3 ms·

Well, it's not so far off. Every time you "look", the wavefunction of the lepton collapses to a point. For the muon, that point is more often inside.

Koshkin 9y ago
That is understood, although it leaves me wondering if this could be interpreted as the hydrogen atom being only slightly larger in "size" than its nucleus. (Point being, nothing is "obvious" at that scale.)
- gus_massa 9y ago
  The proton is something like 100000 times smaller than the orbit of the electron. Both are not usual object, so there are a lot of technical details about how you define the size of each one, but the proton is definitively much smaller than the hydrogen atom. The electron is inside the proton only a tiny amount of time [1] but it's enough to measure it. [1] A better explanation should use probabilities and wave functions, but the main idea is that.
lostmsu 9y ago
That's a kind of common misconception. Nothing collapses. Measurement system (e.g. your eye) just gets entangled with particle in the same way particles get entangled to each other, in a particular state.
- Koshkin 9y ago
  Well, the question of measurement in QM is somewhat deep one, and no theory should be dismissed off-hand. The notion of "collapse", in particular, can be seen as expressing the non-unitarity that is intrinsic to considering measurement as a non-reversible process (which means that it there's too many things that get entangled with the particle - not just the eye but also systems in your brain, for example, so that the process becomes effectively irreversible; one can also say that the process that has lead to creating information cannot be undone).
  - FeepingCreature 9y ago
    It can be undone though, right? https://en.wikipedia.org/wiki/Quantum_eraser_experiment https://en.wikipedia.org/wiki/Quantum_eraser_experiment Or do you mean that the point where it can no longer be undone in principle can be considered as a cutoff for "collapse"?
    - Koshkin 9y ago
      Irreversibility is essential in creation of information, i.e measurement.
  - platz 9y ago
    I thought that unitarity was also preserved in quantum mechanics, which is linked to the law of preservation of information , which induces reversibility. This was the central question about black holes destroying information being a problem, which gives rise to the problem of black hole firewalls. If information is truly destroyed, then quantum mechanics has a deep flaw
    - Koshkin 9y ago
      Even if information can be destroyed ("erased"), it is not by way of reversing the process that lead to its creation, the latter thus being necessarily non-unitary. This, in fact, is a requisite for the notion of measurement to make any sense.
      - platz 9y ago
        The point here is to consider what the claimed "non-reversible process" means in a quantum theory that as of current does _not_ allow for destruction of information.

Koshkin 9y ago

That is understood, although it leaves me wondering if this could be interpreted as the hydrogen atom being only slightly larger in "size" than its nucleus. (Point being, nothing is "obvious" at that scale.)

gus_massa 9y ago
The proton is something like 100000 times smaller than the orbit of the electron. Both are not usual object, so there are a lot of technical details about how you define the size of each one, but the proton is definitively much smaller than the hydrogen atom. The electron is inside the proton only a tiny amount of time [1] but it's enough to measure it. [1] A better explanation should use probabilities and wave functions, but the main idea is that.

lostmsu 9y ago

That's a kind of common misconception. Nothing collapses. Measurement system (e.g. your eye) just gets entangled with particle in the same way particles get entangled to each other, in a particular state.

Koshkin 9y ago
Well, the question of measurement in QM is somewhat deep one, and no theory should be dismissed off-hand. The notion of "collapse", in particular, can be seen as expressing the non-unitarity that is intrinsic to considering measurement as a non-reversible process (which means that it there's too many things that get entangled with the particle - not just the eye but also systems in your brain, for example, so that the process becomes effectively irreversible; one can also say that the process that has lead to creating information cannot be undone).
- FeepingCreature 9y ago
  It can be undone though, right? https://en.wikipedia.org/wiki/Quantum_eraser_experiment https://en.wikipedia.org/wiki/Quantum_eraser_experiment Or do you mean that the point where it can no longer be undone in principle can be considered as a cutoff for "collapse"?
  - Koshkin 9y ago
    Irreversibility is essential in creation of information, i.e measurement.
- platz 9y ago
  I thought that unitarity was also preserved in quantum mechanics, which is linked to the law of preservation of information , which induces reversibility. This was the central question about black holes destroying information being a problem, which gives rise to the problem of black hole firewalls. If information is truly destroyed, then quantum mechanics has a deep flaw
  - Koshkin 9y ago
    Even if information can be destroyed ("erased"), it is not by way of reversing the process that lead to its creation, the latter thus being necessarily non-unitary. This, in fact, is a requisite for the notion of measurement to make any sense.
    - platz 9y ago
      The point here is to consider what the claimed "non-reversible process" means in a quantum theory that as of current does _not_ allow for destruction of information.