Narrator: Serious scientists, like myself, believe our solar system was formed by the ... This theory was known as the heliocentric model. It was controversial as accepted wisdom at the time ...

Finding physical evidence that our planet revolves around the Sun took some clever thinking to prove that this heliocentric model of our solar system represents reality. The idea is ancient.

The Oort cloud is traditionally thought of as a vast shell of perhaps trillions of icy objects encasing our solar system ... spiral arms of our galaxy. At a heliocentric distance ranging from ...

TIMHi, I'm Tim Peake. I'm an astronaut based here at the European Space Agency in Germany, and from December 2015, to June 2016, I spent six months orbiting Earth on the International Space Station.