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Asked by to Nancy on 25 Jun 2014. This question was also asked by .
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Nancy Carlisle answered on 25 Jun 2014:
I think it was something about gravity and particles and stuff… 🙂
You’d be better off asking a scientist in the ‘Astronomy ‘ zone about that one!
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James commented on :
The astronomers can answer this better but in case they don’t see it – I’ll give you a brief answer.
About 4.6 billion years ago, the solar system as we know was actually just a “giant molecular cloud” – all the same atoms are in it at this point but they aren’t arranged into planets, everything is spread out much more and moving around within the cloud.
To get from there to Earth, you need gravity. As objects get bigger, their gravitational attraction to other objects increases. Initially the aggregation of the bits of the early solar system was slow but gradually, chance collisions between particles creates bigger particles, which in turn attract more material (so the bigger they get, the faster they grow). Most of the mass within the early solar system collapsed into a dense clump which we now know as the sun, whilst the rest (less than 1% of the total) become a “protoplanetary disc” that orbited the newly formed sun.
The atoms in this disc grew into small pieces of dust and ice, which grew and grew with the bigger bits attracting smaller bits until nearly all of the remaining mass in the disc is used up and the result is the planets and asteroids that orbit the sun.
Early Earth was very chaotic. This is what geologists know as the ‘hadean eon’ – quite literally hell on earth!! – because of the heat from all the impacts from asteroids that today are part of Earth, the surface of the Earth was a sea of lava. Over a very long time, the surface cooled (so that now only the middle of the Earth is still liquid) to form land masses and water in the atmosphere and from ice in comets condensed to form the oceans