**New Delhi:**

3.14, 22/7, the Archimedes' constant-- Pi, the mathematical constant, celebrates the 31st Pi Day today. Physicists, mathematicians and Pi-enthusiasts have thanked the constant and have outpoured their happiness and tribute on social media on Pi Day today. "Happy 'Pi day'! Today's date, March 14, resembles 3.14159, the common approximation of the mathematical constant Pi. Pi is the ratio of the circumference of a circle to its diameter. It doesn't matter how big or small the circle is - the ratio stays the same," tweeted the official page of the Nobel Prize.

American astrophysicist Neil deGrasse Tyson has wished all the "pi-maniacs" a happy Pi day.

In 1988, Physicist Larry Shaw first recognized the Pi Day. March 14 was chosen as the Pi Day, because the date in mm/dd format represents the value of the Pi constant up to first two decimal digits. An interesting fact is that the first million decimal places of Pi consist of 99,959 zeros, 99,758 1s, 100,026 2s, 100,229 3s, 100,230 4s, 100,359 5s, 99,548 6s, 99,800 7s, 99,985 8s, and 100,106 9s.

Mathematically, this constant can't be expressed as a common fraction. It has a never ending and repeating decimal representation of its value. Originally it is defined as the ratio of a circle's circumference to its diameter or twice its radius.

The celebration for the Pi day officially begins at 1.59 pm so as to make it the approximate value of the constant, 3.14159.

Renowned mathematician and physicist, Albert Einstein, known for the “general theory of relativity” was born on Pi Day in 1879. Today the world is celebrating his 140^{th} birthday.

Last year, Google had dedicated a doodle for Pi Day with a salted caramel apple pie baked by award-winning pastry Chef Dominique Ansel.

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