# Day 728 - Pi Day

It's 14 March, or 3-14 to some people. That's probably enough pi for most of us, for most practical purposes.

Most of us can rattle off a handful of digits, like 3.141592653 (which is how far I'm confident...because it's the size of a phone number). And I know that last should be rounded to a 4, because I think its next digit is a 5. (And after looking for things, that's correct...so I know more digits than I am confident to say.)

According to NASA's JPL,they use 15 digits for their math. This brings radial math at the radius of the Voyager mission to about an inch and a half, and math on Earth to within the size of molecules.

If we need to do radial math within the size of the accepted known universe, a radius of about 46 billion light years, only 40 digits are needed to get within that molecule of accuracy.

Using pi to about 62 digits gives us that universal math accurate within the Planck length, the accepted shortest measurement.

So for the largest reasonable calculations, we need to know fewer digits than some people can confidently memorize or calculate.

Someone has calculated pi to 62.8 trillion digits. It's not useful for additional accuracy, but is a fun test of a bunch of geeky math fun.

Today should be about pie, though. I don't think we have any on the menu, though.

Everyone's healthy.