Discovered the earth was round due to the shadow of the earth during a solar eclipse.
Created the first geocentric model. Where the sun, stars, planets, and moon revolves around the earth.
Created a model where the sun was the center of the solar system.
Measured and fixed the positions of over 777 stars in the solar system and was the most accurate data before the telescope. He also supported the heliocentric model.
Used the telescope to prove the heliocentric model but, he went to prison for defending his work. He also discovered the first four moons of Jupiter.
He discovered the planets revolved around the sun in ellipses. He also discovered the three major laws of planetary motion.
He discovered the three laws describing motions of forces between objects. He also discovered gravity.
He discovered that there were other galaxies beyond the Milky Way. He also discovered that the universe is expanding. He also created Hubble's law about galaxies.