Pi and the size of the Universe - Numberphile

Pi is famously calculated to trillions of digits - but Dr James Grime says 39 is probably enough.
More links & stuff in full description below ↓↓↓

An extra note from Dr Grime: "Since pi39 ends in 0, you may think we could use pi38 instead - which has even fewer digits. Unfortunately, the rounding errors of pi38 are ten times larger than the rounding errors of pi39 - more than a hyrdogen atom. So that extra decimal place makes a difference, even if it's 0."

NUMBERPHILE

Videos by Brady Haran

[RMoribayashi]

My favourite representation of π is 355/113. It's easy to remember as 113355 and is accurate to six decimal places. It often puzzled my maths teachers when my results didn't match the rest of the class using who were using 22/7. I always hoped that I'd made their lessons a little more interesting for them. At least they never penalized me for doing it.

[robinaretz]

I want this guy to be the next Doctor in Doctor Who. :D

[AsymptoteInverse]

I memorized the first 100 digits in high school. For some reason, I've managed to retain 75 of them, despite having a crappy memory for important things like people's birthdays, etc.

[ThatBasedGuy]

Humans: "Well, we only need 39 digi..."
Pie: "2000 ready and 10 trillion more on the way"

[williamhunter]

What if you used pi to calculate the size of the observable universe to the accuracy of a planck length. Wouldn't that create an accuracy of pi that is all that we could ever need in any way?

[gedstrom]

Way back some 52 years ago, I memorized Pi to 50 decimal places and can still recite the digits to this day. The only reason I didn't go further was because I didn't have access to more digits in any of my books at that time. I did not use any mnemonic...I simply memorized the digits in groups of 5...I had no particular reason for doing it other than I wanted to do it.

[Grand-Massive]

at what digit of pi would we be measuring to the accuracy of a planck length

[roast_possum]

You only need 61 digits to find the circumference of the observable universe using planck lengths. Much more fundamental than hydrogen atoms...

[brandonblack]

So, I got lost when he said "But one of my favorite pi facts..."

[dekippiesip]

 Could you make a video about infinite series converging to pi and other algorithms used to calculate it to a high degree of accuracy? To me it's astonishing that something like 4-4/3+4/5-4/7+... has anything to do with a circle. It's so neat it really deserves a video.

[nostalgia_]

1:13 standard hilarious James moment :D

[jkadoodle]

I love how in 1940 700 digits was the standard and had been for 100 years. 70 years later we know pi to 10 trillion digits ... that's crazy

[bigleebrink]

All this talk of pi has made me wanna eat a piece of pie.

[gauravudiyavar]

Oh how I wish I had this bloke for my math teacher in school. I had an incredibly amazing professor for accounting in college, which is why I'm very well versed in that subject and I have the ability to learn new concepts quickly, but my math isn't great by any stretch of the imagination. However, every video of this gentleman that I've watched, I've found it interesting and fun to learn.

[Sevish]

Love this series but I hate the sound of pen scratching away on card or paper... sends shivers down my spine... much love to all the numbers of the world!

[Jimpozcan]

All this talk of pie is making me hungry.

[mikiaibres]

The amazing thing about Pi is that you can make up any number sequence of any length and it resides within Pi

[chrismboyle]

I was thinking more along the lines of how to arrive at Pi, I understand the unit circle equation and the calculus behind it but it is always cool seeing it explained in simple terms... and maybe with a little history thrown in!

[amitnagpal]

I understand very little but his enthusiasm makes it endearing and watchable.

[coopergates]

So you only have two significant figures in the diameter of the universe, try using 8.82*10^26 meters (which would still round to 8.8), and you get thrown off completely, more so even than with using 3.142 for Pi versus