The story of a planet

The planet Earth, on which we live, dates back to four and a half billion years ago, when huge, ancient stars exploded. The stellar explosions melted the chemical elements known now, including iron, carbon, and gold, and radioactive elements such as uranium. Over time, gravity took control of the situation and this mass of star dust collapsed in on itself to form a massive rotating disk, or what is called a solar nebula cloud. In the center of this disk, the temperature rose, the pressure i...