• Question: How come satellites don't float away if there is no gravity is outer-space?

    Asked by babybel to Andrew, Emma, Marianne on 14 Jun 2010 in Categories: .
    • Photo: Andrew Maynard

      Andrew Maynard answered on 12 Jun 2010:

      Hi babybel,

      The secret is that there is gravity in outer-space – but only if there’s a large lump of stuff (like the Earth) close by.

      The gravitational field of a planet, a sun or a moon extends a long way into space, but it gets weaker the further away you get. This is why satellites are possible – because they are still close enough to be captured by the earth’s gravity. It’s also why the moon doesn’t fly off into space – because the Earth’s gravitational field is strong enough to keep it there, even though the moon is 230,000 miles away from the earth. And it is also why the Earth continues to revolve around the Sun. We are just over 94 *million* miles away from the Sun, yet the Sun’s gravity is still strong enough to stop the Earth spinning off out of the Solar System!

    • Photo: Marianne Baker

      Marianne Baker answered on 13 Jun 2010:

      Well I’m not a physicist but I know there certainly is gravity in space!

      Gravity keeps the Earth going around the Sun, the moon going around the Earth and indeed satellites orbiting the Earth too.

      Massive things like suns and planets exert their gravitational pull on other bodies. The Earth’s gravity keeps our atmosphere (all the gases we breathe) close to the planet’s surface but outside of the atmosphere, gravity still acts – that means the satellites stick around.

    • Photo: anon

      anon answered on 14 Jun 2010:

      Think these dudes have covered it. There may be gravity in space but there’s a need for more levity in my office today….(long faces on a Monday morning in Edinburgh).

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