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Message: <blockquote data-quote="freyar" data-source="post: 6681043" data-attributes="member: 40227">Sorry for a short delay, everyone --- had a couple of busy days.It should tell you something about my answer that I had to look things up to make sure I wasn't forgetting about a new variant or something. <img src="https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f61b.png" class="smilie smilie--emoji" loading="lazy" width="64" height="64" alt=":p" title="Stick out tongue    :p"  data-smilie="7"data-shortname=":p" />  Short answer: not a big fan.  I don't like the loss of locality vs other interpretations (more below), and it's also pretty ugly.Longer answer with explanations: quantum physics is very weird compared to our intuition from daily life or even a very rigorous understanding of Newtonian mechanics.  Many brilliant physicists of a century ago (including Einstein) had real problems coping with it.  A famous example of that weirdness is the Schrodinger's cat thought experiment, in which a poor feline's fate is tied to a quantum event like a nuclear decay and ends up 50% dead/50% alive until someone looks at it.  In a standard view of quantum physics, that cat is neither and both dead/alive until you look at it --- we say that standard quantum physics lacks "reality" in that .  In classical physics or a pilot wave version of quantum mechanics, that cat is either dead or alive, but you just don't know which.  The thing about the pilot wave version is that, just like normal quantum mechanics, if you perform the experiment 100 times, about 50 of the cats will come out dead and 50 alive.  But don't do this experiment, because then you should be arrested for cruelty to animals (quite justly IMO).Anyway, the pilot wave theory is a way to explain the probabilistic nature of quantum mechanics as a measure of our ignorance rather than as a fundamental thing.  It seems to have the benefit that it allows a derivation of the Born Rule (named for Max Born) that tells us how to assign probabilities based on a wavefunction.  However, it has a couple of big flaws.  One is that it does require quite a bit of extra machinery to it that seems unnecessary and is pretty ugly.  What's probably worse in most physicists' minds is that it is written in terms of mathematics that violates locality (there looks like there is instantaneous communication in the math), and it's pretty tricky to avoid that instantaneous communication.  I'd also say that it looks like it would be difficult to describe a quantum field theory with pilot waves (though apparently it has been done).Of course, this raises the question of the "right" way to think about quantum mechanics.  There are quite a few ideas. The standard presentation of quantum mechanics is the "Copenhagen Interpretation" since Niels Bohr, one of the earliest quantum physicists and promoter of this interpretation (and his collaborators) worked in Copenhagen.  This interpretation says that the cat turns alive or dead when someone "measures" it.  That leads to a lot of questions about what counts as a measurement and requires breaking the world into a "quantum part" and a "classical part."  This is of course silly, since all physics is supposed to be quantum.  But this is still a popular view, since it was how the mathematics were developed, and most physicists learn to "shut up and calculate"  (yes, that's a quote often attributed to Feynman but probably is due to David Mermin instead).  I personally prefer something like the "many worlds approach," in which the whole universe is quantum and branches into many possibilities any time an interaction happens between two different systems.  Apparently the Born rule can be derived in this approach, as well, though that's a recent result that may not have been scrutinized a lot yet.  I'm also intrigued by the "consistent histories" approach, which basically says that interactions with the (quantum) environment is important for the evolution of a quantum system (like Schrodinger's cat).  But I can't explain that one in too much detail because the explanations I've seen are philosophically very heavy and honestly hard for me to decipher.  I do have a sense that it's somewhat related to the "many worlds" approach.Anyway, as fuindordm and Umbran have indicated, there's a lot to say on this subject, and I think a thread just devoted to this topic might be really interesting if someone cared enough to start one.Incidentally, as of the last informal poll taken, a plurality of physicists prefers the Copenhagen Interpretation.</blockquote>

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