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Why Quantum Mechanics?

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Re: Why Quantum Mechanics?

#211

Post by bawolff »

deltaonefour wrote: post #157
bawolff wrote: post #86

Earlier quoted context omitted.

Not entirely what my view is. Although arguably much depends on the meaning of the word "why" My original point was: say logic is false. That's hard to concieve of, and if so we basically can't reason. The rules of logic are independent of the physical world in a way the physical world following QM is not. I wouldn't say it is gradual layers but a hard line between physical and non-physical theories. As to your point…

Elegance and natural and simple are just attributes of a system. There is no law that says all systems must be elegant. You're saying finding attributes of a mathematical model to be simple or elegant answers this question of "why?". For me such an attribute is arbitrary. If we determine something to be elegant it doesn't mean anything at all. But "why" is it elegant means something.

I think the underlying (somewhat irrational) claim is that nature prefers to work in elegant ways. Thus if you can show that QM is the most elegant solution under some contraints, it helps explain the "why".

Re: Why Quantum Mechanics?

#212

Post by PaulDavisThe1st »

platz wrote: post #206
PaulDavisThe1st wrote: post #204

Earlier quoted context omitted.

But he's not asking whether or not QM is the obvious conclusion when trying to explain the data we have. He's asking why a creator/creation process would use QM in a universe rather than something else.

2 sides of the same question. its a special case of the cases described here https://news.ycombinator.com/item?id=30117928 .

I don't think so. Here's Scott from further down his own comment section:

> Most importantly, people keep wanting to justify QM by reminding me about specific difficulties with the classical physics of the 19th century: for example, the ultraviolet catastrophe. To clarify, I never had any quarrel with the claim that, starting with 19th-century physics (especially electromagnetism), QM provided the only sensible completion.

But, to say it one more time, what would’ve been wrong with a totally different starting point—let’s say, a classical cellular automaton? Sure, it wouldn’t lead to our physics, but it would lead to some physics that was computationally universal and presumably able to support complex life (at least, until I see a good argument otherwise).

Re: Why Quantum Mechanics?

#213

Post by sdwr »

jiggawatts wrote: post #99
dboreham wrote: post #2

Q1: because that wouldn't be consistent with simulation. Q2: because that's how the simulator works. Joking aside, I wonder if there's some principle that: physics will always look like you'd expect it to look if it's a simulation. Perhaps that's what Yang-Mills Gauge Theory is about?

I'm the type of person that likes to visualise the space of all possible theories of everything like a surface. A table, let's say. I like to imagine placing similar theories together, like stacking papers. Likely candidates closer to the middle of the table, fringe theories physically further away, under a pile of other junk. I've never been able to mentally put the "we're in a simulation" paper away. It's always be…

I'm partial to that idea too.

I don't know much about the nuts and bolts of QM, but on the surface, entanglement and the observer problem lines up nicely with our universe being a lazily evaluated simulation, crunching numbers at the last second for our benefit like a game engine.

It's all personal though, a fisherman sees God in the ocean, why wouldn't a programmer see God in complex digital systems?

Re: Why Quantum Mechanics?

#214

Post by sdwr »

rocqua wrote: post #128
MichaelRazum wrote: post #80

Im just taking the easy course of QM by Suesskind. He had an example like you have two coins and give them randomy to your kids. The they move far away. Then one kid discovers what it got, it knows what the other has. So what I dont get is why QM you could argue that there is some hidden shared state. Guess this is a typical question. But anyway I‘m somehow not convinced that it is really random.

That example cannot describe the 'spooky action at a distance'. Because it involves 'local variables' which have been dis-proven by the bell-inequality in actual experiments. Taking the standard example of an entangled pair of photons. Those must have opposite spin. We then move the photons rather far apart measure the spin on one side. Then because of entanglement and conservation, the spin someone will measure on t…

Thanks for the clear explanation. I'm less clear on what particle spin is though.

Re: Why Quantum Mechanics?

#215

Post by _0w8t »

eigenket wrote: post #144
_0w8t wrote: post #62

Earlier quoted context omitted.

