  Ever since the first pulsar was discovered by Bell and Hewish over 40 years
ago, we've known that not only are pulsars fascinating and truly exotic
objects, but that we can use them as powerful tools for basic physics and
astrophysics as well. Taylor and Hulse hammered these views home with their
discovery and timing of the spectacular "binary pulsar" in the 1970s and 1980s.
In the last two decades a host of surprises and a promise of phenomenal
scientific riches in the future has come from the millisecond pulsars. As our
instrumentation has become more sensitive and better suited to measuring the
pulses from these objects, they've given us new tests of general relativity,
fantastic probes of the interstellar medium, constraints on the physics of
ultra-dense matter, new windows into binary and stellar evolution, and the
promise of a direct detection of gravitational waves. These things really are
cool, and there is much more we will do with them in the future.
