7 ms·

I've always wondered - what constitutes an "observation"? How does the particle know it has been observed?

burkaman 6y ago
Particles don't know anything, but you have to interact with it in order to observe it. You have to bounce a photon off of it or something like that in order to get any information out of it.
thaumasiotes 6y ago
https://en.wikipedia.org/wiki/Quantum_decoherence https://en.wikipedia.org/wiki/Quantum_decoherence You can't observe something without sending information. In order to make an observation, you must interact with whatever is being observed, so that information about the interaction can come back to you. In the bag example above, we can observe the Australian ball and know the color of the American ball, and we cannot use this interaction in Australia to send information to America. But we cannot avoid sending information to the Australian ball when we observe it. >> You cannot send information by merely observing something. This is, at the least, very poorly phrased. As explained above, not only can you send information by observing something, it's impossible not to do so. The question here is where the information goes.
warent 6y ago
My understanding is that any kind of measurement will do, it doesn't matter how you get it. You could use photons to do the measurement but there are other ways which all have the same result. It's a mystery how the particle "knows" (In other words, nobody knows when the wave function collapses) but one popular interpretation is that the particle exists in all states, i.e. in a pure description of reality. When any quantum system interacts with it, then it becomes entangled with the result of that measurement, branching it into a new universe (edit for clarification: a new world where it was as if it was never a wave, and it was always a particle). That's my understanding of the many-worlds theory. That entanglement propagates across nearby particles, so it doesn't have anything to do with eyes or consciousness. If the air molecules around your body interact with the particle then that entanglement propagates through your body and places you in the new world.
- tabtab 6y ago
  Re: When any quantum system interacts with it, then it becomes entangled with the result of that measurement, branching it into a new universe. That's my understanding of the many-worlds theory. This is a case of a simple theory that indeed models the mystery well. However, it seems "wasteful" in that it would branch into gazillion trees of reality. In Occam's Razor, does "simplicity" include quantity of "stuff" needed? Because sometimes the brute force algorithm/model is the "simplest" if we ignore quantity of stuff and time, such as bubble-sort. Bubble-sort is one of the simplest sorting algorithms known, but is inefficient from a time and resource standpoint. If there are "free" dimensions to spare out there, then the "wasteful" multi-verse model may not really be wasteful. We humans are used to thinking in terms of economic trade-offs, and a model that uses up large quantities of space/time rubs our instincts wrong. If true, the theory means that in some universe somewhere I'm a billionaire who married a supermodel.
  - tim333 6y ago
    If the universe is a mathematical object there being an infinity of universes isn't any more wasteful than there being an infinity of integers for example. From Occam's point of view it's simpler if all integers exist rather than there being a cap if that were even logically possible. So yeah go supermodel!
    - tabtab 6y ago
      Re: If the universe is a mathematical object... Math is a modeling technique, not a "thing". To me it doesn't make sense to say the universe "is" math. Maybe it's a machine "running" math notation (programming code), but that's not the same as it "being" math. (Is "God" the server admin?)
      - tim333 6y ago
        It's been hypothesised: "the physical universe is not merely described by mathematics, but is mathematics" https://en.wikipedia.org/wiki/Mathematical_universe_hypothesis https://en.wikipedia.org/wiki/Mathematical_universe_hypothes... not proven of course.
flubert 6y ago
"A new interpretation of quantum mechanics suggests that reality does not depend on the person measuring it" https://phys.org/news/2020-10-quantum-mechanics-reality-person.html https://phys.org/news/2020-10-quantum-mechanics-reality-pers... https://www.mdpi.com/2073-8994/12/9/1533 https://www.mdpi.com/2073-8994/12/9/1533
- jdashg 6y ago
  Phew!
tabtab 6y ago
Re: "How does the particle know it has been observed?" It's as if God's code looks something like: if (event.thisParticle.isBeingObserved()) { thisParticle.assignAttributes(); }
- pjmorris 6y ago
  "extreme late binding of all things?"
  - tabtab 6y ago
    Lack of compile-time type-checking gives us dodgy politicians and lawyers.
cgh 6y ago
You might find this helpful: https://en.wikipedia.org/wiki/Quantum_decoherence https://en.wikipedia.org/wiki/Quantum_decoherence
centimeter 6y ago
In many formulations, e.g. multiverse, the apparatus doing the measuring (doesn't have to be a human or anything) becomes entangled with the thing being measured. This is still not super well understood.
brlewis 6y ago
I assume, for the sake of my own sanity, that "observation" means the particle becomes a cause for some kind of effect, e.g. colliding with something in a way that changes the something's state. Quantum mechanics experts, please don't tell me it's weirder than that.
HackOfAllTrades 6y ago
In Quantum Mechanics things travel as waves and interact as particles. Between interactions, everything is described by the Schrodinger Wave Function, which evolves to include every possible path. But at the point of an interaction the wave function must collapse to satisfy conservation rules. Consider an electron fired at a dual slit with a phosphor screen. While traveling from the electron gun, thru the slits, to the screen, the electron is described by a Wave Function. It has no fixed position or momentum. The Schrodinger wave passes through both slits and interferes with itself on the other side. The wave function evolves into a series of lines. But when the electron interacts with the screen it always appears as a single point. It must do so by the laws of conservation. At the interaction it must have a specific location and momentum in order for there to be conservation of charge, momentum, energy, etc. This interaction is enough to 'collapse the wave function'. No 'observation' is required. How does this happen? There is no localized mechanism that can possibly make this work. The conservation laws are not local restrictions. They are universal. Please note that this is my own explanation of now QM works, and does not necessarily reflect the official position of any school of thought. It does, however, reflect the actual use of Quantum Mechanics, in that systems evolve via the Schrodinger Equation and interactions must obey conservation laws. And No, it cannot explain how entanglement works.
- kgwgk 6y ago
  > In Quantum Mechanics things travel as waves and interact as particles. Between interactions, everything is described by the Schrodinger Wave Function, which evolves to include every possible path. But at the point of an interaction the wave function must collapse to satisfy conservation rules. That would make some sense if by interaction you mean "interaction with the macroscopic environment". When small-enough quantum systems (like two particles) interact there is no collapse and the evolution is unitary. > This interaction is enough to 'collapse the wave function'. No 'observation' is required. How do you distinguish the interactions that 'collapse the wave function' from those who do not?
  - HackOfAllTrades 6y ago
    The idea that Measurement = "interaction with the macroscopic environment" is part of the Copenhagen interpretation, not a requirement of QM itself. Aside: (Personally, I see this more as Bohr's way of dodging questions he had no answer to, and not a viable way to think about Quantum Mechanics. A better answer would have been "I don't know. Let's figure it out." But that was impossible for political reasons. Bohr was being attacked by Einstein for 's sake. He can be forgiven for adopting Ali's "rope-a-dope" tactics if he felt that Einstein was trying to destroy his entire field in its infancy. But I find "there is no quantum world" simply unacceptable.) Now to answer your question as best I can, an interaction must collapse the wave function when it is required to fulfill a conservation rule. For example, if an electron is captured by a nucleus it becomes bound and emits a photon. This is an interaction that must conserve momentum, angular momentum, energy, and charge. Because of that, the electron can no longer be represented by a non-localized wave function. The universe must concentrate those properties down to a point in order to "do the accounting" necessary for the conservation rules. No, I don't know how it does that. But then, NONE of the available interpretations answer that question. This indicates to me we are thinking about it wrong. What I like about Stuckey's paper is that it adds another factor: besides conservation rules the universe seems to require that "measurements" obey the Relativity Principle (No Preferred Frame of Reference). I have yet to figure out how to incorporate that.

