Cosmology is the study of the structure and evolution of the universe. Ancient astronomers conducted the first studies of the cosmos by simply observing the nighttime sky without the aid of sophisticated instruments. Ptolemy, building on the work of Aristotle and Hipparchus (second century b.c.), placed the Earth at the center of the "universe" with every other heavenly body revolving in perfect circles about it. This concept remained unchallenged for 1,300 years, in large part because it fit so well with the dogma of the early and medieval Christian era. Nicholas Copernicus challenged ancient cosmology in the sixteenth century when he placed the Sun at the center of the universe rather than the Earth. Copernicus did not at first create a furor; his book was very technical, making it unintelligible to the masses. Copernicus once said he would be extravagantly pleased if he could make his theory agree...