Radioactiviy in uranium was discovered. At the time he was researching atoms, molecules, nuclei, mass, and energy.
Radium is a radioactive material. The Curie's were following Becquerel's work and were able to separate one gram of radium salts from eight tons of pitchblende.
If mass could be converted into energy then large quantities of energy could be liberated.
They had produced nuclear fission and transformed mass into energy 33 years after Einstein said it was possible.
"In the course of the last four months it has been made probable to the work of Joliot in France as well as Fermi and Szilard in America-that it may become possible to set up nuclear chain reactions in a large mass of uranium... This new phenomenon would also lead to the constructions of bombs,,, A single bomb of this type, carried by boat or exploded in a port, might very well destroy the whole port togerther with some of the surrounding territory.
The first nuclear test that took place in Alamogordo, New Mexico, to test how far the reaction will go.
This was the second atomic bomb drop and killed 75,000 people.
An American airplane drops the first atomic bomb ever used in warfare on Hiroshima, Japan. 142,000 ultimately died.
Soviets launch the first space vehicle to orbit the Earth.