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Gravity was never a leading explanation for collapse; it was always a fringe idea. Gravity is local and apparent collapse is non-local; it doesn’t even pass th

Gravity was never a leading explanation for collapse; it was always a fringe idea. Gravity is local and apparent collapse is non-local; it doesn’t even pass the smell test.

trenchgun 6y ago
The first paragraph seems to be pretty much all misleading or wrong: It’s one of the oddest tenets of quantum theory: a particle can be in two places at once—yet we only ever see it here or there. Textbooks state that the act of observing the particle “collapses” it, such that it appears at random in only one of its two locations. But physicists quarrel over why that would happen, if indeed it does. Now, one of the most plausible mechanisms for quantum collapse—gravity—has suffered a setback.
- ksaj 6y ago
  As soon as it says "here or there" the writer is clearly trying to make it binary again. It isn't "here or there" but a function of probability between those two "places." It's an infinite number of possible "locations," but we narrow it down to a large number of decimal places because otherwise we wouldn't be able to make use of it at all. If things were as written here, you could do all quantum calculations with a straight up coin toss (although some might argue that can with an adequately tiny coin, but that still only gets at the most basic understanding of "spin" and only becomes an accurate analogy if the coin is flipped randomly in zero-g). Our higher level concept of gravity (at least in the classical sense) has been known to break down to the point that it doesn't apply to quantum mechanics for quite a long time now. The writer should just google "quantum gravity" to discover what a complicated subject that becomes.
  - trenchgun 6y ago
    Indeed. The weird thing is that the writer of that article has apparently written a popular science book about quantum mechanics too: https://us.macmillan.com/books/9780374536619 https://us.macmillan.com/books/9780374536619
    - ksenzee 6y ago
      Never underestimate the damage an editor can do to a correctly written piece of prose.
andi999 6y ago
Yes, but at least a in principle testable fringe theory. (And by penrose!)
- alpineidyll3 6y ago
  For the past several decades Penrose has been a fountain of nothing but frivolous fringe theories. Physicists are like investments: past performance is not indicative of future returns ;P
  - andi999 6y ago
    As long as they are testable, it is good enough.
alpineidyll3 6y ago
Collapse is only mysterious to people who never learned thermofield theory, or non-equilibrium quantum dynamics. Unfortunately this is also a sizable fraction of all physicists. Thus we have articles like this :/ Basically all the work in getting large scale quantum computers to work lies in these fields. They will continue to grow.
- macspoofing 6y ago
  >Collapse is only mysterious to people who never learned thermofield theory, or non-equilibrium quantum dynamics. Oh yeah? Then what is the physical explanation for collapse?
  - btilly 6y ago
    What is the physical evidence that collapse actually happens? Flash news. Nobody has ever produced any. To the contrast we have lots of lines of evidence that an observer described by quantum mechanics should, upon observing a quantum experiment, be thrown into a superposition of observers. Each of which appears to have observed collapse. The notion is utterly repugnant to our biases so many reject the idea out of hand. But as we create ever more complex but controlled systems, we can perform ever more elaborate experiments verifying that quantum mechanics works exactly as predicted. At some point if we take seriously the idea that the most successful scientific theory of all time is an accurate description of ourselves, then we have to accept that perhaps there is no collapse after all.
    - tsimionescu 6y ago
      But this doesn't answer the question. If you claim that all of these possible observers 'exist', how does this have a physical meaning? This is what I never understood about MWI, in what physical sense can the many worlds be said to exist? Where are they in our universe? What direction would we have to travel to find them? Do they exert gravity on us? If not, then how can we claim that they exist in a physical sense?
      - 6y ago
gus_massa 6y ago
I agree. There are a (very) few experiments that show the effect of gravity in a system with strong quantum effects. Fox example you can split a ray of neutrons, direct each beam through a different path with different height and then make them collide and see the interference pattern. The idea is that the split creates a superposition and each half has a different gravity potential, changing the orientation of the experiment produce different interference patterns. (The details are in the book of Sakurai "Modern Quantum Mechanics" pp127-129, with data from an experiment of Colella, Overhauser, Werner (1975).) I don't understand why the old experiment was not enough to falsify this theory.
macspoofing 6y ago
>Gravity was never a leading explanation for collapse; it was always a fringe idea. Why not? Gravity is (probably) mediated by a particle, and therefore all matter will interact with all other matter ... so why shouldn't gravity therefore cause a collapse?
- akvadrako 6y ago
  My second sentence?
- gus_massa 6y ago
  (Nobody is sure about the graviton, but IMHO it is a good bet.) Electromagnetism is also mediated by particles (photons) and the quantum states can survive a lot of electromagnetic interactions without collapsing. One of my favorites https://en.wikipedia.org/wiki/Stern%E2%80%93Gerlach_experiment#Sequential_experiments https://en.wikipedia.org/wiki/Stern%E2%80%93Gerlach_experime...

