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Physicists bid farewell to reality?
Nature ^ | 4/18/07 | Philip Ball

Posted on 04/19/2007 5:36:46 PM PDT by LibWhacker

Quantum mechanics just got even stranger.

There's only one way to describe the experiment performed by physicist Anton Zeilinger and his colleagues: it's unreal, dude.

Measuring the quantum properties of pairs of light particles (photons) pumped out by a laser has convinced Zeilinger that "we have to give up the idea of realism to a far greater extent than most physicists believe today."

By realism, he means the idea that objects have specific features and properties —that a ball is red, that a book contains the works of Shakespeare, or that an electron has a particular spin.

For everyday objects, such realism isn't a problem. But for objects governed by the laws of quantum mechanics, like photons and electrons, it may make no sense to think of them as having well defined characteristics. Instead, what we see may depend on how we look.

This notion has been around ever since the advent of quantum mechanics in the early twentieth century. The theory seemed to show that, in the quantum world, objects are defined only fuzzily, so that all we can do is work out the probability that they have particular characteristics — such as being located in a specific place or having a specific energy.

Allied to this assault on reality was the apparent prediction of what Albert Einstein, one of the chief architects of quantum theory, called 'spooky action at a distance'. Quantum theory suggests that disturbing one particle can instantaneously determine the properties of a particle with which it is 'entangled', no matter how far away it is. This would violate the usual rule of locality: that local behaviour is governed by local events.

Einstein could not believe that the world was really so indeterminate. He supposed that a deeper level of reality had yet to be uncovered — so-called 'hidden variables' that specified an object's properties precisely and in strictly local terms.

Failed test

In the 1960s the Irish physicist John Bell showed how to put locality and realism to the test. He deduced that if both ideas applied to the quantum world, then two particular quantities calculated from measurements made on a pair of entangled photons would be equal to one another. If so, there would be nothing 'spooky' about entanglement after all.

Experiments were done to test his prediction in the ensuing two decades, and results showed that Bell's equality was violated. Thus, either realism or locality, or possibly both of these ideas, do not apply in the quantum world.

But which is it? That's what Zeilinger, based at the University of Vienna in Austria, and his colleagues tried to find out.

They came up with a similar test to Bell's, to see whether quantum mechanics obeys realism but not locality. Again the experiment involves comparing two quantities calculated from measurements on entangled photons, to see if they are equal. But whereas in Bell's test these quantities are derived from the so-called 'linear' polarization of the photons — crudely, whether their electromagnetic fields oscillate in one direction or the other — Zeilinger's experiment looks at a different sort of polarization, called elliptical polarization.

Like Bell's, Zeilinger's equality proved false. This doesn't rule out all possible non-local realistic models, but it does exclude an important subset of them. Specifically, it shows that if you have a group of photons that all have independent polarizations, then you can't ascribe specific polarizations to each. It's rather like saying that you know there are particular numbers of blue, white and silver cars in a car park — but it is meaningless even to imagine saying which ones are which.

Truly weird

If the quantum world is not realistic in this sense, then how does it behave? Zeilinger says that some of the alternative non-realist possibilities are truly weird. For example, it may make no sense to imagine what would happen if we had made a different measurement from the one we chose to make. "We do this all the time in daily life," says Zeilinger — for example, imagining what would have happened if you had tried to cross the road when a truck was coming. If the world around us behaved in the same way as a quantum system, then it would be meaningless even to imagine that alternative situation, because there would be no way of defining what you mean by the road, the truck, or even you.

Another possibility is that in a non-realistic quantum world present actions can affect the past, as though choosing to read a letter or not could determine what it says.

Zeilinger hopes that his work will stimulate others to test such possibilities. "Our paper is not the end of the road," he says. "But we have a little more evidence that the world is really strange."


