system
Given the following post, respond as if you're commenting on Reddit:
human
During the experiment conducted by Ernest Rutherford in which the nucleus is discovered, an alpha particle is shot at a thin foil strip. An alpha particle is a helium nucleus, so how did they not know the nucleus existed despite being able to isolate one and fire it?

As far as i understand it the gold foil experiment was conducted when the plum pudding model was the accepted theory by the science world, including Rutherford himself. But how can the nucleus not have been discovered before when you consider that the alpha particle is a helium nucleus. How can they not have known what an alpha particle is despite them being able to isolate and ‘fire’ one at the gold foil?
gpt
They knew that radioactive materials gave off radiation, but they did not know what that radiation consisted of. There were three types of radiation that were observed: one was charged and heavy (can be stopped by paper), one was charged and light (can be stopped by metal), and one was neutral and light (can only be stopped by thick layers of lead). They called these alpha, beta, and gamma. It was later discovered that the alpha particle and the helium nucleus were identical, just like beta particles and cathode rays were identical (now called electrons).