Physicists provide support for retrocausal quantum theory • Hacker News Board

Re: Physicists provide support for retrocausal quantum theory

#121

Post by JadeNB » Sat, Jul 08, 2017, 8:19 PM UTC

gnaritas wrote: post #119

JadeNB wrote: post #117

Earlier quoted context omitted.

> Testable mathematical models are the result of progress in science, not the foundation of it. I think that the information can flow either way. For example, the existence of anti-matter, and portions of quantum mechanics (and, let's say, much of Witten's scientific work—though here I am tossing out a bit of folk knowledge, and couldn't point to anything in particular), are examples of letting the math guide the phy…

The math certainly points at places to look for physics, so yes I agree to a point, but the math itself didn't just happen, it came from a mathematician using his intuition and understanding of physics to explore possible ideas that might be true with most of the possible maths not leading to possible physics. Math is just a language to communicate ideas accurately, those ideas however came from someones intuition ab…

> the math … came from a mathematician using his intuition and understanding of physics to explore possible ideas that might be true with most of the possible maths not leading to possible physics.

This is famously not true for the matrix mechanics in Heisenberg's picture of quantum mechanics and the Riemannian geometry underlying relativity, both of which were created without (so far as I, and history, know) any intended or perceived connection to physics.

On the other hand, I guess you could argue that that math was irrelevant to physics until Heisenberg and Einstein came along and found it an appropriate expression of their physical intuition.

Re: Physicists provide support for retrocausal quantum theory

#122

Post by Simon_says » Sat, Jul 08, 2017, 9:34 PM UTC

mikeash wrote: post #120

Simon_says wrote: post #116

Earlier quoted context omitted.

Not exactly equivalent . The Copenhagen Interpretation has a pretty big theoretical hole in that the condition for when a wavefunction collapse occurs is not defined within the theory itself. Supposedly collapse occurs during a "measurement". Well, what's a measurement? Your measuring apparatus are all made up of matter that supposed to be following the same fundamental physical laws. I think you'd be hard pressed to…

Thanks. I must have gotten mixed up with the equivalence of some of these interpretations, and the lack of actual experiments to distinguish the others.

The mix up is not your fault. I see it routinely written that the interpretations don't make any difference to predictions, and I never see anyone talk about or acknowledge the issues I just raised. I feel like I'm taking crazy pills.

Re: Physicists provide support for retrocausal quantum theory

#123

Post by EliRivers » Sat, Jul 08, 2017, 9:35 PM UTC

ridewinter wrote: post #33

mikeash wrote: post #24

Earlier quoted context omitted.

That seems to be begging the question. Qubits do more than this universe is capable of, therefore there must be multiple universes. The obvious refutation is: qubits don't do more than this universe is capable of, because the universe does not run on classical limits. 10^80 atoms implying on the order of 10^80 computations that can be done implicitly assumes that these things operate on classical-ish rules. There's a…

Explain the double slit experiment to me. The single photon somehow calculates the interference pattern with photons that don't exist, in our world at least. If there's not parallel universes, how does a single atom calculate that interference pattern? Where do those calculations occur? All other theories say it happens by magic and give all sorts of complicated non-real obfuscations to explain it.

When I let go of something, it falls to the floor and hits it at exactly the correct speed. The correct speed accounting for gravity and the air and air currents and all sorts of other things. That's a lot of calculations to make. And it was exactly correct at every instant of the fall as well! Somehow, all these calculations are being made instantly. Where are those calculations occurring?

Re: Physicists provide support for retrocausal quantum theory

#124

Post by gnaritas » Sun, Jul 09, 2017, 1:35 AM UTC

JadeNB wrote: post #121

gnaritas wrote: post #119

Earlier quoted context omitted.

The math certainly points at places to look for physics, so yes I agree to a point, but the math itself didn't just happen, it came from a mathematician using his intuition and understanding of physics to explore possible ideas that might be true with most of the possible maths not leading to possible physics. Math is just a language to communicate ideas accurately, those ideas however came from someones intuition ab…

> the math … came from a mathematician using his intuition and understanding of physics to explore possible ideas that might be true with most of the possible maths not leading to possible physics. This is famously not true for the matrix mechanics in Heisenberg's picture of quantum mechanics and the Riemannian geometry underlying relativity, both of which were created without (so far as I, and history, know) any int…

> I guess you could argue that that math was irrelevant to physics until Heisenberg and Einstein came along and found it an appropriate expression of their physical intuition.

Exactly.

Re: Physicists provide support for retrocausal quantum theory

#125

Post by lisper » Tue, Jul 18, 2017, 6:01 AM UTC

graycat wrote: post #79

ridewinter wrote: post #33

Earlier quoted context omitted.

Explain the double slit experiment to me. The single photon somehow calculates the interference pattern with photons that don't exist, in our world at least. If there's not parallel universes, how does a single atom calculate that interference pattern? Where do those calculations occur? All other theories say it happens by magic and give all sorts of complicated non-real obfuscations to explain it.

Double slit experiment? It appears that some people, e.g., Feynman, believe that this experiment is profound. I don't have an explanation as good as I would like, but from what I studied in physics class, reading Feynman, etc. here's my explanation. So, shoot a photon, or an electron, neutron, proton, alpha particle, etc., at the double slit barrier. Only one particle, please. Well, now give up on the idea that we sh…

> So, the wave function hits the barrier. Nearly all that wave function hits the barrier and disappears.

No, it doesn't disappear. The barrier itself is illuminated. Most of the wave function that hits the barrier is absorbed (or reflected) by the barrier. But the light that hits the barrier is uninteresting so it is ignored.

(On the other hand, if you make a reflective barrier with a lot of slits, not just two, then you have a diffraction grating and things get interesting again.)