Virtual photons are weird creatures

And the rest of what you wrote seems okay to me.

The small ball is of course a 'ball' only in its momentum, as it has no 'rest mass', like matter has. "The invariant mass, intrinsic mass, proper mass or just mass is a characteristic of the total energy and momentum of an object or a system of objects that is the same in all frames of reference" and that is what defines matter, that it always will have an invariant mass, even though the 'weight' might differ. But it works for me when thinking of it, and using the analogy I can connect the way molecules release heat, to the way photons interacts with atoms. And, that's probably why I let 'bounce' slip through, two times

and now three.

)

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In some ways the definition is a little vague though, thinking of it. The same way a photon can be seen to be red or blue shifted depending on your 'frame of observation', traveling towards it or from it, so can a piece of matter be seen to have more, or less, 'total energy' depending on its direction relative yours. And that's also what's called 'relative mass' or 'potential energy'. The 'potential energy' here is a description of your 'frame of reference' relative the 'frame of reference' of the photon, towards you, or, away from you.

'Away' will show itself as a redshift with a photon/wave, but with matter you won't see any difference, except in its 'relativistic geometry', it shrinking with speed/velocity, I think? Coming towards you the photon/wave will show itself as a blue shift, but with matter you won't see a difference, except in the way its geometry transforms.

But the same way as matter consists of this 'invariant mass', so can a photon be defined to be of a so called 'light quanta'. That light quanta, again as I understands it, will also be 'invariant' no matter what frame you observe it from. Meaning that looked on as a 'light quanta' you can say that this photon also have a defined 'invariant energy', well, as I understands it

Analogous to matters 'invariant' mass.

There have to be something more to that definition. They say that it is invariant in all 'frames of reference' right? And treated so it can only be the matter itself, and its own transformation into energy, that defines invariant matter, not the 'total energy' (aka + velocity/speed) as it seemed to say to me when I reread it.

But the question is still, if a 'light quanta' also is of a invariant energy/momentum, doesn't that definition of invariant mass lose some of its uniqueness? The only way around it seems to be to assume that a light quanta only is defined versus your frame of reference, meaning that it have no defined energy/momentum, only the combination of yours, as well as its own, 'frame of reference'?

(Light quanta: In physics, a photon is an elementary particle, the quantum of the electromagnetic interaction and the basic "unit" of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force.)

Now why did I have to wonder about that one?

Sh*

Short history of light quanta And if you read that one you will wonder what the he* they meant by 'intensity'.

"According to Einstein’s photoelectric effect in where he proposed that light is made up of packets of energy called photons. Photons have no mass, but they have momentum and they have an energy given by: Energy of a photon : E = hf (where E= energy in J and F = frequency unit in 1/s or hertz and h= 6.693*10^-4J*s, or Planck's constant) So, E= Planck's constant (h) multiplied by its frequency (f)

The photoelectric effect works like this. If you shine light of high enough energy on to a metal, electrons will be emitted from the metal. Light below a certain threshold frequency, no matter how intense, will not cause any electrons to be emitted. Light above the threshold frequency, even if it's not very intense, will always cause electrons to be emitted. It takes a certain energy to eject an electron from a metal surface. This energy is known as the work function (W), which depends on the metal. Electrons can gain energy by interacting with photons. If a photon has an energy at least as big as the work function, the photon energy can be transferred to the electron and the electron will have enough energy to escape from the metal. And a photon with an energy less than the work function will never be able to eject electrons. Knowing that light is made up of photons, it's easy to explain now. It's not the total amount of energy (i.e., the intensity) that's important, but the energy per photon."

The point being here that it was the 'discrete light quanta/photons' that dislodged the electrons.

Anyway.

I must be missing something simple here.

It's probably much clearer mathematically