Comment by amluto | Hacker News Reader

Comment by amluto | Hacker News Reader

I think that these oil droplet experiments are incredibly neat, but I'm surprised by the conclusions about the universe that people try to draw from them.

There are fascinating lab experiments related to black holes [1]. Researchers have figured out how to build things in the lab that obey some laws that are mathematically very similar to those that we think that black holes obey. These black hole analogues end up doing similar things to what we expect real black holes to do.

Nonetheless, no one seems to see those experiments and conclude that "Wow! Our universe must contain black holes that emit Hawking radiation!".

These oil droplet experiments do something quite similar. They create an environment that is reasonably well described by the same equations as pilot waves, and, since those equations are known to make the same predictions as quantum mechanics, the oil droplets do the things that we would imagine quantum particles to do.

This may be beautiful, but just as the existence of black hole analogues in the laboratory does not imply that black holes are real, the existence of pilot-wave-following oil droplets does not imply that pilot waves are better than quantum mechanics.

[1] http://www.nature.com/nphys/journal/v10/n11/full/nphys3104.h...

I believe you may have the implication going the wrong way.

If the Copenhagen model and the pilot-wave model make the same predictions, which I believe they do since I believe they're mathematically equivalent, then you can't say one is better than the other on the basis of their predictions alone. But there are other evaluation criteria.

The pilot-wave model has a (ideally, complete) simple physical analogue that can act as an aid to intuition; the Copenhagen model, IIUC, asserts that there can be no analogue---all you have is the wave function. In which case, the pilot wave model has an advantage.

Further, if it were possible to experimentally separate the particle from the pilot-wave, the two models would not be equivalent. But you would never look for that kind of experimental evidence if you are only using the Copenhagen model.

On the other hand, from the article:

"Quantum physicists tend to consider the findings less significant. After all, the fluid research does not provide direct evidence that pilot waves propel particles at the quantum scale. And a surprising analogy between electrons and oil droplets does not yield new and better calculations. “Personally, I think it has little to do with quantum mechanics,” said Gerard ’t Hooft, a Nobel Prize-winning particle physicist at Utrecht University in the Netherlands. He believes quantum theory is incomplete but dislikes pilot-wave theory."

I'm thinking he is saying the same thing you are.

It appears tHooft's theory has determinism in common with Bohmian theory, but differs in that it proposes hidden local variables as not violating Bell's inequalities, rather than a wave equation which has non-local dependencies?

Thanks for neatly explaining my scepticism of laboratory analogues and trying to draw conclusions from them. They're basically poor-man's computational simulations, with more errors because you've gone through another layer of model approximation:

    physical system -> theoretical description -> physical system

instead of

    physical system -> theoretical description

followed by solving it with a computer.

It's not surprising that when you set out to simulate a black hole you end up with a black hole! The main reason I could accept them being useful for is when some emergent aspect of the theory is very expensive to simulate.

Pretty much everyone actually thinks black holes are real.

IANAP.

Pretty much everyone actually thinks black holes are real. I am a physicist.

I think he was referring to Hawking radiation - which is far more controversial in physics circles and a major WTF idea for non-physicists - and other theoretical black-hole behavior, not existence of black holes themselves.

Yes of course, but not because we can create approximate analogues of them in the laboratory.

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