Gresham College Lectures
Gresham College has been providing free public lectures since 1597, making us London's oldest higher education institution. This podcast offers our recorded lectures that are free to access from the Gresham College website, or our YouTube channel.
Gresham College Lectures
Four Colours Suffice?
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Gresham College
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How many colours are needed to colour a map so that neighbouring countries are coloured differently? At first it seems that for very complicated maps, many colours are needed, but surprisingly four colours suffice for all maps - a fact that took over a hundred years to prove. In this lecture we...