1. Galileo Galilei made several important astronomical discoveries in the early 1600s using one of the earliest telescopes, including mountains on the Moon's surface, spots on the Sun, and the planets Jupiter, Saturn and Neptune.
2. Johannes Kepler was the first to discover that planets orbit the Sun in ellipses rather than perfect circles, and Nicolaus Copernicus established the heliocentric model where the Sun is at the center of the solar system in 1543.
3. Isaac Newton later built upon these scientific revolutionaries by formulating his law of universal gravitation and laws of motion, providing an explanation for how objects like planets and moons move through space.