Particles don't know anything, but you have to interact with it in order to observe it. You have to bounce a photon off of it or something like that in order to get any information out of it.

thaumasiotes 6y ago

https://en.wikipedia.org/wiki/Quantum_decoherence https://en.wikipedia.org/wiki/Quantum_decoherence You can't observe something without sending information. In order to make an observation, you must interact with whatever is being observed, so that information about the interaction can come back to you. In the bag example above, we can observe the Australian ball and know the color of the American ball, and we cannot use this interaction in Australia to send information to America. But we cannot avoid sending information to the Australian ball when we observe it. >> You cannot send information by merely observing something. This is, at the least, very poorly phrased. As explained above, not only can you send information by observing something, it's impossible not to do so. The question here is where the information goes.

warent 6y ago

My understanding is that any kind of measurement will do, it doesn't matter how you get it. You could use photons to do the measurement but there are other ways which all have the same result. It's a mystery how the particle "knows" (In other words, nobody knows when the wave function collapses) but one popular interpretation is that the particle exists in all states, i.e. in a pure description of reality. When any quantum system interacts with it, then it becomes entangled with the result of that measurement, branching it into a new universe (edit for clarification: a new world where it was as if it was never a wave, and it was always a particle). That's my understanding of the many-worlds theory. That entanglement propagates across nearby particles, so it doesn't have anything to do with eyes or consciousness. If the air molecules around your body interact with the particle then that entanglement propagates through your body and places you in the new world.

tabtab 6y ago
Re: When any quantum system interacts with it, then it becomes entangled with the result of that measurement, branching it into a new universe. That's my understanding of the many-worlds theory. This is a case of a simple theory that indeed models the mystery well. However, it seems "wasteful" in that it would branch into gazillion trees of reality. In Occam's Razor, does "simplicity" include quantity of "stuff" needed? Because sometimes the brute force algorithm/model is the "simplest" if we ignore quantity of stuff and time, such as bubble-sort. Bubble-sort is one of the simplest sorting algorithms known, but is inefficient from a time and resource standpoint. If there are "free" dimensions to spare out there, then the "wasteful" multi-verse model may not really be wasteful. We humans are used to thinking in terms of economic trade-offs, and a model that uses up large quantities of space/time rubs our instincts wrong. If true, the theory means that in some universe somewhere I'm a billionaire who married a supermodel.
- tim333 6y ago
  If the universe is a mathematical object there being an infinity of universes isn't any more wasteful than there being an infinity of integers for example. From Occam's point of view it's simpler if all integers exist rather than there being a cap if that were even logically possible. So yeah go supermodel!
  - tabtab 6y ago
    Re: If the universe is a mathematical object... Math is a modeling technique, not a "thing". To me it doesn't make sense to say the universe "is" math. Maybe it's a machine "running" math notation (programming code), but that's not the same as it "being" math. (Is "God" the server admin?)
    - tim333 6y ago
      It's been hypothesised: "the physical universe is not merely described by mathematics, but is mathematics" https://en.wikipedia.org/wiki/Mathematical_universe_hypothesis https://en.wikipedia.org/wiki/Mathematical_universe_hypothes... not proven of course.

