Galileo Galilei was a scientist who made many discoveries in astronomy and physics, such as four of the moons of Jupiter, the phases of Venus, Saturn's rings and that an object accelerates at a constant rate. Although Galileo did not invent the telescope, he is famous for making modifications to it. He worked with pendulums and established that they have a constant period.
Galileo is also famous for disagreeing with the concept of geocentrism that was the accepted theory in his time. He agreed with the Copernicus' theory of a heliocentric system in which the Earth revolved around the sun. From a religious perspective, he was at odds with the Catholic church and spent time under house arrest.
Galileo was born in 1564 in Italy. He was an intelligent and gifted thinker who studied math, physics, art and music. He died in 1642 after spending 8 years under house arrest.