Physicists provide support for retrocausal quantum theory • Hacker News Board

Re: Physicists provide support for retrocausal quantum theory

#101

Post by BoiledCabbage » Fri, Jul 07, 2017, 4:08 AM UTC

Simon_says wrote: post #97

BoiledCabbage wrote: post #70

Earlier quoted context omitted.

Clearly this is all subjective, but Pilot Wave theory (De Broglie & Bohm) is the simplest least "crazy" of all the explanations. Horribly simplified: Space isn't empty, there is an "ether". Matter moving through the ether interacts with it and produces waves just like a very light boat in a lake - these crests and troughs exactly line up with the magical waveform. All of the quantum behavior we see is explained by th…

The Pilot Wave Interpretation is one of the strangest contortions I've ever seen. You go to all the trouble to set up the wave equation acting on phase space of the entire universe, but then you remember that you think particles are fundamental elements of reality, so you drop them in and say they're guided by your wave equation. If you take Pilot Wave Interpretation and just take out the particles, you're left with…

> If you take Pilot Wave Interpretation and just take out the particles, you're left with the Many Worlds Interpretation with exactly the same predictions. To paraphrase Netwon, there's no need for that hypothesis.

And if you take Many World and simply add a particle you have Pilot Wave hypothesis. No need for the crazy multiple universes nonsense. All 3 produce (including Copenh) the exact same predictions, so that's not gonna be the distinguishing factor.

Which is more contorted? Waves are physical and particles exist? Or we live in a countless number of simultaneously subdividing universes?

It's fascinating to hear people discuss PW vs MWs - because (in my opinion) it becomes very clear which they became comfortable with first.

If you were to stop a random person on the street and give them a summary of the two theories it's pretty clear that someone unfamiliar with both would say the PW is a ton simpler. But it's fascinating to see that a good number of people who are comfortable with many worlds will argue that it's less complex. My view is obviously their opinion is shaped by what they've been exposed to first.

Re: Physicists provide support for retrocausal quantum theory

#102

Post by BoiledCabbage » Fri, Jul 07, 2017, 4:29 AM UTC

jostylr wrote: post #77

BoiledCabbage wrote: post #70

Earlier quoted context omitted.

Clearly this is all subjective, but Pilot Wave theory (De Broglie & Bohm) is the simplest least "crazy" of all the explanations. Horribly simplified: Space isn't empty, there is an "ether". Matter moving through the ether interacts with it and produces waves just like a very light boat in a lake - these crests and troughs exactly line up with the magical waveform. All of the quantum behavior we see is explained by th…

While one can take a bit of issue with using the ether as analogy for a number of reasons, the most important difference to keep in mind is that the wave function exists in configuration space. For 10^80 particles, this is a space with 3^(10^80) dimensions. This is the source of nonlocality. While PWT is the most sensible to me, it is strange though solely because of the wave function which is common to all theories,…

So here I may be stepping past my knowledge, but I thought that the reason for appearing to require so many would be simply due to using the wrong "basis" to calculate the wave function. Or separating the concept of how to generate the wave function from the values it produces.

Via analogy, let's imaging the perfectly still lake. In the lake at an (x,y) position is a mechanical oscillator which moves up and down and continuously produces waves. Knowing the position of the oscillator and it's phase I can calculate the position of crests and troughs of waves on the surface and the height of the water at any location.

If now I had 100 oscillators spread on the surface of the lake, I would need 100 inputs of x,y coordinates of where the oscillators are and each their phases. In this case i'd need 3100 inputs/dimensions to calculate the wave function.

At first, this seems like a lot; but I don't need 3100 dimensions to describe the resultant wave function. It still is simply the surface of a lake. It can always be described at any moment in time in 2 dimensions (x,y) with a height value for each point of the surface. If you want to capture it changing over time you need 3 dimensions (x,y,t) with height values for each.

