Can Quanta Change Color?

[cubed]

I want a yes or no answer and a short explanation.

 

[cubed]

hello, anyone there?

 

[cubed]

please

someone just please tell...
just say yes or no...
I need to know badly...

 

[HallsofIvy]

Why? What color are they normally?

 

[El Hombre Invisible]

First, a caveat. A photon can be emitted, a photon can be absorbed. In between, you cannot measure the energy of the photon to see whether or not it can change - if you do, that's an absorption event and that same photon cannot be said to be observed again.

But other than that, no I don't think so. Different observers may well disagree on what the photon energy is, but a given photon of that energy will not change in transit to anyone observer.

An observer at rest relative to a monochromatic light source will say that the source is emitting photons at a constant energy. A second moving with constant velocity away from the source will agree that it is emitting photons at a constant energy, but will disagree on what that energy is. A third observer accelerating away from the source will say the source is emitting photons of lower and lower energies. None are wrong, none are right. But this can't be explained by a photon changing colour in transit, as the photon would have to know which observer was going to observe it.

 

[Adrian Baker]

First, a caveat. A photon can be emitted, a photon can be absorbed. In between, you cannot measure the energy of the photon to see whether or not it can change - if you do, that's an absorption event and that same photon cannot be said to be observed again.

But other than that, no I don't think so. Different observers may well disagree on what the photon energy is, but a given photon of that energy will not change in transit to anyone observer.

An observer at rest relative to a monochromatic light source will say that the source is emitting photons at a constant energy. A second moving with constant velocity away from the source will agree that it is emitting photons at a constant energy, but will disagree on what that energy is. A third observer accelerating away from the source will say the source is emitting photons of lower and lower energies. None are wrong, none are right. But this can't be explained by a photon changing colour in transit, as the photon would have to know which observer was going to observe it.

A very good answer, but what about Red-shifted photons? Now they DO change energy as they get stretched out. That's why the Microwave background radiation consists of microwaves, rather than the high energy photons that they originally were.

I posted a question on PF a year or so ago about where this energy went and there was some good discussion, but I never really got to grips with where actually it went. It is 'spread out over a larger spacetime' I suppose, but that is hard to put into context with the equation E=hf

 

[marlon]

I want a yes or no answer and a short explanation.

do you mean colour-charge or are you referring to colour as being the visible range of the EM energy spectrum. The first is changed by the strong force (respecting colour neutrality at all times) and the second is changed by Doppler-effect and friends :)

marlon

ps YES is the answer

 

[dextercioby]

The Compton effect shifts the frequency/energy of the photons,too.

Usually,the Doppler-FIZEAU (the "Doppler effect" is a name for the frequency shift of sound waves in the presence of Galilean boosts) is interpreted in terms of electromagnetic waves and not photons.Surely,one can discuss it for photons,but,back in ~1860,there were no such thing as photons,there was only LIGHT...

Daniel.

Daniel.

 

[El Hombre Invisible]

A very good answer, but what about Red-shifted photons? Now they DO change energy as they get stretched out. That's why the Microwave background radiation consists of microwaves, rather than the high energy photons that they originally were.

Does a single photon get red-shifted? How can you say a photon measured as being at the red end was emitted nearer the blue end? Also, how does a possibly dimensionless particle get 'stretched'? I don't know - I'm asking (these aren't loaded questions). To my knowledge, photons from background radiation measured as microwaves would always have been measured as microwaves in that same reference frame. Of course, those frames would not have necessarily have been feasible back when the background radiation was bluer, but that's cosmology for you.

 

[RandallB]

Does a single photon get red-shifted? how does a dimensionless particle get 'stretched'?

Chalk this one up to another Physics / QM paradox that just isn’t answered. From the Hubble expansion we can see how Red Shift occurs using wave theory but explaining it for an individual particle, a photon. How can it lose energy and change frequency as measured by observers in the same reference frame but separated by distance with expansion?

We can measure it. We can mathematically predict it. We can even describe it as “stretching” a partial. But that doesn’t explain it any better than we can explain entanglement or young’s double slit.
I’ll have to add this to my list of paradox’s to be answered.

