[jeffreyH]

@Halc This is worth a read.

https://physicsworld.com/a/does-general-relativity-violate-determinism-inside-charged-black-holes/

[Halc]

@Halc This is worth a read.
physicsworld :does-general-relativity-violate-determinism-inside-charged-black-holes

Interesting link. Yes, it says that Newton envisioned a classic billiard-ball sort of physics, and it was that way all the way down, and relativity didn't really challenge that (except maybe it does, as the article points out). 
Quantum mechanics definitely threw a wrench into the works for the determinists, but it as well doesn't disprove it since there are very much deterministic interpretations of QM.

I think we'd need a unified field theory to begin to say whether relativity has any concrete stance on the issue.

From the article:

Newton’s mechanics allow us in principle to calculate the exact state of a physical system at any point in the future, provided that we know its initial state perfectly. So too with general relativity: a precise knowledge of space’s geometry and its rate of change in the present enables us in theory to predict exactly how space-time will evolve.

This is clearly false, and known to Einstein at the time.  QM theory says no amount of measuring of a system will allow you to predict it. Einstein was definitely a determinist, as evidenced by his "God doesn't throw dice" quip, but I don't think any of the deterministic interpretations where developed or well known at the time.  There was the 'hidden variables' postulate which said there are variables which cannot be known, but if they were, the future would be perfectly predictable.

As such, Einstein’s theory is considered by most physicists to be entirely deterministic.

... as it doesn't contradict Newton's 'classic all the way down' assumption.  But the theory also doesn't posit this assumption. It merely declines to challenge it. QM very much challenges it.

Charged black holes, however, challenge this deterministic picture. The “Reissner-Nordström” solution of general relativity describes a black hole created when a star that is electrically charged and spherical collapses in on itself under the force of gravity. Hidden from view inside such a black hole’s event horizon lies a second boundary known as the Cauchy horizon, beyond which space-time is smooth but indeterminate. In other words, the future can no longer be predicted.

It has also yet to be demonstrated that it is meaningful to speak of the physics inside the event horizon.  It is mathematically infinitely far into our future, and since the black hole will evaporate in finite time, it is questionable if anything 'gets in' so to speak.  Again, a unified theory would help.  The subject has proponents on both sides, and this would best be discussed in a separate thread. I'm quite opinionated on it myself, having the luxury of not completely knowing what I'm talking about.

[alancalverd]

QM theory says no amount of measuring of a system will allow you to predict it.

Be careful how you state this. The test of quantum mechanics is not merely that it explains obvious quantum phenomena like line spectra, but that it scales to classical mechanics for large assemblies. And it does.

The wave function of a billiard ball is negligible in comparison with its apparent diameter, so for all practical purposes (e.g. potting the black) it is adequately predictable. But its structure, mass and elasticity are all calculable from quantum mechanics.

Indeed the "measuring" test isn't fundamental to QM. The classical model of bouncing a photon off an electron sort of illustrates the problem of measurement influencing the measurand, but masks the inherent indeterminacy of Heisenberg's statement that Δp.Δx ≥ h.

[alancalverd]

In English Billiards, scoring is as follows:
........
A pot: This is when the red ball is struck by the player's cue ball so that the red ends up entering a pocket. This scores three points. If the player’s cue ball strikes the other cue ball resulting it going down the pocket, then this scores two points...…..

My apologies, there are pockets, but the target ball is red, not black.

Anyway, the fact remains that for a billiard ball p and x are so large compared with h that the indeterminacy of its position is negligible even when p is zero, which makes the game playable and double-slit diffraction (or spontaneous appearance in another pocket)  of a billiard ball very difficult to observe. Or, if you like wave functions, the wave function barely extends beyond its classical surface.

[jeffreyH]

Macroscopic objects follow deterministic paths which is why combining relativity and quantum mechanics is so hard. You need a very small scale and high energies. These conditions are found when particles are close to an event horizon. So it is going to be difficult to observe. It may be possible to recreate these condition in future particle accelerators.

[alancalverd]

Yes, I misinterpreted your scenario. We are in fact in perfect agreement. Because the wave function of a large object is negligible outside its classical radius (indeed you can use that as a definition of "mesoscopic") we can predict where a billiard ball will go. Because the wave function of an electron is much bigger than its radius, atoms and molecules do not collapse.

[Halc]

In English Billiards ...

My apologies, there are pockets.

I guess what I've played isn't English Billiards. Thanks for the education.

Anyway, the fact remains that for a billiard ball p and x are so large compared with h that the indeterminacy of its position is negligible even when p is zero

Totally agree, but you're talking about measuring it, and not about predicting where it will be in the future. Yes, I can measure the position and momentum of a billiard ball to a lot of zeros of accuracy. No argument there.

Kindly interpret my post as talking about predictions (from a wave function) of the future, and not of measurement of its current state.

Because the wave function of a large object is negligible outside its classical radius (indeed you can use that as a definition of "mesoscopic") we can predict where a billiard ball will go.

If this were true, they could publish tonight's billiards scores in today's paper. Only the one interpretation I mentioned actually asserts the game is fixed (completely determined) like that, and even then there is neither a way to 1) take anywhere near the necessary measurements, nor 2) perform the calculation, so no computer, even hypothetical, can actually perform such a calculation.

This is what I was talking about when discussing predictions of macroscopic objects.

[yor_on]

 "   enough charge, damping wins out over amplification and the oscillations die away quickly. As Cardoso explains, the charge and cosmological constant essentially provide repulsive forces that counteract the pull of gravity and so diminish its amplifying effects. "

" In the context of cosmology the cosmological constant is a homogeneous energy density that causes the expansion of the universe to accelerate. Originally proposed early in the development of general relativity in order to allow a static universe solution it was subsequently abandoned when the universe was found to be expanding. Now the cosmological constant is invoked to explain the observed acceleration of the expansion of the universe. The cosmological constant is the simplest realization of dark energy, which is the more generic name given to the unknown cause of the acceleration of the universe. Its existence is also predicted by quantum physics, where it enters as a form of vacuum energy, although the magnitude predicted by quantum theory does not match that observed in cosmology. "

Maybe?

[alancalverd]

If this were true, they could publish tonight's billiards scores in today's paper.

Indeed, if you knew in advance what shot each player was going to make. Problem is, you don't. Billiards is a competitive game of skill, not random chance. At least that's what good players tell me! You always  have a choice of shots and, like snooker, you can choose a shot that gives you a score or one that puts your opponent in a position from which he cannot score but is likely to foul. The fact that good players rarely foul suggests that for all practical purposes, the behaviour of billiard balls is predictable.

If we took your assertions at face value, nobody would dare to drive a car because it is impossible to predict where it will go.

[hamdani yusuf]

I watched as single photons passed through a single slit producing a single bar pattern.

I believe this only happens in simulation, never really happens in actual experiment. The images below show what you'd get from single slit and double slit experiment.

With a normal single slit apperture, you will still get interference pattern due to diffraction effect.

[Lloyd (OP)]

That's interesting hamandi ... a lot of information I am coming across is based on simulation and not the results of experimentation. Simulation is fine up to a point I suspect. But there comes a point when the simulation has to be replicated by experiment in order for it to carry any credence.

[alancalverd]

It has been argued elsewhere in this forum that interference and diffraction are not the same, and the difference between Hamandi's excellent images shows this. It's a bit academic and a lot of the maths is common to both phenomena but logically you need two sources or particles to interfere, and only one edge to diffract.

The quantum two-slit problem is that a single particle seems to interfere with itself, thus showing that classical continuum wave equations don't adequately model very sparse (single photon) systems.