Gyula Gombos, a far-right radical, is the Hungarian prime minister.

Lausanne. At Italy’s urging, an international conference is held to discuss the possible cancellation of war debts and the removal of barriers to trade between nations. Belgium, France, Germany, Japan, Great Britain, and Italy participate. The plan fails because the U.S. Congress rejects the agreement. Germany immediately suspends outstanding payments, and other nations do the same, with occasional exceptions. Finland is the only country to pay to the last dollar.

Universal Studios’ Scarface hits theaters; it covers Al Capone-inspired mafia themes.

Judge James Wilkerson convicted Al Capone of tax evasion. He received the maximum sentence: 10 years in federal prison plus one year in a low-security prison. Indeed, one receipt was found, just one, in his name, even though he was officially penniless.

Ernest Walton places a lithium target in front of a 250 kV proton accelerator. He observes a shower of alpha particles: helium nuclei resulting from the split lithium nucleus. This is the first nuclear disintegration. The discovery will be made public at the Royal Society a few days later, on April 28.

Grand Council of Fascism. Mussolini approves a motion stating: “To overcome a crisis (…) that now has more political and moral aspects than purely economic ones, it is necessary to: 1) Resolve the problem of reparations and interstate war debts by canceling the former and renouncing the latter; 2) Remove restrictions on international trade before they lead to total anemia in all countries’ trade.” In June of the same year, an international conference on these issues will begin.

The last emperor of China was a Japanese puppet. Henry Pu Yi, the last emperor of China from 1908 to 1912, became regent of the Japanese puppet state of Manchukuo. Enthroned when Emperor Hsüan-T’ung was three years old, he was forced to abdicate four years later by Sun Yat-sen’s republican revolution. He took the name Henry and continued to live in Beijing’s Forbidden City until 1924, when he was exiled. He settled in Japanese-occupied Tianjin, where he lived until 1932, when he was installed as the puppet leader of the state of Manchukuo. In 1934, he became K’ang Te, Emperor of Manchukuo, holding the title until his capture by the Soviets at the end of World War II. In 1950, Pu Yi returned to China and was held prisoner, until Mao Zedong granted him amnesty in 1959. Once free, he found work in a Beijing machine shop.

San Lazzaro Asylum in Reggio Emilia: construction of the Buccola Pavilion for female workers.

RA Fischer, pioneer of neo-Darwinism, hypothesizes for the first time the genetic point of view of evolution

James Chadwick discovers the neutron, at the Cavendish Laboratory

Carl David Anderson experimentally discovers antimatter (anti-electron or positron), predicted by Dirac only the year before

Karl Jansky discovers radio noise from the center of the Milky Way

Between 1900 and 1932 the US Patent Office issued more than 350 patents on the water closet.

Danish carpenter invents Lego (made of wood); the commercial version will have great worldwide success in the 1950s.

The circular reducer is used by the Japanese company Sumitomo as a reducer for electric motors

The Institute for Advanced Study in Princeton is founded, which will take over the baton of the mathematical mecca, abandoned by Göttingen in 1943.

Tuskgee Study. At the Macon County Health Center in Alabama, the progression of untreated syphilis was analyzed in 600 Black farmers, 399 of whom were infected. The patients were injected with a serum, actually a placebo. Years passed, and only in 1972 did a former member of the health commission confess to the experiment, which incredibly was still ongoing in this remote corner of the American province. Faced with public and scientific outrage, the experiment was immediately suspended. Its sole purpose was essentially to ensure continued state funding. In 1990, a commission of inquiry condemned the incident as immoral, racist, and poorly conducted. In 2006, it was deemed the most infamous study in American history, and organizations were created to prevent its repetition.

The National Socialist Party, the People’s Party and the Labour Party were founded in Hungary.

Gambling is legalized in Nevada

World War I is over, and only a few years have passed since the American president attempted to usher in a new era of trust in international affairs, and his Secretary of State even went so far as to dismantle the Black Chambers office (composed of about twenty cryptanalysts), solemnly declaring that “gentlemen should not reach each other’s mail.” But there is one nation that cannot relax. It is Poland, caught between two uncomfortable neighbors: the Soviet Union and Germany. On November 8, 1931, Hans-Thilo Schmidt arrives at the Grand Hotel in Versiers, Belgium. Hans-Thilo is a German who hates Germany, where he has failed to establish himself, unlike his brother Rudolph, who has made a career in the army. And Hans-Thilo seeks redemption. He is in Belgium to contact a French secret agent, codenamed Rex, in exchange for 10,000 German marks. Schmidt has Rex photograph some documents detailing how to use an Enigma machine, which allows the Allies to build a replica of the Enigma machine (which obviously doesn’t mean they’re able to decipher the messages, since the key is unknown and changed daily, but it’s a first step nonetheless). In Poland, Biuro Szyfrow is tasked with trying to decrypt Enigma. He recruits the country’s best mathematicians, including Marian Rejewski, who begins to attack the problem, starting with some weaknesses: repetition is the enemy of security, for example. Repetition leads to patterns, which are a boon to cryptanalysts. For example, the Enigma key is encoded twice at the beginning of each message. By also analyzing the mechanical structure of the Enigma machine, he manages to make the problem 10 billion times easier than it was initially. Then, using other “tricks,” such as partially decoded phrases that can be guessed, such as “alliveinbelrin” (arrive in Berlin), he adds the finishing touches. The Poles are thus able, not without enormous decoding effort, to decode the current version of Enigma (which, however, would later be made much more complex). When Hermann Göring visits Warsaw in 1934, he is completely unaware that his communications are in clear to the Poles.

Dirac comes to the theoretical conclusion that positrons must exist: all the negative energy states are already occupied but occasionally some holes form which appear to us as positive energy particles (positive mass) identical to the electron, if the electron occupies the hole it is annihilated (the anti-electron, that is, disappears).

First International Conference on Nuclear Physics: held in Rome at the Physics Institute on Via Panisperna. Participants included Orso Mario Corbino, Enrico Fermi, Niels Bohr, Marie Curie, Werner Heisenberg, and Guglielmo Marconi.

Numerous internationally renowned physicists visit Fermi’s group in Rome, including Hans Bethe, Felix Bloch, Edward Teller

The aircraft use “Rotary Pistons” engines (example: DC3)