Lanyon Quoit, a Neolithic dolmen in Cornwall, England

An ancient angle on Pi. Celebrating Pi Day

Long before pi had a name, people were drawn to its mystery. Every year on March 14, Pi Day highlights one of math's most recognisable constants. The date reflects the first three digits of pi (π), the ratio of a circle's circumference to its diameter: 3.14. Pi's infinite, nonrepeating decimal has fascinated thinkers for a long time. The modern celebration began in 1988, when physicist Larry Shaw marked the day with a fitting tribute: serving pie.

Today's image takes us to Cornwall in southwestern England, where Lanyon Quoit—in the shape of π—rises from open moorland. Built between 3,500 and 2,500 BCE, this Neolithic dolmen once stood as part of a larger structure. Raising its massive capstone required knowledge of balance and proportion. These early concepts helped builders work with shape and scale long before written mathematics existed.

On Pi Day, sites like this remind us that mathematical thinking evolved from practical challenges. Even before symbols appeared on chalkboards, ideas about measurement were already shaping the world in stone.