Answer:
That the Sun is at the center of the solar system, not orbiting around the Earth.
Step-by-step explanation:
Galileo Galilei, an Italian astronomer born in 1564, made discoveries about our universe that changed our understanding of our world as we know it.
Upon learning about the spyglass, a new technology at the time, he wanted to use the invention for his astronomy experiments, so he built his own improved model. In 1609, using his early version of the spyglass, Galileo became the first person to record observations of the sky made with the help of a telescope.
After finding a few discoveries about the Moon, Jupiter, and Venus, he managed to create a hypothesis that the planets orbited around the Sun, not around Earth as many people believed at the time. This supported Copernicus, a previous astronomer's guesses many years before.
Looking to support his theory, he turned his gaze towards the Sun. Not knowing that the star would harm his eyesight, he observed that the sun had sunspots, which supported his theory.
After carefully poring over his research, he concluded that the sun, in fact, is at the center of the solar system, not the earth, which at the time was believed to have all the other planets orbit around it.
Galileo passed away on January 8, 1642 from a fever. His work is remembered to this day.
Hope this helps you! Good luck!