RB

 

[Adrian Baker]

We can measure it. We can mathematically predict it. We can even describe it as “stretching” a particle. But that doesn’t explain it any better than we can explain entanglement or young’s double slit.
I’ll have to add this to my list of paradox’s to be answered.

RB

It has been top of my list for a long time RandallB. Glad I'm not on my own!

 

[Hans de Vries]

How can it lose energy and change frequency as measured by observers in the same reference frame but separated by distance with expansion?
RB

It doesn't. There's just a rule of thumb that galaxies at a larger distance have
a higher velocity relative to us.

f_{redshifted}\ \ =\ \ \sqrt{\frac{c-v}{c+v}}\cdot f

Regards, Hans

 

[Adrian Baker]

It doesn't. There's just a rule of thumb that galaxies at a larger distance have
a higher velocity relative to us.

f_{redshifted}\ \ =\ \ \sqrt{\frac{c-v}{c+v}}\cdot f

Regards, Hans

But the photons we receive DO have lower frequencies than when they set out... otherwise we couldn't measure red shift! If the frequency is lower, the energy is lower... How does your reply explain this?

 

[El Hombre Invisible]

But the photons we receive DO have lower frequencies than when they set out... otherwise we couldn't measure red shift! If the frequency is lower, the energy is lower... How does your reply explain this?

I think if you stick to what we can actually say for sure, you'd find that a hard statement to back up. You cannot measure the energy of a photon that is being emitted - only one being absorbed - i.e. by you and whatever you're detecting it with. That photon energy might have been measured differently by someone in a difference frame of reference (one in which the galaxy was getting closer or at rest, rather than receding). If you take the view that the photon you measure has the exact same energy as the photon emitted, IN THE SAME FRAME OF REFERENCE, it becomes less paradoxical. I think.

 

[RandallB]

It doesn't. There's just a rule of thumb that galaxies at a larger distance have a higher velocity relative to us.

f_{redshifted}\ \ =\ \ \sqrt{\frac{c-v}{c+v}}\cdot f

No Hans I think your missing the point of the Paradox.
Red Shift is explained by E X P A N S I O N the word the same just gotten bigger because the space between the letters has gotten larger.
Expansion is important because we see Red Shifts that seem to show thinks traveling faster than light. But with expansion they don’t go FTL. It’s just over great distances and the extra time it takes to cover the expanded space makes it seem like the source was moving FTL.
With Expansion, (Hubble etc.) in hand and using WAVE theory, we can explain how Red Shift is occurring.

BUT when we look at the individual photon, which must lose energy to shift Red it no so clear how that happens. That's the Paradox.

Therefore I'm not 100% OK with idea of expansion itself.

Like I said - sure something to work on.
RB

 

[Hans de Vries]

Red Shift is explained by E X P A N S I O N the word the same just gotten bigger because the space between the letters has gotten larger.

OK, but if it's a GR thing (cosmological redshift versus doppler redshift) then
you shouldn't talk about "In the same reference frame" The concept reference
frame gets lost in General Relativity. And, as far as I now, Energy is not
conserved in General Relativity at least not without an adaptation of the
definition of Energy.

John Baez has a lot of good stuf on GR on the web, for instance:

http://math.ucr.edu/home/baez/physics/Relativity/GR/energy_gr.html

This link handles the cosmological redshift as well.

Regards, Hans.

 

[Adrian Baker]

I think if you stick to what we can actually say for sure, you'd find that a hard statement to back up. You cannot measure the energy of a photon that is being emitted - only one being absorbed - i.e. by you and whatever you're detecting it with. That photon energy might have been measured differently by someone in a difference frame of reference (one in which the galaxy was getting closer or at rest, rather than receding). If you take the view that the photon you measure has the exact same energy as the photon emitted, IN THE SAME FRAME OF REFERENCE, it becomes less paradoxical. I think.

I still think not. If you look at line spectra from distant Galaxies, all of the spectral lines are at lower frequencies than they should be. As these Spectral lines correspond to energy levels between atomic orbitals, either the atoms are lower in distant galaxies, OR the photon frequencies have changed.
As atoms should be the same everywhere (we have no evidence to contradict this) the photons MUST have been emitted at one frequency and absorbed at another. Of course, relativistically speaking, the photon was emitted and absorbed at the same instant (from the photon's frame of reference), but the energy level changes.

