Galileo's observations

Hoe did Galileo’s observations of the phases of Venus provide the strongest evidence against a geocentric universe?

help!?

It showed that Venus orbited the Sun rather than the Earth. When Venus was near the sun in the sky, he observed that it either was close to a full disk, or a crescent. And when far from the sun, it was half a disk. Very similar to how a ball looks when circling a light as viewed from outside.