6 hours ago, Markus Hanke said:

Yes, very valid point +1

I did not mean to make the thread above sound like the last words have been spoken on these matters...it's just that the connection between gravity and thermodynamics seems to be too strong to be a mere coincidence. And thermodynamics is "emergent" in the sense that it is a statistical macroscopic description of systems made up of microscopic constituents (or states).

Lol, I do occasionally teach in real life (it's part of the "job" of being a monk), but of course that's not related to science. In general, I find it easier to explain things in writing than "live" in front of an audience.

I have too much respect for you to want to sound pernickety.

What I am doing is sounding a note of caution about oversimplification and the theoretical physicist's habit (pun intended) of packing too much into too few terms, leading to the danger of circular arguments.

For instance the term 'states' by itself is not as detailed and precise as the original thermodynamic definition of 'state'.

For QM only energy is considered, but then you need a definition of energy, invoking the danger of circular arguments.

Considering Relativity v Navier Stokes.

By not including compressibility and viscosity variables you will arrive at the conclusion that there is zero force on a circular object in a flow.

Physicists would love to drop the Lambda term in the GR packed equation, for the sake of 'elegance', which is a similar mistake (in my opinion).

[math]{G_{\mu \nu }} + \Lambda {g_{\mu \nu }} = \frac{{8\pi G}}{{{c^4}}}{T_{\mu \nu }}[/math]

13 hours ago, studiot said:

What I am doing is sounding a note of caution about oversimplification and the theoretical physicist's habit (pun intended) of packing too much into too few terms, leading to the danger of circular arguments.

And that is a very valid concern! I appreciate you pointing it out.

My main problem is, and always has been, that I’m just an amateur - I haven’t gone into the same amount of depth as someone who has formally studied those things, so there’s always the possibility that I’m missing something. That’s why it’s important to get reality checks from professionals like yourself

15 hours ago, exchemist said:

what interests me is whether the basic concept - of treating the EM interaction in terms of 5D geometry of what could I suppose be called space-charge-time can in principle be adapted to fit with QFT, or whether the two approaches are inherently mutually exclusive.

Well, the proof is always in the pudding, meaning in whether the chosen approach fits observational data or not. Fact is that we have no evidence or indication of extra dimensions, microscopic or otherwise, much less of the extra required scalar field. Also, AFAIK some of the actual predictions that KK theory makes are different from those of QFT, and thus wrong - the Wiki article mentions the electron mass for example. So we can say that these two approaches to modelling EM are not equivalent, and that QFT fits the data much better. I guess this is why we don’t hear so often about KK theory - interesting attempt, but QED works better

6 hours ago, Markus Hanke said:

And that is a very valid concern! I appreciate you pointing it out.

My main problem is, and always has been, that I’m just an amateur - I haven’t gone into the same amount of depth as someone who has formally studied those things, so there’s always the possibility that I’m missing something. That’s why it’s important to get reality checks from professionals like yourself

Well, the proof is always in the pudding, meaning in whether the chosen approach fits observational data or not. Fact is that we have no evidence or indication of extra dimensions, microscopic or otherwise, much less of the extra required scalar field. Also, AFAIK some of the actual predictions that KK theory makes are different from those of QFT, and thus wrong - the Wiki article mentions the electron mass for example. So we can say that these two approaches to modelling EM are not equivalent, and that QFT fits the data much better. I guess this is why we don’t hear so often about KK theory - interesting attempt, but QED works better

Yes, so that would suggest to me the EM interaction and the weak and strong interactions are qualitatively different from gravitation, in that only the last can be modelled as due to geometrical effects of spacetime (or spacetime + nnn).

17 hours ago, exchemist said:

Yes, so that would suggest to me the EM interaction and the weak and strong interactions are qualitatively different from gravitation, in that only the last can be modelled as due to geometrical effects of spacetime (or spacetime + nnn).

Yes, I would tend to agree.

There are, however, topological QFTs that seem to capture some aspects of the Standard Model via topology (as opposed to geometry) of spacetime. To be clear, none of the fundamental interactions as we know them now can be fully described by pure TQFTs, as all of them contain local propagating degrees of freedom (ie moving particles). But still, there are intriguing connections here.

6 hours ago, Markus Hanke said:

But still, there are intriguing connections here.

Indeed yes, and these should be fully explored.

But we are not there yet.