10 min
How big is a molecule? Spreading one drop of oil on water
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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11 min
How far away is the sun? A pea, a ball and a long walk
A ball a metre wide for the sun and a pea for the Earth: how many steps it takes to put the pea in the right place.