The fact I'd need to go through all 3100 inputs to calculate the wave, doesn't mean I need 3100 values to store the results of that calculation. This it what I mean by using the wrong "basis" to describe the wave function.

In programmer terms you can describe a resultant value as either a function, and all of its required parameters. Or you can just describe the output value. 310^80 is describing all of the inputs and the "function" to call.

And one note, on the math. I believe there be 3(10^80) dimensions as inputs. Which would mean R^(3*(10^80)) possible configurations. You wrote 3^(10^80) which is significantly larger.

Re: Physicists provide support for retrocausal quantum theory

#103

Post by BoiledCabbage » Fri, Jul 07, 2017, 4:41 AM UTC

ridewinter wrote: post #61

mikeash wrote: post #55

Earlier quoted context omitted.

He might say that, but so what? It's clear that he favors many-worlds, but that doesn't mean the rest of us have to. My point is that he's attempting to prove many-worlds by assuming that none of the other explanations are true, i.e. he's begging the question.

Well the other explanations say that the atom doesn't really exist, it's just an abstraction. And many-worlds says the atom does exist, and this is why you see these quantum effects. That's a meaningful difference.

Pilot Wave is to Many Worlds, as Many Worlds is to Copenhagen.

Pilot wave is the most "concrete". If you're moving away from abstraction, then why stop at Many Worlds?

Re: Physicists provide support for retrocausal quantum theory

#104

Post by BoiledCabbage » Fri, Jul 07, 2017, 4:47 AM UTC

amoruso wrote: post #52

John Cramer has been pointing this out for years (since the 1980s I think): "The Transactional Interpretation of Quantum Mechanics and Quantum Nonlocality" https://arxiv.org/abs/1503.00039 Also, Bell's inequality shows the state vector is nonlocal, and and that implies causality violation in relativity. Third, quantum information theory has retrocausality in the form of negative entropy: "Negative entropy in quantum…

What happened to John Cramer?

He hit the popular science media as he was leading up to his modified delayed-choice quantum eraser for retro-causality. According to him that was a supposed paradox meaning the result of the experiment was going to have to give a result that conflicted with our theories and thus give an avenue for new discover (ie allow us to use a test that doesn't match our model).

It's been a decade and no results were ever discussed. That seems bizarre to me.

Re: Physicists provide support for retrocausal quantum theory

#105

Post by BoiledCabbage » Fri, Jul 07, 2017, 4:58 AM UTC

euyyn wrote: post #76

miltondts wrote: post #34

Earlier quoted context omitted.

They don't here is what Bell said: "There is a way to escape the inference of superluminal speeds and spooky action at a distance. But it involves absolute determinism in the universe, the complete absence of free will. Suppose the world is super-deterministic, with not just inanimate nature running on behind-the-scenes clockwork, but with our behavior, including our belief that we are free to choose to do one experi…

Ok, and barred that?

I could be mixing things here, but aren't the three options losing one of

locality, definitiveness and non-conspiracy?

https://en.wikipedia.org/wiki/Counterfactual_definiteness#Ov...

Re: Physicists provide support for retrocausal quantum theory

#106

Post by BoiledCabbage » Fri, Jul 07, 2017, 5:00 AM UTC

alasdair_ wrote: post #78

rf15 wrote: post #35

Earlier quoted context omitted.

don't remind me that people actually believe that you can infer the existence of a simulation only with data points that are created and controlled by it.

There doesn't seem to be anything wrong with this basic idea. As a (bad) analogy, think about how computer code can be written to detect whether or not it is running inside a virtual machine or on a "real" device. It's usually almost impossible to tell but by probing at the extremes and forcing the system to do things that never happen under common usage, it's possible. (It's also possible to break out of the system…

> It's usually almost impossible to tell but by probing at the extremes and forcing the system to do things that never happen under common usage, it's possible

Yes, but it's only possible by comparing the results to those same results when that action is performed outside of a VM.

