**Question:** If you divide the circumference of the sun by its diameter, what will you have?

**Answer:** Pi in the sky!

Corny jokes aside, Pi Day 2018 is almost here. While there will be countless events and activities to observe the importance of this mathematical constant , some of the best programs and activities will be hosted by the Exploratorium Museum and Learning Center in San Francisco – the place where Pi Day originated on 03.14.1988.

Pi Day is a great opportunity to have a slice of pie. While you are waiting on that order in a restaurant or baking one at home, here are 10 pi facts that will keep you busy until the sweet pie is ready:

- The symbol for pi is the sixteenth letter of the Greek alphabet and is taken from the Greek word for “perimeter.”
- Pi is used in mathematics to represent a constant and is the ratio of the circumference of a circle to its diameter.
- Oddly enough, the day is also the birthday of Albert Einstein. He was born on March 14, 1879.
- At position 763 there are six nines in a row. This is known as the Feynman Point.
- Pi plays a prominent role in navigation, especially when it comes to large-scale global positioning….when you locate yourself on Earth using a GPS device, pi must play an important role in these calculations.
- Pi is a famous irrational number. We cannot write down a simple fraction that equals pi. The popular approximation of
^{22}/_{7}= 3.1428571428571… is close but not accurate. Another clue is that the decimal goes on forever without repeating. - Meandering rivers: Pi has a fascinating and unexpected relationship to meandering rivers. A river’s path is mostly described by its sinuosity—its tendency to wind from side to side as it traverses a plain. This can be described mathematically as the length of its winding path divided by the length of the river from its source to its mouth. It turns out that regardless of the river’s length, or how many twists and turns it takes along its path, the average river has a sinuosity of roughly pi.
- Some people believe pi contains the answers of the universe.
- In the
*Star Trek*episode “Wolf in the Fold,” Spock foils the evil computer by commanding it to “compute to last digit the value of pi.” Spock is the only being who can rationally solve a problem using an irrational number. - Pi is used to calculate both normal distributions and the distribution of prime numbers.
- Pi is used in the Buffon’s Needle Problem, a proof that determines the probability of whether a needle will land on a line or not when it is dropped onto a plane containing parallel lines.

Sources Cited Include:

*Unique Facts of Pi*, http://www2.mtsd.k12.wi.us/Homestead/users/ordinans/The%20Unique%20Facts%20of%20Pi.htm*Top 10 Fascinating Facts About Pi*, by Nick Logan, April 13, 2017, https://listverse.com/2017/04/13/top-10-fascinating-facts-about-the-number-pi/*10 Pi Facts for the most irrational Pi Day of your life*, https://mashable.com/2015/03/13/perfect-pi-day/#VkBIdAy6NZq6

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