• Question: How many atoms would it take to make something I could see?

    Asked by Zealousy to Rob on 26 Jun 2015.
    • Photo: Rob Temperton

      Rob Temperton answered on 26 Jun 2015:

      I think humans can’t see anything smaller than 50 microns without scattering light off them or using some other sort of clever optical trick.

      You can work it out if you know what type of atoms you want to use. Lets take the smallest of them all: H

      1 hydrogen atom has a radius r=25e-12 m

      So the volume of one atom is:
      V=4/3*pi*r³ = 4/3 x 3.1 x (25e-12 m)³ = 7e-32 m³

      So, lets take our 50micron sphere. It has a volume of 4/3*3.1*(25e-6)³ = 7e-14 m³

      Divide one by the other
      7e-14 / 7e-32 = 1e+18

      So I make that 100000000000000000 atoms.

      Feel free to check my maths – I haven’t got time to check it right now!!

      Rob

Comments