Normal Physics
Quantum Physics
Any questions?
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."
To the professor: what is reality a? well my name is Grimmjaw jaggerjack and I’m gonna eat your soul. AHAHAHAHAHA!
Quantum ping!
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.”
And I was trying to be so series ...
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.
...”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.
I think Parmenides tried something like this 2400 years ago. Socrates kicked his butt.
LOL!
Pardon me, but isn’t this rather a restatement of the proposition of Schrödinger’s Cat?
Normal Physics
Quantum Physics
Any questions?
Is there a relationship with Quantum Mechanics?
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.
Im having a hard time with normal physics
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.
No comment.
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