Horace Babcock (b.1912), US astronomer. Babcock worked for the most part at the Mount Wilson Observatory with his father, Harold. In 1948 the Babcocks developed equipment capable of measuring the splitting of spectral lines in the light from stars caused by strong magnetic fields (the Zeeman effect). Using their techniques, they were able to determine the strength of the Sun's magnetic field and that of many other stars. They also discovered that the Sun's magnetic polarity flipped periodically. Some of the other stars they studied also turned out to be 'magnetic variables'. Horace Babcock was the director of the Mount Wilson Observatory from 1964 to 1978.