That is the paradox that I have never yet had a satisfactory answer to...

______________________________________________________________-


I posted this before seeing your last post Hans - sorry. I followed your suggested link and had a read. I'm sure the answer is there, but my Physics knowledge just isn't up to understanding it... Seems like I'll not be able to get a 'simplistic' answer to my query.

 

[El Hombre Invisible]

Two observers, one source of photons.

Observer A is a loooooong way from the source C, but remains at rest relative to it throughout the experiment. Observer B starts very near the source and moves towards A throughout the experiment. In the meantime, both are detecting photons from the source C.

A will observe no redshift - he knows that C is emitting photons with the same energy that he is observing them with. B, on the other hand, does observe redshift because he is moving away from the source of the photons. If B is accelerating towards A, he will see the redshift increase (the photon energies decrease) as he approaches A.

If you agree with this, you will see that it is the idea of photons 'changing colour' that is the paradox, as by the time B reaches A, both will be observing photons that have traveled the same path. If photon energies decreased between C and A, why would A not observe the lower energies? This is because in B's frame of reference, the photons being EMITTED are redder than they are in A's frame of reference.

Here the experiment is about the motion of bodies rather than the expansion of space in between them, but the same principal holds.

 

[ZapperZ]

I still think not. If you look at line spectra from distant Galaxies, all of the spectral lines are at lower frequencies than they should be. As these Spectral lines correspond to energy levels between atomic orbitals, either the atoms are lower in distant galaxies, OR the photon frequencies have changed.
As atoms should be the same everywhere (we have no evidence to contradict this) the photons MUST have been emitted at one frequency and absorbed at another. Of course, relativistically speaking, the photon was emitted and absorbed at the same instant (from the photon's frame of reference), but the energy level changes.

That is the paradox that I have never yet had a satisfactory answer to...

______________________________________________________________-


I posted this before seeing your last post Hans - sorry. I followed your suggested link and had a read. I'm sure the answer is there, but my Physics knowledge just isn't up to understanding it... Seems like I'll not be able to get a 'simplistic' answer to my query.

Here's where the "problem" lies.

You are using the atomic energy levels calculated using non-relativistic QM. Implicitly, such calculations will work if you and the atom are in the same rest frame. However, you then use that same energy level and tried to do energy conservation in a different frame. Now we already know this will lead into a lot of problems even in classical mechanics (an object is stationary in one, and moving in the other, so where did the extra KE came from?)

What you should have done is to doppler shift the whole atom, and THEN, recalculate the apparent energy level in your frame. When you do this, the coulombic potential that you put into the Schrodinger equation will be shifted also (it is, after all, an EM property). You will find that the energy level is not the same good old level that you got in the rest frame.

Zz.

 

[RandallB]

OK, but if it's a GR thing (cosmological redshift versus doppler redshift) then you shouldn't talk about "In the same reference frame" The concept reference frame gets lost in General Relativity.

But Hans
It’s GR, cosmological red shift, Hubble expansion, that depend on "In the same reference frame" to keep from producing nonsense FTL events.
Let’s use El Hombre’s example:

Two observers, one source of photons.
Observer A is a loooooong way from the source C, but remains at rest relative to it throughout the experiment. Observer B starts very near the source and moves towards A throughout the experiment. In the meantime, both are detecting photons from the source C.

A will observe no redshift - he knows that C is emitting photons with the same energy that he is observing them with.:

This can only be true if we ignore Hubble for that “a loooooong way from the source C” comment. So let us insert the source of CBR here! Since we see a major red shift this source must not be in our reference frame, right. Just a little math should show us just how fast that frame is moving, SR should do. It the answer is, FTL! And way Faster Then Light.
Now this will never do, how can we have FTL!
That’s where GR, Hubble, and Expansion sort’s it out. The point here is that the CRB Source and us as observer A are both in pretty much the same reference frame, therefore no FTL. How to account for the huge Red Shift with no FTL? With the magic of “expansion” between the source C to the observer A. Now frequency of the light has reduced considerable, undisputed and well observed. Easily understood using Wave thinking in the large Cosmos.

