" you will kill us both.

Now if we delete the misleading bullshit
Quote
Clock 3 will observe clock 2 as less redshifted (ie:blueshifted) than it observes clock 1 to be, and it observes electromagnetic radiation from light source on ground as more redshifted, (ie: reshifted) than clock 2 will observe that light to be.

In other words, the redshift of all signals depends only on the relative gravitational potential of the source and receiver. KISI.
Title: Re: Gravitational shift or not?
Post by: Colin2B on 08/04/2018 08:16:41
I don't know why it is that you guys seem to get so defensive.
Not being defensive, just trying to help you understand reality   ;)

The GR equations 'are' using a double dollop of the difference in gravity potential, in that they are accounting for time being faster in the higher gravity potential, via the difference in gravity potential between source and receiver, and they are accounting for the frequency change due to kinetic energy loss for light via the difference in gravity potential between source and receiver.
Let’s take a simple maths eg of rt angled triangle. We are given an angle and length of hypotenuse. We can find the length of other 2 sides but it is 2 separate calculation each using the angle and hypothesis, so they are used twice. However, we can’t say this has doubled the angle or the hypotenuse.
This separation of calculations happens a lot in maths.

Just to emphasise what Alan is saying: shift implies that the frequency of a single source has changed, you can’t use it to describe differences in frequency between separate sources.
Title: Re: Gravitational shift or not?
Post by: timey on 08/04/2018 13:20:09
@Colin2B , that is b/c you are using a mathematical process to determine a 'predetermined' geometrical shape from a start point of limited information.

Calculating via the difference in gravity potential between source and receiver is using a determined physicality, (physicality (a)), to determine the 'magnitude' of a physicality.

By using the 'magnitude' of the determined physicality (a), that occurs only once in the observation process, in order to calculate both the 'magnitude' of the faster ticking clocks in the higher potential, (physicality (b)), and the magnitude of the frequency drop due to kinetic energy loss for electromagnetic radiation escaping into the higher potential, (physicality (c)), physicality (a) has been used twice to describe the 'magnitude' of physicality (b) and the 'magnitude' of physicality (c).

There is a distinction between the way that physicality (a) is being used twice in the GR equation, once on the left, and once on the right.
In the left side of the GR equation clocks in the higher potential are used as ticking faster via the difference between source and receiver and this extends the hypotenuse for the GR geometry.
In the right side of the equation electromagnetic radiation is calculated as losing frequency in the higher potential due to kinetic energy loss via the difference in gravity potential between source and receiver. And is done so on the basis that each observer in his reference frame observes his clock to be ticking 'normally'. (ie: no energy change for the clock)

You say:
shift implies that the frequency of a single source has changed, you can’t use it to describe differences in frequency between separate sources.

But that is exactly what Jeff, and Evan suggested doing when they said that the shifted clock is measuring the shifted photon. (remembering that electromagnetic radiation itself is a separate phenomenon from a source of electromagnetic radiation)

Anyway, I've got my paper to be getting on with now, so I don't have time for this thread anymore really.

@alancalverd Huh? If you told me to go 'less left' I'd have to steer to the right a little.
Clock 3 observes clock 2 to be less redshifted than it observes clock 1 on the ground to be.  Clock 3 can then deduce that clock 2 is blueshifted compared to clock 1.
Title: Re: Gravitational shift or not?
Post by: alancalverd on 08/04/2018 13:53:11
@alancalverd Huh? If you told me to go 'less left' I'd have to steer to the right a little.Clock 3 observes clock 2 to be less redshifted than it observes clock 1 on the ground to be.  Clock 3 can then deduce that clock 2 is blueshifted compared to clock 1.

No No No. Less redshifted is not blueshifted. Steer 350 rather than 340 is still left of north, whereas 010 is to the right of north. The compass only has north as a reference.

Observer 3 will observe the hydrogen spectrum from a source at 2 to be less redshifted than the hydrogen spectrum from a source at 1, compared with his own hydrogen source. An observer at 1 will see 2 and 3 as blueshifted.

Good luck with your paper, but beware of misusing conventional terminology. 
Title: Re: Gravitational shift or not?
Post by: Colin2B on 08/04/2018 14:38:55
Calculating via the difference in gravity potential between source and receiver is using a determined physicality, (physicality (a)), to determine the 'magnitude' of a physicality.

By using the 'magnitude' of the determined physicality (a), that occurs only once in the observation process, in order to calculate both the 'magnitude' of the faster ticking clocks in the higher potential, (physicality (b)), and the magnitude of the frequency drop due to kinetic energy loss for electromagnetic radiation escaping into the higher potential, (physicality (c)), physicality (a) has been used twice to describe the 'magnitude' of physicality (b) and the 'magnitude' of physicality (c).

There is a distinction between the way that physicality (a) is being used twice in the GR equation, once on the left, and once on the right.
In the left side of the GR equation clocks in the higher potential are used as ticking faster via the difference between source and receiver and this extends the hypotenuse for the GR geometry.
In the right side of the equation electromagnetic radiation is calculated as losing frequency in the higher potential due to kinetic energy loss via the difference in gravity potential between source and receiver. And is done so on the basis that each observer in his reference frame observes his clock to be ticking 'normally'. (ie: no energy change for the clock)
I’m afraid you are misreading the maths

But that is exactly what Jeff, and Evan suggested doing when they said that the shifted clock is measuring the shifted photon. (remembering that electromagnetic radiation itself is a separate phenomenon from a source of electromagnetic radiation)
Moving  clock or source is different from stationary clock or source.

Anyway, I've got my paper to be getting on with now, so I don't have time for this thread anymore really.
Probably a good idea to drop this thread as it really isn’t helping you.
Title: Re: Gravitational shift or not?
Post by: timey on 08/04/2018 15:39:51
Ah - well b/c general relativity is the 'general theory', what happens @alancalverd is that as soon as a 'reference point' like North is stated, physicists then switch to special relativity and flat spacetime.

Thanks for the well wishes.

@Colin2B Electromagnetic radiation is not a source, and is never stationary.

Within the maths of the stress energy tensor, and the metric tensor, there are units of half g that might have been worth a mention, but anyway, I agree, this isn't helping me do my paper, so I'm out of here.