Summarizes the development of the Earth's age calculation including the work of Archbishop Ussher, James Hutton, Lord Kelvin, Ernest Rutherford, Bertram Boltwood, and Arthur Holmes. Describes the changes in radioisotope dating methods. (YP)

Intense radiation at microwave frequencies is emitted by certain nebular regions and stellar atmospheres. It is generated by maser action, which does for microwaves what laser action does for light. Describes in detail the types of masers and their action. (Author/MA)

Describes a way to construct from aluminum foil and a tin can a detector of ionizing radiation in the environment. (Author/SA)

Described is a way for an amateur to build a mercury-vapor ion laser which was devised by Dean Morelli. Morelli's laser emits bright pulses of green light and dimmer pulses of red-orange light and is the first gaseous-ion laser. (Author/DS)

Outlines the Cosmic Background Explorer (COBE) mission to measure celestial radiation. Describes the instruments used and experiments involving differential microwave radiometers, and a far infrared absolute spectrophotometer. (YP)

The construction and use of an instrument to monitor ultraviolet radiation from the sun are discussed. A diagram of the ultraviolet-B radiometer which is connected to a digital voltmeter is provided. (CW)