People in the land of Babylonia Iraq and Syria in modern times created a large city on the banks of the Euphrates River. From roughly to BC, Babylonia grew from a small town to a large city and at last became the capital of an empire. How could they understand the will of the gods to predict what would occur in their future? Astronomy began by serving the Babylonians not as a science but as a part of their religion.
Particular devotion was given to the movements of Jupiter, which they identified with their chief god Marduk , and Venus, associated with Ishtar , their goddess of war and love. The movements of Jupiter, Venus, and the other planets were believed to be messages from the gods rather than the gods themselves and were very important in Babylonian religion. Priests would then perform various rituals, attempting to prevent the disaster.
Because the movements of the planets and stars were so important, Babylonians began to develop an exact science to analyze their positions. They began to examine the same planets and stars in the sky at different times of year and in different places. They created MUL. Babylonia would eventually fall to the Persians in BC and lose its power and independence, but its people would always be fascinated by the stars, and a newer group of scholars in Greece would learn from them.
The Greek scholars brought changes to the study of the stars. They were famous for their schools of higher knowledge, which were rather different from ours. Students would gather around a teacher, perhaps in a beautiful grove, and ask questions and discuss among themselves what might be the answers and the best ways to figure out those answers. Many of today's colleges still aspire to this way of learning. Over the centuries, this model of discovery and debate brought many changes and new discoveries to the study of astronomy.
Thales of Miletus was one of the first great mathematicians of Western civilization and the first BC to successfully predict the timing of an eclipse. Because the telescope had not yet been invented, many early debates centered around heavenly bodies that could easily be seen from Earth and what the structure of the solar system was. Heracleides of Pontus first proposed the concept that the Earth made a daily rotation, although he also believed that the Sun and the other planets orbited the Earth each day.
Aristarchus of Samos was the first Greek philosopher to believe the solar system was organized around the Sun, rather than the Earth. Ptolemy was an astronomer and mathematician. He believed that the Earth was the center of the Universe. The word for Earth in Greek is geo, so we call this idea a "geocentric" theory. Even starting with this incorrect theory, he was able to combine what he saw of the stars' movements with mathematics, especially geometry, to predict the movements of the planets.
His famous work was called the Almagest. To make his predictions true, he decided that the planets must move in epicycles smaller circles and the Earth itself moved along an equant. None of this was true, but it made the math work for his predictions. This flawed view of the Universe was accepted for many centuries. He is sometimes called the grandfather of science. He, too, believed in a geocentric Universe and that the planets and stars were perfect spheres, though Earth itself was not.
He further thought that the movements of the planets and stars must be circular since they were perfect and, if the motions were circular, then they could go on forever.
Today, we know that none of this is the case, but Aristotle was so respected that these wrong answers were taught for a very long time. Outside of astronomy, Aristotle was a champion observer. He was one of the first to study plants, animals, and people in a scientific way, and he did believe in experimenting whenever possible and developed logical ways of thinking.
This is a critical legacy for all the scientists who followed him. Another Greek, Eratosthenes c. He is also known as the Father of Geography. You can read more about him in Measuring the Earth. People across the Western world had little time for the deep thought and theory they once did, and interest in astronomy was lost in many places.
For more than a thousand years, astronomy had been based on the Ptolemaic, or Geocentric Model of the Universe, which stated that the Earth was the center of all creation, with the Sun, planets, and stars all orbiting it. Copernicus studied law and medicine at the Universities of Bologna and Padua, then returned to Poland after witnessing a lunar eclipse in Rome in In he went back to Italy for further studies at the Universities of Padua and Ferrara and received a doctorate in canon law from the later in It was in this period that he probably read ancient Greek theories on the movement of the Earth through the heavens, including some writings that espoused a heliocentric view that all of the planets, including the Earth, orbited the Sun.
This was in direct contradiction of the teachings of the Catholic Church, which espoused the Ptolemaic view of the Universe. In , Copernicus began the research that culminated in his heliocentric theory. In his new position, he was able to devote more time to his study of astronomy and had an observatory built in one of the towers in the town wall. Until just before his death, Copernicus conducted most of his astronomical observations and calculations there, usually working alone.
In , he distributed a hand-written, unpublished manuscript entitled the Little Commentary that included the following axioms:. However, he spent most of his time studying mathematics and astronomy. Due to his uncle's influence, Copernicus did become a canon in Warmia, but he asked to return to Italy to study medicine and to complete his law doctorate.
Of course, he may also have been thinking that the skies above Italy were clearer than above Warmia, according to Famous Scientists. While attending the University of Bologna, he lived and worked with astronomy professor Domenico Maria de Novara, doing research and helping him make observations of the heavens.
Copernicus never took orders as a priest, but instead continued to work as a secretary and physician for his uncle in Warmia. When he returned to Poland to take up his official duties, his room in one of the towers surrounding the town boasted an observatory, giving him ample time and opportunity to study the night sky, which he did in his spare time. In Copernicus' lifetime, most believed that Earth held its place at the center of the universe.
The sun, the stars, and all of the planets revolved around it. One of the glaring mathematical problems with this model was that the planets, on occasion, would travel backward across the sky over several nights of observation. Astronomers called this retrograde motion. To account for it, the current model, based on the Greek astronomer and mathematician Ptolemy's view, incorporated a number of circles within circles — epicycles — inside of a planet's path. Some planets required as many as seven circles, creating a cumbersome model many felt was too complicated to have naturally occurred.
In , Copernicus distributed a handwritten book to his friends that set out his view of the universe. In it, he proposed that the center of the universe was not Earth, but that the sun lay near it. He also suggested that Earth's rotation accounted for the rise and setting of the sun, the movement of the stars, and that the cycle of seasons was caused by Earth's revolutions around it.
Finally, he correctly proposed that Earth's motion through space caused the retrograde motion of the planets across the night sky planets sometimes move in the same directions as stars, slowly across the sky from night to night, but sometimes they move in the opposite, or retrograde, direction. In it, Copernicus established that the planets orbited the sun rather than the Earth. He laid out his model of the solar system and the path of the planets.
He didn't publish the book, however, until , just two months before he died.
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