Why Quantum Mechanics? • Hacker News Board

Re: Why Quantum Mechanics?

#241

Post by GoblinSlayer » Mon, Jan 31, 2022, 7:47 AM UTC

dekhn wrote: post #237

Huh. What he's not talking about is QM, he's talking about the enormous math industry that built up around QM. Actual QM is experiments in labs with lasers and cryocooling. You can sit around with your complex amplitudes and fancy math but none of that is really necessary to appreciate or make forward progress in the actual underlying physics. Sort of like string theory. Not exactly, but sort of.

Applied physics doesn't work without fundamental physics. Can you prove experimentally whether FTL communication is possible? How would you make progress there?

Re: Why Quantum Mechanics?

#242

Post by simiones » Mon, Jan 31, 2022, 10:07 AM UTC

Eratosthenes wrote: post #219

simiones wrote: post #169

Earlier quoted context omitted.

Nothing in classical mechanics can explain the double-slit experiment; nor the relativity of simultaneity. Furthermore, action-at-a-distance (non-locality) makes classical mechanics inconsistent even with itself, so it's a non-starter (it implies grandfather paradoxes).

Fundamentally, orbital mechanics still relies on the same old action-at-a-distance that plagued Newton. You can look under the hood of any software that simulates orbits and see that this is the case. No time delay is assumed for gravitational interaction. Celestial bodies effect each other's orbits instantaneously (the Poynting-Robertson effect also makes this obvious). IF you assume that photons have mass and inter…

> IF you assume that photons have mass and interact gravitationally (there are good reasons for making this assumption), then you can explain the double slit experiment classically via gravitational interaction.

No, you can't. The double slit experiment has nothing to do with mass or gravity. It is well known that it happens with electrons, protons, and has even been demonstrated with some large molecules (thousands of atoms). Gravity can't explain anything about it though.

And even if I can imagine some gravitation-based interactions in the case of a stream of huge numbers of particles (though not the actual quantitative explanation), the double slit experiment has been reproduced with things like 1 photon emitted every hour - over the course of a few days, the same interference pattern emerges IF the photon's path is NOT observed; but NO interference pattern emerges if the photon's path IS observed.

> You can look under the hood of any software that simulates orbits and see that this is the case. No time delay is assumed for gravitational interaction.

The fact that simulation software takes shortcuts to make its computations feasible is not proof that this is how the world works. Einstein's GR equations are famously intractable to solve in their base form, and approximations are strictly necessary. But given the distances and observational precision for the positions of planetary objects, I would bet the effect of gravitational waves having a finite speed is negligible for most predictions.

Not to mention, we have actually measured the speed of gravity: we have detected gravity waves and they are moving at the "speed of light", or as near to that as we have been able to determine. Definitely not instantaneously.

> the Poynting-Robertson effect also makes this obvious

That is a General Relativity effect, which assumes that gravity is a local interaction (i.e. no action at a distance). That is precisely Robertson's contribution to the Poynting-Robertson effect, per the WIkipedia article (Poynting first understood the effect, but described it in terms of the luminiferous aether).

Re: Why Quantum Mechanics?

#243

Post by cannabis_sam » Mon, Jan 31, 2022, 1:57 PM UTC

platz wrote: post #194

cannabis_sam wrote: post #152

>Why didn’t God just [MAKE THE PLANETS ORBIT AROUND EARTH] and be done with it? What would’ve been wrong with that choice? Okay then, can you explain the math behind that solution? How in the world does the words “God”, “just” and “be done with it” in anyway whatsoever help elucidate this issue…?

You're either getting caught up in the incidental religious reference, or failed to interpret Scott's conciseness. See this comment for elaboration on exactly what kind of counterfactual Scott is asking https://news.ycombinator.com/item?id=30117928 . He's asking about a hypothetical alternative in a very specific way, which is to see whether it sheds any light on the logical foundation of QM, not just to consider alt…

Also, can you at least attempt to mathematically explain a QM+“god” argument?

Re: Why Quantum Mechanics?

