## Perfect π

Got an iPhone? Bring up the Control Center by swiping up from the bottom of the screen. At the bottom center right of the Control Center, click the icon for the Calculator. Or shortcut these first two steps by simply telling Siri, “Run Calculator.” With the Calculator onscreen, turn the device to landscape view to access the scientific calculator. Near the center of the bottom of the scientific calculator display, click the π button. The scientific calculator displays the value of pi rounded to 16 significant digits: 3.141592653589793. Without clearing the calculator, turn the device to portrait view; the simple calculator now displays the value of pi rounded to 9 significant digits: 3.14159265. Or shortcut all of these steps by asking Siri, “What is the value of pi?” — via Wolfram Alpha, to 29 significant digits: 3.1415926535897932384626433832. Or let Siri take it out farther by asking something like, “What are the first 240 digits of pi?”

Or on your slide rule, it’s just to the right of the 3

(or just to the left of 3 on the reverse scale).

Since the slide rule doesn’t have the limitations on decimal places imposed on digital equipment, you can actually luck into getting something there that the iPhone display of digits can’t achieve: Perfect π! Sure, you’ll never quite reach that perfection by trying to actually place that red line of your slide rule’s viewer at rest directly over the π symbol, since our eye and hand aren’t that exact, except by happy accident. But you can move through perfection and back by sliding the viewer over π then back again. Try it! Passing over perfect π is fun!!

And just like that spatial encounter with π, soon we will have a rare opportunity to experience that same fun in a once-in-a-lifetime temporal representation of π: Pi Day of the Century. Using sequential time, pi enthusiasts recently have been celebrating every March 14 (that is, using the first three significant digits of pi, 3.14) as Pi Day. And this year, sequential time for pi can be carried out to five significant digits: 3.14.15. And during the morning of that special day, 53 seconds after 9:26, sequential time will be able to carry pi out to ten significant digits!— 3.14.15 9:26.53. And now, for that temporal experience of perfection: a fraction of a second before 3.14.15 9:26.54, sequential time will pass through pure pi — the exact value of pi!!! Touch it, feel it, enjoy it! Like a comet, it won’t come again until the year 2115.

And since we don’t know of anyone who celebrated this moment in 1915 or 1815 or any 15s in previous centuries, we can think of this as the Inaugural Pi Day of the Century. Hurray!

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