In the Seventeenth Century, the Italian scientist and philosopher Galileo Galilei came under fire from the Catholic Church for his views on astronomy. In his treatise, Sidereus Nuncius (The Starry Messenger), he wrote about the observations he made regarding moons of Jupiter, sunspots and the phases of Venus. These findings supported Copernicus's theories and were in direct opposition to the Church's teachings that everything revolved around Earth.

Who was Galileo?

Galileo Galilei was a Sixteenth and Seventeenth Century scientist and philosopher whose achievements include the invention of the telescope which he used in observing the Sun, the Moon, and various planets like Jupiter and Venus. Because of the telescope, Galileo was able to observe sunspots, how the Moon interacted with Earthly tides, and that Earth orbited around the Sun instead of the other way around. Up until then, the Aristotelian view of geocentrism (everything revolves around Earth) was the model that the Catholic Church used. Then Galileo showed that Copernicus' model of heliocentrism (everything revolves around the Sun) was the correct one to use.

Heliocentrism and Geocentrism

Geocentrism is the belief that the Earth remains stationary and that all heavenly bodies operate in orbit around it. Opposite to that is heliocentrism which states that the Sun is the center of the universe and acts as an anchor to all that orbit around it. The first model of geocentrism was proposed in Ancient Greece by Anaximander and further supported by Plato and Aristotle. They theorized that because they could see the sun and stars moving each day that the earth must be stationary.

However, in the Sixteenth Century, the Polish scientist Nicolaus Copernicus introduced heliocentrism; one flaw in his argument was that orbits were circular and it wasn't until Johannes Kepler's work that the heliocentric model stated that they were actually elliptical.

Conflict with the Catholic Church

When Galileo published his treatise that outlined how and why heliocentrism operated, the Catholic Church was fairly incensed. Authorities accused him of heresy and treason, and he was tried by the Roman Inquisition in 1616. Despite his defence of the Copernican model of heliocentrism, he was forced to stand trial in 1633 and found guilty of heresy against the Catholic Church. Galileo was then sentenced to lifetime house arrest and his book that contained his findings, Dialogue, was banned, as was future publication of any and all works by him.

How the Two Views Line Up Today

It wasn't until the Eighteenth Century that the Catholic Church finally ceded to Galileo's view that heliocentrism is the correct model to use in astronomy. They lifted their ban on the publication of books that promoted this view in 1758, but did not take steps to clear Galileo's name until 1820 when they refused to publish books that discredited heliocentrism. Finally, in 2000, Pope John Paul the Second issued a formal apology for Catholic mistakes committed in the last two millenia which included the indictment and imprisonment of Galileo.