In the months before and after a major stock market crash, price
fluctuations follow patterns similar to those seen in natural
phenomena such as heartbeats and earthquakes, physicists write
in the 17 February Physical Review Letters. A University of
Tokyo team studied the Standard & Poor's S&P 500 index, focusing
on small deviations from long-term index trends. Such up-and-
down blips in stock prices are usually "Gaussian," or "normally"
random, at least when measured over sufficiently long time
scales -- for example, for more than one day. That means that
fluctuations are likely to be small, while larger fluctuations
are less likely, their probabilities following a bell curve. the
team looked at 2-month periods surrounding major crashes such as
the Black Monday event of October 19, 1987, they saw a different
story: Fluctuations of all magnitudes were equally probable. As
a consequence, the graph of index fluctuations looked
statistically similar if plotted over different time scales,
anywhere between time sca