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Is the Schrödinger Equation True?

scientificamerican.com

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Re: Is the Schrödinger Equation True?

#111

Post by KirillPanov »

FeepingCreature wrote: post #67
lmm wrote: post #65

The Schroedinger Equation is the most true thing I've ever encountered. It is clear, simple, obvious in its correctness; the greatest piece of physics since Maxwell. Once you've understood it it becomes almost impossible to imagine that the universe could possibly work any other way. (Contrary to this article's claim, the equation describes the behaviour of Helium atoms perfectly well; it's a failure of our imaginati…

This is also the thrust of the original LessWrong Quantum Physics Sequence. https://www.lesswrong.com/posts/7FSwbFpDsca7uXpQ2/quantum-ex... > In the coming sequence on quantum mechanics, I am going to consistently speak as if quantum mechanics is perfectly normal; and when human intuitions depart from quantum mechanics, I am going to make fun of the intuitions for being weird and unusual.

> This is also the thrust of the original LessWrong Quantum Physics Sequence

Thanks for linking to this! Absolutely agree with his gripes in the first article about the traditional historically-oriented introduction to QM confusing students.

The rest of the articles (still reading them) appear to be pretty much the route taken by Feynman's _QED_ book (which, of course, is fantastic). It's also very interesting how his 1960's Feynman Lectures books seem to tell the student "QM is confusing and weird and hard and scary" roughly every ten pages or so, whereas by the 1980's with _QED_ he dropped the fearmongering language.

Re: Is the Schrödinger Equation True?

#112

Post by [deleted] »

tasty_freeze wrote: post #102

> The “laws” of physics, Wigner adds, have little or nothing to say about biology, and especially about consciousness, the most baffling of all biological phenomena. Starting with the laws of physics, no, we cannot in practice calculate a consciousness. But we also can't inspect a lottery machine and predict the balls which come out either. Nobody thinks the latter is is because lottery machines also contain magic, y…

[deleted]

Re: Is the Schrödinger Equation True?

#113

Post by drran »

mmmBacon wrote: post #40
jiggawatts wrote: post #31

Earlier quoted context omitted.

Neutrons are countable with integers. Waves -- even in classical mechanics -- are not "countable", and are best represented in physical models with a continuum, such as field of real numbers. They're fundamentally different. Quantum Mechanics glosses over this difference because when it was developed, this was too hard to deal with. A lot of people who briefly studied QM at an undergraduate level assume that it "keep…

A neutron is a particle but also a wave. You can’t have one without the other. If a neutron is a wave then is it countable?

Neutron is 3 quarks (u-d-d), which are bouncing around each other. The bouncing creates waves.

Re: Is the Schrödinger Equation True?

#114

Post by eyelidlessness »

ukj wrote: post #110
eyelidlessness wrote: post #44

Earlier quoted context omitted.

I’m confused. I’m not saying there’s “meaning” to it of any kind, only that the ratio is present and observable. I’m not “insisting” anything. Maybe you’re accustomed to every thought being a conflict, but if I wasn’t clear already I was expressing wonder around a fairly common phenomenon whose commonality isn’t well known or understood.

It's not at all a conflict. I am simply pointing out that where both of us observe/experience the pattern, your mind ascribes to it significance by relating it to the Mathematical construct called "Golden ratio". My mind doesn't make that relation. I call that pattern (and other patterns like it) a "snail shell pattern". We index the experience differently. From your perspective a Mathematical expression describes th…

It sounds like we understand it the same way, with different words.

Re: Is the Schrödinger Equation True?

#115

Post by KirillPanov »

kirrent wrote: post #105
KirillPanov wrote: post #101

Earlier quoted context omitted.

> Did they really expect that the behaviour of the very small would be exactly like that of everyday macroscopic objects? I expect a theory predicting otherwise to bear the burden of demarcating exactly where the boundary between "macroscopic" and "weird not-macroscopic" lies (waving your hands and mumbling "thermodynamics" does not count). I expect that such a theory's proponents should be absolutely burning with in…

There's a discontinuous boundary? That's news to me. It's pretty well known that classical mechanics is reproduced by quantum mechanics in the large scale. There's no discontinuity between the two. There's also a whole heap of people competing on trying to put ever and ever larger objects in superposition. Finally, decoherence has seen plenty of study and seems to be exactly what you're lamenting the lack of.

> There's a discontinuous boundary? That's news to me.

I too find it unlikely that there is such a discontinuity. Quite a large number of physicists (and quantum computing people) seem to speak as if there is one.

> Finally, decoherence has seen plenty of study

I get the impression that decoherence is treated as merely a problem for technicians working on experimental apparatus, or an engineering issue to be dealt with on the road to quantum computation. Are there any results on fundamental limits to the degree of entanglement in a system? We've been trying to get that damn cat into superposition for ~85 years now, with no luck.

Re: Is the Schrödinger Equation True?

#116

Post by thisrod »

dls2016 wrote: post #71
lmm wrote: post #65

The Schroedinger Equation is the most true thing I've ever encountered. It is clear, simple, obvious in its correctness; the greatest piece of physics since Maxwell. Once you've understood it it becomes almost impossible to imagine that the universe could possibly work any other way. (Contrary to this article's claim, the equation describes the behaviour of Helium atoms perfectly well; it's a failure of our imaginati…

> it's a failure of our imagination or exertion that we can't find closed-form stable solutions You better not say that when any solitons are floating by...

