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Permalink Reply by Danielle on October 31, 2009 at 10:49pm

Hah yeah, I was a bit skeptical about the title at first, too - but it's not what it sounds like it is. It is quite a bit of speculation, but if you're reading Brian Greene and can tolerate his description of string theory, it's pretty much at the same level as that.

Ah! How could I forget about Michio Kaku?! Definitely read "Physics of the Impossible".

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Permalink Reply by Reggie on October 31, 2009 at 11:04pm

Definitely read "Physics of the Impossible".

Already in my queue! ;) I'll have to bump it into my cart.

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Permalink Reply by Dave G on November 1, 2009 at 2:29pm

I also recommend Kaku's book Hyperspace: A Scientific Odyssey Through Parallel Universes, Time Warps, and the Tenth Dimension. Both are highly enjoyable.

Permalink Reply by Atheist Ninja on November 1, 2009 at 8:08pm

I get the feeling that perhaps modern quantum mechanics is a close approximation based on evidence, and formulated to reproduce that evidence as closely as possible. However is still missing some fundamental variables.

I would be very grateful if you could provide a source from a scientific publishing that outlines the experiment you've described, especially regarding the pattern being different when observed prior to hitting the screen.

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Permalink Reply by Philip on November 2, 2009 at 8:14pm

Yep. This is essentially what I mentioned in one of my previous posts. Hidden variables are virtually ruled out as likely explanations for any and all of this phenomena. We'd have to make a hell of a lot more assumptions were we to assume hidden variables, and that would just be incredibly bad science.

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Permalink Reply by Danielle on November 1, 2009 at 9:34pm

You can read almost any "popsci" physics book, and it has a description of that experiment usually, Brian Greene's (who is a very good theoretical physicist) Fabric of the Cosmos has a good description of it in the chapter "Time and Quantum". Here is a quote from it: "When a single photon hits a beam splitter, classical intuition says that it will either pass through or will be reflected. Classical reasoning doesn't even allow a hint of interference, since there is nothing to interfere: all we have are single, individual, particulate photons passing from source to detector, one by one, some going left, some going right. But when the experiment is done, the individual photons recorded over time do yield an interference pattern. According to quantum physics, the reason is that each detected photon could have gotten to the detector by the left route or by going via the right route. Thus, we are obliged to combine these two possible histories in determining the probability that a photon will hit the screen at one particular point or another. When the left and right probability waves for each individual photon are merged in this way, they yield the undulating probability pattern of wave interference... you can insert additional detectors, but if you do, you will find two things. First, each electron and each photon will always be found to go through one and only one of the detectors; that is, you can determine which path each electron or photon follows, and you will find that it always goes one way or the other, not both. Second, you will also find that the resulting data recorded by the main detectors have changed. Instead of getting the interference patterns, you get the results expected from classical physics."

This is also a good description of the experiment:
http://grad.physics.sunysb.edu/~amarch/

And here are some papers:
http://grad.physics.sunysb.edu/~amarch/Walborn.pdf
http://arxiv.org/PS_cache/quant-ph/pdf/9903/9903047v1.pdf


At this point, there's no reason to think there are hidden variables - no evidence points to it whatsoever. It very well might be the case that there are in fact hidden variables, but again there's never been any trace of these variables in any experiments thus far. It doesn't intuitively make sense, but it works, and all the experimental data points towards it, and that's all that matters until evidence to the contrary comes along.

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Permalink Reply by Reggie on November 1, 2009 at 10:45pm

Follow the evidence, no matter how bat shit crazy it may seem. I loved reading about that experiment in (I think) The Elegant Universe.

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Permalink Reply by Philip on November 2, 2009 at 8:20pm

This sums up the experiment rather nicely.

Ninja, if you're still not satisfied you can easily find information on other important experiments in QM. The book by Heisenberg I mentioned earlier has a whole chapter dedicated to outlining these important experiments: (C.T.R. Wilson Experiments, more diffraction experiments, emission, absorption and dispersion of radiation, interference & conservation laws, Compton Effect, radiation fluctuation phenomena, ...)

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Permalink Reply by a7 on November 17, 2009 at 2:05pm

Danielle your right, it makes no sense but what great reading. It's really starting to hurt my wee scots heid.

p.s I love intellegent woman, you dont happen to have a nasty violent streak in you ? That would be the icing on the cake of my second wedding.

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Permalink Reply by Doug Reardon on November 1, 2009 at 12:12am

Feynman said: If you think you understand quantum mechanics, then you haven't got a clue!

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Permalink Reply by Reggie on November 1, 2009 at 12:20am

A wise man.

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Permalink Reply by Doug Reardon on November 1, 2009 at 12:57am

He was a hoot too! You need to read some of his books Reggie! I suggest: why do you care what other people think?

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