• Question: How much smaller than the earth is an atom?

    Asked by to Alan, Deepak, Francesca, Lilly, Nick on 19 Mar 2014. This question was also asked by .
    • Photo: Francesca Day

      Francesca Day answered on 19 Mar 2014:


      Well, the Earth has a radius of 6378.1 km = 6378100 m. Different atoms are different sizes, and it’s hard to define exactly what the radius of an atom is because they don’t have definite boundaries. We could define the radius of the smallest atom, Hydrogen, as the most likely distance between the proton and the electron. In this case the radius of Hydrogen atom (called the “Bohr radius”) is 5.2918/100000000000 m.

      This means that a Hydrogen atom is about 8000000000000000000 times smaller than the Earth. That’s 8 followed by 18 zeroes, or 8 billion billion!

    • Photo: Alan Fitzsimmons

      Alan Fitzsimmons answered on 19 Mar 2014:


      The Earth is 12,742 kilometres across. An atom is about 0.0000000001 metres across. So dividing one by the other tells you that an atom is about 800000000000000000 times smaller than the Earth.

      See how I got the same answer as Francesca? In science that’s really important! We never rely on just one person calculating something. Some other scientist always has to check a result so that we are sure it is right.

    • Photo: Nick Wright

      Nick Wright answered on 20 Mar 2014:


      Atoms are tiny! There are billions and billions of atoms in just a teaspoon of jam (or any other material), and you know that the Earth is much bigger than that. To be precise the Earth is about 10 billion billion times bigger than the average atom, though there are atoms with a lot of different sizes!

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