But now when El H and Adrian want to think about a individual photon to understand it all, things get a little uneasy. Sure, If you want use ZapperZ’s idea, where you need “to doppler shift the whole atom, and THEN, recalculate the apparent energy level” or in our case the photon.
Problem with that is applying a “doppler shift” to a individual photon is treating it like a wave, so although it might work in the math, for me it is far short of an explanation.
So what does this mean?
It means we have a PARADOX!
Not some wimpy “Twins Paradox” that can be answered. (Therfore NOT a Paradox)
But a real honest to goodness Paradox, (There are more Young’s double slit, etc.) a puzzle where you don't get to look at the end of the book to find a satisfactory solution.

RB

RB

 

[seratend]

So what does this mean?
It means we have a PARADOX!
Not some wimpy “Twins Paradox” that can be answered. (Therfore NOT a Paradox)
But a real honest to goodness Paradox, (There are more Young’s double slit, etc.) a puzzle where you don't get to look at the end of the book to find a satisfactory solution.

RB

Where do you see a paradox? Is it so complicated to apply the lorentz transformation between different frames?
Why do you want to complicate and invoke GR to explain a simple doppler effect and the difference of energy between 2 frames?

Seratend.

 

[Hans de Vries]

But Hans
It’s GR, cosmological red shift, Hubble expansion, that depend on "In the same reference frame" to keep from producing nonsense FTL events.
RB

As far as I can see Space is expanding and EM waves (photons) are expanding
but, galaxies, stars and atoms keep the same size in the explanation of cosmological
redshift. (They just get farther apart)

Would the logical explanation not be that the latter continuously shrink back,
after expanding with space, to their original size which is determined by an
equilibrium of forces.

Photons can't shrink back since there is nothing what attracts the front to
the back. Moreover, no information/force from the back can ever reach the
front because it moves with c.

Regards, Hans.

 

[RandallB]

Where do you see a paradox?

Right here:

As far as I can see ... EM waves (photons) are expanding

I agree a perfectly good and acceptable view. EXCEPT that El H & Adrian are looking at a particle view of the photon and that works fine most of expansion until they get down to looking at just the photon as a particle. There the logic breaks down and is only resolved by suddenly saying “lets let the particle expand too".
What to expand if not a wave? You have a drawing of this particle, is it made of quarks? What kind of math other than a wave interpretation can you do this with?

If the only way to understand it is to switch between wave and particle views, then it is just not a complete understanding, nor a complete explanation.
That’s not to say an incomplete understanding is not useful, I think on the whole we’ve done quite well at working most things out form nuclear to cosmic level even with this Paradox unresolved.

So I’m OK with keeping the paradox as a paradox,
without using some kind of Meta-Physics, or Psycho-Physics just to rationalize it away.

RB

 

[El Hombre Invisible]

For the love of...

Right here:

I agree a perfectly good and acceptable view. EXCEPT that El H & Adrian are looking at a particle view of the photon and that works fine most of expansion until they get down to looking at just the photon as a particle. There the logic breaks down and is only resolved by suddenly saying “lets let the particle expand too".
What to expand if not a wave? You have a drawing of this particle, is it made of quarks? What kind of math other than a wave interpretation can you do this with?

There is no problem looking at the photon as a particle when dealing with redshift, and there is no paradox. When people say a photon has been redshifted from when it A) left the source to when it B) arrived at the observer, they are naturally measuring the photon energy at A) in a frame of reference in which A is at rest and measuring the photon energy at B) in the frame of reference in which B) is at rest. There is no paradox. Photon energies, like kinetic energy, mass energy, etc, will change when viewed from different frames.

Are you holding out for a paradox perhaps because you have some preference for the wave model?

 

[RandallB]

Are you holding out for a paradox perhaps because you have some preference for the wave model?

No just a truly honest view of a particle model without forcing in a wave view.
RB

 

[El Hombre Invisible]

Well, you don't need the wave view at all to explain redshift in photons. It's just relativity.

 

[Adrian Baker]

Thanks for a a great discussion about something that has puzzled me for such a long time. I get it now! (I think). I really hadn't thought about the frame of reference properly and this is, as is made clear, why I just didn't get it.

Thanks!

