416 years ago today, on August 21, 1609 (July 22, 1609, the world's first telescope was on display. On August 21, 1609, Italian scientist Galileo exhibited the first telescope in human history built in accordance with scientific principles. It was not Galileo who first discovered the secret of the telescope, but a Dutch optician named Liposse. When this person was making lenses, he combined a convex lens and a concave lens and looked out, and things in the distance became closer. Galileo was very interested in this discovery. He used mathematical calculations to study what kind of lenses to use and how to combine them together would work better. Finally, Galileo made two tubes, one with a convex lens at one end and the other with a concave lens at one end: one of them was slightly thinner and could just fit into the other tube and slide freely. In this way, when observing, you can adjust back and forth to select the appropriate distance. In this way, after repeated development and testing, the world's first telescope with a magnification of 32 times was finally invented in 1609. Galileo used this tool to conduct astronomical observations. First, he found that the surface of the moon was neither smooth nor pure, and there were cracks in volcanic craters; second, he discovered that there were four moons next to Jupiter, orbiting Jupiter. Galileo compiled his astronomical discoveries into the "Star Bulletin" and reported them to the world, which immediately shocked the intellectual community. Orders for the telescope poured in from Galileo, but he dedicated the invention to the Duke of Venice without any reward. The Duke ordered him to be hired as a tenured professor in Padua. Soon after, he was invited to Florence to serve as court professor of mathematics.