Footnotes for "Scientists Put the Deep Freeze on Light"

1A microkelvin is 10-6 Kelvins.

2A nanokelvin is 10-9 Kelvins.

3Cryogenics is the science of low temperatures.

4A photon is a "particle" of light. Due to quantum mechanics, light of a particular color comes in packets of fixed energy called photons.

5One centimeter per second is about a half an inch a second.

6A millikelvin is 10-3 Kelvins.

7Evaporation is the process in which the constituents of a substance -- usually atoms or molecules -- exit from the surface of a substance into the surroundings. Because the more energetic constituents are more likely to escape, less energetic constituents are left behind thereby cooling the substance. All of us are familiar with evaporative cooling -- water in perspiration evaporates to keep our skin cool.

8A bound state consists of two or more particles tied together by attractive forces.

9A neutron star is the dead remains of a star that has exploded as a supernova. A typical neutron star is sphere with a radius of about 10 miles having a mass of about the Sun. A neutron star is like a giant, incredibly dense, heavy nucleus of mostly neutrons. About 7% of it, however, consists of protons and electrons.