Two of Jupiter's satellites, Europa and Ganymede, pull Io into an elliptical orbit around Jupiter. Differences in the strength of Jupiter's gravitational pull as the distance between the planet and Io varies causes slight changes in Io's shape. Scientists believe that Io heats up internally when it changes shape.
The Atomic Age, also known as the Atomic Era, is the period of history following the detonation of the first nuclear (atomic) bomb, Trinity, on July 16, 1945 during World War II.
The generally accepted age of the Earth is based on a simple but elegant model for the evolution of lead isotopes. This model was developed independently by Houtermans (65) and Holmes (63), and first applied to meteorites and the Earth by Clair Patterson, now at the California Institute of Technology, in 1953.