The heliocentric and the geocentric models of the solar system include some central principles. One of these principles is that the speeds of the sun, moon, and stars are perfectly uniform and unchanging. A second principle is that _____?

1. the Earth is at the center of the planets and the sun

2. the sun is at the center of the Earth and the other planets

3. the orbit of a planet around the sun is an ellipse

4. the orbits of the sun, moon, and stars are perfect circles

Ancient Greek philosophers tried to explain the solar system. One of them was Ptolemy an ancient astronomer who gave the "geocentric model" of the solar system considering Earth as the center but later Copernicus in 1543 proposed the heliocentric model of the solar system with Sun at the center.

Both the models share central principles such as:

1. Speed of astronomical bodies- sun, moon and stars are constant.

2. The astronomical bodies- sun, moon and stars move in circular orbits.

Thus, option 4 is the correct answer.