What is the deepest mystery of physics and why is it so?

[Strange]

31 minutes ago, swansont said:

I also disagree with this. I'm not sure who is making that claim.

I think it is what Max Tegmark argues: "our physical world is an abstract mathematical structure" (https://arxiv.org/abs/0704.0646)

 

2 hours ago, geordief said:

If maths was * up to the task that would be a nice question .

Is the Universe  made from ideas or from things,?(an ancient discussion I think ..     Plato?)

It is an old idea.

"The [mathematical universe] theory can be considered a form of Pythagoreanism or Platonism in that it proposes the existence of mathematical entities; a form of mathematical monism in that it denies that anything exists except mathematical objects; and a formal expression of ontic structural realism."

https://en.wikipedia.org/wiki/Mathematical_universe_hypothesis

[dimreepr]

3 hours ago, swansont said:

Does the universe follow rules?

If we dont know the rules how can we tell?

[Strange]

20 minutes ago, dimreepr said:

If we dont know the rules how can we tell?

We can invent our own rules that seem to describe the universe and then check to see how well the universe follows them. But maybe that doesn't really tell us if it is following that rule, or any rule.

[swansont]

1 hour ago, dimreepr said:

If we dont know the rules how can we tell?

Have you met this thing we call science?

Have you ever watched a sporting event, even without knowing the rules? Could you tell that there were rules, despite this? And that you could even figure out a few of them from repeated observation?

The thing is, even randomness follows rules. That's one reason why I can't accept the notion that the universe doesn't follow rules.

 

[Strange]

Appropriately, this article has just been published: https://www.quantamagazine.org/puzzle-does-nature-need-elegant-math-20191205/

Quote

Does Natural Law Need Elegant Mathematics?
Many of us are drawn to beauty in mathematics. But is that the way nature really works?

 

[dimreepr]

22 hours ago, swansont said:

The thing is, even randomness follows rules. That's one reason why I can't accept the notion that the universe doesn't follow rules.

science can explain why, but not when. That seems a fundamental flaw in the rules.

[swansont]

Just now, dimreepr said:

science can explain why, but not when. That seems a fundamental flaw in the rules.

If we knew when, it would not be random. Not liking the rules is not the same as them not existing.

[dimreepr]

but if random follows rules why can't we know when? If we know the fundamental rule?

[Strange]

22 minutes ago, dimreepr said:

but if random follows rules why can't we know when? If we know the fundamental rule?

We may not know the rules.

Even if we knew the rules, the mathematics might be too complex to be solved.

Even if the rules (and the mathematics) were simple it might still be unpredictable (see also, chaotic systems).

So there is a difference between there being rules, us knowing the rules and us being able to use the rules.

(If there are rules but they are unusable, is that practically any different from the rules not existing? I don't know.) 

[swansont]

Because "when" isn't one of the rules. 

[dimreepr]

6 minutes ago, Strange said:

Even if the rules (and the mathematics) were simple it might still be unpredictable (see also, chaotic systems).

6 minutes ago, swansont said:

Because "when" isn't one of the rules. 

Doesn't that mean a weather forecast is essentially a guess?

 

[Strange]

22 minutes ago, dimreepr said:

Doesn't that mean a weather forecast is essentially a guess?

Why would you think that?

Weather forecasts are based on simulations of complex systems. Too complex to model completely accurately and chaotic so they are unpredictable on long time scales. This is why multiple simulations are performed with slightly different initial conditions, to see where the most likely outcomes are. I can't think of anything much less like a guess.

[dimreepr]

7 minutes ago, Strange said:

Why would you think that?

because "when" isn't one of the rules.

[swansont]

52 minutes ago, dimreepr said:

Doesn't that mean a weather forecast is essentially a guess?

Weather isn't random, so I don't see how you got here from where we were, and: no, it's not.

[Strange]

1 hour ago, dimreepr said:

because "when" isn't one of the rules.

That doesn't mean we cant work out when it will start raining, for example.

[Strange]

Maybe relevant/interesting

Why the Laws of Physics Are Inevitable: https://www.quantamagazine.org/how-simple-rules-bootstrap-the-laws-of-physics-20191209/

Quote

By considering simple symmetries, physicists working on the “bootstrap” have rederived the four known forces. “There’s just no freedom in the laws of physics,” said one.

 

[Strange]

Another timely article on octonions, and whether they have any physical significance:

Quote

The octonions themselves will never be "the answer" to how reality works, but they do provide a powerful, generalized mathematical structure that has its own unique properties. It includes real, complex, and quaternion mathematics, but also introduces fundamentally unique mathematical properties that can be applied to physics to make novel — but speculative and hitherto unsupported — predictions.

Octonions can give us and idea of which possibilities might be compelling to look at in terms of extensions to known physics and which ones might be less interesting, but there are no concrete observables predicted by the octonions themselves. 

https://www.forbes.com/sites/startswithabang/2019/12/14/ask-ethan-could-octonions-unlock-how-reality-really-works/#606b4b487c1e