Daniel Gillespie

Who is Daniel Gillespie?

Daniel Thomas Gillespie is a physicist who is best known for his derivation in 1976 of the stochastic simulation algorithm, also called the Gillespie algorithm. The SSA is a procedure for numerically simulating the time evolution of the molecular populations in a chemically reacting system in a way that takes account of the fact that molecules react in whole numbers and in an essentially random way. Since the late 1990s, the SSA has been widely used to simulate chemical reactions inside living cells, where the small molecular counts of some reactant species often invalidate the differential equations of traditional deterministic chemical kinetics.

Gillespie's original derivation of the SSA began by considering how chemical reactions actually occur in a well-stirred dilute gas. Reasoning from physics, he showed that the probability that a specific reaction will occur in the next very small time dt could be written as an explicit function of the current species populations multiplied by dt.