Trivia/Maths Q. - Circumference of the Earth

This is another 'off-topic topic', but a fun one to share with fellow star gazes ... (although it does bring back the horrors of 7th grade math)

Q. If I had a string which went around the equator of the Earth so it was snug and I added 1 metre to its length, so it raised itself off the ground/sea, how far would it be from it's original position (ie. what is the increase in radius)?

Radius of Earth in meters - (((2 * Pi * Radius of Earth in meters) + 1 meter ) / 2 * Pi )

Well ... OK, but in terms of mm's which is what spun me out. New radius is bigger by approx 159mm!

Reminds me of something I heard the other day about a nerd who calculated Pi to several trillion decimal places.

I was quite surprised that you only need to know Pi to 9 decimal places in order to calculate the circumference of a circle the size of the earth to an accuracy of +/- 1mm. 47 decimal places of Pi is enough to calculate the circumference of the known universe to an accuracy of +/- the width of a hydrogen atom.

So why calculate Pi to trillions of decimal places?!

(When I was at school, me and some friends memorised Pi to about 150 decimal places, and to this day I still know about 40 or 50, so I'm sorted should someone ask me to do a major culculation! )

Yeah that is a little surprising especially when after the Xmas indulgences loosening my belt by an inch does not seem to have made that much difference

Adrena1in wrote in post #9431790
Reminds me of something I heard the other day about a nerd who calculated Pi to several trillion decimal places.

I was quite surprised that you only need to know Pi to 9 decimal places in order to calculate the circumference of a circle the size of the earth to an accuracy of +/- 1mm. 47 decimal places of Pi is enough to calculate the circumference of the known universe to an accuracy of +/- the width of a hydrogen atom.

So why calculate Pi to trillions of decimal places?!

(When I was at school, me and some friends memorised Pi to about 150 decimal places, and to this day I still know about 40 or 50, so I'm sorted should someone ask me to do a major culculation! )

nerd.....

Well, obviously we need pi to at least 94 decimal places so we can calculate our known universe and the parallel one next to use, like in Futurama.

Chris, you mean to tell me after December celebrations you gained 4.04mm of insualtion from eating (1inch/2*pi)??? You sure it wasn't just your winter coating?

What I like about the Earth question is you tell someone who doesn't actually think about it (aka nerdn'ts) and then ask them the same question but instead of the Earth, use a golf ball as an example and it's the same answer! They struggle with the concept, it's fun to watch!

legoman_iac wrote in post #9435605
What I like about the Earth question is you tell someone who doesn't actually think about it (aka nerdn'ts) and then ask them the same question but instead of the Earth, use a golf ball as an example and it's the same answer! They struggle with the concept, it's fun to watch!

So therefore the answer would be the same for a piece of string wrapped right round the circle of the known universe?! That is pretty mind-bending!


Talking of the earth, did you know that relatively speaking it's as smooth as a pool ball?

And if it really was as smooth as a pool ball, it would be covered all over by a 2-mile deep sea.

Well, obviously know one knows for sure as there isn't a piece of string long enough to go around both universes!

Pool balls aren't smooth? Well, not in any of the pubs I've been to lately! But interesting to know, so Waterworld could come true some day! Shotgun gills!!!