Free Republic
Browse · Search
News/Activism
Topics · Post Article

Skip to comments.

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
Navigation: use the links below to view more comments.
first previous 1-2021-4041-6061-80 ... 101 next last
To: LibWhacker
this guy has gone from physics to making a philosophical argument. His opinion is no more relevant then anyone else.

To the professor: what is reality a? well my name is Grimmjaw jaggerjack and I’m gonna eat your soul. AHAHAHAHAHA!

41 posted on 04/19/2007 6:35:40 PM PDT by tranzorZ
[ Post Reply | Private Reply | To 1 | View Replies]

To: SirKit

Quantum ping!


42 posted on 04/19/2007 6:36:26 PM PDT by SuziQ
[ Post Reply | Private Reply | To 1 | View Replies]

To: Steely Tom

One day, Werner Heisenberg was pulled over for speeding. The Police officer asked him: “Do you know how fast you were going?”

Werner replied: “No, but I knew exactly where I was.”


43 posted on 04/19/2007 6:37:24 PM PDT by stefanbatory
[ Post Reply | Private Reply | To 38 | View Replies]

To: Frank Sheed

And I was trying to be so series ...


44 posted on 04/19/2007 6:38:03 PM PDT by MHGinTN (You've had life support. Promote life support for others.)
[ Post Reply | Private Reply | To 40 | View Replies]

To: MHGinTN

Have you heard of this? I’m speechless!

http://www.freerepublic.com/focus/f-news/1820369/posts


45 posted on 04/19/2007 6:40:49 PM PDT by Frank Sheed (Dead Ráibéad)
[ Post Reply | Private Reply | To 44 | View Replies]

To: LibWhacker

The whole QM magic show is debunked here:

http://www.springerlink.com/content/7001651u4726jk51/


46 posted on 04/19/2007 6:42:01 PM PDT by neuron2
[ Post Reply | Private Reply | To 1 | View Replies]

To: Brilliant
Just because their statistics don’t come out, they conclude that the universe is bazaar beyond belief.

It's a big sale? That IS strange...
47 posted on 04/19/2007 6:46:04 PM PDT by beezdotcom
[ Post Reply | Private Reply | To 24 | View Replies]

To: Frank Sheed

I have a beautiful niece/relative who lives in K-ville in the age range of this couple. I had no knowledge of this heinous evil. Reading the particulars will now haunt my mind for a time.


48 posted on 04/19/2007 6:53:52 PM PDT by MHGinTN (You've had life support. Promote life support for others.)
[ Post Reply | Private Reply | To 45 | View Replies]

To: LibWhacker

...”objects governed by the laws of quantum mechanics”...

I don’t want to be an obscurantist, but if the scientific
community doesn’t know what “reality” is at the Planck
length level, how would they know that “objects are
governed by the laws of quantum mechanics?”
I think they have a BELIEF that the objects are governed
by some law or laws but until they know and verify those
laws it is still a BELIEF. It is quite obvious that the
concepts and laws that are currently acceptable are
not capable of elucidating the workings of nature.
The hopeful belief is that we will eventually figure it all
out..but that is still yet to be seen.


49 posted on 04/19/2007 7:03:55 PM PDT by Getready (Truth and wisdom are more elusive, and valuable, than gold and diamonds)
[ Post Reply | Private Reply | To 1 | View Replies]

To: LibWhacker

I think Parmenides tried something like this 2400 years ago. Socrates kicked his butt.


50 posted on 04/19/2007 7:07:11 PM PDT by mkmensinger
[ Post Reply | Private Reply | To 1 | View Replies]

To: martin_fierro

LOL!


51 posted on 04/19/2007 7:12:45 PM PDT by Reaganesque
[ Post Reply | Private Reply | To 4 | View Replies]

To: Phsstpok

Pardon me, but isn’t this rather a restatement of the proposition of Schrödinger’s Cat?


52 posted on 04/19/2007 7:19:57 PM PDT by Oberon (What does it take to make government shrink?)
[ Post Reply | Private Reply | To 10 | View Replies]

To: LibWhacker
Here's an easy way to remember the difference:

Normal Physics

Quantum Physics

Any questions?

53 posted on 04/19/2007 7:21:29 PM PDT by Reaganesque
[ Post Reply | Private Reply | To 1 | View Replies]

To: maxsand

Is there a relationship with Quantum Mechanics?


54 posted on 04/19/2007 7:24:42 PM PDT by ew73
[ Post Reply | Private Reply | To 26 | View Replies]

To: boris

I know you cannot help me to understand this stuff now, but I’m pinging you anyway, my FRiend. Rest in Peace big guy, you have all the answers now.


55 posted on 04/19/2007 7:27:29 PM PDT by MHGinTN (You've had life support. Promote life support for others.)
[ Post Reply | Private Reply | To 1 | View Replies]

To: Reaganesque

Im having a hard time with normal physics


56 posted on 04/19/2007 7:28:38 PM PDT by woofie
[ Post Reply | Private Reply | To 53 | View Replies]

To: LibWhacker
"But we have a little more evidence that the world is really strange."

For proof-positive that the world is really strange, look no further than here. VDH defines an alternative reality that I would dearly love to live in.

57 posted on 04/19/2007 7:29:25 PM PDT by ProtectOurFreedom
[ Post Reply | Private Reply | To 1 | View Replies]

To: woofie

No comment.


58 posted on 04/19/2007 7:30:14 PM PDT by Reaganesque
[ Post Reply | Private Reply | To 56 | View Replies]

To: SpaceBar
Seems like physics now is just an academic exercise to fill in the details and confirm the genius of great minds long dead.

While I tend to feel the same way, remember that everyone said the same thing in the 1890s.... In fact, I believe it was the parents of Max Planck who told their son not to go into physics since everything was already solved.... We could just as well be on the brink of another revolution...we just need another Einstein to come along.
59 posted on 04/19/2007 7:47:08 PM PDT by newguy357
[ Post Reply | Private Reply | To 27 | View Replies]

Comment #60 Removed by Moderator


Navigation: use the links below to view more comments.
first previous 1-2021-4041-6061-80 ... 101 next last

Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.

Free Republic
Browse · Search
News/Activism
Topics · Post Article

FreeRepublic, LLC, PO BOX 9771, FRESNO, CA 93794
FreeRepublic.com is powered by software copyright 2000-2008 John Robinson