Pi Day

Pi Day is an annual celebration of the mathematical constant π (pi). Pi Day is observed on March 14 (3/14 in the month/day date format) since 3, 1, and 4 are the first three significant digits of π. In 2009, the United States House of Representatives supported the designation of Pi Day.

Pi Approximation Day is observed on July 22 (22/7 in the day/month date format), since the fraction ²²⁄₇ is a common approximation of π, which is accurate to two decimal places and dates from Archimedes.

History

The earliest known official or large-scale celebration of Pi Day was organized by Larry Shaw in 1988 at the San Francisco Exploratorium, where Shaw worked as a physicist, with staff and public marching around one of its circular spaces, then consuming fruit pies. The Exploratorium continues to hold Pi Day celebrations.

On March 12, 2009, the U.S. House of Representatives passed a non-binding resolution (HRES 224), recognizing March 14, 2009 as National Pi Day. For Pi Day 2010, Google presented a Google Doodle celebrating the holiday, with the word Google laid over images of circles and pi symbols.

Pi

The number π is a mathematical constant, the ratio of a circle's circumference to its diameter, commonly approximated as 3.14159. It has been represented by the Greek letter "π" since the mid-18th century, though it is also sometimes spelled out as "pi" (/paɪ/).

Being an irrational number, π cannot be expressed exactly as a fraction (equivalently, its decimal representation never ends and never settles into a permanent repeating pattern). Still, fractions such as 22/7 and other rational numbers are commonly used to approximate π. The digits appear to be randomly distributed; however, to date, no proof of this has been discovered. Also, π is a transcendental number – a number that is not the root of any non-zero polynomial having rational coefficients. This transcendence of π implies that it is impossible to solve the ancient challenge of squaring the circle with a compass and straightedge.

Ancient civilizations needed the value of π to be computed accurately for practical reasons. It was calculated to seven digits, using geometrical techniques, in Chinese mathematics and to about five in Indian mathematics in the 5th century CE. The historically first exact formula for π, based on infinite series, was not available until a millennium later, when in the 14th century the Madhava–Leibniz series was discovered in Indian mathematics. In the 20th and 21st centuries, mathematicians and computer scientists discovered new approaches that, when combined with increasing computational power, extended the decimal representation of π to, as of 2015, over 13.3 trillion (10¹³) digits. Practically all scientific applications require no more than a few hundred digits of π, and many substantially fewer, so the primary motivation for these computations is the human desire to break records. However, the extensive calculations involved have been used to test supercomputers and high-precision multiplication algorithms.

Day (automobile)

The Day Utility was an automobile manufactured in Detroit, Michigan by the Day Automobile Company from 1911-14. The Day used a four-cylinder, 30 horsepower (22 kW) engine and shaft drive. Removal of the rear seat and doors allowed the car to be converted from a five-seater touring car to a light truck in one minute. As a truck, the Day was able to carry up to 1,000 lb (450 kg) in a 36-inch (910 mm) by 96-inch (2,400 mm) cargo space. The rear seat could be lifted away by triggering two spring locks. The Day had an advertised price of $950US.

References

Day (Michelangelo)

Day is a marble sculpture by Michelangelo, datable to 1526–31. It is a pair with Night on the tomb of Giuliano de' Medici in the Medici Chapel in San Lorenzo in Florence.

External links

Day (surname)

Day is a surname. Notable people with the surname Day include:

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