hairy ball
<topology> A result in topology stating that a continuous vector field on
a sphere is always zero somewhere. The name comes from the fact that you can't
flatten all the hair on a hairy ball, like a tennis ball, there will always be a
tuft somewhere (where the tangential projection of the hair is zero). An
immediate corollary to this theorem is that for any continuous map f of the
sphere into itself there is a point x such that f(x)=x or f(x) is the antipode
of x. Another corollary is that at any moment somewhere on the Earth there is no
wind.
(2002-01-07)
Nearby terms:
ha ha only serious « hair « hairy « hairy ball
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