Balthasar van der Pol (1889-1959) was a Dutch physicist, Engineer and mathematician famous for the non-linear van der Pol equation. The differential equations of coupled electrical systems drew his interest, and he developed the idea of " relaxation oscillation". With J. van der Mark he applied the idea to the heartbeat, which provided one of the earliest quantative models of the action potential. Van der pol was born on this day (January 27) in 1889.
