four colour theorem

four colour theorem

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Computers, for example, were essential experimental testing tools in the celebrated proof of the famous Four Colour Theorem, that only four different colours are needed on a flat map so that each country can be given a colour, without sharing any part of a border with another country which has the same colour.
But it took more than 100 years for someone to establish beyond significant doubt that the Four Colour Theorem was true.
Some mathematicians argue that the Four Colour Theorem has never really been proved because the proof developed by Kenneth Appel and Wolfgang Haken and published in 1977 needed a computer to demonstrate it.