According to scientists, the earth is about 4.5 billion years old. However, because of the constant upheavals in climate, plate tectonics, asteroid strikes and other events, most of the evidence of the earth's beginnings are lost.
The earth and the rest of the solar system are believed to have formed out of a cloud of dust and gas called a nebula. Over time, this cloud condensed and became a flat, rotating cloud with a dense central region. As more time passed, the central region contracted into a protosun surrounded by rings of gas and dust that collided to form planetesimals. Eventually, the sun ignited, and the solar system was born. Earth was the third planet out.