Do you mean wave packet solutions? The Schrodinger equation is linear, so I don't think it can have solitons.

Re: Is the Schrödinger Equation True?

#117

Post by thisrod »

BeetleB wrote: post #94
ajkjk wrote: post #11

Earlier quoted context omitted.

I mean.. if their problem is not understanding the math of conjugation at all, then yes, they're pretty elementary and are going to have trouble with QM. But if their problem is not being able to stomach the "just-because" explanations that every QM resigns to using to explain wtf complex conjugation has to do with reality, then I completely, totally sympathize. Learning QM consists of learning to silence your object…

> But if their problem is not being able to stomach the "just-because" explanations that every QM resigns to using to explain wtf complex conjugation has to do with reality Having studied both engineering and physics, I can tell you that there is nothing observable in the universe that requires complex arithmetic/algebra/theory. We use it because it makes the math a lot more convenient. BTW, the use of complex math f…

The mathematicians have a saying: the shortest path between two facts about real numbers often passes through the complex plane.

Re: Is the Schrödinger Equation True?

#118

Post by thisrod »

mellosouls wrote: post #39
hawkice wrote: post #4

The author of this piece says he was struggling to understand complex conjugates. If you don't understand what that is, please read the wikipedia, so you can contextualize his level of familiarity with the material he speaks about. I don't think the author is being dishonest. But that admission is extremely striking to me. [edit: Can some admin give me guidance on how to make the point I'm clearly trying to make? I'm…

John Horgan is a long established and excellent science writer, and given that he's commenting on philosophical issues here as much as anything, I don't agree his difficulty with some mathematical elements of the subject - which he's gracious enough to commit to learning, and humble enough to admit to struggling with - affects his point, which isn't without merit. But can you call a theory true if no one understands…

> But can you call a theory true if no one understands it?

I understand non-relativistic quantum mechanics, i.e. the Schrodinger equation, so close to perfectly as makes no difference. So do thousands of other physicists.

We don't all understand it in the same way. The atomic scale is removed from the human scale by an order of magnitude of orders of magnitude, they do things differently there, so humans can't appeal to their experience to say that one self-consistent description of atomic phenomena is real and another isn't. But the way I understand quantum mechanics is self-consistent, so is the way any the next physicist understands it, and we'll all agree what result it predicts for any experiment you can imagine. If you want more than that, science can't help you.

Re: Is the Schrödinger Equation True?

#119

Post by drdeca »

jiggawatts wrote: post #58
cygx wrote: post #55

Earlier quoted context omitted.

Essentially in MWI each neutron in each universe is a point (actually three because of the quarks), but that point is not in the same place in all universes. Note that MWI as originally formulated by Everett does not work this way. Eg quoting from the Discussion section of his thesis: > [I]t seems to us to be much easier to understand particle aspects from a wave picture (concentrated wave packets) than it is to unde…

True. Quantum Mechanics is actually incredibly conservative, with theoreticians simply refusing to abandon notions shown to be incompatible with reality for over a century now. Same with Spin. Okay, so particles aren't literally spinning spheres. We get it. Stop pretending they are and then Spin won't be so mysterious any more!

Do you have a better name for it?

It’s just an evocative name?

Re: Is the Schrödinger Equation True?

#120

Post by ukj »

mhh__ wrote: post #21
ukj wrote: post #17

Earlier quoted context omitted.

And just one post back you recommended a Philosophical essay ;)

It was partly a tongue-in-cheek dogwhistle to the physics crowd, but I do sort of feel that even the essay I cite is useless - interesting, yes. I (and I have tried) really struggle to see what the point is in learning all these philosophy terms when it usually or always ends up being unfalsifiable or a overly proud euphemism for yet another concept. To take a specific example, I'm curious what post-structuralism act…

To me, the value of Philosophy isn't in learning any particular jargon/terminology (any more than learning the jargon of "symmetry groups" is a useful activity) - the value is in the general understanding of the process of how to develop jargon/terminology from first principles. From a physicists' perspective: to develop the language needed to describe/express the physics you are experiencing.

There is certainly an element of wheel re-invention in first principles thinking, but acquiring maker's knowledge seems like a more rewarding endeavour than acquiring only user's knowledge.

This process of creating new languages/jargon has a name in Computer Science: Meta-linguistic abstraction [1], and so the value of Philosophy (to me) is in the first paragraph of the Wikipedia article:

>metalinguistic abstraction is the process of solving complex problems by creating a new language or vocabulary to better understand the problem space.

And so this I find it fascinating when you say that...

>there are certain symmetry groups that seem to apply everywhere we look

Because your meta-language for talking about your experiences is the language of symmetry groups.

Post-structuralism (and all Philosophy, really) is merely an attempt to escape the reductionist nature of that sort of language-centric thinking - it's an attempt to drag us out of the cave of Logocentrism [2]. Mathematics is only up to isomorphism - there's nothing in the symbolic denotation without the human connotation, so if structuralism is about symmetry (equalities) , post-structuralism is about asymmetry (inequalities).

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

[2] https://en.wikipedia.org/wiki/Logocentrism

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