# March 14 is Pi Day: 14 things to know about the irrational number

On Saturday, mathematicians and nerds around the world will honour the most widely known mathematical constant and irrational number - Pi or approximately 3.14.

This year's March 14 event is touted as a once-in-a-lifetime occurrence.

March 14, 2015, or 3.14 '15 would coincide with the first five digits of the number, something that happens once a century. At 9.26am 53 sec on March 14, the time corresponds to the first 10 digits of Pi which are 3.141592653.

Since the day was first marked at San Francisco's science museum, the Exploratorium in 1988, it has gained in popularity.

Here are 14 funky facts about pi and Pi Day:

1. Defined as ratio of the circumference of a circle to its diameter, pi is all around us. The number is the same for all circles of any size.

2. Pi is an irrational number, which means it is an infinite decimal and the number never ends. While you may remember using 3.14 or 22/7 in your geometry homework, computer programmes have calculated its value up to trillions of decimal places.

3. Only 40 digits of pi is needed to accurately calculate the spherical volume of the universe, but mathematicians find it a challenge to figure out and memorise the digits of Pi.

4. The Guinness world record for memorising the digits of pi is held by Chao Lu of China, who recited the number to more than 67,000 decimal places.

5. Pi has been known for almost 4,000 years, but ancient civilisations such as the Babylonians did not have accurate calculations of it. The first calculation of pi was done by Archimedes (287-212 BC).

6. The Exploratorium's physicist Larry Shaw started the tradition of celebrating Pi Day, and they marked it in 1988 by walking around in a circle while eating fruit pies.

7. The US Congress endorsed Pi Day as a day to celebrate math education in 2009. Many institutions mark it as a way to encourage interest in math and science.

8. There are now many events held in conjunction with Pi Day in the US and worldwide. Some involve eating pies, others the memorising of the digits of pi, and other educational activities that 'pi-ticipants' can enjoy.

9. The Singapore Science Centre will open at seven seconds to 9.27am, instead of 10am on Saturday. The first 58 visitors will enter for free, and there will be a Pi Show at 2pm.

10. There is a song about pi by British singer Kate Bush.

11. Some people bake Pi pies.

12. Brace yourself for pi(e) puns and jokes.

13. July 22, or 22/7 is Pi Approximation Day.

14. March 14 is also scientist Albert Einstein's birthday. Just a coincidence?