Saguaro
07-30-2007, 08:06 PM
July 30, 2007 issue - You can tell a lot about a subject by who its muses and mascots are. Neuroscience has philosophers who wax profound about the mind, geology has intrepid explorers and subatomic physics has ... Alice in Wonderland. "Curiouser and curiouser," as Alice said, also describes the subatomic, or quantum, world. With age, this centenarian (quantum physics is 107 years old) has gotten more bizarre. "The surprises keep coming," says physicist David Albert of Columbia University. None is greater than finding loopholes in the hallowed uncertainty principle—and, even more outlandishly, seeing hints that the future may leak into the present.
Since experiments keep proving quantum ideas right, physicists are forced to take them seriously. It isn't easy. They have to admit that a particle can be in two places at once. They have to accept that subatomic systems can become so "entangled" that measuring one affects the other even if the two are light-years apart, which Einstein called "spooky action at a distance." But even as quantum weirdness provides fodder for such drivel as the best-selling book "The Secret," it also fuels debate on subjects as lofty as the nature of reality. Last week a conference at Oxford University explored the idea that every time a subatomic system reaches a decision point—to undergo radioactive decay or not, say—it chooses both possibilities: in this world the particle decays, while in a parallel world it does not. Some physicists buy this "many worlds" interpretation because the alternative is even more unpalatable: that quantum systems choose one possibility or another only when an observer looks. Einstein loathed the idea that reality is created by observers.
New studies suggest, however, that it is possible to measure something without affecting it. The key is doing the experiments, well, gently. Anyone with a vague memory of Physics 101 knows that if you shine a light on what you want to measure, or stick a thermometer in it, you alter it. Taking the temperature of a steak with a cold thermometer, for instance, cools it as heat is transferred from meat to glass. You don't know what the temperature "really" was before you jabbed in the thermometer—a notion enshrined as the uncertainty principle. To circumvent this rule, Israeli physicist Yakir Aharonov got the idea of making "weak measurements," akin to waving your hand over the steak to feel its heat. That's not very precise with meat, but it works with quantum measurements: if you make enough weak measurements, the average comes impressively close to the actual value, experiments are showing. "Weak measurements let you lift the veil of secrecy imposed by the uncertainty principle," says Paul Davies of Arizona State University.
To read more on the subject http://www.msnbc.msn.com/id/19875410/site/newsweek/
Since experiments keep proving quantum ideas right, physicists are forced to take them seriously. It isn't easy. They have to admit that a particle can be in two places at once. They have to accept that subatomic systems can become so "entangled" that measuring one affects the other even if the two are light-years apart, which Einstein called "spooky action at a distance." But even as quantum weirdness provides fodder for such drivel as the best-selling book "The Secret," it also fuels debate on subjects as lofty as the nature of reality. Last week a conference at Oxford University explored the idea that every time a subatomic system reaches a decision point—to undergo radioactive decay or not, say—it chooses both possibilities: in this world the particle decays, while in a parallel world it does not. Some physicists buy this "many worlds" interpretation because the alternative is even more unpalatable: that quantum systems choose one possibility or another only when an observer looks. Einstein loathed the idea that reality is created by observers.
New studies suggest, however, that it is possible to measure something without affecting it. The key is doing the experiments, well, gently. Anyone with a vague memory of Physics 101 knows that if you shine a light on what you want to measure, or stick a thermometer in it, you alter it. Taking the temperature of a steak with a cold thermometer, for instance, cools it as heat is transferred from meat to glass. You don't know what the temperature "really" was before you jabbed in the thermometer—a notion enshrined as the uncertainty principle. To circumvent this rule, Israeli physicist Yakir Aharonov got the idea of making "weak measurements," akin to waving your hand over the steak to feel its heat. That's not very precise with meat, but it works with quantum measurements: if you make enough weak measurements, the average comes impressively close to the actual value, experiments are showing. "Weak measurements let you lift the veil of secrecy imposed by the uncertainty principle," says Paul Davies of Arizona State University.
To read more on the subject http://www.msnbc.msn.com/id/19875410/site/newsweek/