Around 150 years ago, three scientists named Ernest Rutherford, Hans Geiger, and Ernest Marsden exposed a thin gold foil to radiation. Based on how the rays were deflected by atoms in the foil, they figured out that every atom has a dense centre where its mass and positive charge are concentrated.
Seventy years ago, Robert Hofstadter led a team that bombarded electrons at thin foils. The higher energy of the electrons allowed them to ‘probe’ the nucleus. Based on these interactions, the team understood how charges and magnetic fields were arranged inside a nucleus.
In each case, physicists were able to ‘see’ inside stable atoms, and then inside their nuclei, by using other particles.
