What did Galileo discover?

Answer 1

He improved the recently invented telescope to see into space, he discovered Jupiter's moons and Saturn's rings. He observed how Jupiter's moons orbited around it and this convinced him that the Copernicus's Heliocentric model (model of planets orbiting around the sun rather than the earth) was correct.

Galileo published these ideas and was put on trial for supporting the heliocentric models and going against the Roman Catholic Church's beliefs. He avoided execution but spent the rest of his life under house arrest.

Answer 2

Galileo discovered the moons of Jupiter, the phases of Venus, and that the Earth revolves around the sun. These findings were instrumental in confirming the heliocentric model of the solar system.

Answer 3

Thermometer