• Question: how do planets form?

    Asked by iluvwilmas to Adam, Joanna, Marcus on 22 Nov 2012.
    • Photo: Marcus Wilson

      Marcus Wilson answered on 22 Nov 2012:


      We are still not entirely sure. its only the last couple of years that weve even been able to find palnets in other solar systems.
      I think planets are only formed around stars. this happens in a nebula of cosmic gas and dust, with the star at the center, and planets round the edges formed by aggregation, like if you roll a small snowball down a snowy roof. by the time it reaches the bottom its picked up a lot of snow. t

      hese rcoks then collide together making them bigger. the center is under lots of pressure and heat so is liquid and a crust forms on the surface because space is cold! atmospheres come about form volcanic eruptions spewing gasses and these are maintained by magnetic fields created by the shifting core. but this is all just a theory!

    • Photo: Adam Paige

      Adam Paige answered on 22 Nov 2012:


      Marcus is exactly right. All the elements that our world (and us) are made from were actually formed in an ancient star which exploded and sent all this matter into space. Slowly gravity pulled all the matter into giant clumps. The huge pressures of all that matter pressing together created a hot molten ball of matter which slowly cooled down and solidied into rock. The gravity of the rock pulled in lighter elements (gases) that created the atmosphere around us, and water vapour which condensed and fell as rain creating rivers and seas.

      Because of how this planet formed, one thing we know – the moon was not around when the Earth formed. If the moon had been close to the Earth back then, gravity would have pulled them both together and they would have become part of the same planet. The only way to explain how we have a moon is that first the Earth formed as described above. Somewhere else, the moon formed in a similar way (although it did not manage to hang on to any atmosphere or water vapour). The moon was moving through space and it came near enough to the Earth to be caught by our gravity. Fortunately, it did not crash down onto the Earth’s surface (which would have caused a huge, catastrophic explosion) but instead was pulled into orbit around the Earth.

      And the fact that it was is (apparently) crucial to how we came to be alive! The moon’s gravity pulls on the Earth and the seas move as a result which creates the tides. This churning of the sea was really important for mixing the heat throughout the water, and for mixing the chemicals forming in the seas. Without this motion it is very unlikely that the chemical reactions which eventually led to life would have begun. So a big hurrah for the moon!

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