• Question: How much does the Earth weigh?

    Asked by mw._12 to Vinita, Rachel, Pam, Christopher, Brian on 13 Mar 2019.
    • Photo: Rachel Hudson

      Rachel Hudson answered on 13 Mar 2019:

      5.972 × 10^24 kg
      i.e.
      5,972,000,000,000,000,000,000,000 kg

    • Photo: Brian Weaver

      Brian Weaver answered on 14 Mar 2019:

      Weight and mass are not the same. Weight is a force and depends on gravity. Mass is a property of an object and does not depend on gravity. My mass (in kilograms) is the same anywhere. My weight (in Newtons) will be different on earth than on the moon.
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      With that in mind, the SI definition for earth’s mass is 5.9722 ± 0.0006 × 10^24 kg.
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      You can (roughly) calculate the mass of a planet (like earth) with information about an object that orbits that planet (like the moon). All you need to know is:
      …(1) distance between the planet and orbiting object
      ……….- no problem!
      …(2) the time the orbiting object takes to complete one trip around the planet
      ……….- no problem!
      …(3) the “universal gravitational constant” known as G
      ……….- slightly difficult to estimate!
      https://image.gsfc.nasa.gov/poetry/ask/a10448.html
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      I’m really not sure how you could find earth’s mass any other way. I imagine you would need earth’s size (volume) and density. But the density is not uniform and would cause problems!

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