#244

Post by GoblinSlayer » Mon, Jan 31, 2022, 2:16 PM UTC

seiferteric wrote: post #163

GoblinSlayer wrote: post #142

Earlier quoted context omitted.

You can't possibly hope for eliminativism to be meaningful? Like a computer is not on the level of a transistor, "you" is not on the level of a neuron, but on a higher integrative level.

I mean I am saying it does not matter. If "you" is the sum of your experiences, genes and your environment programming your brain over time, but decisions are either deterministic or probabilistic, then "you" really had no input on how your brain/body would ultimately develop. It does not matter how complex your program is, each decision ultimately comes down to a process on the lowest level that you don't control.

Programs have full input on what ultimately happens: the result completely depends on the program. There's no "you" on the lowest level, by looking there you don't see what happens to "you", so your claims about "you" aren't based on knowledge, but prejudice.

Re: Why Quantum Mechanics?

#245

Post by stared » Mon, Jan 31, 2022, 2:32 PM UTC

cevi wrote: post #230

stared wrote: post #197

Earlier quoted context omitted.

I am not sure what is a "meta axiom". Could you give an example for one?

The rules of propositional logic (or first-order logic) would seem to fit: i.e. that fact that "A and B" has the same truth-value as "B and A", or the use of modus ponens as a deduction rule. These rules are usually left out of axiomatic descriptions of mathematical fields.

In formal mathematics, everything needs to be stated explicitly.

For a moment, forget about "and" and use "zxhds" instead. You need to specify how it works.

There is nothing magic, intrinsic or natural about "truth" or "implies". It is all rules of symbol rearrangement.

Re: Why Quantum Mechanics?

#246

Post by dekhn » Mon, Jan 31, 2022, 3:29 PM UTC

GoblinSlayer wrote: post #241

dekhn wrote: post #237

Huh. What he's not talking about is QM, he's talking about the enormous math industry that built up around QM. Actual QM is experiments in labs with lasers and cryocooling. You can sit around with your complex amplitudes and fancy math but none of that is really necessary to appreciate or make forward progress in the actual underlying physics. Sort of like string theory. Not exactly, but sort of.

Applied physics doesn't work without fundamental physics. Can you prove experimentally whether FTL communication is possible? How would you make progress there?

"Prove" FTL impossible? No. however, based on everything we know today, superluminal communication will remain impossible, and if it does become possible, will raise all sorts of interesting implications.

Re: Why Quantum Mechanics?

#247

Post by VirusNewbie » Fri, Feb 04, 2022, 6:21 PM UTC

stared wrote: post #229

VirusNewbie wrote: post #205

Earlier quoted context omitted.

I'm thinking Godel's theorems or AIT.

Gödel's theorem is a theorem, not an axiom.

oops in my original post I meant to say meta axioms and meta theorems, how embarrassing.

As to your reply above, regardless of what you call axioms, semantically speaking there is an isomorphic subset in common for all useful axiomatic system is what I'm postulating. Can you think of an axiomatic system that doesn't have something iso to identity and equivalence for instance?

Re: Why Quantum Mechanics?

#248

Post by stared » Tue, Feb 08, 2022, 6:37 PM UTC

VirusNewbie wrote: post #247

stared wrote: post #229

Earlier quoted context omitted.

Gödel's theorem is a theorem, not an axiom.

oops in my original post I meant to say meta axioms and meta theorems, how embarrassing. As to your reply above, regardless of what you call axioms, semantically speaking there is an isomorphic subset in common for all useful axiomatic system is what I'm postulating. Can you think of an axiomatic system that doesn't have something iso to identity and equivalence for instance?

I never went deep into formal logic, so I can misname a few things as well.

1. When it comes to the Gödel's incompleteness theorem - for non-recursive systems you may you can get without that, vide https://math.stackexchange.com/questions/3359878/what-is-som...

2. In general, you can do a lot without equivalence. For example, in set theory (ZF), you get only trivial equivalence (sets having the same elements are the same set). But you can still do a lot with "contains". A similar thing works with partially ordered sets, in which you have the "<=" operator.