Ultra violet catastrophe and Plank's theory

[swansont]

31 minutes ago, Carrock said:

There is the absorber problem for an empty universe (as well as many popular cosmological models), which has been around for a long time.

 

There is a strong case for claiming photons have time-reversal symmetry.

As photons have infinite range, this symmetry implies they have to be destroyed (i.e. the time-reverse of created) as well as as created. There is no way to destroy photons in empty space without violating conservation laws.

So it may be the only blackbody in infinite and empty space has no way to lose energy and will forever retain its temperature.

 

The empty space would not have the same temperature as the blackbody; the temperature is related to the number of photons per unit volume. After a time t, at a distance ct away, there would be no photons. I think you would not have an equilibrium condition; the distribution function shape and the amplitude would not match.

[Carrock]

12 minutes ago, swansont said:

The empty space would not have the same temperature as the blackbody; the temperature is related to the number of photons per unit volume. After a time t, at a distance ct away, there would be no photons. I think you would not have an equilibrium condition; the distribution function shape and the amplitude would not match.

I'm suggesting there would be no photons in an otherwise matterless universe even near the black body at any time as conservation laws forbid it, assuming time-reversal photon symmetry.

The only reason I can see for any photon time-reversal asymmetry is that many (unverified) cosmological theories require such asymmetry.

[swansont]

1 hour ago, Carrock said:

I'm suggesting there would be no photons in an otherwise matterless universe even near the black body at any time as conservation laws forbid it, assuming time-reversal photon symmetry.

The only reason I can see for any photon time-reversal asymmetry is that many (unverified) cosmological theories require such asymmetry.

Photons are bosons, so there is no restriction on their creation by the blackbody, which has energy. I don't see how energy conservation has a problem here.

[Carrock]

2 hours ago, swansont said:

Photons are bosons, so there is no restriction on their creation by the blackbody, which has energy. I don't see how energy conservation has a problem here.

OK. The photon is generally considered to be its own antiparticle.

It's not currently a popular idea, but AFIK an antiparticle is mathematically equivalent to a particle travelling backwards in time as in e.g. Feynman diagrams.

So a photon travelling forwards in time can alternatively be considered to be an antiphoton (i.e. a photon) travelling backwards in time.

So in the universe we're discussing, the photon is created in the future and travels back in time until it interacts with the black body.

Energy, momentum and spin (i.e. a photon) is created from nothing, violating three conservation laws, and travels back in time until it interacts with the black body.

The alternative, that such photons can be (destroyed but not created/created but not destroyed) is also problematic; I'm not aware of any theoretical basis for that.

Some cosmological theories dodge this bullet with a 'future singularity' i.e. hand waving; others avoid it by e.g. postulating a temporally finite universe.

 

A full consideration would require its own thread but it would soon get hijacked.

On 26/10/2014 at 5:02 PM, John Cuthber said:

At the risk of seeming smug, have a look at my post-count and status as a resident expert....

 

[Butch]

5 hours ago, Carrock said:

There is the absorber problem for an empty universe (as well as many popular cosmological models), which has been around for a long time.

 

There is a strong case for claiming photons have time-reversal symmetry.

As photons have infinite range, this symmetry implies they have to be destroyed (i.e. the time-reverse of created) as well as as created. There is no way to destroy photons in empty space without violating conservation laws.

So it may be the only blackbody in infinite and empty space has no way to lose energy and will forever retain its temperature.

 

Define empty space?

[Carrock]

1 minute ago, Butch said:

Define empty space?

In the context I was using, space with no particles for photons to interact with. Virtual particles are no good here for photon emission/absorption.

[Butch]

12 minutes ago, Butch said:

There is no way to destroy photons in empty space without violating conservation laws.

Or is there? I am no expert, however it seems there must be more ways for photons to interact than just collision with matter. Gravitation leaps to mind as well as cosmic redshift.

Edited March 5, 2018 by Butch

[Carrock]

50 minutes ago, Butch said:

Or is there? I am no expert, however it seems there must be more ways for photons to interact than just collision with matter. Gravitation leaps to mind as well as cosmic redshift.

No gravitation and no cosmic redshift leap to mind in an empty universe.

 

[swansont]

13 hours ago, Carrock said:

 So in the universe we're discussing, the photon is created in the future and travels back in time until it interacts with the black body.

Energy, momentum and spin (i.e. a photon) is created from nothing, violating three conservation laws, and travels back in time until it interacts with the black body.

Why is it created in the future? There is no source for it, and if you run the clock forward, the photon exists in perpetuity. There's no event you can point to for the creation when you run the clock backward.

