Content area
Full Text
Finding a random sequence of numbers is as easy as pi-or is it? Mathematicians often depend on irrational numbers like pi, e (the base of natural logarithms), and sq. Root of 2 to give them an unpredictable stream of digits. But a paper in last week's Proceedings of the National Academy of Sciences is upsetting the conventional wisdom about randomness by showing that some of these numbers are far more predictable than expected. The finding is an early result of a new test of randomness that is also raising concerns in other fields where random-looking sequences crop up, such as cryptography. Ultimately, though, the new test could put those fields on firmer ground.
Randomness has been hard to quantify. Any mathematician could tell you that 01101100 is more random than 01010101, but none could tell you just how much more random. Then, two researchers Steve Pincus, a free-lance mathematician based in Guilford, Connecticut, and Burton Singer, a mathematician and demographer at Princeton University-created a method for measuring a sequence's "entropy," or disorder. "Their method] is one of those tools that makes you say, `Hey, that's a good one!' and you put it in your tool kit," says Max Woodbury, a mathematician at Duke University.
Pincus and...