[gem]

Hi all,

So Yor_on/Colin, thanks both for your considerations,

I understand your concerns I believe there's a couple of separate issues,
So the problem I had with a photon being able to change energy in reality but with no passage of time as postulated by others seemed a nonsense.

So to try to cover this aspect if I may yor_on by using your analogy, and only use one reference frame to try to ascertain whether the photon actually loses/gains energy or if its just frame dependent.

Yor_on

When it comes to a red or blue shift you could think of it as a comparison between frames of reference, because that is what it is. If a photon had a 'proper frame of reference' I think it would be, as Ethan states, 'time less', and it wouldn't change 'energy' intrinsically either. That last one should be able to be tested by knowing the source and then introduce gravity, a mass, between the source and yourself. Move the measuring device so that the mass no longer is in the path of the propagation and then compare the energy between photons. If they are the same then it didn't change anything for that photon deviating by a gravitational potential.

Now if we use this arrangement and measure a photons energy/colour from a distance source with no mass between the source and observer, and then compare it to the colour to one with a photon that had passed by a mass that had traversed between the two points, ( ignoring the deflection due to change in direction due to the field )

in this scenario we will end up with both parts of the Harvard tower experiment.
IE we would have the blue shift of the photon as it traveled towards the mass and red shift as it traveled away.
So no change in colour detected by the observer even though it could be argued the colour had indeed changed towards blue and back to original colour as it passed by the mass.
However if the said mass was spinning at a reasonable velocity I think it would be reasonable to assume the red/blue shift would not be equal and the observer would detect an aspect of whats under discussion.

Now Colin, in regards to my statement of objecting as to the tying of momentum and energy in theory's put forward.     

gem;

Noether’s theorem relies on symmetry, which is a condition in reality doesn’t occur in many situations, for example we don’t have such symmetry on the surface of the earth and therefore our atmosphere doesn’t have such symmetry as per Noether’s theorem.

Hence momentum is continually created in this location, due to the non inertial conditions.

Now as you correctly recall aspects of this were raised previously

And given you were specific as to the conditions as to placing the conservation of momentum equal footing to conservation of energy,
I will restate, my understanding is: those conditions are not met on earth, neither is symmetry, in the accelerated conditions of a gravitational field, so surely its an error to tie the two as equivalent, in the physical world.

Given we cannot observe energy being created on earth but can observe the creation of momentum.

hence the conditions below are not met.

Colin

Again, for a local closed system, momentum is conserved and it is stated like it is for energy./quote]

[TommyJ]

Einstein postulated that time was more like a river, ebbing and flowing depending on the effects of gravity and space-time. Even one second on Earth was not the same length of time everywhere in the universe.
He also mentioned that “The distinction between the past, present and future is only a stubbornly persistent illusion.”

Newton and Einstein did agree that time moves forward.
Everything in the universe wants to move from low to high entropy, or from uniformity to disorder, moving to the almost random arrangement of galaxies in the present day. This is known as the “arrow of time.”

When forced to summarize the general theory of relativity in one sentence: Time and space and gravitation have no separate existence from matter.

[Halc]

Now if we use this arrangement and measure a photons energy/colour from a distance source with no mass between the source and observer, and then compare it to the colour to one with a photon that had passed by a mass that had traversed between the two points, ( ignoring the deflection due to change in direction due to the field )

in this scenario we will end up with both parts of the Harvard tower experiment.

Not really since there is no measurement taken near said mass. You're giving classic properties to what is a quantum thing. It is better to speak of a classic pulse of light rather than a photon since the latter does not have a position, path, or energy except when measured, and the former has all these things.

IE we would have the blue shift of the photon as it traveled towards the mass and red shift as it traveled away.
So no change in colour detected by the observer even though it could be argued the colour had indeed changed towards blue and back to original colour as it passed by the mass.

If we're talking about said pulse, then yes, agree.  The two pulses will be measured at the same energy assuming they were both emitted from locations of identical gravitational potential and had minimal deflection/refraction along the way, and had identical velocity relative to the observer. What they pass by along the way has no effect on the energy measured, but it does affect the time it takes to get there.

However if the said mass was spinning at a reasonable velocity I think it would be reasonable to assume the red/blue shift would not be equal and the observer would detect an aspect of whats under discussion.

No, not even then.

Given we cannot observe energy being created on earth but can observe the creation of momentum.

Did I miss something? Momentum is conserved in a closed system (inertial coordinates), so creation of momentum could be used to generate a perpetual motion machine.

So, in the “reference frame of the photon”

It is always a mistake to consider such an invalid frame. There is no time and only two dimensions of space. All the usual physical terms (velocity say) are meaningless.

it is at rest

Being at rest has no meaning if velocity is meaningless, which is different from zero velocity.

and the bottom of the tower is rushing up to meet it

It most certainly is not. The bottom of the tower is just there, as is the top. There is no spatial separation between the two since this dimension of space is nonexistent.
The light pulse has no proper energy, frequency, or wavelength, so speaking of any of these is also meaningless.

