Nuwanthika Fernando is an astronomy guide at Sydney Observatory, and studies the dynamics of satellite galaxy planes for her PhD at the University of Sydney.

During a recent conference visit to the Astronomical Observatory of Capodimonte in Naples, Italy, I was lucky enough to catch a glimpse of a book that created a true paradigm shift in the way we think. The carefully preserved first edition print of Nicolaus Copernicus’ ‘On the Revolutions of Heavenly Spheres’ is 473 years old and valued at just over US$1 million. Its age is not the only reason why it’s so valuable – this is where he introduced the ‘heliocentric’ model of the solar system, where the Earth is taken out of the centre of the solar system to be replaced with the Sun.

Human civilization was already over 5000 years old by the times of Copernicus (1473-1543). We had built pyramids, great walls, explored the world and moved away from the idea of a flat Earth (good news for all those sailors on long voyages – no risk of falling off the edge). But we still thought that the entire universe was ‘geocentric’, or revolved around the Earth. From the ancient Chinese to the Greeks, the mapped heavens were divided into shells with the Earth in the middle. For scholars like Plato and Aristotle watching the Sun, Moon and stars go across the sky there was not enough reason to think otherwise. But, being early scientists, they did notice something odd about the geocentric model. It couldn’t give accurate predictions of positions of some planets. Mercury and Venus showed ‘retrograde motion’, where, for a few days of the year, the planets appear to change direction of travel. This bothered the scientists, but they were reluctant to give up their idea that humans were the center of everything. And truly, if the gods made the earth for us, why shouldn’t we be the center of all things?

Many scientific advances emerge by someone questioning problems in the status quo, and Aristarchus of Samos (310-230 BCE) was one such person. He was a follower of an earlier scholar named Philolaus (470- 385 BCE), who thought the Earth, Sun and other celestial objects moved around a ‘Central Fire’. Aristarchus’s solution for solving the retrograde motion of the planets and was to place the Sun in the middle. He also thought the stars would move around the Central Fire too. However, some of the most prominent scholars, like Aristotle, dismissed this idea publically, and it remained dismissed in western society for nearly 2000 years.

Enter Copernicus, living in the Kingdom of Poland in the 1500s. Though he was not known as a great mathematician or astronomer during his time, he was good enough to realise that the only way to explain the observations is with a model where the Sun is the centre. It’s known that he was inspired by the works of Aristarchus, borrowed from the books of Plutarch. Though many scientists had attempted to rectify the issues with the geocentric model throughout the centuries, like the Islamic and Hindu scholars who both got close to the idea with partially heliocentric models, a complete leap to a heliocentric system was never accepted. In fact, Tycho Brahe- a famous astronomer of the time- made an updated version of the geocentric model that appeased skeptics and also disregarded the claims of Copernicus. The idea was so contentious that Copernicus’ book was published with a forward that worked as a disclaimer, stating that the presented system was just an idea and might not represent real life. A version of the book was also given to the Vatican and the copy was returned with edits and footnotes that downplayed the significance of the discovery. To justify their edits, the Catholic Church pointed to the Bible, which stated  that the Earth was made to stay still. But, the book was not perceived as a threat to the geocentric model, till Galileo proclaimed the heliocentric solar system a reality, and not just a fantasy. Galileo (Italy, 1564-1642) was already a scientific giant who, among other achievements, had discovered the four largest moons of Jupiter with the aid of a telescope. The Jovian system of moons, and the robust observations and calculations presented by Copernicus convinced him that the heliocentric system made more sense. Due to his vocal objections against the Vatican branding of the heliocentric theory as ‘heresy’ for going against the Bible, Galileo was placed under house arrest and ‘The Heavenly Spheres’ was placed in the ‘Index of Forbidden Books’. Galileo never yielded to the demands of the Church and remained confined to his house for the rest of his life.

The path to the gradual acceptance of heliocentricity was paved by the telescope, a newly discovered instrument that revolutionised our view of the skies. According to Copernicus, with the Sun in the middle and the Earth going around it, we should also see the stars change their position through the years. As stars are significantly further away from us than planets, this apparent motion is almost negligible to the naked eye. But with telescopes, astronomers realised that these tiny specks of light actually do change positions through the years (this discovery was followed by another controversy about how stars can’t possibly be that far way). Although the heliocentric solar system gained scientific support in the late 1600s, it was only in 1785 that Copernicus’ book that lead this revolution was dropped from the Index, and accepted by the Vatican.

So why is this story still relevant? The last event of my conference was a debate on whether the current Standard Model of physics (that describes the Universe) is right or wrong. It works well enough to explain familiar objects like planets, stars and galaxy formation, but we still run into some walls where stuff like Dark Matter and Dark Energy has to be added to make the model match observations. Fortunately, despite a lively conversation between arguing astrophysicists, no one was named a ‘heretic’ or placed under house arrest. Will we figure it out? Sure ! We humans are problem solvers and our curiosity will eventually lead us there. How and when is still up to the brains that will eventually open up hidden doors. It’s also up to all of us to keep an open mind about ideas that challenge our views of space.