Observing, interpreting and understanding celestial bodies and their movement in space like the galaxies and constellations, were not easy in the ancient era, but astronomers of those times still tried to discover what was out there.
Their efforts were not in vain. Early astronomers were among those who actually recognised the power of mathematics in explaining nature. It was a great discovery for the scientific world, that the motions of the Earth and other celestial objects in space could be explained by the laws of mathematics.
This article discusses four important scientific personalities who lived in Europe during the 15th and 16th centuries, and their crucial discoveries about space and the movements of the Earth. They were Nicolaus Copernicus, who introduced the sun-centred solar system model; Tycho Brahe, who introduced outstanding astronomical observation instruments; Johannes Kepler, who made crucial discoveries about the orbits of the planets; and Galileo Galilei who pioneered the concept of experimental science.
The Earth was considered a place of change at that time, a planet stationed at the centre of the universe. The stars and other objects seen above the Earth were believed to be a perfect world with no change, a place that was consistent with the view of heaven. The people of that time thought that all the objects up there were perfect spheres moving in circular orbits.
It was through the findings of the four astronomers mentioned above that such misconceptions about the position of the Earth in the universe and perspectives on the motions of the Earth changed.
Nicolaus Copernicus (1473-1543)
Nicolaus Copernicus, trained in theology, and worked for Christian churches for half a century. Yet, for some reason, he devoted much of his life to shaping the mathematical model of the solar system centred on the Sun (heliocentrism).
Copernicus put forward a model that contradicted Ptolemy’s model. The people of that time had already subscribed to Ptolemy’s model, in which the earth was considered to be the centre of the solar system. The Christian churches supported the earth-centric model. Copernicus studied at the University of Krakow. Later he went to Italy and got trained in medicine and law – all this was meant to be of benefit in his religious profession.
Copernicus’ discovery contradicted Ptolemy’s model of the solar system. In the Earth-centred model, Ptolemy had considered circular orbits. Copernicus concluded that the Earth rotated on its own axis once a day.
He had a habit of recording the positions of the stars and the Moon. His earliest manuscripts on the sun-centred (heliocentric) solar system became popular as early as 1514,, but he did not add the name Copernicus in any of them. In fact, he did not get any recognition for this theory at that time. The reality is that this model of the solar system, which caused much controversy, was not published until after his death in 1543.
Copernican model of solar system
Copernicus’s model of the rotation of spherical bodies in the universe was quite innovative. He discovered that the Earth and other planets orbited the sun while the moon orbited the Earth.
Copernicus’ discovery contradicted Ptolemy’s model of the solar system. In the Earth-centred model, Ptolemy had considered circular orbits. Copernicus concluded that the Earth rotated on its own axis once a day. He suggested that it took the Earth one year to complete one revolution around the Sun. Copernicus’s model was also able to explain the retrograde motion of Mars and some other planets.
However, the model of Copernicus was also based on circular orbits. The complexities of Ptolemy’s model were present in this model as well. In both models, there were epicycles and strange orbits within a circular orbit. Certainly, doubts must have been raised at that time as to which of these were correct.
Copernicus’ model made a few more simple predictions about the positions of the planets. That was the main reason why this model was later widely accepted.
Tycho Brahe (1546-1601)
Tycho Brahe, the Danish astronomer, was assigned to determine the correctness of Copernicus’s solar system model. He was one of the pioneers in the field of astronomy, having designed and built top-class astronomical instruments. Improved and more accurate observation of the sky was made possible by the equipment he built.
The King of Denmark, Frederick II, was a staunch supporter of Tycho’s astronomical research.
Tycho’s contributions
From the age of 27, Tycho began to gain prominence in the field of astronomy with the discovery of a bright star (Supernova). Supernovae are large explosions of stars. Tycho spotted the supernova in the constellation Cassiopeiae. For 18 months, Tycho watched the star closely. Its brightness had diminished.
According to Tycho, the models of Ptolemy and Copernicus did not accurately predict the position of Mars, so he made his own solar-system model, called the Tychonic system.
Tycho discovered things that surprised those who lived at that time. In his opinion, the notion that the objects we see in the sky do not change was wrong. His discovery that celestial objects do change made him famous. The King of Denmark and the King of Norway showered on him rewards and recognition. They built for him a palace on Haven Island, an observatory, and workshops to make aerial surveillance equipment.
Tycho spent the next 20 years on that island, where he did a lot of astronomical research. He tested the solar system models of Ptolemy and Copernicus to see if they were accurate. There were no telescopes at that time. All observations were made with the naked eye.
At the same time, there were some other instruments called Mural Quadrants. One of Tycho’s greatest contributions to science was the design of brass Mural Quadrants that helped determine the positions of planets and stars. Astronomical data recorded by Tycho over a period of two decades pointed out the inaccuracies in the models of Ptolemy and Copernicus.
According to Tycho, the models of Ptolemy and Copernicus did not accurately predict the position of Mars, so he made his own solar-system model, called the Tychonic system. It was a model of the Sun, Moon and other stars orbiting the Earth, but the other planets orbited the Sun. Here, too, the orbits were completely circular. There were also epicycles. In short, the Tycho model did not differ much from its predecessors’ models, and so it went unnoticed. However, some of Tycho’s discoveries gave the world some new insights.
We will explore the contributions of Johannes Kepler and Galileo Galilei in the coming article.
Now put on your thinking hats and think about the following questions for a couple of minutes.
How would you describe the term “heliocentric” to your students?
Can you think of how Copernican model of solar system differed from Ptolemy's model?
How would you describe the contributions of Nicolas Copernicus and Tycho Brahe in the field of astronomy?
Write down your thoughts and discuss them with your students, children and your colleagues. Listen to their views and compare them with your own. As you listen to others, note how similar or different your views are to others’.
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Happy Teaching!
Geniuses Who Revolutionised Astronomy– Part 1