Which of the following was a significant outcome of the Manhattan Project?

The significant outcome of the Manhattan Project was the creation of atomic bombs. This highly secretive American project during World War II was primarily focused on developing nuclear weapons, specifically the atomic bomb. The successful detonation of these bombs not only marked a pivotal moment in warfare but also led to profound global changes in international relations, military strategy, and energy policy. The atomic bombings of Hiroshima and Nagasaki brought about Japan's surrender, effectively ending World War II and demonstrating the destructive power of nuclear weapons.

The other options, while important in their own contexts, do not directly stem from the efforts of the Manhattan Project. NASA was established later, in 1958, to manage the United States' civilian space program and aeronautics research. Radar technology developments were a separate pursuit during the war, aimed at improving detection systems, and advancements in military aviation were ongoing efforts not exclusive to nuclear research or the Manhattan Project. Thus, the fundamental achievement of the project lies in the successful creation of atomic weapons, which changed the course of history.