To the relief of physicists, time really does have a preferred direction
TIME seems to flow inexorably in one direction. Superficially, that is because things deteriorate with age—and this, in turn, is because there are innumerably fewer ways to arrange particles in an orderly fashion than in a jumbled mess. Any change in an existing arrangement is therefore likely to increase its disorder.
Dig a little deeper, though, and time’s arrow becomes mysterious. A particle cannot, by itself, become disordered, so when you examine its behaviour in isolation the past and the future are hard to distinguish. If you film its movement and then give the film to someone else, he will not be able to work out just from the particle’s behaviour which way to run the film through the projector. Essentially, the two ways of doing so are symmetrical. Or so physicists used to think until hints to the contrary emerged in the 1960s. Now a group of researchers at the SLAC National Accelerator Laboratory, near Stanford University in California, have found the first physical evidence that backs those indications up.
The main hint that nature violates the time-reversal (T) symmetry implied by the thought experiment with the film—and thus that there really is an arrow of time—came from seemingly disparate discoveries about matter and antimatter. Mathematically, particles and their anti-versions differ in two ways: they have opposite electrical charges and they are each other’s mirror reflections. But in 1964 some particles called kaons were shown not to respect this charge-conjugation/parity (CP) symmetry, as it is known. Matter and antimatter are not, in other words, quite equal and opposite. However, according to another law, C, P and T symmetries, when lumped together into a single, overarching CPT symmetry, must be conserved. This means that if CP is violated, then T must be too, in order to even things out.
…until reeled the mind
The obvious place to look for this T violation is where C and P are already known to misbehave. Between 1999 and 2008 a laboratory in California was set up to do just that. The old linear accelerator at Stanford was repurposed, turning it from the machine that co-discovered a particle known as the charm quark (thus winning its operators a Nobel prize) into a factory for making particles called B mesons. These are interesting because they and their antiparticles exhibit CP-violating tendencies. They are thus a promising place to look for T violations, too.
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http://www.economist.com/node/21561111
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wouldn't it appear as just another day with lots of deja vu?
LOL
