Changing Views about the Universe (Part I)
MANILA, Philippines - From the time of Claudius Ptolemy, a Greco-Egyptian astronomer, who published his famous astronomical encyclopedia, the Almagest, in 140 AD, humans faithfully believed in his theory of the system of movement of heavenly bodies. The Ptolemaic system was based on the theory that a stationary earth was at the center of the universe, while the sun, moon, planets, and stars revolved around it. The Ptolemaic system endured and remained unchallenged for more than 14 centuries up through the entire Middle Ages.
In 1543, Nicholas Copernicus, a Polish astronomer, was the first ever to challenge the Ptolemaic concept of an earth-centered universe and turned it around into a sun-centered theory. But this revolutionary idea was not readily accepted until sometime at the turn of the next century. It was Galileo Galilei (1564-1642), the Italian astronomer, who confirmed the Copernican sun-centered concept of our solar system through his telescopic observations of the heavens. But Galileo's radical pronouncements in support of the Copernican theory were viewed as heretical by the Inquisition and he was forced to abandon all his astronomical studies.
After Galileo, another great astronomer-mathematician, Isaac Newton, was the first to figure out the nature of planetary movements around the sun and he came forth with a scientific explanation. Newton postulated the theory of universal gravitation which he articulated in a treatise, "The Laws of Motion and Gravitation," published in 1687. It predicted the motions of the sun, the moon, and the planets with a high degree of accuracy. Newton was a professor of mathematics in Cambridge University and a member of the prestigious Royal Society.
In the following 18th and 19th centuries, the prevailing thought among astronomers was that our galaxy, the Milky Way, constituted the entire universe. The astronomers did not know what lay beyond our galaxy. It was the consensus that the universe was static or fixed and eternal.
The 20th century was the golden age for astrophysics. It had two intellectual pillars. Albert Einstein, a theoretical physicist, came out with the "theory of relativity," published in 1916. Einstein's relativity theory revolutionized humans' thinking and views about the cosmos. Then, Edwin Hubble, a well respected astronomer, made two landmark discoveries in the 1920s. Following up on the idea that other galaxies existed beyond our own as theorized by three earlier astronomers, Hubble proved beyond doubt the reality of galaxies. Using the most powerful telescope at the time at Mt. …