461 years ago today, on February 15, 1564 (February 4, 1564 lunar calendar), Galileo Galilei, the founder of modern European natural science, was born. Galileo was observing in 1581, at the University of Pisa in Italy, there was a 17-year-old young man. He did not believe what teachers said like ordinary students. He liked to think independently and often asked professors some strange questions. For example, Aristotle's works were classics read by students, and every sentence in them was regarded as the truth, and no one doubted it. However, the young man said: Scientific truth needs to be tested by actual observation and scientific experiments, and what Aristotle said is not necessarily correct. You see how "arrogant" he is! Therefore, everyone regards him as a "arrogant student". It didn't take long for people to suddenly discover that this "arrogant student" turned out to be a genius. He was in his fifth year of study and left school before he could get his diploma because he couldn't pay the tuition fees. But he didn't go home soon. In 1586, he published a mathematical paper "Gravimetric", which caused a sensation in the Italian mathematics community. In 1589, the University of Pisa hired the student who did not graduate to teach at the university. In 1590, he published a long paper "On Gravity", which was the first to propose the law of free fall. It is believed that objects, regardless of their size and weight, in the process of falling freely, except for the influence of air resistance, their acceleration is exactly the same, negating Aristotle's principle of gravity. In order to prove his law to the teachers and students of the school, he gave a famous experiment on the Leaning Tower of Pisa. A ten-pound iron ball and a one-pound iron ball fell from the leaning tower at the same time, and the practice proved the correctness of his theory. This student was Galileo. He was born on February 15, 1564. It was with this kind of "arrogant" courage that he dared to explore and did not easily follow blindly, and the courage to practice the spirit of dedication to the pursuit of truth. Through perseverance, he made great achievements in the fields of physics, mathematics, astronomy and other sciences, and became one of the founders of modern natural science in Europe. Galileo discovered the four moons of Jupiter