How did people begin to disprove the geocentric model?
In: Technology
[Summarized from this really good article here:](http://tofspot.blogspot.com/2013/10/the-great-ptolemaic-smackdown-table-of.html)
The most important discovery involved the phases of Venus by Galileo in 1610. This gave direct evidence that Venus was sometimes farther than the Sun, and at other times closer. This disproved the Ptolemaic model that had all the planets orbiting Earth. However, Tycho Brahe had a geocentric model that involved all the planets orbiting the Sun, and the Sun and Moon orbiting Earth. The important thing is that if you just consider objects within the solar system, this model is pretty much indistinguishable from a heliocentric one. The key problem with a heliocentric theory was lack of stellar parallax.
Kepler several years before Galileo’s work had published his now famous laws of planetary motion, but for whatever reason they were largely ignored for a few decades. However, in 1687, Newton develops his theory of Gravity. This provides a theory in which the Kepler model *ought* to be true. From this point, no one really questions the heliocentric model even though they still can’t find the stellar parallax.
In 1728, stellar aberration is discovered. While not exactly parallax, it does prove that Earth is moving relative to the stars.
In 1806, stellar parallax is observed.
In 1835, an illusory optical phenomena (Airy disk) was identified that causes stars to appear more disc-like in telescopes. This explains the erroneous calculations Galileo’s contemporaries made that suggested stellar parallax should be significantly larger than it actually is (thus they thought that they should be able to see it when it was actually too small).
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