Pi Day is an annual celebration of the mathematical constant π (pi). It is observed on March 14 (3/14 in the month/day format) since 3, 1, and 4 are the first three significant digits of π.

**History of Pi Day**

Pi Day was first celebrated in 1988 by physicist Larry Shaw at the San Francisco Exploratorium. The date was chosen because it is the birthday of Albert Einstein, who was born on 1879-03-14.

**Pi Day Celebrations**

Pi Day is celebrated in many ways around the world. Some common activities include:

- Eating pie
- Throwing pie-eating contests
- Reciting pi to as many decimal places as possible
- Learning about the history of pi
- Visiting museums and science centers that have pi-related exhibits

**Pi Day Facts**

- The value of π is approximately 3.1415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679.
- Pi is an irrational number, meaning that it cannot be expressed as a fraction of two integers.
- Pi is a transcendental number, meaning that it is not a solution to any polynomial equation with rational coefficients.
- Pi has been calculated to over 100 trillion decimal places.
- The digits of pi appear to be random, but no pattern has yet been found.

**Why is Pi Important?**

Pi is used in many different areas of mathematics, science, and engineering. For example, it is used to:

- Calculate the circumference of a circle
- Calculate the area of a circle
- Calculate the volume of a sphere
- Calculate the probability of an event
- Model the behavior of waves

Pi is a fundamental constant of nature, and it is used to describe many different phenomena in the universe.