• Question: What you define 'space' as?

    Asked by Nucleolus (Ben Sheridan) to Alice, Bose, Christian, Emma, Steve on 16 Mar 2016.
    • Photo: Steve Marsden

      Steve Marsden answered on 16 Mar 2016:

      Loosely speaking, anything higher than 100 km above the Earth is defined to be space.

      The boundary between a planet and space is called the Kármán line. When a wing travels through the air it generates lift. At higher altitudes, the atmosphere is thinner, and a wing must travel quicker to maintain the same lift.

      The Kármán line is the altitude at which a wing must travel at orbital velocity in order to generate substantial lift.

      Because of the different gravity on different planets, and the varying thickness of altitude, the Kármán line is a different altitude for each planet.

      There are a few ways of defining the boundary between Earth and space, but this is my favourite.

    • Photo: Alice Harpole

      Alice Harpole answered on 16 Mar 2016:

      I define ‘space’ as anything outside of the Earth’s atmosphere. Where the Earth’s atmosphere ends is not the easiest thing to define – if you go by the definition that the atmosphere ends at the exosphere, about 10,000km above sea level, then that means satellites like the International Space Station (at around 400km above sea level) aren’t *technically* in space, just really high up in the Earth’s atmosphere!

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