[RadioAstronomer]

Thanks for the bump.

[PatrickHenry]

Nesvizhevsky's team took a beam of ultracold neutrons with tiny energies, moving from left to right at less than eight metres per second. Under the force of gravity, the neutrons fell down onto a reflecting mirror and bounced off it before arriving at a detector.

The team could limit the energies of the neutrons arriving at the detector by placing an absorbing material at different heights above the mirror. The material mopped up all the neutrons that bounced too high.

At last, we know why the toast always falls buttered-side down. The butter mops up all the neutrons.