World War II
The most significant scientific achievement of this time period is the invention of the atomic bomb, and the subsequent developments in nuclear power usage.  The Manhattan Project was a top secret endeavor of scientist from the United States and Europe to create a weapon to stop Germany and Japan during World War II.  Dr. Robert J. Oppenheimer was the chief scientist behind the project which was primarily developed in Los Alamos, New Mexico.  Started in the spring of 1943, the first atomic bomb was produced by July of 1945.  Two atomic weapons were used on Japan. One was dropped on the city of Hiroshima on August 6, 1945, and another was dropped on the city of Nagasaki three days later. Over the next several decades research into nuclear energy and its use became one of America's top scientific priorities.

Space Race
In 1957, the Soviet Union launched Sputnik, a satellite into orbit around the earth.  Soon after, the United States Congress created the National Aeronautical and Space Administration, or NASA to develop American space technology.  This created the Space Race during the Cold War.  The Soviets put the first man into space in 1961, and the U.S. put the first man on the moon in 1969.  Both countries also developed military applications for space, such as spy satellites.

Satellites and Deep Space Probes: From the 1970s through today many countries have sent satellites and probes into space.  The U.S. leads the way today with the largest space program.  In the late 1970s the U.S. developed a reusable space vehicle, the Space Shuttle.  The shuttle has been used to launch hundreds of satellites and probes.  Today these include, weather, television and communication, navigational, and military satellites. Probes have been sent to the ends of our solar system and have explored planets such as, Mars and Venus.  The Hubble Space Telescope has been able to send back amazing pictures of other solar systems, some similar to our own.

High flying spy planes were part of the general space research.  Aircraft such the U-2 and the SR-71 flew missions over the Soviet Union to collect intelligence. In May of 1961, a U-2 aircraft flown by Air Force pilot Gary Powers was forced down over the Soviet Union.  This caused some foreign relations problems between the U.S. and Russia, and intensified the Cold War.
 

Strategic Defense Initiative
The Strategic Defense Initiative, or SDI, is an antiballistic missile weapon first proposed by the Reagan Administration.  Nicknamed "Star Wars", the proposed system would shoot down incoming nuclear ballistic missiles before they could strike their targets.  The system was to use lasers, particle beams, and different types of projectile weapons.  Controversy surrounded SDI because its development was seen as a violation of the Antiballistic Missile Treaty of 1972.  Funding was finally cut on the program in 1993.