Conversation so far:
What is The Manhattan Project?
The Manhattan Project was a research and development undertaking during World War II that produced the first nuclear weapons.
When did The Manhattan Project begin?
The Manhattan Project began in 1942.
Did Joseph Rotblat work on The Manhattan Project with other people?
Joseph Rotblat worked in Egon Bretscher's group investigating high-energy gamma rays, and then with Robert R. Wilson's cyclotron group.

Question: What kind of things did they do on this project?
Self-contained rewrite: What kind of things did Joseph Rotblat do on the Manhattan Project?