You realize all this, but you still made the statements above which is only going to confuse the readers.

[gem]

Hi all,

So Halc

Not really since there is no measurement taken near said mass. You're giving classic properties to what is a quantum thing. It is better to speak of a classic pulse of light rather than a photon since the latter does not have a position, path, or energy except when measured, and the former has all these things.

I'm not sure its to relevant to get bogged down in this regard as its the energy of a photon under discussion whether its a single photon at a time or a stream of, it is still possible to derive the discrete quanta of the packet of electromagnetic radiation which is a photon.

Now on this point:

gem

However if the said mass was spinning at a reasonable velocity I think it would be reasonable to assume the red/blue shift would not be equal and the observer would detect an aspect of whats under discussion.

Halc

No, not even then.

So if this statement is correct
Einstein

As long as we restrict ourselves to purely mechanical processes in the realm where Newton's mechanics holds sway, we are certain of the equivalence of the systems K and K'. But this view of ours will not have any deeper significance unless the systems K and K' are equivalent with respect to all physical processes, that is, unless the laws of nature with respect to K are in entire agreement with those with respect to K'. By assuming this to be so, we arrive at a principle which, if it is really true, has great heuristic importance. For by theoretical consideration of processes which take place relatively to a system of reference with uniform acceleration, we obtain information as to the career of processes in a homogeneous gravitational field.

Then my previous comments of a rotating mass (accelerated motion) have electromagnetic pass by, at say above its equator in either direction there would a delta in the values of interaction of the electromagnetic radiation with the gravitational field/spacetime.

Moving on to,

gem

Given we cannot observe energy being created on earth but can observe the creation of momentum.

Halc

Did I miss something? Momentum is conserved in a closed system (inertial coordinates), so creation of momentum could be used to generate a perpetual motion machine.

Yes you did miss several things !   

I'm afraid Colin was very specific as was I.

you do not have a closed or inertial system and you do not have symmetry so your perpetual motion machine would be powered by sunlight, therefore not perpetual motion of the first or 2nd kind
 

[Halc]

Then my previous comments of a rotating mass (accelerated motion) have electromagnetic pass by, at say above its equator in either direction there would a delta in the values of interaction of the electromagnetic radiation with the gravitational field/spacetime.

Yes, it would interact, but when it finally gets measured well away from said spinning/charged mass, no change to the energy of the light will be measured as compared to light that had not passed by such a mass. I have no idea how you think Einstein's comment suggests otherwise.

I'm afraid Colin was very specific as was I.

Colin says momentum is conserved, as do I.

you do not have a closed or inertial system

If the system is not closed, then momentum is being imported from outside, which is not the creation of momentum, merely the transfer of it. You seem to assert that it can be 'created'.

I say 'inertial system' because momentum is not conserved in many non-iniertial coordinate systems. For instance, relative to the comoving coordinate system, a rock moving at a peculiar velocity of 1000 m/sec will slow continuously in the absence of a force acting on it, losing both momentum and energy, neither of which are conserved in such a coordinate system.

[gem]

Hi all,

So Halc in regards to the physical interaction of electromagnetic radiation with a rotating mass and your denial to a delta to photon energy, consider does gravitational lensing alter in this scenario ?

Now this

Halc ; you stated :
Colin says momentum is conserved, as do I.

also

If the system is not closed, then momentum is being imported from outside, which is not the creation of momentum, merely the transfer of it. You seem to assert that it can be 'created'.

I say 'inertial system' because momentum is not conserved in many non-iniertial coordinate systems. For instance, relative to the comoving coordinate system, a rock moving at a peculiar velocity of 1000 m/sec will slow continuously in the absence of a force acting on it, losing both momentum and energy, neither of which are conserved in such a coordinate system.

My bold in the above quote

So firstly, buoyancy and convection can only occur in a non inertial reference frame.  FACT

so take a body of fluid like oceans or atmosphere here on the Earth.
then consider, there is a particle or fluid parcel at each point that is assigned the average of the properties of atoms in a small region nearby. In particular, it has a density ρ and velocity v that depend on time t and position r. The momentum per unit volume is ρv (density x velocity)

Now lets consider, energy is applied to the air at the earths surface  via heat from the sun to said fluid. it will therefore change the density. and  the droplet accelerates. This acceleration occurs because the fluid in a given volume changes with time, in short the average force per unit volume changes inside the droplet, this known as  the gradient of the pressure.

Forces that can change the momentum of a droplet include the gradient of the pressure and gravity FACT

So no inertial reference frame, no closed system and No symmetry FACT

[Halc]

does gravitational lensing alter in this scenario ?

