Four Color Theorem
Originating as the Four Color Conjecture in 1852, the Four Color Theorem states that no more than four colors are needed to make a map in which each region has a different color and does not share a border with another region of the same color.
While having some practical application to cartography prior to the modern computing and printing era, today, the theorem is not of much use to mapmakers. “Maps utilizing only four colors are rare, and those that do usually require only three. Books on cartography and the history of map making do not mention the four-color property.”. From the beginning, the conjecture was really a mathematical question for which a proof was sought. That proof was finally achieved in 1976, claiming the distinction of being the first major theorem to be proved using a computer.
- Wilson, Robin (2014) , Four Colors Suffice, Princeton Science Library, Princeton, NJ: Princeton University Press, ISBN 978-0-691-15822-8, MR 3235839
- Robertson, N., Sanders, D., Seymour, P., & Thomas, R. (1997). The four-colour theorem. journal of combinatorial theory, Series B, 70(1), 2-44.