We hereby propose that those who Know Better celebrate Real Pi Day at the point in time when the Earth has passed through 1/π of its orbit, as measured from Winter Solstice to Winter Solstice (that’s ‘one’ over ‘pi’, if your browser is rendering things oddly). Based on our current estimation (please help us improve our calculations!), this will be on Saturday, April 17, 2010 at 12:02 AM Coordinated Universal Time. For those of you in the USA, this will be on Friday, April 16, 2010 at 8:02 PM Eastern Daylight Time or Friday, April 16, 2010 at 5:02 PM Pacific Daylight Time.
Update: Another possibility is to calculate from perihelion rather than the solstice (discussion here), which removes some arbitrariness that creeps in when we wonder whose Winter (northern hemisphere or southern hemisphere) we’re referring to! This gives us a possibly improved date of Thursday, April 29, 2010 at around 3pm UTC. Please keep the suggestions coming!
What’s wrong with the other Pi Day?
March 14 is the vulgar Pi Day. Sure, calling 3/14 “Pi Day” may seem cute, and it makes for good media coverage, but the commemoration of a transcendental constant should not be tied to the grubby political vagaries that resulted in the Gregorian calendar’s accidents of number. The U.S. House of Representatives has officially designated 3/14 as Pi Day, but the truth of mathematics is not to be found in the chambers of the legislature.
Think about it. Much of the world will write the date as 14/3, which is more than a bit depressing. Europeans may go in for a Pi Approximation Day on 22 July (22/7, get it?), but that doesn’t really improve matters.
Wikipedia’s page on Pi Day suggests some alternatives. Consider this proposal for April 26:
April 26: The Earth has traveled two radians of its orbit on this day (April 25 in leap years), reckoning from the start of the civil year on January 1. Thus the entire orbit divided by the distance traveled equals π; two radians equals 1⁄π of our orbit. This is celebrated exactly on the 41st second of the 23rd minute of the 4th hour on April 26 or the 116th day. (In leap years, it is celebrated exactly on the 3rd second of the 2nd minute of the 12th hour on April 25 or the 116th day.) This celebration is not a Pi Approximation Day; many, mathematicians included, celebrate April 26 as Pi Day and say that it should be the official Pi Day.
This suggestion would be wholly admirable, were it not for its tie to the arbitrariness of the Gregorian calendar. To rectify this, we suggest that the date of Real Pi Day be calculated from the winter solstice, the point in Earth’s orbit where its axial tilt is furthest from the sun. Last year’s Winter Solstice occurred at 17:47 UTC on December 21, 2009, and the next will occur at 23:38 UTC on December 21, 2010. Based on our these dates, 1/π-th of the period will have passed on Saturday, April 17, 2010 at 12:02 AM Coordinated Universal Time.
How can you help?
Celebrate Real Pi Day! Our recommendation is to get together with some friends and hoist a few pints of your favorite beverage. It doesn’t matter how many, as long as it’s a round number and enough to get you feeling a bit irrational.
Are you an astrophysicist? Please help us refine our calculation of the true Pi Point!