Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Not even wrong: Why does nobody like pilot-wave theory? [pdf]

tcm.phy.cam.ac.uk

Post reply on HN
Print view View original

51–60 of 80 posts

Re: Not even wrong: Why does nobody like pilot-wave theory? [pdf]

#51

Post by XorNot »

AgentME wrote: post #47
millstone wrote: post #42

Earlier quoted context omitted.

The "nonsense news headline" and followup discussion are less critiquing MWI than poking fun at David Deutsch. This is because Deutsch is a prominent critic of PWT. The arguments against MWI from Occam's Razor are indeed weak. The stronger critiques are the difficulty of deriving the Born rule, or indeed quantum randomness at all, from the deterministic MWI. This is presumably what the authors hint at in their "doubt…

Why do you say that quantum randomness is a problem in MWI? I thought it was one of the neat things of MWI that it doesn't require randomness. There are no random events: instead you have a branch for each outcome. The only randomness is which branch you find yourself in as an individual.

It's a problem because it closes off further investigation - same as the anthropic principle. It's an answer for everything, but doesn't tell us anything about where to look next.

So if it's right, it needs to rigourously exclude everything else.

Re: Not even wrong: Why does nobody like pilot-wave theory? [pdf]

#52

Post by jamesrcole »

justinpombrio wrote: post #50
jamesrcole wrote: post #49

Earlier quoted context omitted.

There's two kinds of probability in question. One concerns a lack of knowledge, like in your cards example. In that case, the probability is an expression of your state of understanding of the deck, and is not a property of the deck itself. The physical details of the deck and the situation it is part of could be entirely deterministic and we could still talk about this kind of probability. In this case your knowledg…

There's a third kind -- indexical randomness, or not knowing who you will be -- that appears in many-worlds. Many worlds is in some sense completely deterministic. Yet with indexical uncertainty you still cannot possibly ever know which way you will see a photon go in a half-silvered mirror. Is that fundamental randomness or not? http://lesswrong.com/lw/jlb/logical_and_indexical_uncertaint...

> Is that fundamental randomness or not?

I would say, not. There's no actual randomness from an objective point of view, it's just a lacking in your understanding of things.

I think that map/territory confusions are the source of so many problems and should be rigourously avoided. I think it would be a map/territory confusion to consider it a kind of actual randomness.

Re: Not even wrong: Why does nobody like pilot-wave theory? [pdf]

#53

Post by thisrod »

Pilot waves are not a theory. No experiment can exclude them, unless it falsifies the entire quantum theory of mechanics. One reason to dislike pilot waves is that people, speaking as scientists, take them too seriously. This is not to say that scientists shouldn't talk about them, just that we shouldn't pretend we're doing science when we do.

In particular, don't pretend that anyone can be scientifically right or wrong about the human interface to quantum mechanics. Some interfaces cause fewer errors than others do, and the rest is Vi and Emacs.

Speaking subjectively, there are two reasons that I prefer Everett's relative state interpretation. (It's the serious version of the approach that these slides send up as many worlds.)

Relative states make it blatantly obvious why I can't put a contract on my great-great-grandfather. In other approaches, you have to think about this.

In the pilot wave "theory", there are superpositions, a.k.a. "pilot waves", and a bunch of other things. In the Everett worldview, by contrast, there are superpositions, full stop.

Everett does leave some grey areas, roughly speaking the quantum version of, "Is 7 a random number?" I doubt that any interpretation of quantum mechanics can clarify that, and Everett at least acknowledged the problem and made it fairly explicit.

Re: Not even wrong: Why does nobody like pilot-wave theory? [pdf]

#54

Post by Qwertious »

jamesrcole wrote: post #49
justinpombrio wrote: post #46

Earlier quoted context omitted.

Do you agree that the probability of an event depends on your knowledge? For example, what is the probability that the bottom card of a shuffled deck is an ace? Peek at the top card, it's an ace of spades, now what is the probability? Would you agree that something is determined iff its probability is zero or one? I'm guessing the disagreement is here - what definition would you use?

There's two kinds of probability in question. One concerns a lack of knowledge, like in your cards example. In that case, the probability is an expression of your state of understanding of the deck, and is not a property of the deck itself. The physical details of the deck and the situation it is part of could be entirely deterministic and we could still talk about this kind of probability. In this case your knowledg…

Or to give a slightly better example, suppose you're playing russian roulette with a six-shot revolver. You empty the revolver of bullets, then put one bullet in, spin the barrel, point it at your head and fire.

What is the chance that you're shot? Is it 1/6? What about if you open it up and look in the barrel to see if there's a bullet there?

