-
Most astronomical objects, such as galaxies, stars, and planets, are formed by accretion processes. 4.5 billion years ago, with the rise of the sun, the remaining material (dust&gas) began to clump up. Small particles drew together, bound by the force of gravity, into larger particles. It finally formed into a massive object by gravitational force, which is the Earth.
-
New study supported that moon might be formed by the space debris from a collision between the Earth and another planet whose size was similar to Mars'. Moon was formatted nearly after Earth.
-
When the Earth formed, it was a rotten planet containing a lot of warming elements and radioactive minerals. Therefore, Earth has had a long a complicated cooling history.
-
From 4.5 to 3.8 billion years ago, astroids and comets land and hit on the larger planets formed such as the Earth. The collisions leaved scars and craters to the surface of the Earth.
-
Earth's inner core was formed 1-1.5 billion years ago as it "froze" from the surrounding molten iron outer core. It is composed of an iron–nickel alloy and some light elements with an radius of 1,220 kilometres.
