4 ms·

In the XVII century, the alternative to heliocentrism was Tycho Brahe’s model: Earth at the centre, the Sun and Moon and the stars revolving around it, and the

In the XVII century, the alternative to heliocentrism was Tycho Brahe’s model: Earth at the centre, the Sun and Moon and the stars revolving around it, and the other planets revolving around the Sun. It was basically equivalent to the heliocentric model with a different coordinate system. It’s important to understand that astronomers chose it because it really seemed to provide a better explanation given the knowledge and technology at the time. Tycho Brahe himself noted that his model could be disproved by observing the stellar parallax effect as the Earth orbits the Sun (if the Earth does move, then the stars would look slightly different throughout the year). This is a real effect, but so small that it couldn’t be observed until the XIX century.

matthewdgreen 4y ago
There was even more to it. Cosmographers of the time were willing to consider the possibility that the stars were very far away, far enough to make parallax changes undetectable. The main stumbling point was that they assumed the stars would be similar in size to our sun, but based on naked-eye and telescopic measurements of the diameter of the “disk” of the stars (many taken by Brahe and Galileo themselves), any solution that explained the parallax effect would have resulted in enormous stars, and this they couldn’t accept. Eventually the measurements turned out to be an optical artifact. I read an entire book on this subject, published by a Catholic press. There seems to be an active interest in the Catholic science establishment in rehabilitating some of Galileo’s critics.