Re: Not even wrong: Why does nobody like pilot-wave theory? [pdf]

#55

Post by hasenj »

jamesrcole wrote: post #45
hasenj wrote: post #43

Earlier quoted context omitted.

I did not assume nor imply it's tiny in any "absolute" sense.

Then why is "every second" a "huge claim" and "every nanosecond" "even a bigger claim"?

It's only linearly bigger I suppose.

Re: Not even wrong: Why does nobody like pilot-wave theory? [pdf]

#56

Post by svarnypetr »

madhadron wrote: post #18
Barrin92 wrote: post #8

Earlier quoted context omitted.

Those also don't really play a role in the professional life of a physicist, nowadays you really do stare at computer screens a lot and try to find things in data, it's not like physicists sit around and discuss many-world theory as part of their day job. These are just the popular things that make it out into public discourse

Depends on the physicist. Those working on foundations of quantum mechanics do. There just aren't many of them.

For example the whole group around beyondspacetime.net does that.

Re: Not even wrong: Why does nobody like pilot-wave theory? [pdf]

#57

Post by szemet »

XorNot wrote: post #51
AgentME wrote: post #47

Earlier quoted context omitted.

Why do you say that quantum randomness is a problem in MWI? I thought it was one of the neat things of MWI that it doesn't require randomness. There are no random events: instead you have a branch for each outcome. The only randomness is which branch you find yourself in as an individual.

It's a problem because it closes off further investigation - same as the anthropic principle. It's an answer for everything, but doesn't tell us anything about where to look next. So if it's right, it needs to rigourously exclude everything else.

On the other hand objective randomness is a black box. You can describe how it behaves at the surface level (so functionally it is usable), but by definition you can't have a finite model of it, so what is inside? No answer by definition - something infinite.

So why X happens instead of Y?

1. Let's propose an unexplainable, unmodellable infinite entropy source under everything

vs.

2. X happens and so do Y, and one is observed at a certain probability due to anthropic principle - like this: https://www.youtube.com/watch?v=9R5OWh7luL4

The first is somehow psychologically less satisfying answer for me, although - of course - I accept that calculation works either way. The second at least not an unimaginable infinite, and in the end leaves me with less "why?".

Re: Not even wrong: Why does nobody like pilot-wave theory? [pdf]

#58

Post by shrimpx »

hasenj wrote: post #14
Houshalter wrote: post #12

Earlier quoted context omitted.

It can also be explained by branching. Run a simulation of a universe, and every time a random bit is required, fork into two separate processes. One where the "random" bit is 1 and another where the bit is 0. From the inside, it would seem indistinguishable from true randomness. But the system as a whole is purely deterministic.

How would forking occur? Forking requires copying data. Does the universe get cloned infinitely many copies all the time? That's quite an extraordinary claim.

Copy on write. :D

Re: Not even wrong: Why does nobody like pilot-wave theory? [pdf]

#59

Post by wruza »

Houshalter wrote: post #12
Govindae wrote: post #10

Earlier quoted context omitted.

Any randomness could in principle be predetermined. God could have rolled the dice ahead of time.

It can also be explained by branching. Run a simulation of a universe, and every time a random bit is required, fork into two separate processes. One where the "random" bit is 1 and another where the bit is 0. From the inside, it would seem indistinguishable from true randomness. But the system as a whole is purely deterministic.

>fork

When I was younger and had most interest in non-useful things (in a boring sense) I came to "the theory" that each time observation or logical induction is performed, the universe splits into many variants ahead of time and these variants that produce "oops" in terms of contradiction simply disappear. Each time you see something weird but real, it is oops that survived, because you didn't see something contrary yet (and now you cannot, because only one thing has to be remaining).

That made me sad, because we could come to hyperdrives and FTL journeys to alien worlds, but some people in 20th century made few observations and conclusions that now prevented fun forever. Magic things were easy before the technology, now they are physics-hard. Our universe is spoiled in a very wrong way.

Re: Not even wrong: Why does nobody like pilot-wave theory? [pdf]

#60

Post by wruza »

AgentME wrote: post #27
hasenj wrote: post #14

Earlier quoted context omitted.

How would forking occur? Forking requires copying data. Does the universe get cloned infinitely many copies all the time? That's quite an extraordinary claim.

This answer seems to be assuming the universe must be implemented on a classical computer and computed in a reasonable amount of time (that's not slowing down exponentially over time). That's not necessarily true. I feel that assuming that the nature of how the universe is computed matches up with our first intuition feels a bit like the assumption in geocentrism that the universe matches up with our intuition of Ear…

Also https://xkcd.com/505/ (A bunch of rocks).
Post reply on HN