Russian physicist who won the 1978 Nobel Prize for Physics for discovering superfluidity. He worked for over a decade with fellow Nobel laureate Ernest Rutherford.
His research at Cambridge University in England led him to discover a way to more efficiently make liquid helium.
He went to visit the USSR from Cambridge in 1934, but was not allowed to return, and thus spent the rest of his life in Moscow.
He married Anna Alekseevna Krylova, daughter of another noted Russian academic and the couple had two sons, Sergei and Andrei, together.
He had a falling out with the head of the Russian secret police and survived because Joseph Stalin picked Pyotr's side in the dispute.