For those of you who understand the field and have some knowledge, could you tell me if the following short clip is accurate or not? I am curious as to how I should approach it.

http://www.youtube.com/watch?v=x_tNzeouHC4

Thanks in advance.

w1z4rd, that is certainly a completely conventional quantum theory interpretation of the two-slit experiment.

The bit at the end about the collapse of the wave function is metaphysics, however, not physics. That is, it's part of the interpretation of the theory, rather than the substance of it. There are other interpretations of QT that do not have a wave function collapse.

Einstein strongly objected to the idea of the collapse of the wavefunction as violating relativity, that information cannot travel faster than light.

I'd also say that the conclusions as stated are not so obviously inescapable.

I know everything is accurate up until about the last 30 seconds, and that Im not sure about. I had no idea that when scientists tried to observe which slit the electrons were going through, it somehow knew it was being observed and did not make an interference pattern, as it did when it was not being observed. (collapse of the wave function)

I too would like someone to confirm this fact please. It almost would seem then that consciousness derives from the quantum level if that little tidbit is true.

There is an interesting article in one of the recent Science News magazine about a version of the two-slit experiment where it is claimed that it is simultaneously determined which slit the particle goes through and a diffraction pattern is formed. This one is with light. Apparently the guy who came up with this suffered a lot of vitriol from our supposedly dispassionate physicists.

edit: should have said New Scientist. See below for more.

Hi Wizard---

The interpretations given in the video are perfectly legitimate. The wavefunction collapse is at the heart of the most prevalent interpretation of QM that physicists use today.

Maybe you could ask some questions and I will try to answer them. Wavefunction collapse is conceptually difficult to handle---if you were doing calculations with it, you'd find that it's a lot easier to just do it than to think about it! Essentially, the wavefunction is a probability distribution, and cannot be observed.

Einstein certainly objected to most things quantum, and favored a deterministic interpretation of the universe. I'm sure his mind would be different if he were alive today, however, as he never really saw any utility in quantum mechanics. His late attempts to construct a theory of everything were pretty futile, and I don't know if he ever really accepted any Quantum reasoning.

There is an interesting article in one of the recent Science News magazine about a version of the two-slit experiment where it is claimed that it is simultaneously determined which slit the particle goes through and a diffraction pattern is formed. This one is with light. Apparently the guy who came up with this suffered a lot of vitriol from our supposdly dispassionate physicists.

I would be interested to read this---can you link to it?

The article I mention is in the print version for Feb 17-23. I don't think they let you read them online without a subscription.

It's interesting also in that there is both an editorial about it and an article.

Reading the editorial made my heart jump because I thought maybe somebody had discovered what I have, but previously.

I've been hoping some of you smart guys here will take the time to look at. It is at least very paradoxical, seems to me. I started a thread on it a week or two ago. Here is a link to my gateway page. Click on the PDF link to see the paper:

http://home.comcast.net/~d.lush/dave_30DecY6.htm


I disagree that Einstein would have acquiesced by now to quantum thoeory being free of contradiction. On what basis do you make this assertion? Against it, I would note that he contended in many letters with Bohr specifically about the problem of waveform collapse. The EPR incompleteness problem has never been convincingly explained, either. (If you are going to counter with Bell's theorem, my answer would be that that merely predicts consequences, rather than reconciling QT with SR.)

Well, I would point out that no experiments have ever contradicted quantum theory. And QED (Feynman's quantum generalization of electrodynamics) has been tested even more accurately than Einstein's GR---to one part in a trillion or something like that. Einstein could not have argued with this.

One should keep in mind that many people in the early 20th century had a hard time accepting quantum mechanics. That community has since died down.

I will look at your thread, and make a comment or two.

Thanks! When I get up to 20 posts I'll be able to post a link to the paper. Farsight posted one for me in the thread though.

If you're interested I can share the comment I got on it from Hans C von Baeyer. He didn't find any fault with it but wasn't greatly moved by it, either I'd say.

I do plan on submitting it for publication, though I doubt it will be accepted. It needs considerable refinement in any case. Right now (literally) I am trying to get another part of it up on my site. This other part is how an assumption that angular momentum is a constant of the preferred motion can lead classically to a preferred radius that is on the order of the Bohr ground state radius.

On the subject of QT in general, I would not dispute that Einstein would have accepted the accuracy of QED and the other QFTs. There are still people around today (besides me) however who find the non-locality of QT troubling.

Did you ever read Huw Price's Time's Arrow and Archimedes' Point? It's more than just a lay physics book. His contention, if I may paraphrase, is that one can have causality or locality but not both.

I started working on my theory as a time-symmetric one that is compatible with Wheeler-Feynman Absorber theory, and so would be plausibly local under the Price contention. Unlike other people (Jayme de Luca in particular) doing similar stuff but strictly from the Coulomb force, my aberrational force (derived from the moving intrinsic magnetic moment) does not vanish in the time-symmetric version.

Sorry about hijacking the thread. Please resume the original discussion.

I don't think this is hijacking, but if wizard wants us to quit we will.

There are still people around today (besides me) however who find the non-locality of QT troubling.

Locality only matters when we are talking about observables. If the nonlocality isn't physical, there should be no problem.

Did you ever read Huw Price's Time's Arrow and Archimedes' Point? It's more than just a lay physics book. His contention, if I may paraphrase, is that one can have causality or locality but not both.

Ill have to think about this. Classical physics is both causal and local. Hmm.

Classical physics is both causal and local.

Certainly it claims to be. Certainly it is local. However I would argue (and I am not alone in this) that there is no working theory of causality, either classical or quantum, and whether either is causal is unknown.

This is a major topic of the Price book. He argues that all the arguments for the second law of thermo are in fact circular. So it is more of an observation than a theory. Boltzmann actually appreciated this, according to Price.

If you skip through the crap in the movie, What the Bleep Do We Know, does an awesome job of showing potental of wave function collapse theory. Some of the "science" however is more than questionable, but good discusion movie.

oops, guess that was a clip from "what the bleep, down the rabit hole". Sorry

Hi Wizard---
Essentially, the wavefunction is a probability distribution, and cannot be observed.

Yes, a lot of people mix up the fact that wavefunction is not the sam as the wave pattern made up in such slit experiments. The wavefunction of a particle is present in all experiments whether testing the wave theory of light or not.

A bit like people always mix up (a) the uncertainty principle based on the momentum/position Planck limit and (b) the uncertainty principle based on inherent uncertainty in any quantum measurement

I hate to waste a post on this, but above where I said there was an interesting editorial and article in Science News about a slit experiment that goes contrary to conventional wisdom, I should have said, New Scientist.

I recently switched subscriptions.

I hope BenTheMan isn't off at the library trying to hunt it down.

The article says the paper, by Afshar, is being published in the Foundations of Physics, vol 37, p 295.

I'll try to find it on the arXiv and edit this if I succeed.

Sorry about the confusion.

OK here are some links:

http://www.irims.org/quant-ph/030503/
http://axion.physics.ubc.ca/rebel.html
http://en.wikipedia.org/wiki/Afshar_experiment