Copernicus and the Copernican Revolution

COPERNICUS AND THE COPERNICAN REVOLUTION

Things in astronomy were relatively stagnant after Ptolemy and the Ptolemaic theory was the official Roman Catholic Church doctrine for many centuries until the time of Copernicus, who lived from 1473 to 1543 in Poland. He is credited with reinventing the heliocentric theory of the solar system and was successful in doing this, largely because he published his data and because it came at a time when the Church’s influence on Northern Europe was weaker.

This was when physicists were discovering things like inertia in movement, which could not be explained if the earth did not move. In addition, the idea that the Earth rotated was a better explanation for the apparent diurnal motion of the stars. The heliocentric theory also did not require so much effort to explain the phenomenon of retrograde motion of the planets. This shift to heliocentrism was called the Copernican revolution.

Copernicus believed that the earth was just the center of the local gravity we experience and was the center of gravity for the Moon as well. The also proposed that the Sun was the center of our solar system and that all of the planets rotated around it. This meant that retrograde motion was caused by the earth’s orbit rather than any true planetary motion change.

One of the mistakes that Copernicus made was that he assumed that the rotation of the planets were completely circular, when they are in fact elliptical. He also needed to use some creative mathematics to explain the phenomena seen when circular motion is assumed. He needed to produce complicated tables to explain his theories and didn’t put the entire thing together until his final work was published while he lay dying, called “On the Revolutions of the Heavenly Spheres”. He ultimately did have to use the concept of epicycles and deferents to explain the thing he noted.

Based on Copernican theory, with the sun as the center of the solar system, the planets were now arranged in the way they are known to be: Mercury, Venus, Earth and its Moon, Mars, Jupiter, and Saturn, which are not all of the known planets because Uranus had not been identified at the time. The stars were felt not to be a part of the

solar system at all and do not rotate anywhere in relation to it. The earth was felt to rotate once in 24 hours so that retrograde motion was just an illusion.

Retrograde motion and the new order of the way planets rotate could explain why some planets seem brighter at some times and not as bright at other times. When they are further from us, the planets will seem dimmer. In addition, retrograde motion was explainable using geometric principles.

Even though the rotation of earth explained epicycles, he could not get around using them anyway. This was because he couldn’t get past the “perfect circle” revolution theory. Because he thought the planetary revolutions around the sun were perfect circles, epicycles had to be used to justify the different phenomena seen.

The Copernican revolution happened largely after Copernicus died. It is believed that he did not publish his book until he was on his deathbed because of the fear of retribution by the Church he faced. The Church at the time still believed in Aristotle and in Ptolemy so it was a huge thing to challenge these long-held belief systems.

Besides the issue of heliocentrism and circular versus elliptical orbits, Copernicus had to decide if the planets were made of the same basic stuff that makes up planet earth. Prior to this, it was thought that the other planets were made of some type of special or different substances than earth so this needed to be challenged as well.

While Copernicus was able to make his ideas stick, they weren’t much different from the heliocentric concepts put forth by Aristarchus on the island of Samos off of Turkey. He believed in the rotation of the earth as well as is rotation around the sun itself in 200 BCE. Most of his writings were either lost or discounted by the influence of Aristotle.

There were some “commonsense” issues he couldn’t explain based on what he knew. He couldn’t explain why things didn’t fly off of earth as it spun around or why birds didn’t just get left behind as it moved around the sun. He also didn’t understand why there wasn’t a parallax effect. The reason there is no parallax effect with the stars is that they are so far away that it just isn’t something that can be easily seen. There is a parallax effect but it isn’t big enough to notice. These were the main reasons why Aristarchus was not believed.