Hairy Logic

Are there people on the planet with an equal number of hairs on their head? At the age of 12 I read an article in the newspaper that raised this somewhat unusual question. My mom couldn’t understand why anyone would care – but I was thrilled by the article. The question itself was funny and strange but at that time I felt could not seriously be answered (except for the trivial case for bold people). But as I read on the article showed that with some elementary logic the answer was a clearcut YES.

People with a lot of hair have about 300.000 hairs on their head. Now suppose that the answer would be NO – i.e. no two people have the same number of hairs. Then – to avoid these ‘ collisions’ – you can give some person one hair, the second gets two hairs, the third gets three and so on. But after around 300.000 people you can no longer choose an ‘ unused’  hair number. As there are far more people on the planet than 300.000 it’s easy to understand that there must be people sharing the same number of hairs on their head. It is indeed trivial for me now – but it wasn’t back then and it sparked my lifelong interest in logic.