They believed that Christian faith would collapse, all humans would instantly kill each other and the devil would take care of the last killers - if earth were not the center of God's creation and if there were maybe other "earths" and "moons". Of course, a faith like Christianism lives from ideas, from words and human understanding and not from rocks flying through space. But the medieval cardinals did not trust the core of their faith. In fact the master of scholastic theology, Thomas Aquinus had emphasised that our pictures of God and its creation are just pictures and do not equal "facts of God". But these warnings and their consequences were not understood at his time. (HK)

The Moons of Jupiter :

Galileo observed 4 points of light that changed their positions with time around the planet Jupiter. He concluded that these were objects in orbit around Jupiter. Indeed, they were the 4 brightest moons of Jupiter, which are now commonly called the Galilean moons (Galileo himself called them the Medicea Siderea - the "Medician Stars"). These observations again showed that there were new things in the heavens that Aristotle and Ptolemy had known nothing about. Furthermore, they demonstrated that a planet could have moons circling it that would not be left behind as the planet moved around its orbit. One of the arguments against the Copernican system (and the original heliocentric idea of Aristarchus) had been that if the moon were in orbit around the Earth and the Earth in orbit around the Sun, the Earth would leave the Moon behind as it moved around its orbit. (NASA)