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.
Hadean Eon [4500 Myr - 4000 Myr ] The age of the Earth is projected to be about 4500 Myr from radiometric dating of the oldest rocks and meteorites. There is evidence of a time of intense bombardment of the Earth in the time period from about 4100 to 3800 Myr in what is called the late heavy bombardment.