[tsimionescu]

Professor Hossenfelder and others have written long books about why the probability of finding new physics based on not liking the aesthetics of the current maths (naturalness, supersimetry, grand unification) is extremely likely to fail, and has been constantly failing for ~50 years.

If our way of generating new theories has given bad predictions for 50 years, at what time should we stop and try out other ways of extending the confirmed theories?

It is unknown in advance if putting your hand through a fire will hurt you this time as well, but after 50 years of doing so, perhaps it's time to stop.

[SiempreViernes]

They make qualitative arguments, nobody has any realistic prediction of what the probabilities are.

And the problem has never been making new theories, the problem is always that we have a very good model, and no principled way for choosing between all the possible theories that gives rise to almost precisely that model.

So people tried to invent reasons and so far nobody has had any luck. And Hossenfelder is correct that in hindsight naturalness wasn't a very good rule.

But by the same hindsight, no theory that could be detected in previous experiments would have worked either. In this view, making the experiments at all was a complete waste, we should just have drawn the winning theory from a hat and stopped all further work.

[tsimionescu]

The point is that there are known problems in the foundations of physics (the measurement problem, the reconciliation of general relativity and quantum mechanics to name the 2 best known ones) and that they should be by far the biggest focus for new research - not GUTs and solutions for un-naturalness.

If we have a theory that could solve the measurement problem (or detect quantum gravity etc.), and a plausible experiment for that theory, we should perform this experiment - it may well yield valuable data whatever result we get.

Conversely, if we have a theory that predicts that more particles may exist at higher levels of energy and nothing else, then there is no good reason to perform this experiment. Especially if the precise level of energy is a free parameter of the theory, so the theory won't change if the experiment fails.

> And Hossenfelder is correct that in hindsight naturalness wasn't a very good rule.

I believe that she is correct that naturalness wasn't a very good rule at all, not just in hindsight. It's as good a rule as it would have been to expect all numbers to be multiples of Pi.

[SiempreViernes]

To claim that the standard model has nothing to do with the quantization of gravity is very strange, part of the motivation for a GUT is that it would be a huge help towards making a theory of everything. And a TOE is precisely a unified treatment of the standard model forces and gravity.

The measurement problem isn't a physics thing, just like naturalness that's more of a life-style choice. In fact, the only reason to have problems with wave-function collapse is precisely a naturalness reasoning, technically it makes very accurate predictions just fine.

[tsimionescu]

> part of the motivation for a GUT is that it would be a huge help towards making a theory of everything. And a TOE is precisely a unified treatment of the standard model forces and gravity.

A GUT is specifically the part of a TOE that has nothing to do with gravity... A TOE is a GUT + a theory of quantum gravity.

If we had the Standard Model + a theory of quantum gravity, this could be a complete theory of the universe (pending explanations for dark matter, dark energy etc.). These could very well be completely separate phenomena, there is no reason to believe they reduce to a single phenomenon - that there exists a TOE.

> The measurement problem isn't a physics thing, just like naturalness that's more of a life-style choice. In fact, the only reason to have problems with wave-function collapse is precisely a naturalness reasoning, technically it makes very accurate predictions just fine.

This isn't entirely accurate. There is a very clear quantitative question behind the measurement problem: what kind of system constitutes a measurement device, in the sense of invoking the need for the Born rule? There must be some precise size/kind of system that, when a particle interacts with it, you can no longer use Schrodinger's equation to predict its movement after that interaction - you must apply the Born rule. We know that this doesn't happen after a particle collision, but that it does happen after a collision with a "detector".

This is a clear empirical question (you don't need to call it a problem), well within the realm of physics. It may be extremely difficult to answer, but I see no reason to imagine it is a priori impossible to resolve.