The universe contains huge clouds made up of very large amounts of dustandgas. About 6,000,000,000 (billion) years ago, one of these clouds began tocondense.
Gravitation–the pull that all objects in the universe have forone another–pulled the gas and dust particles together. As the dust cloudcondensed, it began to spin. It spun faster and faster and flattened as itspun. It became shaped like a pancake that is thick at the centre and thinThe slowly spinning centre condensed to make the sun. But the outer partsof the pancake, or disk, were spinning too fast to condense in one piece.
They broke up into smaller swirls, or eddies, which condensed separately toThe forming sun and planets were made up mostly of gas. They containedmuch more gas than dust. The earth was far bigger than it is now andprobably weighed 500 times as much.The large body of dust and gas forming the sun collapsed rapidly to a muchsmaller size. The pressure that resulted from the collapse caused the sunto become very hot and to glow brightly.
The newly born sun began to heat up the swirling eddy of gas and dust thatwas to become the earth. The gas expanded, and some of it flowed away intospace. The dust that remained behind then collected together because ofgravity. Although the shrinking earth generated a lot of heat, most ofthis heat was lost into space. Therefore, the original earth was mostlikely solid, not molten.This hypothesis was developed by a scientest, Harold C. Urey in 1952.
It isalso known as the Urey’s hypothesis. He showed that methane, ammonia, andwater are the stable forms of carbon, nitrogen, and oxygen if an excess ofhydrogen is present. Cosmic dust clouds, from which the earth formed,contained a great excess of hydrogen.Bibliography: