Kenneth Appel Dies: Mathematician Who Proved Century-Old Theorem Passes Away At 80

Dover, NH – Kenneth Appel, one of two mathematicians to first use a computer to solve a major mathematical theorem, has died. He was 80.

Along with fellow mathematician Wolfgang Haken, Kenneth Appel finally proved the 100-year-old “Four-Color Conjecture” (otherwise known as the “Four-Color Map Theorem”) in 1976.

The pair used 1,200 hours of calculations from an IBM computer to prove the theorem, which states a flat map (like the example above) can be colored using just four colors, so that contiguous countries have different colors. The feat was regarded as a major intellectual accomplishment, with an answer having eluded mathematicians for more than a century.

As the use of computers in solving complex mathematical theorems increased in the 1960s and 1970s, Appel and Haken were engaged in a race with other mathematicians to solve the Four-Color Conjecture first. They announced they had proven the formula on June 21, 1976.

Appel and Haken’s proof was widely reported by the news media around the globe, and the math department at the University of Illinois, where the pair had undertaken their study, used a postmark stating “Four colors suffice.” As the first major theorem to be proven with extensive computer assistance, their findings initially aroused considerable controversy.

The Tasker Funeral Home confirmed the death of Kenneth Appel, who was diagnosed with esophageal cancer. He passed away on April 19 while in hospice care.

As well as his work on the Four-Color Conjecture, Appel served as a longtime educator and chair of the University of New Hampshire mathematics department. He retired in 2003 at the age of 70.

Previously, he had been a faculty member at the University of Illinois at Urbana.