‘Hairy Ball Theorem’ (Topology)
1. “You can’t comb the hairs on a coconut.”
2. “There exists a calm point on earth where there is no wind.”
Both 1 & 2 are ‘Hairy Ball Theorem’.
If we have a ball with hairs sticking out from each point on it, then impossible to comb the hairs flat with a continuous movement without leaving at least one hair sticking up vertically (typically, at the center of a swirl). Not applicable to doughnut.
=> Wind pattern:
Ball = Earth
Combed down hairs = wind
Length of hairs = wind’s force
=> there must be a place on Earth where there is no wind at all.