**Pi **(noun “pye”)

This is a mathematical fixed — a quantity whose worth by no means adjustments. Symbolized by the Greek letter π, pi is the ratio of a circle’s circumference — the space across the periphery — to its diameter, the size throughout its middle. That ratio is at all times pi to at least one. The quantity pi is commonly shortened to three.14 or 3.14159. But this quantity is definitely infinite. One quantity cruncher calculated pi out to *50 trillion* digits. The digits after the decimal place, although, go on perpetually, into infinity.

Mathematicians can use pi to find out a circle’s circumference from its diameter. A circle one meter in diameter, as an example, can have a circumference of three.14159 meters. If it measures two meters in diameter, the circumference can be 6.28318 meters.

Pi additionally can be utilized to calculate the realm of a circle. The radius of a circle is one-half its diameter. Space is the same as pi instances the radius squared. That one-meter-diameter circle, then, has a space of 0.79 sq. meter. Scientists would possibly use this equation to find out the scale of craters on the moon, for instance, or to calculate the place a spacecraft travels.

But some mathematicians assume that pi is just too complicated. Instead, they would like to use tau — or τ. Tau is the ratio between a circle’s circumference and its radius. Tau is the same as 2π. Like pi, tau can also be continuing and infinite.

Mathematicians like tau as a result of it’s simpler to make use of to calculate a circle’s radians — the unit for measuring angles — just like the angle on the tip of a slice of pizza. If they reach changing pi, then as a substitute for celebrating the pi day on March 14 (3/14), folks would possibly as a substitute rejoice tau day on June 28 (6/28). But there won’t be as many tasty baked items.

#### In a sentence

Scientists gave an exoplanet the nickname “Pi Earth” as a result of it orbits around its star as soon as every 3.14 days.