Sunday, May 17, 2009

Quantum physics and the questions of our reality

Below is a snippet of a fascinating article I found about quantum physics from Foundational Questions Institute, or FQXi.

Alex Vilenkin and Jaume Garriga ponder how unusual our universe is and whether this is all just a quantum dream.

[...] Other measures had downright bizarre implications, predicting that “normal,” biologically–evolved human brains should be outnumbered by so–called Boltzmann brains—disembodied minds that float in space. Boltzmann brains could be complete human beings, just brains, or maybe even silicon chips—material objects with the thinking power to “hallucinate” the universe we think of as real. Pick the wrong measure, and poof: You’re a Boltzmann brain!

It might sound like crackpot cosmology, but Boltzmann brains are a serious sticking point for some measures. Quantum mechanics tells us that things can pop up from the fluctuating vacuum. These “things” could be as trivial as an electron–positron pair that blinks into existence and then disappears again a split–second later. Particle physicists are well aware of this phenomenon; it happens all the time. Less likely, a whole atom could perform this magic trick. Even more improbably, a whole human being—or Windsor Castle, or a Honus Wagner baseball card, or a fully–formed brain thinking exactly your thoughts—could spontaneously materialize.

“It’s ridiculously improbable!” says Vilenkin. But given an infinite amount of time, even things that are ridiculously improbable are bound to happen. “So how do I know whether I’m a normal person…or a vacuum fluctuation?”

Don’t have an identity crisis just yet. Theorists agree that our universe must contain more “normal” brains than it does Boltzmann brains. “The world around a typical Boltzmann brain looks very different from the world around us,” says Garriga. Plus, a Boltzmann brain likely wouldn’t stick around for long, so the mere fact that we all continue to think coherent thoughts from one moment to the next should be some assurance that we’re real.



Hermes, draw near, and to my pray'r incline, angel of Jove, and Maia's son divine; Studious of contests, ruler of mankind, with heart almighty, and a prudent mind. Celestial messenger, of various skill, whose pow'rful arts could watchful Argus kill: With winged feet, 'tis thine thro' air to course, O friend of man, and prophet of discourse: Great life-supporter, to rejoice is thine, in arts gymnastic, and in fraud divine: With pow'r endu'd all language to explain, of

care the loos'ner, and the source of gain. Whose hand contains of blameless peace the rod, Kerukeion, blessed, profitable God; Of various speech, whose aid in works we find, and in necessities to mortals kind: Dire weapon of the tongue, which men revere, be present, Hermes, and thy suppliant hear; Assist my works, conclude my life with peace, give graceful speech, and me memory's increase.

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