How Do We Know... How Our Solar System Formed?

From our prime position on the third planet out from the Sun, we're finally understanding how our solar neighbourhood came to be.

- Colin Stuart

Asking questions about where we come from is one of the traits that marks us out as distinctly human. Yet this inquisitive streak hasn’t always led us in the right direction, particularly when we think we are more important than we ultimately are. The story of our quest to discover how our Solar System formed is littered with false starts, and one that astronomers are still refining.

The world’s greatest thinkers originally had the Earth at the centre of creation, with the Sun, Moon, planets and stars circling around us. It’s an idea that lasted for more than 1,000 years, dating back to the days of Aristotle and Ancient Greece. It wasn’t until the Polish astronomer and mathematician Nicolaus Copernicus challenged this idea in the 16th Century that the tide of opinion started to shift. He said that the planets – including Earth – orbit around the central Sun. Copernicus was so fearful of the inevitable backlash from religious quarters that he delayed publication of his work until after his death. Legend has it that he only saw a copy on his deathbed.

Galileo! Galileo!

It would take many decades for experimental evidence to confirm that we do indeed live in a ‘solar system’. It was mostly the work of the Italian astronomer Galileo Galilei in the early 1600s that cemented the idea. It wasn’t all plain sailing, of course. Galileo famously had his own run-ins with the Church, and he was only officially pardoned in 1992. But as far as the science was concerned, the clincher came when he observed the planet Venus waxing and waning through phases, much like the Moon. This isn’t possible if both Venus and the Sun orbit around the Earth – only if both planets circle a central source of illumination. So we took our place as just another one of the Sun’s family of planets.