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Comment by lisper | Hacker News Reader

TL;DR: Physicist Angelo Bassi is trying to experimentally test the GRW collapse model [1], which is in fact experimentally testable. Personally, my money is firmly on the side of these experiments failing, but I would not bet my entire life savings on it. These experiments may well succeed, and if they do, that will be the biggest breakthrough in physics in 100 years. It's great that someone is actually testing this.

[1]https://en.wikipedia.org/wiki/Ghirardi%E2%80%93Rimini%E2%80%...

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Interesting that such a potentially grand idea is published unceremoniously in a specialized journal (Physical Review D).

Physicists generally publish their physics in physics journals. There is usually no public ceremony involved.

Physical Review D is not a light weight journal. You don't get published there unless you are being taken seriously in the scientific community.

Foundations work has historically not been taken very seriously within the physics community.

Nice! This is my favorite theory since it's so conceptually simple (I can actually understand it) but that of course has no bearing about it being reality.

> The imprecise talk of “observer” and a “measurement” that plagues the orthodox interpretation is thus avoided because the wave function collapses spontaneously.

Why? Measurement is just a photon you shoot at something. Or electron. Wikipedia is saying we cannot define what an observer is and what constitutes “measurement” - sure we do, measurement interacts with the quantum mechanical system because we need to use something - a photon or an electron or some particle to see how it interacts with the system.

Suppose you fire a photon through a polarizing filter. If the photon's polarization is orthogonal to the filter, it will be blocked however if not orthogonal, the photon can pass through with some probability. Does putting the photon through the filter count as a measurement?

Wouldn't checking if photon is polarized or not (using a 2nd filter) count as a measurement? I am not too versed in quantum mechanics, perhaps you can educate?

Suppose you have two polarized filters at 90 degrees to each other. These block out all the light so you could say that this setup is a form of measurement, since it provides knowledge that zero light is passing through.

In classical mechanics, adding a 3rd filter between the two would have no effect since already no light is getting through.

However with quantum putting a 3rd filter between your two original filters at 45 degrees will allow half of the photons to pass through all 3 filters. This is where things get strange and measurement is not very well defined. Are any of the 3 filters now performing a measurement? We know that half the photons will pass through but have no way of determining which will and which won't.

This experiment works with polarized sunglasses btw, quantum in the palm of your hands.

Thank you, that was a fascinating explanation.

I'm not knowledgable of QM. But I don't think that's necessarily true, because photons/electrons are interacting with the system at all times, but the wave function doesn't collapse until we actually observe the result of one of those photons/scatters/whatever, right?

Same, not too knowledgeable but I thought this was no longer a mystery.

my point is that, a photon bouncing off the system doesn't suffice as a measurement, because photons and electrons are always interacting with the system, but the measurement/wave function collapse doesn't occur until there's some other type of observation that occurs, e.g. a photon that's specifically sent and read by the experimenter

agreed. More physicists (but not all) should be doing something like this. This is what tenure system for.

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