Over 100 years ago Max Abraham and
Hermann Minkowski proposed rival theoretical expressions for the
momentum of light in a medium. Since then a large number of theoretical
and experimental studies have been conducted which have variously
supported one or the other theory. The subject remains controversial to
this day, but the advent of ultracold atoms allows for simple and clean
measurements that may lead to greater clarity. I will discuss this
subject from the perspective of ultracold atoms
and point out some unexpected connections to quite different physics.