In 1609 Galileo used a telescope to observe the planets and became convinced that the Copernican theory of the universe was true--that the planets revolved around the sun and that the earth itself moved.

• 1609年，伽利略用望远镜观察到行星，深信哥白尼的宇宙说是对的--行星绕太阳公转，地球自转。