About 12 billion years ago, a big explosion, presently known as the “Big Bang,” created the universe.
The solar system we live in began to form 7.4 billion years ago. Earth was created by rock, ice, dust, and gas combining together. While forming, the Earth released an enormous amount of energy, causing the planet to heat up. For 100 million years, the components of planet Earth remained molten as they shifted into layers. Heavier minerals like iron and nickel, sank to the center and now form the dense core of the Earth, measuring 2,200 miles wide. The lighter minerals settled towards the surface of the Earth, creating its crust. The core and the crust are separated by 1,800 miles of molten rock, called the mantle. Certain lighter rocks gathered together to form “islands” or land.
Some scientists think that Earth’s crust cooled down, amino acids began to form, and over time, microscopic life emerged. Stanley Miller, a researcher from the University of Chicago showed that anyone can make amino acids just by using chemicals existing in a primitive atmosphere, water, and lightning. Amino acids are one of the basic components of life.
The first life forms emerged 4 billion years ago. 1.9 billion year-old rocks revealed different types of bacteria that had come to exist. The early bacteria fed on mineral-rich water from the young Atlantic ocean. More complex life started to appear on Earth 600 million years later.
Other scientists theorize that the components needed for life came from space instead of Earth. Today, microbiologists and scientists alike continue debating the origins of life and are still attempting to understand how life on Earth emerged.
[Source: The Atlas of the Prehistoric World]