How Bell’s Theorem proved ‘spooky action at a distance’ is real • Hacker News Board

Re: How Bell’s Theorem proved ‘spooky action at a distance’ is real

#231

Post by oolonthegreat » Wed, Jul 21, 2021, 12:28 AM UTC

Kranar wrote: post #46

tylerhou wrote: post #20

Earlier quoted context omitted.

A classical analogy for entanglement: suppose I have two balls in a bag. They are identical in every way, except one is red and the other is blue. I randomly grab one in each hand and show my hands closed. Now the states of the ball are entangled: as soon as you see the color of one ball, that "determines" the color of the other. (Not claiming that this is a perfect analogy, but I don't see where it diverges from how…

>They are identical in every way, except one is red and the other is blue. I randomly grab one in each hand and show my hands closed. Now the states of the ball are entangled: as soon as you see the color of one ball, that "determines" the color of the other. This gets used to explain entanglement but it really has absolutely nothing to do with it. This is nothing that the ancient Greeks wouldn't have known. Not to p…

so true. I have a similar beef about the popular explanation for uncertainty principle: "well you see the light hits the particle very hard so we know where it was but we don't know where its gone now". urgh.

Re: How Bell’s Theorem proved ‘spooky action at a distance’ is real

#232

Post by pontus » Wed, Jul 21, 2021, 12:29 AM UTC

jussij wrote: post #219

Couldn't that 'hidden variable' be just another dimension? So while those particles might have been separated in space by a large distance, on that fifth dimension they haven't moved and are still sitting side by side.

The distance between two points is basically just the Pythagorean theorem: x^2 + y^2 + z^2. If you have extra dimensions, you just add more terms to this. Now, if you know that e.g. x is very large then that puts a lower bound on the distance:

Distance^2 = x^2 + y^2 + z^2 + ... > x^2.

In other words, if x is large there's no way that the two particles are still somehow close together.

Re: How Bell’s Theorem proved ‘spooky action at a distance’ is real

#233

Post by fungiblecog » Wed, Jul 21, 2021, 12:33 AM UTC

georgeecollins wrote: post #228

gameswithgo wrote: post #221

Earlier quoted context omitted.

there are many ways to explain the result and all are extremely strange. particles communicating at FTL speeds? particles actually touching in an unknown dimension?

It is also strange, but I think the many worlds hypothesis makes the most sense to me. Then there is no spooky action at a distance, the observer is just always in a particular version of reality that all states, even distant ones, conform to. I am not a physicist!

But there is still spooky splitting of the universe... Many worlds just replaces one mystery with another

Re: How Bell’s Theorem proved ‘spooky action at a distance’ is real

#234

Post by platz » Wed, Jul 21, 2021, 12:45 AM UTC

pontus wrote: post #232

jussij wrote: post #219

Couldn't that 'hidden variable' be just another dimension? So while those particles might have been separated in space by a large distance, on that fifth dimension they haven't moved and are still sitting side by side.

The distance between two points is basically just the Pythagorean theorem: x^2 + y^2 + z^2. If you have extra dimensions, you just add more terms to this. Now, if you know that e.g. x is very large then that puts a lower bound on the distance: Distance^2 = x^2 + y^2 + z^2 + ... > x^2. In other words, if x is large there's no way that the two particles are still somehow close together.

ER=EPR entanglement could be realized as a non-local distance mapping

Re: How Bell’s Theorem proved ‘spooky action at a distance’ is real

#235

Post by tines » Wed, Jul 21, 2021, 12:47 AM UTC

oolonthegreat wrote: post #231

Kranar wrote: post #46

Earlier quoted context omitted.

>They are identical in every way, except one is red and the other is blue. I randomly grab one in each hand and show my hands closed. Now the states of the ball are entangled: as soon as you see the color of one ball, that "determines" the color of the other. This gets used to explain entanglement but it really has absolutely nothing to do with it. This is nothing that the ancient Greeks wouldn't have known. Not to p…

so true. I have a similar beef about the popular explanation for uncertainty principle: "well you see the light hits the particle very hard so we know where it was but we don't know where its gone now". urgh.

As someone who doesn't know any better than the explanation you have a beef with, I would love if you could explain in layman's terms why it's wrong and what a more accurate understanding is. I always thought that analogy was exactly how it worked, but it seems I have been misled unawares.

Re: How Bell’s Theorem proved ‘spooky action at a distance’ is real

#236

Post by thisrod » Wed, Jul 21, 2021, 12:53 AM UTC

lisper wrote: post #212

feoren wrote: post #132

Earlier quoted context omitted.

This is a great thought experiment, thank you. I'm not totally clear how the machines could work without actually taking a measurement, though. It sounds like you're saying the 2nd machine (P = 0.5) takes measurements (and therefore "paints" the balls), but the other two don't? I've heard of the apocryphal "half-silvered mirror", but I don't get why reflection isn't an observation/interaction there either.

> I don't get why reflection isn't an observation/interaction there either. I know this comment is going to get lost in the noise, but that is a really excellent point, one of the best that has been raised here so far. This is a point that is often glossed over, but it is actually really important, and quite challenging to explain without getting deep into the weeds. The answer is that passing through a half-silvered…

I agree with this. But it's worth pointing out that lots of good physicists don't. It's a statement of the Everett/relative state/many worlds interpretation, which is simply too weird for many people to accept. That's why there are about a dozen other interpretations of quantum measurement theory, which are all weird in other ways that I can't accept.

