The Astronomers

American and Japanese astronomers are followed as they seek to measure cosmic background radiation, the heat remaining from the Big Bang, by launching rockets and satellites above the Earth's atmosphere. Their results contribute to research into the origins of the universe. Also shown are two astonomers who are mapping the universe in 3D and discovering that galaxies have formed into gigantic groups.

Gravity waves, as yet undetected but predicted by Albert Einstein, may contain the answers to many questions about the universe. Soviet scientist Leonid Grishchuk and American scientist Kip Thorne describe their attempts to prove the existence of the waves. The episode also visits a gravity-wave detector prototype and describes the three-mile-long full-scale version, planned for construction in the late 1990's. Grishchuk and scientist Stephen Hawking meet.

The deaths of stars allow human lives to come into being. This episode explains how and looks at the complete life cycle of the stars that make up our galaxy. Two American scientists are shown researching the forces that bring gas and dust together with such intense pressure that nuclear fusion results and a star is born. Hans Bethe, the first scientist to explain in detail how stars are fueled, appears. Three Australian scientists look into the death of a star by studying the remains of the supernova explosion of 1987.

Efforts to discover other planetary systems and to learn more about the planets of our own solar system are examined. Images are shown that have been sent back to Earth by Voyager, the space probe exploring the outer edges of the solar system.