9 min
How much foam does one spoon make? A volcano the size of a plate
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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8 min
How thin is a hair? A drop of water as a magnifier
A hair is about a tenth of a millimetre across. A drop of water on a phone camera lets you see it.
