February 19 – A System Is Born

Today’s Factismal: Nicolas Copernicus, the father of modern astronomy, was born 541 years ago.

If you look at the sky, it is very easy to see why some people thought that the universe revolves around the Earth. Every day, the Sun appears in the East and slowly climbs through the sky until it finally disappears in the West. The Moon and distant stars do the same; up in the East, dance across the heavens and back into bed in the West. Only the “wanderers”, or planets as they came to be known, defied that pattern.

The Solar System as the Greeks saw it

The Solar System as the Greeks saw it

Though some early scientists, such as Philolaus and Aristarchus had proposed that the Earth actually revolved around the Sun, most disagreed. After all, it just made more sense, as long as you ignored those pesky planets. You could have each celestial object be embedded in a transparent sphere centered on the Earth; tomes were written on the exact spacing of the spheres and what musical note each would play. (And you thought that the music of the spheres was just a phrase.) And, if you put each of the wandering planets on a sphere embedded in the principle sphere, you could even almost explain their motion.

The Solar System according to the Romans; this view held for nearly 1,500 years

The Solar System according to the Romans; this view held for nearly 1,500 years

But there is a lot of difference between “almost” and “accurately”. And it was that difference that led Copernicus to derive a system that put the Sun (“Helios” in Greek) at the center of the universe, replacing the Earth (“Geo” in Greek). When Copernicus used his heliocentric (“Sun-centered”) model, he was able to predict where the planets would be much more accurately than the geocentric (“Earth-centered”) model did. Unfortunately, the geocentric model had been accepted for centuries and was considered the equivalent of Holy Writ; anyone disputing it was in for a very bad time indeed. Being a prudent man who did not enjoy the prospect of being visited by the Inquisition, Copernicus waited until he was on his death bed before allowing his ideas to be published.

The Solar System as Copernicus saw it (and Galileo proved)

The Solar System as Copernicus saw it (and Galileo proved)

This clever move allowed his works to be spread further than they would have been if he had faced the Inquisition; it also helped that he had phrased his arguments in such deeply technical language that people who weren’t astronomers had a hard time understanding what his conclusions were. Despite this, Copernicus’ book did eventually make its way onto the official list of banned books. But before that happened, it had lit a fire in the astronomical community. It was read by Tycho Brahe and Galileo, among others, and inspired them to look deeply into the heavens seeking evidence that would either confirm or refute the idea.

Copernicus sees the heavens as they are (Image courtesy Steward Observatory)

Copernicus sees the heavens as they are (Image courtesy Steward Observatory)

Eventually, Galileo would find that confirmation in the phases of Venus and the moons of Jupiter, while Brahe would amass so much data that it would allow Kepler to derive his laws of planetary motion and give Newton the base he needed to show how gravity explained the motions. Today, the search for a better model of the universe goes on, and scientists continue to amass data to help them in their quest. If you’d like to join them, then take a look at the Global Telescope network:
http://gtn.sonoma.edu/

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