The word ‘Copernicanism’ refers to the fundamental theoretical basis of modern astronomy, first revealed in the early 16th century by a mathematician Nicolaus Copernicus. He formulated a model of the Universe showing that Earth and other planet revolves around the motionless Sun.
The astronomical model named Copernican Heliocentrism was published in 1543, positioning the Sun near the center of the Universe, with Earth and other planets revolving around it in circular orbits.
Although the model was not entirely correct, it built a strong foundation for future astronomers to work on and enhance human understanding of how celestial bodies move. Using this model, other scientists did prove that our planet is orbiting the Sun and we are far from the center of the universe.
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Medieval Astronomy: The Ptolemaic Model
Although the ancient Greeks were great philosophers and good at mapping the motion of planets and stars, they developed models of the universe that were more influenced by religious, philosophical and aesthetic considerations than by observations and experiments. It also pleased religious people living the Christian era because it gave pride of place to human beings – God’s special creation.
Ptolemaic system | Image credit: Pearson Scott Foresman
Prior to Copernican Heliocentrism, the Ptolemaic system had prevailed for centuries (up to the 16th century). This geocentric model was built on numerous previous theories that considered Earth as a motionless center of the universe.
The small circle is epicycle and the larger one is deferent
In this model, planets were confined in smaller spheres (one sphere for each planet), while stars were scattered in a large outer sphere, which rotated relatively faster. To take care of anomalies like a planet’s apparent retrograde motion, the model assumed that each planet revolved in a small sphere (called epicycle), which itself revolved in a larger sphere (called deferent).
Nicolaus Copernicus presented a practical alternative to the Ptolemaic system by more accurately calculating the duration of the solar year. He retained many Ptolemaic components that caused inaccuracies, including planet’s uniform speeds, disc-shaped orbits, and epicycles.
However, at the same time he introduced numerous revolutionary elements:
- Earth and many other planets are orbiting the stationary Sun in a specific manner.
- The Sun is not exactly in the center of the Universe, but near it.
- Earth has 3 motions – annual tilting of its axis, annual revolution, and daily rotation.
- Mercury, Venus, Earth, Mars, Jupiter, and Saturn (in this particular order) are revolving around the Sun in a circular orbit.
- There are many stationary stars that lie farther away from the Sun.
Heliocentric model developed by Nicolaus Copernicus
Both stars and planets often move in the same directions across the sky from night to night. However, sometimes you see them moving in the opposite direction. The Copernican model revealed that Earth’s motion causes this retrograde motion of the planets throughout the sky.
In 1532, Copernicus explained these theories in his first book “De Revolutionibus Orbium Coelestium”. However, the book wasn’t published until 1543 (2 months before this death). The Catholic Church banned the book in 1616 but a few years later, they ended the ban citing that Copernicus’s views are entirely hypothetical.
Title page of the book, 1556
Only Copernicus is praised for introducing the concept of heliocentrism. This is, however, not completely true: many Islamic scholars and ancient Greeks from different cultures presented similar theories centuries earlier.
For instance, an ancient Greek mathematician and astronomer, Aristarchus of Samos, unveiled the first known heliocentric model in the 200s BCE.
Copernicus was aware of the contributions made by earlier astronomers and he did mention those names in this book. But he later decided to remove those credits, before submitting the manuscript for publication. This fact didn’t come to light for another three centuries.
Galileo Got Punished For Supporting Copernican Model
From publication until the beginning of the 18th century, some scientists were convinced by the Copernican model. One of them was a great astronomer and physicist, Galileo Galilei. He invented his own telescope and observed:
- The Sun’s rotation about a stationary axis.
- 4 large moons of Jupiter – a proof that there exist bodies in the Solar System that do not revolve around Earth.
- Different phases of Venus – evidence that wasn’t clearly explained by the Ptolemaic model.
Galileo’s championing of Copernicanism and heliocentrism was controversial during his lifetime. He supported heliocentrism and defended his perspective in his book “Dialogue Concerning the Two Chief World Systems” published in 1632, where he compared the Copernican system with the Ptolemaic system.
However, the Church convicted Galileo of ‘strong suspicion of heresy’ for agreeing with Copernicus’s theory and forced him to recant his beliefs. After one day of formal imprisonment, he spent the rest of his life under house arrest.
Wider Acceptance Of Heliocentrism
Further discoveries in the 17th century resulted in wider acceptance of Copernicus’s theory. For instance,
- In 1609, a German astronomer Johannes Kepler presented a theory stating that orbits of the planets in the solar system are elliptical (instead of circular), while supporting the Copernican model.
- In 1639, an Italian astronomer observed the phases of Mercury, using his telescope. His observations showed that planets revolve around the Sun.
- Kepler’s law of elliptical planetary orbits was further supported by Isaac Newton’s universal gravity and the inverse-square law.
Lesser Known Facts About Nicolaus Copernicus
He observed other planets: With small errors of arc, Copernicus made 3 observations of Mercury and 12 observations of Mars, Jupiter, and Saturn (4 of each planet).
Chemical element named after him: If you look at the 7th row of the periodic table, you will find an element Copernicium (Cn) with atomic number 112. It was named in 2010 to honor the contributions of Copernicus. The known isotopes of Copernicium are extremely radioactive, and the most stable one has a half-life of about 29 seconds.
Remains found: In 2008, archaeologists found a skull near Frombork Cathedral (Copernicus used to work there) that did belong to the astronomer. They confirmed his identity by comparing the skull DNA to hairs found in books once owned by the astronomer. They then used the skull to reconstruct an accurate image of Copernicus. In 2010, Polish clergy buried the astronomer for the 2nd time at Frombork.
Monument: One of the several monuments of Copernicus was built in 1853 in his hometown, Toruń. It presents the astronomer in academic dress. His left hand carries an astrolabe while his right hand’s index finger points to heaven, symbolizing his relationship with astronomy and planetary observations.
Modern View of Copernicus’s Theory
Whether Copernicus’ theories were ‘conservative’ or ‘revolutionary’ has been a subject of debate in the history of science. A Hungarian-British author Arthur Koestler portrayed Nicolaus Copernicus as a coward who didn’t publish his findings because he was afraid of ridicule.
Another American physicist and historian Thomas Kuhn documented that all Copernicus did was ‘relocation’: he assigned a few characteristics to the Sun that was previously attributed to the Earth.
While other historians have disagreed with Kuhn’s view, stating that Kuhn underestimated the work of Copernicus. Given that Copernicus had no experimental proof, it would have been very difficult for him to put forward a new cosmic model relying only on simplicity in geometry.
While his theory physically placed the Sun near the center of the universe (wasn’t correct since the universe has no center), it figuratively removed the focus from Earth, making it just another planet in the universe.