The Earth's beginnings have always been - still are - a matter of debate. The currenly accepted view is that it formed at the same time as the rest of the Solar System from a vast spinning disc of dust and gas.

The disc began to condense into solid lumps about 5,000 million years ago, with gravitational forces causing matter to coalesce at the core.

Enormous converging pressures made the temperature rise until eventually it was just enough to sustain atomic reactions that began to radiate heat, and the Sun was born. Across the rest of the disc small concentrations of material began to attract addition matter to themselves and these eventually gave rise to the planets.

As the Earth formed, the heavier materials - particles of iron and nickel - sank to the middle and became the Earth's core. Lighter silicate elements tended to remain on the outside, forming the stony mantle and crust.

Finally the lightest substances - the gases - were attracted to the mass, but remained as an external envelope and constituted the original atmosphere. By about 4,500 million years ago the Earth was in existence, and its long evolution had begun.