Maybe he's been to The Restaurant at the End of the Universe.phinds said:do you have some inside scoop on the universe actually ENDING some day?
No matter what we think about the ontological status of the universes that we aren’t in, we can only observe the universe that we’re in. And QM does just fine with the prediction that we will not observe someone tunneling through a chair.SDM88 said:They will argue anything with a greater than 0 probability happens. What do you say to this?
Don’t you have to estimate the probability of 7x10^4 g person x 6x10^23 atoms/g tunneling through a 0.02 m barrier simultaneously? If that isn’t close to 1/infinity, I don’t know what is.pines-demon said:As this is in the realm of macroscopic stuff, you can use semi-classics, using WKB approximation for a rectangular barrier, you have a transmission for a single particle of
$$T\approx \exp\left[\frac{-2}{\hbar} a \sqrt{2 m V} \right]$$
where ##m## is the mass, ##V## is the energy barrier with length ##a##. For a gravitational barrier of 1cm in height and thickness of 1 mm, a fly has a chance in ##1/10^{10^{24}}## to go through.
In a truly infinite universe or infinite multiverses or in an eternal universe, technically, yes it can happen - sort of by definition.SDM88 said:my goal is to find out if it can technically happen or not.
SDM88 said:I have read that quantum mechanics implies that there is a very small probability that I can fall right through my chair,
Although the paper claims that QM needs no interpretation, the position it is taking is an interpretation, one with which not all other interpretations would agree.Username34 said:Not the case.
"collapse is something that happens in our description of the system, not to the system itself".[1
/Fuchs and Peres
https://pubs.aip.org/physicstoday/article/53/3/70/411209/Quantum-Theory-Needs-No-Interpretation
There is no mainstream interpretation (Copenhagen, Many worlds, Bohm, etc) that suggest a collapse in the system. Obscure ones may but those aren't what textbooks are based onPeterDonis said:Although the paper claims that QM needs no interpretation, the position it is taking is an interpretation, one with which not all other interpretations would agree.
Yes, there is. In Copenhagen, other branches of the wave function besides the one corresponding to the observed result are said to not exist after the measurement, in contrast to Many Worlds, in which those branches are said to exist after the measurement. The former claim is a claim that collapse, or something that produces the same result (only one branch surviving) is a real thing, not just a feature of our description. Copenhagen just refuses to make any claims about how that happens--what is going on "behind the scenes" that makes it the case that only one branch of the wave function survives after a measurement.Username34 said:There is no mainstream interpretation (Copenhagen, Many worlds, Bohm, etc) that suggest a collapse in the system.
"Generally, Copenhagen-type interpretations deny that the wave function provides a directly apprehensible image of an ordinary material body or a discernible component of some such,[43][44] or anything more than a theoretical concept".PeterDonis said:Yes, there is. In Copenhagen, other branches of the wave function besides the one corresponding to the observed result are said to not exist after the measurement, in contrast to Many Worlds, in which those branches are said to exist after the measurement. The former claim is a claim that collapse, or something that produces the same result (only one branch surviving) is a real thing, not just a feature of our description. Copenhagen just refuses to make any claims about how that happens--what is going on "behind the scenes" that makes it the case that only one branch of the wave function survives after a measurement.
That's not the case, because we only observe single results of measurements, but before a measurement, our best current understanding of QM--not just theory or interpretation but experiments showing quantum interference effects--indicates that before measurement, multiple possibilities are physically present. The transition between multiple possibilities and just one result is "collapse".Username34 said:In other words, there is no reason to think it does collapse based on everything else we know about physics.
This is a common viewpoint, but not all interpretations of QM agree with it.Username34 said:Quantum Mechanics imposes fundamental problems of measurement, even in theory, due to the Heisenberg Uncertainty principle. That is is not the case with macroscopic physics, hence why QM is unique.
So even if you had everything at your disposal, you could still not precisely predict future states of the machine due to a fundamental feature of the universe.
PeterDonis said:This is a common viewpoint, but not all interpretations of QM agree with it.
Many worlds says that the wave function is the state of the system (and of the universe as a whole, if we look at its wave function), and it evolves deterministically. There is no uncertainty anywhere.
Bohmian does not have any uncertainty either because the precise state of the system is contained in the particle positions, which are exact; the wave function is just part of the machinery that guides the particles. The particle positions are stated to be unknown to us, and in practice unknowable, but if we could know them exactly, and if we knew the wave function exactly, we could precisely predict future states and results of measurements.
No, that's not correct, because in the MWI, there is no "which world you end up in when performing a measurement". That concept doesn't even make sense in the MWI. You end up in all the worlds. All the possible results of the measurement (i.e., all the ones with a nonzero amplitude in the pre-measurement wave function) happen.Username34 said:The Heisenberger Uncertainty Principle would still hold true for MWI in that you can never know which world you end up in when performing a measurement.
PeterDonis said:No, that's not correct, because in the MWI, there is no "which world you end up in when performing a measurement". That concept doesn't even make sense in the MWI. You end up in all the worlds. All the possible results of the measurement (i.e., all the ones with a nonzero amplitude in the pre-measurement wave function) happen.
You yourself listed Many worlds as a "mainstream" interpretation of QM.Username34 said:You can't see those outcomes hence why it's doubtful to advocate Many Worlds as science in reference to Heisenberger Uncertainty Principle, which is viewed as science.
The uncertainty principle is a constraint on state preparation and has nothing to do with which world you end up in (MWI interpretation) or the certainty of your measurement results (collapse, Copenhagen, Bohm, …).Username34 said:The Heisenberger Uncertainty Principle would still hold true for MWI in that you can never know which world you end up in when performing a measurement.
Please give a reference.Username34 said:MWI advocate David Deutch considers it possible to speak in terms of "which world you end up in" without contradicting yourself.