 

[RandallB]

Well, you don't need the wave view at all to explain redshift in photons. It's just relativity.

Really??
Let's take another look, Take an individual photon particle from the CMB. Given we know it started off very Blue with a high energy (In wave talk, that means high frequency). Now that it has reached us, it is very Red, down into the microwave frequency band, better stated as a particle with lower energy. Still moving at the same speed of c, we might even say the particle has a lower ‘apparent mass’ based on E=mcc.

The starting point and our observing point can be seen as roughly the same reference frame as understood by Hubble and expansion – I.E. we don’t get to claim FTL as an explanation for overly large red shift wave of particle view, expansion applies.

Now as we look at this photon particle without regard to where or when the on ahead or behind it may be, this one has a lower than original energy that needs to be explained.

Best explanation I saw was Zapper Z: “.. doppler shift the whole atom(photon), and THEN, recalculate the apparent energy”
Two ways to do this:
Conceptually just, stretch out the size of the individual photon particle (vs. atom) like the wave ring from dropping a stone in a smooth pool of water.
OR, use the doppler frequency change ratio figured from a wave view and just jam it into a formula to refigure and adjust the individual photon energy change over time or distance.

I’ll agree both give good answers but still a wave view for both. So I’m not holding out to find a Paradox here, I agree with the top people in physics that acknowledge that particle vs. wave duality is unresolved and already is a paradox.

So no, I don’t see where SR & GR alone will do here.

RB

 

[Miserable]

Given we know it started off very Blue with a high energy (In wave talk, that means high frequency). Now that it has reached us, it is very Red

I think this might be the source of your problem. It doesn't matter that the photon started off very far away from us, the red shift is due to the fact that the emitting atom was at a high velocity relative to us. If the photon was emitted in the next room by an atom at the same velocity you would see the same redshift, the distance is immaterial.

Since Hubble says all galaxies are moving away from us with velocities proportional to their displacements, we end up with photons from distant galaxies being more redshifted, but this isn't the source of the effect. El hombre's explanation was spot on.

 

[ZapperZ]

Best explanation I saw was Zapper Z: “.. doppler shift the whole atom(photon), and THEN, recalculate the apparent energy”
Two ways to do this:
Conceptually just, stretch out the size of the individual photon particle (vs. atom) like the wave ring from dropping a stone in a smooth pool of water.
OR, use the doppler frequency change ratio figured from a wave view and just jam it into a formula to refigure and adjust the individual photon energy change over time or distance.

You may have agreed with what I said, but I don't think you understood what it is.

Take an atom. Doppler shift it. When you do that and remeasure the potential energy of that system that you have to put in the hamiltonian, it isn't the same spherical potential well that you normally see. The energy eigenvalues (if one can calculate such a thing in closed form) will not be the same ones you get from before. This will be the doppler-shifted energy state corresponding to the doppler-photons that one observed. It has NOTHING to do with "photon stretching", etc. A photon isn't defined by its size, and certainly was NEVER defined by its longitudinal size.

Zz.

 

[El Hombre Invisible]

Take an individual photon particle from the CMB. Given we know it started off very Blue with a high energy (In wave talk, that means high frequency). Now that it has reached us, it is very Red, down into the microwave frequency band, better stated as a particle with lower energy. Still moving at the same speed of c, we might even say the particle has a lower ‘apparent mass’ based on E=mcc.

This really does seem to be the part you're stumbling over. The photon being emitted from whatever distant galaxy it came from has the exact same photon energy we measure it as in our frame of reference. Viewing it from one frame of reference alone, the photon does not 'change colour' between emission and absorption. The change is due to change of reference frames alone. We look at stars of a similar size closer to us and measure 'bluer' light, and know then that the light from the more distant star has been red-shifted. But the frame in which the closer star is at rest (in which we could accurately measure the energy of the emitted photon) is NOT the same frame as that in which the more distant star is at rest.
It is due to this change of reference frame that the photon energies appear to change. In reality, in our reference frame (i.e. the one in which we are at rest), the photons emitted from stars AT ANY DISTANCE have the same energy that we measure them at. A microwave photon detected by us in a given frame coming from a distant galaxy was emitted as a microwave photon in that frame. It does not change.

