1900s: The Wright Brothers make their historic flight at Kitty Hawk, North Carolina, proving to the world that humans can fly.

1940s: German-born scientist Wernher von Braun develops the V-2 rocket for Adolph Hitler, envisioning it as a means for space travel. Hitler, however, uses the rocket as a weapon during World War II, so von Braun defects to America, where he shares his knowledge with American scientists—who follow von Braun's lead and begin to apply it to space exploration.

Today: Having experienced both extraordinary success and tragic failure, the National Aeronautics and Space Administration (NASA) continues to plan and send exploratory missions into space.

1900s: Einstein proves the existence of atoms.

1940s: The United States is the first to harness the power of the atom and demonstrates the awesome, destructive power of nuclear warfare when it drops atomic bombs on two Japanese...