Yes, Albert Einstein was aware of the Manhattan Project. In fact, his letter to President Franklin D. Roosevelt in 1939, which I mentioned earlier, played a significant role in initiating the project. The letter, co-authored by physicist Leo Szilard, warned of the potential military applications of nuclear fission and the need for the United States to conduct research on atomic weapons.
Einstein's letter emphasized the importance of understanding the science behind atomic energy and the urgency to develop atomic weapons before Nazi Germany. It is believed that this letter had a significant impact on President Roosevelt and led to the establishment of the Manhattan Project in 1942.
While Einstein was not directly involved in the day-to-day operations of the project or its scientific research, he maintained a general awareness of its existence and progress. He was in regular correspondence with some of the key scientists involved in the project, including J. Robert Oppenheimer, and was occasionally consulted on matters related to nuclear physics.
However, it is worth noting that Einstein became increasingly concerned about the destructive potential of atomic weapons and their implications for humanity. After witnessing the bombings of Hiroshima and Nagasaki, he became a vocal advocate for peace and nuclear disarmament.