The ancient Greeks proved over 2,000 years ago that the Earth was round and figured out how big it was by using simple observations of the Sun. But how do people know this today? When you drop ...

The International Astronomical Union (IAU) defined a dwarf planet in 2006 as a celestial body that orbits the Sun, is round in shape, but has not cleared its orbital neighborhood of objects of ...

This article was originally published at The Conversation. The publication contributed the article to Space.com's Expert Voices: Op-Ed & Insights. Brad Gibson, Director of the E.A. Milne Centre for ...

Swinburne University of Technology provides funding as a member of The Conversation AU. Our Solar System is a pretty busy place. There are millions of objects moving around – everything from planets, ...

How far it is from the sun: 886 million miles (1.4 billion kilometers), on average How big it is: 72,400 miles (116,500 km) across, or almost 10 times the size of Earth. How many moons it has: At ...