You violate the conservation laws because of the false boundary condition you have put on the problem — the creation event.

13 hours ago, Carrock said:

The alternative, that such photons can be (destroyed but not created/created but not destroyed) is also problematic; I'm not aware of any theoretical basis for that.

Photons do not have a conservation of number law associated with them. And it's trivially observed to be true in any number of reactions.

 

[Butch]

15 hours ago, Carrock said:

No gravitation and no cosmic redshift leap to mind in an empty universe.

 

A universe that empty would not contain photons or any form of energy.

 

[swansont]

16 hours ago, Butch said:

Or is there? I am no expert, however it seems there must be more ways for photons to interact than just collision with matter. Gravitation leaps to mind as well as cosmic redshift.

Those do not create or destroy photons. It's referred to as an adiabatic invariant; the number is not changed by slow (compared to the photon frequency) processes, like gravitation. But not absorption or emission. 

[Carrock]

4 hours ago, swansont said:

Why is it created in the future? There is no source for it, and if you run the clock forward, the photon exists in perpetuity. There's no event you can point to for the creation when you run the clock backward.....

Given that photons are their own antiparticles, whether observed photons go from the future to the past or vice versa is an arbitrary choice. (See earlier post.)

The fact that future photon destruction/creation is problematic is not IMO adequate justification for saying photons must go from the past to the future.

4 hours ago, swansont said:

....You violate the conservation laws because of the false boundary condition you have put on the problem — the creation event....

I offered an alternative with no boundary conditions.

4 hours ago, swansont said:

17 hours ago, Carrock said:

The alternative, that such photons can be (destroyed but not created/created but not destroyed) is also problematic; I'm not aware of any theoretical basis for that.

Photons do not have a conservation of number law associated with them. And it's trivially observed to be true in any number of reactions.

True, but rather ignored my point, which from context was that photons cannot be created or destroyed in empty space without violating conservation laws.

Photons have infinite range and do not experience any sort of time or duration. If a photon is created and destroyed elsewhere, those two events are entangled. If a photon is created and never destroyed or vice versa the photon is 'aware' of the asymmetry. I suspect this would prevent such a photon existing as anything but a virtual particle.

I've DuckDuckGone quite extensively, and can't find any discussion of this issue.

 

In cosmology there are theories which avoid this possible issue in the real universe.

 

 

 

 

 

 

[Butch]

13 minutes ago, swansont said:

Those do not create or destroy photons. It's referred to as an adiabatic invariant; the number is not changed by slow (compared to the photon frequency) processes, like gravitation. But not absorption or emission. 

These can change the frequency of the photon certainly at some point this can cause decay?

[swansont]

1 hour ago, Carrock said:

Given that photons are their own antiparticles, whether observed photons go from the future to the past or vice versa is an arbitrary choice. (See earlier post.)

The fact that future photon destruction/creation is problematic is not IMO adequate justification for saying photons must go from the past to the future.

I offered an alternative with no boundary conditions.

Photon creation or destruction is a boundary condition. You have a destruction/creation (depending on which way time is running) which does not reflect the actual conditions of the problem. That's the source of your violation of physical laws.

1 hour ago, Carrock said:

True, but rather ignored my point, which from context was that photons cannot be created or destroyed in empty space without violating conservation laws.

And no such events happen in this scenario. 

Photons are created by the blackbody. That's it.

1 hour ago, Carrock said:

Photons have infinite range and do not experience any sort of time or duration. If a photon is created and destroyed elsewhere, those two events are entangled. If a photon is created and never destroyed or vice versa the photon is 'aware' of the asymmetry. I suspect this would prevent such a photon existing as anything but a virtual particle.

You can't analyze this from the photon's frame of reference, because it is not a valid frame. We have no physics to apply to it. 

 

1 hour ago, Butch said:

These can change the frequency of the photon certainly at some point this can cause decay?

No. Photons do not decay.

[CaroCross]

21 hours ago, Carrock said:

OK. The photon is generally considered to be its own antiparticle.

It's not currently a popular idea, but AFIK an antiparticle is mathematically equivalent to a particle travelling backwards in time as in e.g. Feynman diagrams.

So a photon travelling forwards in time can alternatively be considered to be an antiphoton (i.e. a photon) travelling backwards in time.

So in the universe we're discussing, the photon is created in the future and travels back in time until it interacts with the black body.

Energy, momentum and spin (i.e. a photon) is created from nothing, violating three conservation laws, and travels back in time until it interacts with the black body.

