8 min
How big is a grain of pollen? Dust from a flower on tape
A Number a Week
A short letter every Sunday with one number from the week's video, how I found it and how you can find it too.
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10 min
How big is a molecule? Spreading one drop of oil on water
One drop of oil on a tray of water spreads into a film, and its thickness tells you how big the pieces are.
