  We review the Mpemba effect, where intially hot water freezes faster than
initially cold water. While the effect appears impossible at first sight, it
has been seen in numerous experiments, was reported on by Aristotle, Francis
Bacon, and Descartes, and has been well-known as folklore around the world. It
has a rich and fascinating history, which culminates in the dramatic story of
the secondary school student, Erasto Mpemba, who reintroduced the effect to the
twentieth century scientific community. The phenomenon, while simple to
describe, is deceptively complex, and illustrates numerous important issues
about the scientific method: the role of skepticism in scientific inquiry, the
influence of theory on experiment and observation, the need for precision in
the statement of a scientific hypothesis, and the nature of falsifiability. We
survey proposed theoretical mechanisms for the Mpemba effect, and the results
of modern experiments on the phenomenon. Studies of the observation that hot
water pipes are more likely to burst than cold water pipes are also described.
