Tuesday, 24 April 2007

Reality isn't what it used to be

And what's more it never was.
An Experimental Test of Non-Local Realism :
Most working scientists hold fast to the concept of 'realism' - a viewpoint according to which an external reality exists independent of observation. But quantum physics has shattered some of our cornerstone beliefs. According to Bell's theorem, any theory that is based on the joint assumption of realism and locality (meaning that local events cannot be affected by actions in space-like separated regions) is at variance with certain quantum predictions. Experiments with entangled pairs of particles have amply confirmed these quantum predictions, thus rendering local realistic theories untenable. Maintaining realism as a fundamental concept would therefore necessitate the introduction of 'spooky' actions that defy locality. Here we show by both theory and experiment that a broad and rather reasonable class of such non-local realistic theories is incompatible with experimentally observable quantum correlations. In the experiment, we measure previously untested correlations between two entangled photons, and show that these correlations violate an inequality proposed by Leggett for non-local realistic theories. Our result suggests that giving up the concept of locality is not sufficient to be consistent with quantum experiments, unless certain intuitive features of realism are abandoned.
Simple summary : "Spooky Action at a Distance" is not enough to save common sense interpretations of Reality. If a tree falls over in a forest, then it must make a noise, because if there's no-one there to observe it, the tree doesn't exist. Neither does the forest. Though if the Forest is observed, the tree does exist, as the Forest observes the tree...

A very insightful comment over at Slashdot :
You're not getting this.

Consider a cat of the Schroedinger subspecies. In the experiment, it is neither alive nor dead until observed. A rock, positioned near the detection apparatus, can observe the result. So for the rock, the cat is either alive or dead. But until YOU observe the rock, you don't know whether the rock is happy that the cat is alive, or sad that the cat will never again rub it's tail against the quartz inclusion on the rock's lower anterior surface. The quantum wave-function describing the cat has collapsed with respect to the rock, but to you the quantum wave-function of the cat and the rock are now entangled; in fact, by observing the rock and causing its quantum wave function to collapse, you will also cause the quantum wave function of the cat to collapse... but in both cases, it is collapsing for YOU, the observer. Every other observer has to make them collapse for themselves by either observing something the cat/rock, or observing something that has already collapsed those wave-functions for itself.

Sorry man, but the universe isn't obliged to live up to the expectations that you've developed based on your highly limited experience with the laws of physics. You've observed light in the 300nm to 800nm range, you've observed matter in the 1 milligram to 10 tonne range moving at velocities in the 0.0 m/s to 600.0 m/s range, and just maybe some matter in the 10 gram to 1 microgram range moving at velocities up to 1000 m/s. But man, that ain't shit. The world contains matter moving at up to 0.999999 C, blocks of matter so cold that void of space is over a trillion times warmer, particles that change from antimatter to matter for no apparent reason, and photons energetic enough to shred the nuclei of atoms like a Kattus-Schroedingerus shreds catnip-infused kleenex. There are particles whose position is so inherently imprecise that they have trouble turning because they would start colliding with themselves (like humble electron, for example). There are gobs of matter so weighty that they curve space forming telescopes that are light-years long.

If you think you have even the vaguest conception of how the universe works, then you are inherently wrong, because Human's can't conceive of how the universe works by any means. If you even attempt to apply common sense to the universe, you'll never be able to accept any of the research that actually explains how computers, lasers, DNA, proteins, and light-bulbs work.
Of course another insightful post replying to that one starts off "It isn't that simple....."

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