The weird part is precisely this: "you can get back to a state where you can no longer tell what the outcome of the 'measurement' was." In other words, at lunchtime you believed that a horizontally polarised photon hit your nose at 10am in morning, and you were right. Now it's dinner time, you don't believe that, and you would be wrong if you did. If the Everett interpretation doesn't pose a massive challenge to your ideas about reality and human identity, you haven't understood it. There are physics professors who picture photons choosing which way to go at a beam splitter, then transmitting the news backwards in time, because that seems more plausible to them.

Of course, interpretations are not science. Everyone agrees how an experiment would go: any attempt to reverse the interaction of the photon with your nose and brain would fail, because thermodynamics. From a purely scientific viewpoint, it simply doesn't matter how many other yous are superposed in parallel universes, because their existence or lack of it has no consequences that (any of?) you can observe. But scientists are as fascinated by this as everyone else is.

Re: How Bell’s Theorem proved ‘spooky action at a distance’ is real

#237

Post by kgwgk » Wed, Jul 21, 2021, 12:53 AM UTC

oolonthegreat wrote: post #231

Kranar wrote: post #46

Earlier quoted context omitted.

>They are identical in every way, except one is red and the other is blue. I randomly grab one in each hand and show my hands closed. Now the states of the ball are entangled: as soon as you see the color of one ball, that "determines" the color of the other. This gets used to explain entanglement but it really has absolutely nothing to do with it. This is nothing that the ancient Greeks wouldn't have known. Not to p…

so true. I have a similar beef about the popular explanation for uncertainty principle: "well you see the light hits the particle very hard so we know where it was but we don't know where its gone now". urgh.

That’s not just the popular explanation. It’s the original argument from Heisenberg.

Re: How Bell’s Theorem proved ‘spooky action at a distance’ is real

#238

Post by tmccrary55 » Wed, Jul 21, 2021, 12:57 AM UTC

feoren wrote: post #135

naasking wrote: post #126

Earlier quoted context omitted.

One is an assertion with no logic to justify it, the other is an assertion with a somewhat persuasive argument justifying it [1]. They are simply incomparable. [1] https://www.simulation-argument.com/simulation.html

Of the 3 assertions in the abstract, the obviously false one is #2: "Any posthuman civilization is extremely unlikely to run a significant number of simulations of their evolutionary history". When you realize that running a simulation of the universe requires more processing power than is available in the universe, this is very obviously false. I respect people who believe in a bearded White omnipotent homophobic Go…

Who says humans and/or earth are an interesting or even desirable phenomenon in a simulated universe scenario?

Re: How Bell’s Theorem proved ‘spooky action at a distance’ is real

#239

Post by tbabb » Wed, Jul 21, 2021, 1:00 AM UTC

nwallin wrote: post #227

tbabb wrote: post #91

Earlier quoted context omitted.

> that makes a strong implication towards a many world interpretation You say that like it's a shortcoming. :) There are many who take the (very reasonable) position that the many worlds interpretation is the most epistemologically parsimonious one. Contrary to some misunderstandings of it, it doesn't "add" extra worlds; it removes the concept of "wave function collapse", and leaves all the other known laws of quantu…

The problem with interjecting an implication that many worlds is true (regardless of how persuasive the arguments in its favor are) into a layperson's explanation of why quantum entanglement doesn't permit FTL communication are threefold: 1. It doesn't have anything to do with the topic at hand. It is, at best, a distraction. 2. It is impossible to design an experiment which is capable of distinguishing between a uni…

> It doesn't have anything to do with the topic at hand.

To the contrary, it provides an intuitive model that produces correct predictions. That is inherently valuable and extremely relevant.

> Arguing about Copenhagen vs many worlds is literally no different than arguing about Jesus vs Mohamed.

Strongly disagree— See further discussion[1] under my original post for support.

> You guarantee that everybody is going to stop discussing entanglement+FTL communication and will start arguing about interpretations of quantum mechanics

Not wrong >_>

[1] https://news.ycombinator.com/item?id=27900738

Re: How Bell’s Theorem proved ‘spooky action at a distance’ is real

#240

Post by kgwgk » Wed, Jul 21, 2021, 1:02 AM UTC

tylerhou wrote: post #56

Kranar wrote: post #46

Earlier quoted context omitted.

>They are identical in every way, except one is red and the other is blue. I randomly grab one in each hand and show my hands closed. Now the states of the ball are entangled: as soon as you see the color of one ball, that "determines" the color of the other. This gets used to explain entanglement but it really has absolutely nothing to do with it. This is nothing that the ancient Greeks wouldn't have known. Not to p…

> Rather, both balls are in a superposition of being both red and blue simultaneously, and it is not possible in principle to assign a color to either one of them until the moment a measurement is made. I don't disagree, and (clearly) I make a measurement when I show you the color of a ball. Before I show you a ball, I would also say that the colors of the balls are in a superposition. > major revolution in physics i…

> I make a measurement when I show you the color of a ball

You “make a measurement” well before that, when you say that you have a red ball and a blue ball.

The point of entanglement is that until you make a measurement they don’t have a color. You could measure something else than color and you would also find a correlation.

But if they have a defined color the entanglement is broken. Sure, one is red and the other is blue. But if you measure anything else (a non-commuting observable, that is) there will be no correlatiom.

And not knowing which one is what (already defined) color is not a superposition. It’s just a mixture.