How to do it
5 steps. Tap one when it's done.
Six cups in a row, three with coloured water, three empty, and folded paper towels bridging them. Leave it alone and come back to a full rainbow. The water walks uphill.
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Nothing sharp, nothing hot, nowhere far. Tell someone what you're up to, then go ahead and do it on your own.
5 steps. Tap one when it's done.
Paper towel is made of tiny fibres with tiny gaps between them. Water clings to the fibres and pulls itself along, gap by gap, even uphill. That's called capillary action, and it's the same trick plants use to lift water from their roots to their leaves.