[pigpang]

It's just an interpretation. Your interpretation is similar to the Big Bang model of visible Universe expansion. If you can convince us that your model is better than other models, then we will use your model, but nobody can prove than a model is correct, unless we will find a hidden recorder somewhere which was turned on for few dozens of billion years.

Photon will hit something, or will travel until it will be redshifted to obvilion, or will travel until end of the medium (photon is a wave, so it waves something).

[pdonis]

> It's just an interpretation

No, it's not, it's our best current model's description of the actual physical reality of our universe.

> nobody can prove than a model is correct

That's true, but it's also true that we can show models to be incorrect, as in, falsified by the data. For example:

> Photon will hit something, or will travel until it will be redshifted to obvilion, or will travel until end of the medium

For the scenario that was posed, a laser beam that never hits anything, none of your statements here are true. The first is ruled out by the scenario; the second is known to be false because there is no "gravitational redshift" of light in the universe as a whole (because models in which there would be such a redshift are known not to correctly model our data on the universe as a whole), and there is no "end of the medium" (again, models in which there would be an "end of the medium", i.e., where the universe stopped containing matter and started being just vacuum, are known not to correctly model our data).

I have described what actually happens in my own response to the GP upthread.

> (photon is a wave, so it waves something).

Light is an electromagnetic wave; what "waves" is the electromagnetic field. (If you use a "photon" model, you are using the quantum electromagnetic field as opposed to its classical approximation.) There doesn't have to be any other "medium"; the electromagnetic field is present everywhere.

[pigpang]

> No, it's not, it's our best current model's description of the actual physical reality of our universe.

OK, it's our best model, but it doesn't invalidate other models, less complete or less popular, it compete with them.

> That's true, but it's also true that we can show models to be incorrect, as in, falsified by the data.

Yep. The article is about the Huble Tension, which invalidates Big Bang model. We still use it.

> the second is known to be false because there is no "gravitational redshift" of light in the universe as a whole (because models in which there would be such a redshift are known not to correctly model our data on the universe as a whole)

The Big Bang model is incomplete too: galaxies with FTL speeds, different speeds of expansion, no center of bang, no flows, no source of energy, it stretches time and space, etc.

I assume that the only infinite thing in infinite Universe is Universe itselft. All other things are finite. Thus, a photon has finite life, like any other wave.

> there is no "end of the medium"

The right-hand rule in EM suggests that we are in north hemisphere of something, so south hemisphere will have symmetrical rule, unless you believe that God chose right-hand rule for the whole infinite universe. If we are in a sphere, then that sphere rotates and have a boundary.

> what "waves" is the electromagnetic field.

"Field" is an array of numbers. You are mixing model and reality.

[pdonis]

> it doesn't invalidate other models

One model can't invalidate other models. Only data can invalidate a model.

What other models do you have in mind?

> the Huble Tension, which invalidates Big Bang model

No, it doesn't. It means we have more work to do, to figure out why two calculations of the Hubble constant, by different routes, give different answers.

Invalidating the Big Bang model would be finding evidence that there was no Big Bang at all. The Hubble tension is nothing of the sort.

> The Big Bang model is incomplete too: galaxies with FTL speeds, different speeds of expansion, no center of bang, no flows, no source of energy, it stretches time and space, etc.

None of these are issues at all. The model accounts for them all in a perfectly self-consistent fashion.

Also, your nomenclature is biased: for example, the "FTL speeds" you refer to are coordinate speeds, which have no physical meaning. "FTL" in General Relativity means "moving outside the light cones", and that does not happen.

> The right-hand rule in EM suggests that we are in north hemisphere of something

The right-hand rule is a human convention. It tells us nothing about physics.

> You are mixing model and reality.

No, you are incorrectly assuming that the word "field" can only refer to the model. That's not the case. Physicists commonly use the word "field" to refer to both the mathematical object in the model and the actual physical thing that is being modeled. Light is "waves of the electromagnetic field" in the latter sense.

[denton-scratch]

> (photon is a wave, so it waves something)

That sounds suspiciously like postulating the 'ether'. Surely what a photon 'waves' is the electromagnetic field, which is not a medium, and which fills the whole of spacetime. There is no 'end of the medium'.

[pigpang]

"Field" means 3d array of numbers. Spacetime means 4d array of numbers. You are talking about mathematical model of Universe, while I'm talking about physics. Mountain is not just an excitement in a height field. If photon is not waving something, then it's not a wave. Physicists prove that photon is a wave.

[michaelsbradley]

> If photon is not waving something, then it's not a wave.

No, you’ve simply hit the limits of needing/wanting to understand something in terms of something else similar or more familiar.

Makes the same point on a related matter: https://youtu.be/Q1lL-hXO27Q