The Universe _______________________________________________________________________________________________________________________________________________________________________________________________________________________
8. Geocentric and Heliocentric models of the Universe
Figure 10.4 The Geocentric UniverseCertainly no one today doubts that Earth orbits a star, the Sun.
Photos taken from space, observations made by astronauts, and the fact that there has been so much successful space exploration that depends on understanding the structure of the solar system all confirm it.
But in the early 17th century saying that Earth orbited the Sun rather than the reverse could get you tried for heresy, as it did Galileo.
Let’s explore the evolution of the idea that Earth orbits the Sun.
The Geocentic Universe
To an observer, Earth appears to be the centre of the universe.
That is what the ancient Greeks believed. This view is called the geocentric model, or "Earth-centered" model, of the Universe.
In the geocentric model, the sky, or heavens, are a set of spheres layered on top of one another.