ASTB03 – Assignment 2 – Copernicus

copernicusNicolaus Copernicus (Mikolaj Kopernik) was born in Torun, Poland. In his early life he had studied mathematics,
but later became interested in astronomy as well. While studying astronomy, he would eventually write Commentariolus
where he would explain his reasoning behind his belief of the heliocentric model. He also wrote De revolutionibus orbium
coelestium, which was banned by the catholic church because it was contrary to what was believed at the time. Some of his most important findings was that the earth spun on it’s axis, and that there was a large distance to the background stars, which was why they appear motionless; the earth actually orbited the sun and was not the centre of the universe, and that the sun was “motionless” at the centre of the planetary system.

One of the counter arguments to the earth spinning around it’s axis was that there would always be high winds
from east to west due to it’s rotation. Copernicus, however, said that as long as the air rotated in the same
direction and at the same speed as the earths rotation, then there would be no constant high winds. He noted that
the earths roation is what made the stars look like they moved

He also said that the distance that the earth travelled was only a fraction of the distance to the stars in the sky,
and thus the movement of those stars couldn’t be measured. This explained why those stars were “motionless” in the sky.
Motionless meaning that the positions of the stars did not change.

This stellar parallax argument is what critics tried to use as a counter example to the earth rotating around the
sun. They felt that if it were true, then the universe would be too large. Also, by having the earth rotate the sun,
the retrograde motion of some of the planets could be explained by saying that the retrograde appearence was a result
of the earth passing that planet. This made for a much simpler model than Ptolemy’s model and got rid of the need
for the epicycles used to explain the planets movements in the geocentric model.

Copernicus was also able to explain the varying brightness of the planets by placing the sun at the centre of
his system. In his model, since the earth is not at the centre, the other planets end up being different distances
away from the earth, which in turn causes the different brightness. If the earth had been at the centre, then the
brightness of the planets would not vary as much.

For these reasons, Copernicus felt that the geocentric model which was the commonly accepted model at the time, was
not correct, and that the heliocentric model, with the sun at the centre of the “universe” was the correct model.

While Copernicus was the first person to provide a model of a heliocentric model, he was not the first to have the
idea that the earth was not at the centre of the “universe”. Greek philosopher Pythagoras believed that the earth
“travelled around the sun”. Heracleides was another Greek philosopher, who figured out that Mercury and Venus rotated
around the sun. Aristarchus was a Greek astronomer who believed that the earth rotated on it’s axis and around the
sun, and also calculated sizes for the sun and the moon.

In my opinion, I feel that Copernicus’ most important statement was that the sun was at the centre of the planetary
system, and not the earth. While there were others that had this thought before him, none were able to really convince
anyone at the time that the earth was not at the centre. Copernicus managed to convince a few others with his models,
and while there were still many critics, his ideas would eventuall lead to the heliocentric model becoming the accepted
model over the geocentric one. It is also important because of the time in which Copernicus lived. Since the church
and many scholars at the time supported the geocentric system, it would’ve been very difficult to convince them
otherwise, but Copernicus’ models gave better explainations of how the planets and distant stars behaved, which in turn
laid the groundwork leading to the change from the geocentric belief to the heliocentric belief.

While he died before the heliocentric model became truly accepted, his findings would help in paving the way for
ancient astronomy to move forward.

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