 

[RandallB]

Doppler shift it. When you do that and remeasure ... in the hamiltonian, it isn't the same ... NOTHING to do with "photon stretching", etc. A photon isn't defined by its size ...

You can dress it up with all the math you want, but to "Doppler Shift" any part of a “particle“, stretching & changing the energy, then you are selectively treating that part of it like a wave. Just because you define the rules to say you can not stretch a point particle and then mathematically go ahead and stretch it anyway does not give you the right to claim a particle view only analysis of the event.

In my opinion a complete particle view only explanation has yet to be done here, no more than it has been done for Young’s double slit without inserting the uncertainty principle to stand in for not using waves.

RB

 

[ZapperZ]

You can dress it up with all the math you want, but to "Doppler Shift" any part of a “particle“, stretching & changing the energy, then you are selectively treating that part of it like a wave. Just because you define the rules to say you can not stretch a point particle and then mathematically go ahead and stretch it anyway does not give you the right to claim a particle view only analysis of the event.

In my opinion a complete particle view only explanation has yet to be done here, no more than it has been done for Young’s double slit without inserting the uncertainty principle to stand in for not using waves.

RB

I'm not dressing it up with the math, because the WHOLE thing started with the hamiltonian in the first place! So how can you dismiss it as being nothing but mathematical dressing? The energy level of an atom IS an agreement between the hamiltonian and the experimental observation. If not, you know NOTHING about the kind of atom that is emitting so-and-so spectra.

It is also definitely a lot more valid to deal with rather than a "handwaving" argument of "stretching" that is not based on ANY physics. Can you give an exact citation where such a thing has been described and formulated?

Furthermore, I was explaining why you were "bastardizing" what I mentioned earlier. It had nothing to do with what you had in mind. It certainly does not contain any "stretching" effects of any photons, thank you. If you wish to do such a thing, you cannot piggyback onto what I have described. You will have to make things up on your own.

Zz.

 

[Miserable]

Substitute the words "Doppler shift" for "Lorentz transform". You can now use all the above arguments without ever needing to refer to a wave.

 

[RandallB]

Guys, I’m not the one stretching anything,
But using “Doppler Shift” or "Lorentz transform" on a point particle IS.
I’m not saying you don’t get accurate answers or good predictions. Just that is not a clean and complete purely particle view.
If you don’t see that, then your not seeing the forest for all the trees in the way.

RB

 

[ZapperZ]

Guys, I’m not the one stretching anything,
But using “Doppler Shift” or "Lorentz transform" on a point particle IS.

Can you derive on here how a Lorentz transformed photon is stretched, especially when the dimension of a photon at a particular frequency is undefined?

Zz.

 

[RandallB]

Can you derive on here how a Lorentz transformed photon is stretched, especially when the dimension of a photon at a particular frequency is undefined?Zz.

?
I’m the one saying a particle should not be “stretched” at all! Your the one using (Doppler, Lorentz, Hamiltonian) whatever in a non-particle way to do just that (post #19). So of course I cannot explain it – the point is no one can.

I much prefer the particle view myself, and in the long run that it has the best shot at giving us a better understanding of physics. But we will never improve the use of the particle view if we don’t recognize where it is incomplete.

RB

 

[ZapperZ]

?
I’m the one saying a particle should not be “stretched” at all! Your the one using (Doppler, Lorentz, Hamiltonian) whatever in a non-particle way to do just that (post #19). So of course I cannot explain it – the point is no one can.

Read again. I said if you view an atom that is dopper-shifted, the potential that you have to put in for the Hamiltonian is NOT the same spherical potential that one solve normally. It is BASED on this that one gets a different energy state that would produce a transition corresponding to the photons being observed. At no point did I infer any "stretching" of any kind. You did!

Best explanation I saw was Zapper Z: “.. doppler shift the whole atom(photon), and THEN, recalculate the apparent energy”
Two ways to do this:
Conceptually just, stretch out the size of the individual photon particle (vs. atom) like the wave ring from dropping a stone in a smooth pool of water.
OR, use the doppler frequency change ratio figured from a wave view and just jam it into a formula to refigure and adjust the individual photon energy change over time or distance.