Gravity was never a leading explanation for collapse; it was always a fringe idea. Gravity is local and apparent collapse is non-local; it doesn’t even pass the smell test.

trenchgun 6y ago

The first paragraph seems to be pretty much all misleading or wrong: It’s one of the oddest tenets of quantum theory: a particle can be in two places at once—yet we only ever see it here or there. Textbooks state that the act of observing the particle “collapses” it, such that it appears at random in only one of its two locations. But physicists quarrel over why that would happen, if indeed it does. Now, one of the most plausible mechanisms for quantum collapse—gravity—has suffered a setback.

ksaj 6y ago
As soon as it says "here or there" the writer is clearly trying to make it binary again. It isn't "here or there" but a function of probability between those two "places." It's an infinite number of possible "locations," but we narrow it down to a large number of decimal places because otherwise we wouldn't be able to make use of it at all. If things were as written here, you could do all quantum calculations with a straight up coin toss (although some might argue that can with an adequately tiny coin, but that still only gets at the most basic understanding of "spin" and only becomes an accurate analogy if the coin is flipped randomly in zero-g). Our higher level concept of gravity (at least in the classical sense) has been known to break down to the point that it doesn't apply to quantum mechanics for quite a long time now. The writer should just google "quantum gravity" to discover what a complicated subject that becomes.
- trenchgun 6y ago
  Indeed. The weird thing is that the writer of that article has apparently written a popular science book about quantum mechanics too: https://us.macmillan.com/books/9780374536619 https://us.macmillan.com/books/9780374536619
  - ksenzee 6y ago
    Never underestimate the damage an editor can do to a correctly written piece of prose.

andi999 6y ago

Yes, but at least a in principle testable fringe theory. (And by penrose!)

alpineidyll3 6y ago
For the past several decades Penrose has been a fountain of nothing but frivolous fringe theories. Physicists are like investments: past performance is not indicative of future returns ;P
- andi999 6y ago
  As long as they are testable, it is good enough.

alpineidyll3 6y ago

Collapse is only mysterious to people who never learned thermofield theory, or non-equilibrium quantum dynamics. Unfortunately this is also a sizable fraction of all physicists. Thus we have articles like this :/ Basically all the work in getting large scale quantum computers to work lies in these fields. They will continue to grow.

macspoofing 6y ago
>Collapse is only mysterious to people who never learned thermofield theory, or non-equilibrium quantum dynamics. Oh yeah? Then what is the physical explanation for collapse?
- btilly 6y ago
  What is the physical evidence that collapse actually happens? Flash news. Nobody has ever produced any. To the contrast we have lots of lines of evidence that an observer described by quantum mechanics should, upon observing a quantum experiment, be thrown into a superposition of observers. Each of which appears to have observed collapse. The notion is utterly repugnant to our biases so many reject the idea out of hand. But as we create ever more complex but controlled systems, we can perform ever more elaborate experiments verifying that quantum mechanics works exactly as predicted. At some point if we take seriously the idea that the most successful scientific theory of all time is an accurate description of ourselves, then we have to accept that perhaps there is no collapse after all.
  - tsimionescu 6y ago
    But this doesn't answer the question. If you claim that all of these possible observers 'exist', how does this have a physical meaning? This is what I never understood about MWI, in what physical sense can the many worlds be said to exist? Where are they in our universe? What direction would we have to travel to find them? Do they exert gravity on us? If not, then how can we claim that they exist in a physical sense?
    - 6y ago

gus_massa 6y ago

I agree. There are a (very) few experiments that show the effect of gravity in a system with strong quantum effects. Fox example you can split a ray of neutrons, direct each beam through a different path with different height and then make them collide and see the interference pattern. The idea is that the split creates a superposition and each half has a different gravity potential, changing the orientation of the experiment produce different interference patterns. (The details are in the book of Sakurai "Modern Quantum Mechanics" pp127-129, with data from an experiment of Colella, Overhauser, Werner (1975).) I don't understand why the old experiment was not enough to falsify this theory.

macspoofing 6y ago

>Gravity was never a leading explanation for collapse; it was always a fringe idea. Why not? Gravity is (probably) mediated by a particle, and therefore all matter will interact with all other matter ... so why shouldn't gravity therefore cause a collapse?

akvadrako 6y ago
My second sentence?
gus_massa 6y ago
(Nobody is sure about the graviton, but IMHO it is a good bet.) Electromagnetism is also mediated by particles (photons) and the quantum states can survive a lot of electromagnetic interactions without collapsing. One of my favorites https://en.wikipedia.org/wiki/Stern%E2%80%93Gerlach_experiment#Sequential_experiments https://en.wikipedia.org/wiki/Stern%E2%80%93Gerlach_experime...