A schematic diagram of the experiment James Chadwick used to discover the neutron in 1932 — At left, a polonium source was used to irradiate beryllium with alpha particles, which induced a type of uncharged radiation initially thought to be gamma rays. When this radiation struck paraffin wax, protons were ejected with ca. 5.5 MeV kinetic energy. The protons were observed using a small ionization chamber, called a counter, that detected a signal recorded on an oscillograph. Adapted from J. Chadwick, The Existence of a Neutron, Proc. Royal Society London, Series A, 136, 692-708, 1932.
Photo Credit: By Bdushaw - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=63982002

James Chadwick —
Photo Credit: By Los Alamos National Laboratory - Los Alamos National Laboratory, Attribution, https://commons.wikimedia.org/w/index.php?curid=36283260

Lise Meitner and Otto Hahn in 1912 —
Photo Credit: Public Domain, https://commons.wikimedia.org/w/index.php?curid=90954251

Otto Hahn —
Photo Credit: By Basch / Opdracht Anefo - Dutch National Archives, The Hague, Nederlands Persbureau (ANEFO), 1945-1989 bekijk toegang 2.24.01.04 Bestanddeelnummer 923-4491, CC BY-SA 3.0 nl, https://commons.wikimedia.org/w/index.php?curid=36966973

Lise Meitner —
Photo Credit: By Smithsonian Institution - Flickr: Lise Meitner (1878-1968), lecturing at Catholic University, Washington, D.C., 1946, No restrictions, https://commons.wikimedia.org/w/index.php?curid=18386027

Former Kaiser-Wilhelm-Institut for Chemistry in Berlin — The place at which nuclear fission was first detected
Photo Credit: By Fridolin freudenfett (Peter Kuley) - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=18058567

Entrance of the administrative headquarters of the Max Planck Society in Munich —
Photo Credit: By Maximilian Dörrbecker - Own work, CC BY-SA 2.5, https://commons.wikimedia.org/w/index.php?curid=2131565

Logo of the Max Planck Society —
Photo Credit: By Original webpage: https://www.mpg.de/enArchived webpage: https://web.archive.org/web/20220827110914/https://www.mpg.de/en, Fair use, https://en.wikipedia.org/w/index.php?curid=71618053

Budapest University of Technology and Economics — Building K, 2019.03.19
Photo Credit: By Bonpethu - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=77446370

seal of Budapest University of Technology and Economics —
Photo Credit: https://kth.bme.hu/document/1964/original/BME_Code_of_Studies_1Dec2017.pdf

Einstein Refrigerator Annotated patent drawing — Clarified and annotated version with colors showing phases
Photo Credit: Public Domain, https://commons.wikimedia.org/w/index.php?curid=21931943