The sun-centered model 4

Figure1
Tyco made the same mistake as Ptolemy. He placed the earth in the center, and believed that

the sun orbited around it. The other planets revolved around the sun. Though he suspected the

validity of the sun-centered model, he couldn¡Çt shift the earth-centered paradigm.

Figure 2
Kepler proved that the nearer the earth is to the-sun, the faster it orbits. This conclusion

was deduced from one of his axioms that the planets move in ellipses. If the earth moves in

a perfect circle, the orbiting speed would never change.

Figure 3
If the sun-centered model is true, Venus would show less than half its side. ( in the left).

However, the observation by Galileo ranged from the full shape to no shape. This

contradiction was a serious problem for the sun-centered model.