March 14 is “pi-day”, not the Apple pie day (by Dr Surjit Singh Bhatti)

March 14 is the day the Indian new year (solar as well as lunar) starts. Do you know that March 14 (also written as 3/14), is called‘ pi Day?’ This has nothing to do with the fruit pie in which the principal filling ingredient is apples and served with whipped cream, ice cream, custard, or cheddar cheese. This is a unique and very important mathematical entity. You would be surprised to learn that it even helps to explore new planets

Pi (or π) is the ratio between a circle’s circumference (πD) to its diameter (D). It is also written as 22/7 and its approximate value is 3.14. Hence, March 14 is called the ‘pi day. Mapping the unknown worlds is one of the many ways in which the world uses the magnitude of this symbol, Spacecraft orbiting other planets make maps of processes like the flow of water on these planets.  Their cameras have rectangular fields of view, which capture many images of the planet’s surface. For the whole planet, scientists use a formula that includes pi.

Powerful telescopes in space and on Earth track the light emitted by distant stars. When a planet outside our solar system (called an exoplanet) passes by a star, a dip is detected in the amount of light emitted by that star. Scientists use this dip and the formula (for area based on pi) to find the size of the planet.  An exoplanet is habitable if it is neither too far from the star it is orbiting nor too close to it so that it receives the right amount of heat. Scientists use pi to find the inner and outer edges of this (so-called goldilocks) zone. Kepler’s laws of planetary motion calculate how much time an exoplanet takes to make one full orbit of a star, using pi. This period is proportional to the size of its orbit. It reveals the planet’s location and whether it is in the correct (goldilocks) zone.  Also, pi helps to decide how big parachutes are needed so that they can generate enough drag to slow down their descent on the planet.

Pi also helps in determining how fast asteroids and comets are rotating.