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[Home]
[Prog summaries - [Ice World] [The
Earth was Born] [Out of Eden]
[In perspective]]
[Out of chaos - [Introduction]
[Divine guidance] [Tools
of knowledge] [Religious conflict]
[Search goes on]]
[Survival - [Introduction]
[Exodus] [New
Technology] [Moving on]]
[The Globe - [Introduction] [Star
Dust] [Water of life]]
[Find out more]
[Credits]
[Full site with images]
Our Earth was formed out of the dust of huge exploding stars that had reached the ends of their lives. From these supernovas erupted all the elements — iron, carbon, gold and radioactive elements, such as uranium.
As the stardust cooled, it became denser. Gravity collapsed the dust cloud towards its centre forming a giant rotating disc: the solar nebula with the sun at its centre.
Hydrogen and helium were swept to the outer edges to form gas planets leaving behind dust grains in orbit round the sun. As the grains collided, some stuck together to form larger rocks, their gravity increasing as they grew, pulling in more rock and dust.
Eventually these rocks and dust combined to become planets, including Earth, which was covered with molten lava.
By using radioactive dating on meteorites, which formed at a similar time to our planet, scientists have calculated that the Earth's date of birth was 4.6 billion years ago.
Volcanoes spewed lava on to the hot surface, which was further heated by debris dragged in by gravity. Meanwhile radioactive elements, trapped when the planet was formed, heated the globe from inside.
When the temperature reached 1200°C the heaviest element, iron, sank and the lightest, such as carbon and water, floated to the top.
As the liquid iron swirled around, convection currents inside the core behaved like a dynamo and generated electric currents, turning the planet into a magnet with north and south magnetic poles. This magnetic field creates a protective shield deflecting deadly solar particles and maintaining our atmosphere.