Galileo missed Neptune. Galileo first observed and described Neptune on February 28th 16 12, and observed it again on October 27th 16 13. However, because the observation position is close to Jupiter in the night sky, Galileo mistook Neptune for a star twice. I believe it is a star, but I don't believe my own discovery because it was first observed at 16 12, 12. Neptune stays in the retrograde position, because the motion at the beginning of retrograde is so small that Galileo's small telescope can't detect the change of position. The experiment of Madame Curie's daughter's son-in-law: α ions hit beryllium 9 to produce neutrons, but they were mistaken for γ rays. Chadwick repeated the experiment and found that its speed was only one tenth of the speed of light, its mass was about equal to that of protons, and it was uncharged, so it was named neutron and won the 1935 Nobel Prize in physics. Cavendish, a British scientist, found that there are some gases in the air besides nitrogen, oxygen, carbon dioxide and water vapor. However, this discovery was not taken seriously, and it was not until a long time later that scientists determined that this tiny gas was an inert gas. Pauling missed the rare gas compounds. 1933, it was predicted that rare gases such as xenon hexafluoride (XeF6), krypton hexafluoride (KrF6), xenon acid and its salts (then called inert gases) could be prepared by calculating the ion radius. However, due to a series of failures, in 196 1, Pauling also denied his original prediction. But the year after Pauling denied his prediction, British chemist Butler, who worked in Canada, reacted platinum hexafluoride vapor with oxygen to obtain a new deep red solid. He imitated the method of oxygen oxidation, and mixed platinum hexafluoride with xenon in an equal molar ratio at room temperature to obtain an orange solid, that is, the first rare gas compound XePtF6, and the inert gas was renamed as rare gas.