Strand & Fleet Street Undressed

Take a Chance 4

Scientists put randomness to work - Science that is..

Since the dawn of written history, people have exploited the randomness of a roll of a die to inject their games with the thrill of the unpredictable. Today, randomness is finding myriad other uses, such as encrypting credit card numbers in Internet transactions, deciding how to allocate treatments in drug trials, choosing precincts to call in national polls, running online gambling sites, and helping physicists simulate phenomena ranging from the weather to traffic patterns. These applications, however, require many more random numbers than can be obtained from rolling a die. A busy commercial Web site, for example, uses hundreds of thousands of random numbers every minute to mask its users' credit card numbers. And in the research world, computer simulations eat up millions of random numbers in a matter of seconds. To accommodate these needs, researchers are creating a precise science out of something at which toddlers excel: making chaos at breakneck speed.

Randomness is a slippery concept, easier to talk about than to define. Scientists instead tend to say what it isn't. A random number is one that can't be predicted.

Knowing some of the random numbers in a list doesn't make it easier to figure out the others. Over the past few decades, computer scientists have designed computer algorithms that produce a good approximation of true randomness. These algorithms churn out long sequences of pseudorandom numbers, which are scattered about the number line in roughly the same distribution as random numbers are. These pseudorandom numbers are unpredictable enough for many, but not all, purposes.

Now, physicists and computer scientists are figuring out ways to pull true randomness out of the physical world. One Web site, for instance, generates random numbers from the noise of a radio tuned between stations. And a commercial device put on the market last March harnesses nature's ultimate source of randomness: quantum physics, which Albert Einstein famously described as God playing dice.

More soon...

SM

-----------------------------------------------------------------------------

29.11.06 09:35