Three, as Schoolhouse Rock! told children of the 1970s, is a magic number. Three little pigs; three beds, bowls and bears for Goldilocks; three Star Wars trilogies. You need at least three legs for a stool to stand on its own, and at least three points to define a triangle.
The number 3 also suggests a different way of counting. Our familiar base 10 decimal system uses the 10 digits from zero to 9. Binary, our digital lingua franca, represents numbers using only the two digits zero and 1.
But mathematicians have long explored counting in threes. Consider, for example, base 3, or ternary, which uses three digits. The standard convention is to use the digits zero, 1 and 2.