I never invoked any stretching, either conceptually or mathematically. You did. You were the one who equate a Lorentz transformation/Doppler shift to "stretching".

Zz.

 

[RandallB]

And as I said in my post that you did not include in quoting me
"but still a wave view for both"
I’ll go with your definition, stretching and Doppler shift are different things and you way define how.
But both are wave based and not particle views.
That was the point.
If they were you would be able to draw for me what photon looks like at different energies, no one can.
RB

 

[El Hombre Invisible]

But we will never improve the use of the particle view if we don’t recognize where it is incomplete.

I really don't get what you think is incomplete. As far as I can tell, you've taken the wave model of light and a property (the Doppler effect), then tried to apply it to the particle model, when in fact the same phenomenon in the particle model is described by another mechanism (relativity). Whichever model you want to use, you have a description of the phemonenon you wish to describe. But you can't take unobservable aspects unique to one of them and try to seek an explanation for them in the other - they are different models. Trying to fit a square peg into a round hole does not constitute a paradox.

 

[ZapperZ]

And as I said in my post that you did not include in quoting me
"but still a wave view for both"
I’ll go with your definition, stretching and Doppler shift are different things and you way define how.
But both are wave based and not particle views.
That was the point.
If they were you would be able to draw for me what photon looks like at different energies, no one can.
RB

Eh?

When I dopper-shift an atom, where exactly does the "wave picture" comes in?

Zz.

 

[Hans de Vries]

RandallB,

We were discussing Cosmological Redshift here, which is not caused
by the doppler effect in modern interpretations and has nothing to do with
Special Relativity or the Lorentz transformation.


There are three totally different reasons why photons get redshifted:

1) Doppler Redshift, caused by a moving object. emitting light
2) Gravitational RedShift, from the escape out of a gravitational field.
3) Cosmological Redshift, (Hubble) caused by the expansion of space.



The paradox you were mentioning (what happens with the energy) does not
exist in Doppler redshift, so I suppose you want to discuss the Cosmological
redshift according to Hubble's law.

There is quite some difference between the Doppler and Cosmological
redshift. If the Hubble effect was the result of the doppler effect then the
Cosmic Background Radiation would not continue to get lower and lower in
frequency.

I found this old thread from Marcus:

https://www.physicsforums.com/showthread.php?t=2825&goto=nextnewest

A few other useful links:
http://curious.astro.cornell.edu/question.php?number=278
http://www.astro.ucla.edu/~wright/cosmology_faq.html#FTL

Regards, Hans

 

[RandallB]

RandallB,
We were discussing Cosmological Redshift here,

That OK, if this thread has changed that's fine we can leave it on red shift
All I'd done is addressed the orig line of questions El H and Adrin had on how to understand a particle "changing color" that all. And why they would find no simple answer, because it is a PARADOX.

I'm guessing it will stay a paradox till the Wave / Particle duality paradox is resolved. Thats all.

Other that using assumtions made from a wave view doing a doppler shift of an "atom" or a photon just cannot be done or diagramed.

So continue with the Cosmological Redshift discussion.
I'll make a prediction there on the expansion of space, I think time we will find if it is there at all the Hubble constant is actually very small, less than 5.
Yes, I understand most disagree, so only Time will tell.

RB

 

[RandallB]

you can't take unobservable aspects unique to one of them and try to seek an explanation for them in the other - they are different models.

Correct, that's why you shouldn't accept using doppler shift as an acceptable solution if you want to stay only in the particle view.

 

[ZapperZ]

I'm guessing it will stay a paradox till the Wave / Particle duality paradox is resolved. Thats all.

I am sure that, having done QM rigoriously, you would have noticed that in QM, there is no such thing as a "wave/particle duality". There is only ONE description of light (and electron, and proton, and neutron, etc) in QM, not two different ones for particle and for wave.

Thus, where is the "paradox" when there is no "duality"?

Zz.

 

[RandallB]

Zz
You can not be saying you’ve never heard of duality.
So it’s just within QM that we cannot have duality?
Maybe by QM’s definition of it’s self, that it doesn’t use “wave” functions. But the results coming out of QM using Cosine Squared or Sin Squared -- that tells me the wave function is just hidden from view in there. Which is part of why what happens to an individual particle is so hard to describe completely. And using “Doppler Shift” is just a part of getting wave results out of QM.