TOPICS: Miscellaneous
KEYWORDS: farewell; physics; quantum; reality; stringtheory
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1 posted on 04/19/2007 5:36:49 PM PDT by LibWhacker
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To: LibWhacker

-b-


2 posted on 04/19/2007 5:37:57 PM PDT by rellimpank (-don't believe anything the MSM states about firearms or explosives--NRA Benefactor)
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To: LibWhacker

ping


3 posted on 04/19/2007 5:39:20 PM PDT by beef (Who Killed Kennewick Man?)
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To: LibWhacker
Already posted

in a quantum sense

4 posted on 04/19/2007 5:40:27 PM PDT by martin_fierro (< |:)~)
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To: LibWhacker

Reality isnt all its cracked up to be anyway


5 posted on 04/19/2007 5:41:01 PM PDT by woofie
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To: Physicist; SunkenCiv; RadioAstronomer

Multi-Dimensional PING


6 posted on 04/19/2007 5:41:29 PM PDT by martin_fierro (< |:)~)
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To: martin_fierro

that was unreal man ...like a deja vu thing


7 posted on 04/19/2007 5:42:22 PM PDT by woofie
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To: martin_fierro

funny


8 posted on 04/19/2007 5:43:23 PM PDT by spanalot
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To: LibWhacker

A recent article to be published in Foundations of Physics involves laser light experiments which indicate that light consists of waves and particles, presumably very fast particles of some sort and waves which those particles create as they travel through some sort of a medium.


9 posted on 04/19/2007 5:43:32 PM PDT by rickdylan
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To: LibWhacker

Albert Einstein is considered one of the greatest natural philosopher in history. Most people are familiar with his famous statement dismissing quantum physics uncertainty principle:  

"God does not play dice with the universe."

However, most people do not know that he made the statement to his colleague and friendly rival, Niels Bohr, who made the less famous reply:

"Albert, stop telling God what to do."


I tend to agree with Bohr, and with God, of course. 

I also tend to use this quote when dealing with many televangelists, most Imams and Mullahs and just about anyone prattling on about man made global warming. 

10 posted on 04/19/2007 5:44:52 PM PDT by Phsstpok (Often wrong, but never in doubt)
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To: LibWhacker

Dang, all this time I was sure my Z car is gold. This shakes that all up. I can’t be sure it’s gold, or if it’s even a car.


11 posted on 04/19/2007 5:46:07 PM PDT by needlenose_neely
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To: woofie

Must be supernatural ;0)


12 posted on 04/19/2007 5:47:20 PM PDT by KyHammer ( If they say they want you dead, believe it.)
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To: LibWhacker
Einstein could not believe that the world was really so indeterminate. He supposed that a deeper level of reality had yet to be uncovered — so-called 'hidden variables' that specified an object's properties precisely and in strictly local terms.

I'll vote with Einstein; the only problem is that he's dead and we don't have a replacement for him.

13 posted on 04/19/2007 5:47:26 PM PDT by xJones
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To: LibWhacker

gnipyt sdrawkcab


14 posted on 04/19/2007 5:48:12 PM PDT by Drango (A liberal's compassion is limited only by the size of someone else's wallet.)
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To: LibWhacker
"Our paper is not the end of the road," he says. "But we have a little more evidence that the world is really strange."

...or charm - but what color is it?

15 posted on 04/19/2007 5:48:47 PM PDT by lepton ("It is useless to attempt to reason a man out of a thing he was never reasoned into"--Jonathan Swift)
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To: martin_fierro
Quantum non-locality placemarker ...
16 posted on 04/19/2007 5:50:02 PM PDT by MHGinTN (You've had life support. Promote life support for others.)
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To: KevinDavis; sig226

ping


17 posted on 04/19/2007 5:50:30 PM PDT by JerseyJohn61 (Better Late Than Never.......sometimes over lapping is worth the effort....)
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To: martin_fierro
Already posted
18 posted on 04/19/2007 5:50:36 PM PDT by lepton ("It is useless to attempt to reason a man out of a thing he was never reasoned into"--Jonathan Swift)
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To: martin_fierro

Thanks for the ping. Thanks for the ping to the GB Probe thread as well. Too bad the stuck on stupid types got there first. (Why I did not post on it)


19 posted on 04/19/2007 5:51:41 PM PDT by RadioAstronomer (Senior and Founding Member of Darwin Central)
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To: lepton
but what color is it?

I believe its mauve

20 posted on 04/19/2007 5:51:43 PM PDT by woofie
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