flubert 6y ago

"A new interpretation of quantum mechanics suggests that reality does not depend on the person measuring it" https://phys.org/news/2020-10-quantum-mechanics-reality-person.html https://phys.org/news/2020-10-quantum-mechanics-reality-pers... https://www.mdpi.com/2073-8994/12/9/1533 https://www.mdpi.com/2073-8994/12/9/1533

jdashg 6y ago
Phew!

tabtab 6y ago

Re: "How does the particle know it has been observed?" It's as if God's code looks something like: if (event.thisParticle.isBeingObserved()) { thisParticle.assignAttributes(); }

pjmorris 6y ago
"extreme late binding of all things?"
- tabtab 6y ago
  Lack of compile-time type-checking gives us dodgy politicians and lawyers.

cgh 6y ago

You might find this helpful: https://en.wikipedia.org/wiki/Quantum_decoherence https://en.wikipedia.org/wiki/Quantum_decoherence

centimeter 6y ago

In many formulations, e.g. multiverse, the apparatus doing the measuring (doesn't have to be a human or anything) becomes entangled with the thing being measured. This is still not super well understood.

brlewis 6y ago

I assume, for the sake of my own sanity, that "observation" means the particle becomes a cause for some kind of effect, e.g. colliding with something in a way that changes the something's state. Quantum mechanics experts, please don't tell me it's weirder than that.

HackOfAllTrades 6y ago

In Quantum Mechanics things travel as waves and interact as particles. Between interactions, everything is described by the Schrodinger Wave Function, which evolves to include every possible path. But at the point of an interaction the wave function must collapse to satisfy conservation rules. Consider an electron fired at a dual slit with a phosphor screen. While traveling from the electron gun, thru the slits, to the screen, the electron is described by a Wave Function. It has no fixed position or momentum. The Schrodinger wave passes through both slits and interferes with itself on the other side. The wave function evolves into a series of lines. But when the electron interacts with the screen it always appears as a single point. It must do so by the laws of conservation. At the interaction it must have a specific location and momentum in order for there to be conservation of charge, momentum, energy, etc. This interaction is enough to 'collapse the wave function'. No 'observation' is required. How does this happen? There is no localized mechanism that can possibly make this work. The conservation laws are not local restrictions. They are universal. Please note that this is my own explanation of now QM works, and does not necessarily reflect the official position of any school of thought. It does, however, reflect the actual use of Quantum Mechanics, in that systems evolve via the Schrodinger Equation and interactions must obey conservation laws. And No, it cannot explain how entanglement works.

kgwgk 6y ago
> In Quantum Mechanics things travel as waves and interact as particles. Between interactions, everything is described by the Schrodinger Wave Function, which evolves to include every possible path. But at the point of an interaction the wave function must collapse to satisfy conservation rules. That would make some sense if by interaction you mean "interaction with the macroscopic environment". When small-enough quantum systems (like two particles) interact there is no collapse and the evolution is unitary. > This interaction is enough to 'collapse the wave function'. No 'observation' is required. How do you distinguish the interactions that 'collapse the wave function' from those who do not?
- HackOfAllTrades 6y ago
  The idea that Measurement = "interaction with the macroscopic environment" is part of the Copenhagen interpretation, not a requirement of QM itself. Aside: (Personally, I see this more as Bohr's way of dodging questions he had no answer to, and not a viable way to think about Quantum Mechanics. A better answer would have been "I don't know. Let's figure it out." But that was impossible for political reasons. Bohr was being attacked by Einstein for 's sake. He can be forgiven for adopting Ali's "rope-a-dope" tactics if he felt that Einstein was trying to destroy his entire field in its infancy. But I find "there is no quantum world" simply unacceptable.) Now to answer your question as best I can, an interaction must collapse the wave function when it is required to fulfill a conservation rule. For example, if an electron is captured by a nucleus it becomes bound and emits a photon. This is an interaction that must conserve momentum, angular momentum, energy, and charge. Because of that, the electron can no longer be represented by a non-localized wave function. The universe must concentrate those properties down to a point in order to "do the accounting" necessary for the conservation rules. No, I don't know how it does that. But then, NONE of the available interpretations answer that question. This indicates to me we are thinking about it wrong. What I like about Stuckey's paper is that it adds another factor: besides conservation rules the universe seems to require that "measurements" obey the Relativity Principle (No Preferred Frame of Reference). I have yet to figure out how to incorporate that.