So for me, I like the view from Quantum Physics as larger than just QM, that can recognize a paradox when looking at Quantum Mechanics. But I can understand how the view from within QM with only the QM rules etc. to go by or “QM trees” can block the view of the “Forest” of the full view of Quantum Physics. And a paradox is not seen and maybe doesn’t matter from inside QM. I just like the view of the whole forest rather than only the trees of QM.

If my view starts to produce better results I’ll let you know.

RB

 

[selfAdjoint]

the results coming out of QM using Cosine Squared or Sin Squared -- that tells me the wave function is just hidden from view in there.

The "duality" is not a property of the particle, but of the observation, The state of the particle is represented by a ray in some vector space over the complex field, Because QM is unitary, and since conservation of probability implies the observable operators have determinant +1, the group of L.T's generated by the observables is some extension of U(1), so complex functions like e^{i\phi t} come into play. You CAN interpret these functions as defining a wave - that's how Schroedinger started out - but you don't HAVE to. You can just take them to be complex functions. They are only connected to events in spacetime by the Born rule. Mystique of waves does not really seem appropriate.

 

[ZapperZ]

Zz
You can not be saying you’ve never heard of duality.
So it’s just within QM that we cannot have duality?

You shouldn't be asking this IF you have done any formal work in QM.

The "duality" that most people have used is because the CLASSICAL IDEA of "wave" and "particle" are two different things. We have no such thing in QM. We have been taught by our classical observation that there is a "wave" property, and there is a "particle" property, and they are incompatible with each other.

ALL of the wavelike and particlelike property can be described by QM with just ONE single formulation. PERIOD!

Don't take my word for it. Look for yourself.

Zz.

 

[RandallB]

... so complex functions like e^{i\phi t} come into play. You CAN interpret these functions as defining a wave - that's how Schroedinger started out - but you don't HAVE to. You can just take them to be complex functions. They are only connected to events in spacetime by the Born rule.

And yet we come down to needing to modify a point particle, a photon and as Zz put it:
“A photon isn't defined by its size, and certainly was NEVER defined by its longitudinal size.”
But one of the things that describes the photon is it's Energy that has changed. Describing that change or the energy in a point particle with nothing to reduce, stretch, or Doppler Shift is not simple. Even if in QM I can work out the change in energy using, complex functions connected in space-time by the Born rule, the change in the point particle comes with no real description how the photon should look different.

I know this leaves me back in the dark ages with Einstein, accepting Quantum Physics as an approach, but not able to accept or “spooked by” Quantum Mechanics.

I could even bail myself out and just use “String Theory” and define the photon as in our three dimensions as a point particle, but allowed to be or at least move about in one or more extra dimensions in a manner to account for the Energy. There allowance for reducing the size, shape, and/or timing of that part of the photon to account for holding, reducing, stretching, or Doppler shifting the energy and it’s changes can be described. This is likely at least part of what the string idea is trying to accomplish, but it strikes me as a bit too contrived for the convenient results.

So that leaves me stuck at the same place Einstein was, wondering about a undefined variable - – all I can do is work on it.

RB

 

[ZapperZ]

And yet we come down to needing to modify a point particle, a photon and as Zz put it:
“A photon isn't defined by its size, and certainly was NEVER defined by its longitudinal size.”
But one of the things that describes the photon is it's Energy that has changed. Describing that change or the energy in a point particle with nothing to reduce, stretch, or Doppler Shift is not simple. Even if in QM I can work out the change in energy using, complex functions connected in space-time by the Born rule, the change in the point particle comes with no real description how the photon should look different.

I know this leaves me back in the dark ages with Einstein, accepting Quantum Physics as an approach, but not able to accept or “spooked by” Quantum Mechanics.

May I suggest you go to a library, and read Ref. [1] and [2], unless you prefer to be stuck in the dark ages.

Zz.

[1] D. Benredjem et al. J. Phys. B: At. Mol. Opt. Phys. v.34, p.1369 (2001).
[2] L. Parker, Phys. Rev. Lett v. 44, p.1599 (1980).