On this day 133 years ago, on January 20, 1892 (December 21, 1891 lunar calendar), Becquerel, the first person to discover radioactivity, came to mind. Becquerel mentioned radioactivity, and people naturally thought of the Curies. In fact, the earliest discovery was a man named Becquerel. Becquerel was a Frenchman born in 1852. His father and grandfather were both physicists, so that he received a good education from an early age and qualified as an engineer at the age of 25. In 1892, at the age of 44, Becquerel had already studied physics very well. On January 20 of that year, the French Academy of Sciences held an important academic seminar. At the meeting, scientists from all over the country listened attentively to the famous mathematician and physicist and astronomer Pengalle give academic reports. Poincaré showed the participants a photograph of the x-rays that Röntgen had just sent him, which aroused great interest among scholars. At this time, a middle-aged physicist stood up and asked the lecturer which part of the x-ray emission area should be precisely. Poincaré said that the glass frozen wall irradiated by cathode rays, Becquerel immediately expressed his disagreement with this view, and immediately suggested that cathode rays would cause the entire vitreous body to fluoresce, and under the irradiation of cathode rays, there may be other substances that also emit similar rays. To test his idea, he immediately conducted experiments. Becquerel chose uranium oxide as the main target, and he carefully designed a research plan. He wrapped a photosensitive negative with a piece of black paper, and placed two small pieces of a mixture of uranium salt and potassium salt on the negative. A silver dollar was placed between one of the pieces and the negative, and then these things were placed in the sun for a few hours, so that the negative was slightly sensitive to light. Although it was not very clear, it could also decompose the image of the silver dollar. But it happened to be raining continuously, so he had to lock the experimental things in the drawer intact. Five days later, the sky cleared up and the interrupted experiment continued. He was a very careful person, and he re-examined the experimental objects before the experiment. To his surprise, in the absence of sunlight, there was a clear light-sensitive phenomenon on the negative. This shows that uranium itself is glowing! The next day he announced this new discovery in the academic report of the Academy of Sciences. He used an electroscope to quantitatively study this ray, and finally revealed the mystery of radioactivity. In the early days of the discovery of radioactivity, people did not know its dangers. Becquerel's health was seriously damaged due to long-term exposure to radioactive substances without protection, and he died in his 50s. In recognition of his outstanding contributions, the scientific community named the radiation of radioactive substances "Becquerel rays."