I Does the Photon Play a Crucial Role in Quantum Mechanics?

[Vanadium 50]

This seems to be going pretty far afield.

Photons can be created and the creation describe with well understood questions.
Photons can be absorbed, again with well understood consequences/effects on the environment.
Photons can be counted.

What would be a better definition of "exist"?

 

[Dale]

What would be a better definition of "exist"?

Philosophers have been debating that for centuries. As far as I can tell, they don't have a better definition.

 

[phinds]

Philosophers have been debating that for centuries. As far as I can tell, they don't have a better definition.

Doesn't that make this about the right time to close this thread?

 

[neobaud]

This seems to be going pretty far afield.

Photons can be created and the creation describe with well understood questions.
Photons can be absorbed, again with well understood consequences/effects on the environment.
Photons can be counted.

What would be a better definition of "exist"?

Ya I realize that I didn't do a very good job of framing the question.

 

[neobaud]

This seems to be going pretty far afield.

Photons can be created and the creation describe with well understood questions.
Photons can be absorbed, again with well understood consequences/effects on the environment.
Photons can be counted.

What would be a better definition of "exist"?

I think Dale's answer makes sense for an observer watching the transfer of momentum/energy through the em field. If there was no Photon, they would see energy disappear and then reappear at some later time. This is not allowed.

I was wondering about the perspective of the photon where this problem with the "energy glitch" would not happen. The photon itself never "sees" the disappearance of energy so the photon is really unnecessary. Even if the interaction happened across vast distances of space and time. Seems from one point of view you could say that photons, light and other massless particles aren't involved with events in the universe (events = transfer of momentum and energy).

 

[PeterDonis]

I was wondering about the perspective of the photon where this problem with the "energy glitch" would not happen.

Yes, it would. See below.

from one point of view you could say that photons, light and other massless particles aren't involved with events in the universe

No, you cannot say that. It's wrong. The fact that the arc length along a photon's worldline is zero does not mean that "photons don't experience time" or that there are not distinct spacetime events along a photon's worldline or that a photon's worldline is not part of the universe. If the photon did not carry energy and momentum from source to emitter, there would be a "gap" in spacetime between them that would cause local non-conservation, even though the arc length along the photon's worldline is zero.

 

[neobaud]

Yes, it would. See below.No, you cannot say that. It's wrong. The fact that the arc length along a photon's worldline is zero does not mean that "photons don't experience time" or that there are not distinct spacetime events along a photon's worldline or that a photon's worldline is not part of the universe. If the photon did not carry energy and momentum from source to emitter, there would be a "gap" in spacetime between them that would cause local non-conservation, even though the arc length along the photon's worldline is zero.

Isn't spacetime an emergent property of the universe?

I maintain that massless particles don't experience time. They are incapable of having internal clocks. I don't know why you would argue this point.

 

[Dale]

I was wondering about the perspective of the photon

There is no "perspective of the photon". Photons don't even have a position operator.

Seems from one point of view you could say that photons, light and other massless particles aren't involved with events in the universe

That “point of view” doesn’t exist.

 

[Vanadium 50]

Philosophers have been debating that for centuries

I pay them as little mind as I can.

To me, the key is countability. "They don't really exist but this box contains four of them" seems nonsensical.

 

[Dale]

I pay them as little mind as I can.

Always wise, in my opinion. (Which I realize is itself philosophical, but I don't have to get into a debate about it).

 

[Vanadium 50]

that massless particles don't experience time

Does an electron? After all, an electron that is 1000 years old acts identically to one that was just created.

This seems to be a) philosophical and not something subject to test via measurement and b) a set of properties unnecessary for understanding how matter behaves. Does an inclined plane experience time? How do you know, and what difference does it make?

 

[PeterDonis]

Isn't spacetime an emergent property of the universe?

What does this even mean?

I maintain that massless particles don't experience time. They are incapable of having internal clocks.

If by this you mean that the concepts of "experienced time" and "internal clocks" are not even well-defined for massless particles, that is correct. I covered this way back in post #3. However, that does not justify the further claims you made.

I don't know why you would argue this point.

I am not. I am simply pointing out, as above, that the correct point that I am not arguing does not justify the further claims you made that I did argue.

 

[PeterDonis]

Thread closed for moderation.

 

[PeterDonis]

After moderator review, the thread will remain closed.

 

[bhobba]

I know the tread is closed, but ages ago, I found an excellent paper that can be understood after a first course in QM (Susskind would be enough with persistence) that explains why a photon must exist. It was historically first worked out by Dirac. The issue is spontaneous emission. Einstein explained it in one of his famous papers that high school students these days learn about. But Dirac used the principles of QM to explain those rules. It was the first 'taste' of Quantum Field Theory, the foundation of the modern standard model. Without further ado:

https://www.physics.usu.edu/torre/QFT/Lectures/QFT_text.pdf

Thanks
Bill