both mathematics and astronomy. Despite his interest in science, he had promised his dying father he would study law. He went to Oxford University as a Rhodes Scholar, graduating in 1912. Having found that legal work did not hold his interest, he dissolved his Kentucky practice soon after he established it. He did retain from his Oxford experience a rather affected English accent and a taste for Savile Row tailoring—clothes made by the finest tailors in London.

Resuming his interrupted study of astronomy, Hubble returned to the University of Chicago. He received his Ph.D. in 1917. After serving in World War I, he obtained a staff position at the Mt. Wilson Observatory in California, where he worked with the 100-inch telescope there. At the time it was the mostpowerful telescope in the world.

It was in studying a type of variable stars called Cepheids that Hubble founded the discipline of extragalactic astronomy. Cepheids are particularly useful objects to observe because the period of their variability is related to their absolute magnitude, or intrinsic brightness. By comparing their absolute magnitude to their brightness as seen from Earth, it is possible to determine their distance. Hubble was able to observe Cepheids within some of the nebulae. These fuzzy objects were assumed to be within our Milky Way galaxy, which was the entirety of the known cosmos. To his surprise, his calculations indicated they were millions of light years away. In fact, he announced in 1924, those nebulae were "island universes," galaxies in their own right.

This was a major paradigm