If you can never baseline your data outside the VM, then you'll never know you're seeing odd results. You'll just think "that's the way the world works".

Re: Physicists provide support for retrocausal quantum theory

#107

Post by nazgul17 » Fri, Jul 07, 2017, 5:30 AM UTC

Lxr wrote: post #18

I never fully understood the Bell experiments. How exactly do they discount hidden variables?

The way I understood it is in a YouTube video by Looking Glass Universe. I watched it time ago, but if I remember correctly, if there were hidden variables, the distribution of outcomes of his experiment would look different compared to what it actually looks. Sorry it's a half-assed explanation :)

Re: Physicists provide support for retrocausal quantum theory

#108

Post by raverbashing » Fri, Jul 07, 2017, 7:51 AM UTC

jerf wrote: post #58

ridewinter wrote: post #53

Earlier quoted context omitted.

It's more of a recognition that many-worlds actually has a physical basis to it, while the others talk about an obfuscated non-physical construction.

"Many worlds has a physical basis to it" has no physics-meaning that I can discern. In order to have one, it would have to deviate from the other isomorphisms and cease to be an isomorphism, and thus somehow be testable, which it isn't. (My previous post is word salad to some extent too, since I'm jamming it into an HN post. But the core insight there is basically, let the math be the math and stop imposing your glob…

Pretty much. Seems that the "shut up and do the math" QM interpretation is still the important one

Re: Physicists provide support for retrocausal quantum theory

#109

Post by Simon_says » Fri, Jul 07, 2017, 11:21 AM UTC

BoiledCabbage wrote: post #101

Simon_says wrote: post #97

Earlier quoted context omitted.

The Pilot Wave Interpretation is one of the strangest contortions I've ever seen. You go to all the trouble to set up the wave equation acting on phase space of the entire universe, but then you remember that you think particles are fundamental elements of reality, so you drop them in and say they're guided by your wave equation. If you take Pilot Wave Interpretation and just take out the particles, you're left with…

> If you take Pilot Wave Interpretation and just take out the particles, you're left with the Many Worlds Interpretation with exactly the same predictions. To paraphrase Netwon, there's no need for that hypothesis. And if you take Many World and simply add a particle you have Pilot Wave hypothesis. No need for the crazy multiple universes nonsense. All 3 produce (including Copenh) the exact same predictions, so that'…

Copenhagen isn't even a proper theory, because it never tells you precise criteria for when wavefunction collapse occurs. It's not a surprise that nobody noticed this at the time, because the Copenhagen Interpretation was invented prior to the foundational work on computation and formalization of what an algorithm is. But looking at it now, it should be clear that there's no formal definition of what a "measurement" is. As soon as you give precise criteria for wavefunction collapse, then you have a difference in predictions between Copenhagen and MW.

And PW is strictly more complicated than MW, because you still need to track the same wavefunction on phase space, but then you add this particle to have something to point to and say "this is reality". But all the complexity of the wavefunction is still there. If you try to reduce this complexity by collapsing the wave function, you're back to having the same problems as Copenhagen.

Re: Physicists provide support for retrocausal quantum theory

#110

Post by mikeash » Fri, Jul 07, 2017, 1:55 PM UTC

gnaritas wrote: post #92

mikeash wrote: post #65

Earlier quoted context omitted.

Seems like it's the opposite to me. We never progressed anywhere with "explanations." Progress comes when those explanations are condensed to testable mathematics. I'm curious as to what you think consists of "an explanation" that's more useful than mathematics. Let's take a simple classical phenomenon to keep it easy, such as kinetic energy. The mathematical statement is E_k = 1/2 m v^2. What non-math explanation wo…

Maths are models of reality which may or may not be correct and can only be verified by comparing them to reality. While they serve as the most simple way to explain reality, don't confuse them with reality. The map is not the territory.

What prompts this reply? I'm not saying that math is reality, merely that solid mathematical models have been the foundation of progress in science, not "explanations."