• Question: How much does the sky weigh?

    Asked by mw._12 to Rachel on 13 Mar 2019.
    • Photo: Rachel Hudson

      Rachel Hudson answered on 13 Mar 2019:

      The area of the Earth’s surface is roughly five hundred and ten million square kilometres by a simple 4πr^2 calculation. The pressure exerted by the Earth’s atmosphere at sea level is about 101 kPa, namely 1.01×10^5 Newtons per square metre, which works out to 1.01×10^11 Newtons per square kilometre. Multiplying, we get about 515×10^17 or 5.15×10^19 Newtons. That’s a lot of weight.

      In case you meant the mass, well, each kg exerts 9.81 Newtons of force, so about 5.25×101^8 kg. Call it five thousand million million tonnes. That’s roughly a millionth the mass of the entire Earth.

      (I may have asked the internet for help on that one…)

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