[AtomicX (OP)]

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!

[evan_au]

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

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...

[timey]

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?

[Kryptid]

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.

[timey]

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.

[Kryptid]

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:

- 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.

[timey]

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?

[timey]

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?

[evan_au]

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).

[timey]

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)

[timey]

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...

[Colin2B]

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.

[timey]

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?

[jeffreyH]

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.

[evan_au]

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

[timey]

@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.

[Colin2B]

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.

[jeffreyH]

@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.

[timey]

@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.

[Colin2B]

@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.