Galileo Galilei of her life. Vincenzo was later legitimised as the legal heir of Galileo and married Sestilia Bocchineri. Although Galileo seriously considered the priesthood as a young man, at his father's urging he instead enrolled in 1580 at the University of Pisa for a medical degree. In 1581, when he was studying medicine, he noticed a swinging chandelier, which air currents shifted about to swing in larger and smaller arcs. To him, it seemed, by comparison with his heartbeat, that the chandelier took the same amount of time to swing back and forth, no matter how far it was swinging. When
Galileo Galilei of a star of first magnitude to be no more than 5 arcseconds, and that of one of sixth magnitude to be about / arcseconds. Like most astronomers of his day, Galileo did not recognise that the apparent sizes of stars that he measured were spurious, caused by diffraction and atmospheric distortion (see seeing disk or Airy disk), and did not represent the true sizes of stars. However, Galileo's values were much smaller than previous estimates of the apparent sizes of the brightest stars, such as those made by Tycho Brahe (see Magnitude) and enabled Galileo to counter anti-Copernican arguments