The notion that quantum mechanics is associated with inherent chance in the universe thus explaining free will is itself problematic. There is no chance in the equations of quantum mechanics as the equations are fully deterministic. The probabilities appear only when we try to explain interaction of classical systems with quantum ones. Traditional explanation is that those probabilities are inherent to the world. But…

If you take this reasoning seriously you get the Everettian / "many worlds" interpretation of quantum mechanics. If a human experimenter is treated as a fundamentally quantum object then they end up entangled with the particle they're measuring. This is (to me) a highly appealing model for what is going on, but we still don't really know how to go from this viewpoint to what we observe in experiments, which is the Bo…

The topic of appearance of a classical objects in the quantum world is far from settled. My favorite hypothesis is that when an object is entangled with too many particles in the Universe that sort of cancels interference patterns leading to classical world. This avoids the need for multi-world or similar hypothesis.

Re: Why Quantum Mechanics?

#216

Post by SAI_Peregrinus »

MichaelRazum wrote: post #91
Schroedingers2c wrote: post #90

Earlier quoted context omitted.

You can think of scenarios in which any classical state (i.e. the shared state is completely specified by the local states of the two kids) does the task with some success probability that is upper bounded, say by 75%. And you can even include some unspecified hidden variable in your classical state and could even allow the two kids to share some classical randomness (think: each of them has a button that returns the…

But as I understand if you break the non locality assumption for the state, then you could make it kind of work. So lets just say by introducing a global variable for the shared state you could explain it (hidden dimension or whatever). Ok maybe it breaks a classical assumptions. I have no doubt that QM works, just wondering if it is really the final resolution we can get.

Non-local hidden variable theories can work. The Wikipedia page on interpretations of quantum mechanics has a comparison table sortable by different properties[1]. de Broglie-Bohm and Time-symmetric theories are non-local with hidden variables.

[1] https://en.wikipedia.org/wiki/Interpretations_of_quantum_mec...

Re: Why Quantum Mechanics?

#217

Post by trixie_ »

EMM_386 wrote: post #203
ninkendo wrote: post #177

Earlier quoted context omitted.

Nothing about superdeterminism says you can't find ways out of suffering... to use the movie example, the movie may play out such that your life gets better! Or it won't... superdeterminism just says that those frames are already printed on the film, we just don't know what they look like yet because we can't perceive the future.

> Nothing about superdeterminism says you can't find ways out of suffering Actually it does. Your movie is going to play out the way it plays out, regardless of whatever you do. Throw your feet up in the recliner or struggle for that next promotion, doesn't matter. Brain cancer. I just find this rubbish.

Religious people would say brain cancer was just part of gods plan. Determinism basically is the same plan just no god involved. Why is that rubbish? Because you don’t like it?

Re: Why Quantum Mechanics?

#218

Post by trixie_ »

EMM_386 wrote: post #101
rep_lodsb wrote: post #38

Earlier quoted context omitted.

IMO the concept of free will doesn't make sense, at least not without also believing in the existence of a soul. If you were to make a decision that is not in some sense pre-determined by the structure of your brain (as shaped by biology and past experiences), it would be essentially random and just as meaningless as an uranium atom "deciding" to decay at some specific moment and not another.

Free-will fits perfectly fine into the evolutionary theory. When prey are faced with predators on the open savannah, they may be in "unconscious mode" when grazing the grass, but if they glimpse a predator, ears and tail go up, head swings, and they have to make a decision.

How is that any different from an artificial neural network taking inputs and making decisions. Are you saying the ANN has free will as well?

Re: Why Quantum Mechanics?

#219

Post by Eratosthenes »

simiones wrote: post #169
Eratosthenes wrote: post #161

> Why didn’t God just make the universe classical and be done with it? He did. Physicists just never managed to properly grapple with the concept that classical mechanics involves action-at-a-distance.

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 interact gravitationally (there are good reasons for making this assumption), then you can explain the double slit experiment classically via gravitational interaction.

Re: Why Quantum Mechanics?

#220

Post by entropicgravity »

stared wrote: post #145
stared wrote: post #135

> Why didn't God just make the universe classical and be done with it? What would've been wrong with that choice? I hear it over and over and still don't understand the premise. Classical mechanics is not something sacred. It is our first serious model of physics. Our first approximation is based on the scales at which we operate and our senses as humans. Furthermore, even "regular" quantum mechanics is a non-relativ…

To elaborate on this a bit: One may argue that "a state" is a simpler concept than "a superposition of all state". Even in pure mathematics [1], I don't think that (say) real numbers are less fundamental than natural (unlike Kronecker in "Natural numbers were created by God, everything else is the work of men"). What's true for the set theory route, does not need to be true for any possible mathematics, including tho…

In other words, is mathematics invented or discovered. For me it's clearly discovered.
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