To repeat it, but more exactly:
So long as the respective path lengths do not change over time, or change at the same rate, what they pass by along the way has no effect on the energy measured.
So to give an example where the energy does actually change, the one path is direct from the emitter to the detector, and the second path bounces off a moving mirror that changes the path length over time. In that case, the one pulse will be a different energy at the detector as compared to the other pulse.
A mass can act as a mirror of sorts, deflecting a light pulse at any angle you please. If said mass is not moving relative to the aparatus, then the two pulses will be measured the same regardless of spin, charge, lensing, whatever. Motion of the mass or mirror in a way that alters the pathlength is what will make a difference.

no closed system and No symmetry FACT

Again, you seem to suggest that momentum of a system can be created. Indeed I don't see a closed system identified in the quoted post. What's your system? Earth? It's momentum is constantly changing due to the pull of the sun and other objects. This is momentum transfer, not momentum creation. I don't see what heat expansion (or buoyancy of all things) has to do with it. Maybe your system is much smaller, but you've not identified it. Creation of momentum is the foundation of reactionless thrust, the invention of which would make anybody a billionaire.

I made no mention of a symmetry requirement for momentum conservation, so I don't know why you're dragging that  into it.

An inertial reference frame is an abstract choice and can be pretty much applied locally to anything, as a coordinate frame to anything, or to anything at all with gravity ignored. Hence your first and third FACTs seem not to be facts at all since I can effortlessly think of counterexamples.

So please be more concise and identify a system that can change its own system momentum without import of momentum from outside the system.

[Colin2B]

You realize all this ......

Yes, I do know it. I was trying to use examples of the inconsistencies in gem’s argument and terminology, and did qualify, for eg, that the ground could not be rushing up and is why I said  “This is why everyone is telling you that the reference frame of the photon is meaningless”.

My comments on the posts were not intended as a criticism of anyone, but a reflection of the nature of the type of question in the OP, as I was in a hurry to catch the tide (and wifi) they might not have come across as I had intended, sorry if they were misunderstood. It is in the nature of this type of thread that posts are often longer and more technical, each generating a number of replies that could easily become topics in their own right making them difficult for some people to follow. That doesn’t mean the replies should be curtailed.
Note that our attempts to explain might be in vain despite the fact that you also stated “Energy (that of light, KE, some others) is definitely coordinate system dependent”. See:

use one reference frame to try to ascertain whether the photon actually loses/gains energy or if its just frame dependent.

Gem, this doesn’t make any sense to me and I can’t understand what you mean by actually or just frame dependent.. As we have said, KE measurements are always frame dependant, but we are so used to measuring KE relative to the earth’s surface, eg for a car, that we tend to forget. In the frame of the car (its proper frame) it is at rest and so its KE is zero. So we are only ever considering frame dependent measurements, which is what we ‘actually’ measure at the top and bottom of the tower, trying to do it from the point of view of the photon is meaningless.

in this scenario we will end up with both parts of the Harvard tower experiment.
IE we would have the blue shift of the photon as it traveled towards the mass and red shift as it traveled away.
So no change in colour detected by the observer even though it could be argued the colour had indeed changed towards blue and back to original colour as it passed by the mass.
However if the said mass was spinning at a reasonable velocity I think it would be reasonable to assume the red/blue shift would not be equal and the observer would detect an aspect of whats under discussion.

Again I don’t see how any of this relates to what’s under discussion. To add to comment by @Halc the only measurement you have is the final state. If a car travels down a motorway speeding up and slowing down the speed camera only measures its speed at that point; and that speed, and the related KE, are both measured relative to the ground. There is no other ‘actual’ speed. A similar situation occurs when light leaves a gravitational well and then enters another distant one, it is the nett change that results in what we measure.

no closed system and No symmetry FACT

My interest in your discussion on atmospheric momentum was only in trying to dispel Petro’s false ideas about atmospheric circulation on a rotating planet.
It’s worth noting that a more energetic atmosphere does not imply an increase in momentum.
Interestingly, I did discuss some ideas on transfer of atmospheric momentum with a colleague who studies it. He recommended some interesting papers, partly because I have a passing interest in meteorology and it has implications for weather systems. I’ll dig them out when I have time.
At the moment I’m sailing so my only interest in atmospherics is predicting the next wind shift.

So please be more concise and identify a system that can change its own system momentum without import of momentum from outside the system.

As @Halc says, but please do it in another thread.

[gem]

Hi all.

Hi Colin,

yes point taken, things have gone away from the OP
 
In regards to the photon frame, if you look back I was taking issue with this aspect also, given the zero time aspect stated in the frame of the photon, as there clearly are net changes that have been measured to the energy of a photon as it goes up/down in a gravitational field.   

So Halc

An inertial reference frame is an abstract choice and can be pretty much applied locally to anything, as a coordinate frame to anything, or to anything at all with gravity ignored. Hence your first and third FACTs seem not to be facts at all since I can effortlessly think of counterexamples.

Ok Halc hold that thought for now, we can revisit this else where.