The alternative, that such photons can be (destroyed but not created/created but not destroyed) is also problematic; I'm not aware of any theoretical basis for that.

Some cosmological theories dodge this bullet with a 'future singularity' i.e. hand waving; others avoid it by e.g. postulating a temporally finite universe.

 

A full consideration would require its own thread but it would soon get hijacked.

 

The Feynman interpretation of antiparticles is just an mathematical sign change to have an antiparticle with positive energy and not negative (which would be a disaster -> see the Diracs sea problem and his interpretation). So all in all its an interpretation to solve this problem. The antiparticles do not really travel back in time. And after all, Quantum electrodynamics isnt a complete theory at all...but in our energy range it is a reeaaally good tool

[Carrock]

1 hour ago, swansont said:

Photon creation or destruction is a boundary condition. You have a destruction/creation (depending on which way time is running) which does not reflect the actual conditions of the problem. That's the source of your violation of physical laws.

And no such events happen in this scenario. 

Photons are created by the blackbody. That's it.

"You have a destruction/creation (depending on which way time is running) which does not reflect the actual conditions of the problem."

"Photons are created by the blackbody."

In what way is the creation in the second sentence different from the first?

 

1 hour ago, swansont said:

2 hours ago, Carrock said:

 

Photons have infinite range and do not experience any sort of time or duration. If a photon is created and destroyed elsewhere, those two events are entangled. If a photon is created and never destroyed or vice versa the photon is 'aware' of the asymmetry. I suspect this would prevent such a photon existing as anything but a virtual particle.

You can't analyze this from the photon's frame of reference, because it is not a valid frame. We have no physics to apply to it.

I was anthropomorphising a bit.

I think it's pretty generally accepted photons cannot experience duration, which is implied by there being no valid frame. A lack of a property is still physics.

I would say a photon is simply a transient which occurs instantaneously as two objects in the same place at the same time exchange energy, momentum, spin etc. Necessary if a photon doesn't experience duration.

This transient is infinitely stretched from the viewpoint of a valid frame and can be inferred to be a photon travelling a frame dependent distance with some frame dependent properties such as energy and at frame independent speed c. This photon is no more or less 'real' than the length contraction of a massive object with relativistic velocity w.r.t. some valid frame.

The issue is how does this transient occur if there is only one object - in this instance a black body in an otherwise empty universe.

 

 

Can't delete this. $^%"%&**(##@ forum software....

1 hour ago, swansont said:

 

 

11 minutes ago, CaroCross said:

The Feynman interpretation of antiparticles is just an mathematical sign change to have an antiparticle with positive energy and not negative (which would be a disaster -> see the Diracs sea problem and his interpretation). So all in all its an interpretation to solve this problem. The antiparticles do not really travel back in time. And after all, Quantum electrodynamics isnt a complete theory at all...but in our energy range it is a reeaaally good tool

If it's just an interpretation it should be easy to solve this problem without assuming antiparticles really travel back in time.

[swansont]

26 minutes ago, Carrock said:

"You have a destruction/creation (depending on which way time is running) which does not reflect the actual conditions of the problem."

"Photons are created by the blackbody."

In what way is the creation in the second sentence different from the first?

The first is made up, by you. A "photon is created in the future and travels back in time" But there is no creation, because in forward time, there is no destruction.

The second is part of the stated problem.

26 minutes ago, Carrock said:

I was anthropomorphising a bit.

I think it's pretty generally accepted photons cannot experience duration, which is implied by there being no valid frame. A lack of a property is still physics.

All of the physics we know requires a valid frame of reference. It's only guaranteed to work in a valid frame, as per relativity. You can't transform our physics into/out of the photon's frame.

26 minutes ago, Carrock said:

I would say a photon is simply a transient which occurs instantaneously as two objects in the same place at the same time exchange energy, momentum, spin etc. Necessary if a photon doesn't experience duration.

This transient is infinitely stretched from the viewpoint of a valid frame and can be inferred to be a photon travelling a frame dependent distance with some frame dependent properties such as energy and at frame independent speed c. This photon is no more or less 'real' than the length contraction of a massive object with relativistic velocity w.r.t. some valid frame.

Length contraction is real, so I'm not sure what limitation you think you're introducing here.

 

[Carrock]

26 minutes ago, swansont said:

 

....The second is part of the stated problem.

All of the physics we know requires a valid frame of reference. It's only guaranteed to work in a valid frame, as per relativity. You can't transform our physics into/out of the photon's frame.

Length contraction is real, so I'm not sure what limitation you think you're introducing here.

