The number pi () can be found everywhere from Shakespearean thought puzzles and baking challenges to the physics of pendulums and river bends. As the ratio of circle circumference to diameter, pi is also a central figure in math, physics, engineering, statistics and other fields – for instance it can be used as part of formulae for length of arcs or other curves, areas of ellipses/sectors as well as volumetric calculations for cylinders and spheres.
Pi is known as a constant or universal number because it never ends or repeats, making it the foundation for many mathematical and scientific discoveries. Pi serves as an indispensable part of mathematics, trigonometry, geometry and fractal geometry studies; we use it to understand phenomena like star rotation and pendulum oscillation as well as light’s wavelike behavior on sunny days – it even helps determine our sunburn risk!
Pi has fascinated people for millennia. From its inception among Babylonians approximately 2000 BCE to Archimedes’ “Elements of Mechanics,” which calculated pi to within several decimal places, its appeal transcends cultures and centuries – from Archimedes himself calculating pi up to within three decimal places! Pi is found everywhere from building design formulae to measuring time or measuring land; in formulae for designing buildings to its presence in pendulums and springs physics as well as fluid dynamics dynamics vibrations biophysics biophysics as well as spiral galaxies!
At first, progress on calculating pi was slow to come by after its discovery in 1686; however, Indian mathematician Srinivasa Ramanujan developed an efficient formula for doing it faster in 19th-century India. By 1949, ENIAC could calculate 2,000 digits in 70 hours–still an outstanding speed record today. Modern computers have since driven an effort to calculate more and higher digits; on March 14, 2025 scientists from Linus Media Group and Kioxia reported reaching 300 trillion digits!
Pi’s endless sequence of digits is not only fascinating to mathematicians and engineers; its continuous pattern also serves as an effective cipher. In World War II, the Allies used pi to code secret messages because its random digits make decoding it much harder.
Pi is a fundamental number that plays a pivotal role in our universe and provides students with a way to introduce them to geometry and physics concepts. That’s why we celebrate Pi Day every year since 1988 at San Francisco’s Exploratorium science museum where physicist Larry Shaw came up with the concept for honoring it due to its resonance with Earth, spacecraft and aircraft orbits, nature patterns and circularity of Earth itself. Discover its story as well as activities for students of all ages here from Exploratorium Science Education Specialist Jennifer Stubbs.