The Heliocentric Theory

28. The Earth and the planets do not have a motion of their own

Common people confuse true inherent motion with mere movement. They call the motion of a body its movement from one place to another.

This is true. But it is not the same as the motion of the body itself. This is because the body does not move of its own accord.

Instead, it is moved by the motion of its gravitational territory. In the same way, our sky is immediately moved by the motion of the Earth.

Therefore, there is no inherent motion in the Earth or in the other planets.

29. The Earth does not move by itself, even if it and the other planets are seen to move.

Common people set the positions of the stars by thinking that the Earth is immobile.

Then they judge the stars to move as they recede from such positions.

This is convenient and therefore reasonable for the purposes of life.

All of us from childhood have thought that the Earth:

• is flat
• everywhere on it the same up and down, East, West, South, and North—exist

But any philosopher would notice that:

• the Earth is a globe contained in a fluid and mobile space.
• the Sun and fixed stars always keep the same position among themselves

Philosophically, place should not be determined by very distant bodies, such as the fixed stars, but by those contiguous to that which is said to move.

Our mind thinks that the universe is infinite.

If we consider the immensity of God and the weakness of our senses, we can suspect that beyond all those fixed stars are other bodies comparable to the stars and the planets.

30. All planets revolve around the Sun.

The motion of the Earth is similar to the motion of the other planets.

The Earth and the other planets are carried along by a common vortex, with the Sun at its center and move in the motion of the vortex.

If obstructions are placed in the water where rivers flow, the water forms a vortex and carries along with it the obstructions.

• Some of them even turn around their own centers and perform a complete rotation faster than the center of the vortex.

The motion of the planets is always circular.

• But it is rare for them to describe perfect circles.
• Instead, they deviate slightly in longitude and latitude.