Taylor , Joseph Hooton

(1941–) American astrophysicist

Born in Philadelphia, Taylor was educated at Haverford College, Pennsylvania, and at Harvard, where he gained his PhD in astronomy in 1968. He moved to the University of Massachusetts, Amherst, in 1969 and was appointed professor of astronomy in 1977, a post he held until 1980 when he was elected professor of physics at Princeton.

In 1974 Russell Hulse, a research student of Taylor, while working at the Arecibo Radio Telescope in Puerto Rico, discovered a binary pulsar. The pulsar orbited its invisible companion with a period of 7.75 hours, and rotated about its axis every 0.05903 seconds. Taylor and Hulse continued to observe the pulsar and to establish the details of its orbital behavior as precisely as possible.

Taylor also saw that the pulsar could provide an important observational test of Einstein's theory of general relativity. In 1916 Einstein had argued that an accelerating mass should radiate energy in the form of gravitational waves. Any such energy radiated by Hulse's pulsar, 16,000 light years away, would be so weak by the time it reached Earth as to be undetectable. In fact, so far no direct reproducible evidence has been obtained for the existence of gravitational waves, despite the experiments of Joseph Weber carried out since the 1960s.

Taylor realized there was another way for the gravitational waves to be detected. Any system radiating gravitational waves will be losing energy. This loss of energy will cause the pulsar and its companion to approach closer to each other and a consequent decrease in the pulsar's orbital period. The orbital shrinkage would amount to only 3.5 meters a year, too small to be detected; a decrease of 75 millionth of a second per year in the orbital period, however, should be detectable. After four years careful observation and analysis Taylor announced in 1978 that he had detected just such a decrease in the orbital period. “Hence 66 years after Einstein predicted the existence of gravitational waves,” Taylor concluded, “an experiment has been done that yields clear evidence for their existence.” For his discovery of this evidence Taylor shared the 1993 Nobel Prize for physics with Hulse.