Question

Which of these statements best explains why Galileo's model of the solar system was different from Ptolemy's model of the solar system?

Different models help make results more reliable.

Different models help find several applications of the results.

Their scientific models were created at different periods in history.

Their scientific interpretations were influenced by their backgrounds.

Answer 1

The third, I guess. Galileo had access to much better obsevational data, both through communication with others, with access to more extensive written records, and most especially through the use of the telescope, which Ptolemy didn't have.

In the time of Ptolemy, the geocentric and heliocentric models were about equally complicated, and each required about the same number of special explanations -- things that the model didn't fit well. For example, the geocentric model needs a special explanation for the retrograde movement of Mars, while the heliocentric model needs a special explanatio for why the stars show no parallax (the closer ones don't move against the night sky as the Earth goes around the Sun).

But that's because Ptolemy only had naked-eye observation that the models needed to fit. By the time of Galileo, there was much more accurate data. To fit this data, the geocentric model had to become much more complicated. But the heliocentric model, particularly with Kepler's insight that the orbits were ellipses, did not. So while Ptolemy had a choice between two equally simple models, Galileo had the choice between a very complex model and a much simpler one. Not surprisingly, he suggested the simpler one was more likely.