It was 400 years ago when Galileo sparked a transformation of thinking on this planet. What Galileo found immediately astonished him and established the first large step in observational astronomy.
Photo credit: Adam Block and Tim Puckett
He saw that the Milky Way, the luminous band in the night sky, was composed of innumerable stars. He observed the phases of Venus and discovered four little moons orbiting Jupiter. He witnessed sunspots and saw Saturn’s rings, although he mistook them for moons that were poorly resolved. When Galileo observed the Moon, he saw numerous mountain ranges, craters, and other geographical features.
Galileo’s path to greatness was an unusual one. Born in Pisa, Italy, to a musician and music theorist, Galileo considered the priesthood but then enrolled in medical school. Switching to mathematics, he completed his studies and obtained a teaching position at the University of Padua.
At the age of 45, entrenched in his faculty assignments, Galileo stumbled into discoveries that would change the world. The implications of his observations of the phases of Venus were huge, he realized: Ptolemy’s geocentric model of the cosmos, then universally accepted, placed Earth in the center of everything and would not have permitted venusian phases.
By contrast, the heliocentric model proposed by Nicolaus Copernicus would explain the phases of Venus — that both it and Earth orbited the Sun, placed in the cosmic center. The Sun-centered universe was heretical, however. It wasn’t long before Galileo’s discoveries, and his promotion of them, placed him in hot water with the Roman Catholic Church.
Galileo’s initial observations, published in 1610 as
Sidereus Nuncius (“Starry Messenger”), cast a long shadow. In an age when astronomy and astrology were still not quite separate entities, other scientists began observing the sky, discovering and cataloging.
TO BE CONTINUED ...
Links to
Part One and
Part Two