 

If all of the physics we know requires a valid frame of reference, is the description of gravitational redshift, Doppler shift etc of photons without valid reference frames not physics? Indeed, without valid reference frames, are photons completely unknown physics?

Length contraction is a function of reference frame; a reference frame can be chosen for no or any desired contraction. I only meant that it is a function of frame choice. As with e.g. photon energy, which has no upper or lower limit, the reference frame is chosen for convenience in calculations involving interactions.

 

1 hour ago, Carrock said:

I would say a photon is simply a transient which occurs instantaneously as two objects in the same place at the same time exchange energy, momentum, spin etc. Necessary if a photon doesn't experience duration.

This transient is infinitely stretched from the viewpoint of a valid frame and can be inferred to be a photon travelling a frame dependent distance with some frame dependent properties such as energy and at frame independent speed c.

I'd be interested in any response you have to this rather informal description.

(I don't see how a photon could experience duration without having a valid reference frame. The claims I've seen to that effect violate well established physics.)

[swansont]

17 hours ago, Carrock said:

If all of the physics we know requires a valid frame of reference, is the description of gravitational redshift, Doppler shift etc of photons without valid reference frames not physics? Indeed, without valid reference frames, are photons completely unknown physics?

We don't measure e.g. the Doppler shift in the photon's frame, we measure it in ours.

Quote

Length contraction is a function of reference frame; a reference frame can be chosen for no or any desired contraction. I only meant that it is a function of frame choice. As with e.g. photon energy, which has no upper or lower limit, the reference frame is chosen for convenience in calculations involving interactions.

Sure. All I except the photon's frame, which isn't valid. 

Quote

I'd be interested in any response you have to this rather informal description.

(I don't see how a photon could experience duration without having a valid reference frame. The claims I've seen to that effect violate well established physics.)

We don't have any physics to describe what happens in the photon's frame. Any description you offer suffers from an inability to gain experimental confirmation 

[Strange]

17 hours ago, Carrock said:

I don't see how a photon could experience duration

I don't know what it would mean for a photon to experience duration. They don't change over time or decay so what would their "experience" consist of?

[Carrock]

27 minutes ago, Strange said:

They don't change over time or decay so what would their "experience" consist of?

I was guilty of anthropomorphising earlier....

 

I don't think a photon 'experiences' anything. It's just an instantaneous transient of an interaction between objects separated by a lightlike interval. Any valid reference frame infinitely 'stretches' this instantaneous transient into what's called a photon. The photon is just an artefact of any valid frame.

I'm just wondering if you can have a photon sourced by one object but with no interaction with a second object. There is no momentum etc transference. I suspect at most only a virtual photon could be created.

I can't find any good reference on this (non?) issue.

 

[Strange]

4 minutes ago, Carrock said:

I'm just wondering if you can have a photon sourced by one object but with no interaction with a second object.

I can't see why not, in principle. A photon (say in the CMB) could continue going through space and missing the  hydrogen atoms and stars, which are few and far between. 

Quote

There is no momentum etc transference. 

Momentum is transferred from the source to the photon. It doesn't then need to be transferred to something else, does it?

[Carrock]

3 hours ago, Strange said:

3 hours ago, Carrock said:

I'm just wondering if you can have a photon sourced by one object but with no interaction with a second object.

I can't see why not, in principle. A photon (say in the CMB) could continue going through space and missing the  hydrogen atoms and stars, which are few and far between. 

That's the fate of most photons in most cosmological models.

It's still possible that yet unknown physics may mean we're in e.g. a cyclic universe where all photons eventually interact in the future so there's no direct evidence that (no second interaction) photons exist.

3 hours ago, Strange said:

3 hours ago, Carrock said:

There is no momentum etc transference.

Momentum is transferred from the source to the photon. It doesn't then need to be transferred to something else, does it?

I suggested a photon is an instantaneous transient of an interaction between objects separated by a lightlike interval. I'm not convinced that such an instantaneous transient in one object can give rise to a photon which never interacts with another object.

I suppose the only way forward is to have a good look at the maths.

 

[Moreno]

Does blackbody radiation shows such properties as interference and diffraction? If yes, how can it co-exist with quantum theory?

[Strange]

11 minutes ago, Moreno said:

Does blackbody radiation shows such properties as interference and diffraction? If yes, how can it co-exist with quantum theory?

Interference and diffraction are independent of the source of the radiation. However, interference is only easily seen with monochromatic light.

And why is quantum theory a problem? Both interference and diffraction can be explained in quantum theory (it wouldn't be a very good theory otherwise, would it).