• Question: why doesnt the earth ever crash into any planets whilst in orbit?

    Asked by anon-174244 to Alex, Carl, Hayley, Melanie, Tim, Yewande on 13 Jun 2018.
    • Photo: Tim Craig

      Tim Craig answered on 13 Jun 2018:

      All of our 8 (or 9 in you count Pluto!) planets are in stable orbits around our Sun. These orbits are roughly circular, centred on the Sun, but at different distances out. The orbital paths never cross, and do the planets never collide.

      But if we go back to the early stages of our solar system, when planets were first forming, they infact formed through the collision and combination of lots of small planets (called ‘planetesimals’). Anything that was in a similar orbit to Earth was incorporated into it at that point in time, clearing our orbit for the future.

    • Photo: Carl Barford

      Carl Barford answered on 14 Jun 2018:

      Gravity and momentum.
      Everything is moving just fast enough not to move inwards or outwards and collide.
      I think the moon is moving away from us at an incredibly slow speed, and I am told that some planets will move and collide in the very, very distant future

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