The centre of it all
Each planet was thought to reside in its own ‘heavenly sphere’
1 Middle Earth
According to the geocentric model, Earth was stationary and at the centre of the universe.
2 in orbit
Stars and planets all revolved around the Earth.
3 Far stars
Since the planets appeared to move faster than the stars, the Greeks placed them closer to Earth, with the stars located in the outermost sphere.
4 circling back
All objects in the sky were attached to spherical shells, and therefore followed circular paths around the Earth.
5 Seeing red
Mars’ retrograde motion was particularly problematic for Ptolemy, and his geocentric model failed to accurately predict the Red Planet’s position.
6 speed limit
The geocentric model assumed that all objects obeyed the rules of ‘natural motion’, meaning they orbited around Earth at the same speed.