1958 - The U.S. launches the Explorer. This spacecraft discovers the Van Allen belts. These are doughnut-shaped regions in Earth's magnetic field which trap charged particles from the solar wind.
1961 - Soviet cosmonaut Yuri Gagarin becomes the first person in space. He orbits Earth one time.
1961 - One month after Gagarin, American Alan Shepard rides a Mercury spacecraft, spending only 15 minutes in space. The second Mercury mission, carrying Virgil I. Grissom, also completes only a partial orbit of Earth and remains 16 minutes in space.
1962 - In the third Mercury spacecraft, John Glenn becomes the first American to orbit Earth.
