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I thought the current fad was to use holography to explain it. The problem is that to measure something in quantum mechanics requires separating the world into
by philipov 8y ago
I thought the current fad was to use holography to explain it. The problem is that to measure something in quantum mechanics requires separating the world into two systems. To make exact measurements, the observing system has to be infinitely large to avoid quantum fluctuation, and the experiment has to be repeated infinitely often because it is probabilistic.
To deal with the infinite size, particle physicists push the observer systems out to infinity. This is fine for scattering experiments because collider detectors are so large and far away from a collision it might as well be infinity, but this poses a problem for quantum gravity and cosmology.
It seems that the most popular approaches to dealing with it have been based on Juan Maldecena's AdS/CFT correspondance, which is a toy model that allows those observers off at infinity to live on the boundary of spacetime and to describe the behavior of the interior entirely in terms of the projection of that behavior onto the boundary.
The challenge is that our universe doesn't look like Anti de Sitter space, but rather like (plain) de Sitter space, and so there is no natural boundary to project onto, which has led some physicists to question the legitimacy of dividing the quantum mechanics need to divide the world into 2 systems.
The measurement problem seems like an artifact of that, and what's really happening is that measurement causes the two systems to become entangled. Wave function collapse would then be the subjective result of the two systems entering a mixed state, because the observed system can no longer be described independently of the system that just observed it.
- whatshisface 8y agoA route other than "dividing the world into two categories," has been available since the early days of quantum mechanics, if you believe in many worlds you don't have that problem. It is important to recognize that we are not talking about physics here, we are talking about philosophy. If anything, the greatest shock of quantum mechanics is how it shows that "questions we naturally want to ask about the natural world" and "totally unresolvable philosophical disputes" are not completely disjoint.
- philipov 8y agoAnd that is exactly why it isn't a paradox in quantum mechanics. Quantum mechanics is consistent for the domain of questions it was designed to ask: particle scattering experiments. It's when people push it into philosophy or other unintended domains that they run into problems.
- whatshisface 8y agoQuantum mechanics is also totally consistent for materials science problems, astrophysical problems (pending gravity), chemical problems (including human beings), and so on. It's really the philosophy that has a quantum mechanics problem. ;)
- TheOtherHobbes 8y agoQM and GR are inconsistent. If you don't see that as a fundamental research problem you're not doing science, you're just treading water.
- philipov 8y agoA paradox is an internal inconsistency. Noone claims that quantum mechanics is the fundamental theory of everything. Like the convergence of a taylor series, there is a range of energies within which it produces correct calculations, and if you go outside that the result is undefined.
- whatshisface 8y agoStrictly speaking that is a QFT problem, or really a standard model problem, moreso than a quantum mechanics problem. In order for it to be a quantum mechanics problem it would have to happen everywhere in quantum mechanics, and the single electron Schrodinger equation hydrogen atom definitely has no (theoretical) problem.
- TheOtherHobbes 8y agoHere's a nice paradox: https://arxiv.org/pdf/1902.05080.pdf https://arxiv.org/pdf/1902.05080.pdf