# The Naked Scientists Forum

### Author Topic: Why Calculate Pi to So Many Decimal Places ?  (Read 20838 times)

#### neilep

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##### Why Calculate Pi to So Many Decimal Places ?
« on: 24/08/2008 18:12:12 »
Dearest Piologists and eaters of all things pastry lined !

see this Pi ?

Nice eh ?...being delivered Tuesday !

As a sheep the nature of Pi taunts me every day and night !!

We can calculate Pi to a trillion decimal places !...I know this because I have counted them !.....but why ? Why calculate Pi to a trillion places when apparently only 40 decimal places is enough to calculate the circumference of the visible Universe ?

Whilst I await your answers, I think I'll count them again..I think i missed a '3' somewhere around 425 billion !

Thank Ewe

Hugs the Klevur peeps

Shmishes them too !

Neil

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

#### syhprum

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##### Why Calculate Pi to So Many Decimal Places ?
« Reply #1 on: 24/08/2008 19:11:36 »
I think the object is to test out algorithms for computing such numbers and to demonstrate computer power

#### neilep

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##### Why Calculate Pi to So Many Decimal Places ?
« Reply #2 on: 24/08/2008 19:42:14 »
I think the object is to test out algorithms for computing such numbers and to demonstrate computer power

Thank Ewe syhprum

So, it's really just a mater of ' because we can '...but also as a tool to demonstrate efficiency....

.......I know this might be a silly question but how do we know if Pi to a trillion decimal places is calculated correctly ?

#### lyner

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##### Why Calculate Pi to So Many Decimal Places ?
« Reply #3 on: 25/08/2008 23:55:36 »
One way of 'knowing' is based on various mathematical proofs which can show that pi must lie between two values which can actually be calculated - therefore they can say that they 'know' pi to a certain accuracy i.e. between those limits.
I'm not sure I put that in the most understandable way - sorry.

#### lyner

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##### Why Calculate Pi to So Many Decimal Places ?
« Reply #4 on: 26/08/2008 15:11:30 »
The real answer to the "why?" question is that Mathematicians are all on a different track to the rest of us. Some of them are really loopy. Brilliant but loopy and what would be do without them?
Try to have an ordinary conversation with a good Mathematician about a commonly discussed topic and you can rely on them to take you to places that you would never normally go. Some of my best friends are Mathematicians, I have to say.

#### blakestyger

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##### Why Calculate Pi to So Many Decimal Places ?
« Reply #5 on: 26/08/2008 19:13:16 »
Possibly...sometime, somewhere, someone will discover that after the umpteenth billion places you have counted up to...it will start to repeat itself. [:0]

#### lyner

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##### Why Calculate Pi to So Many Decimal Places ?
« Reply #6 on: 26/08/2008 21:16:52 »
That would imply that pi is rational (a ratio of two integers). 'They' can prove, quite conclusively, that it isn't. So you won't find a repeat.

#### Alan McDougall

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##### Why Calculate Pi to So Many Decimal Places ?
« Reply #7 on: 27/08/2008 13:27:14 »
To see if there would be some pattern.

#### lyner

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##### Why Calculate Pi to So Many Decimal Places ?
« Reply #8 on: 27/08/2008 20:51:43 »
If the sequence is constantly changing then you might expect the occasional, apparently meaningful, embedded pattern. But what would that prove? It's just like monkeys and typewriters.

#### Bored chemist

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##### Why Calculate Pi to So Many Decimal Places ?
« Reply #9 on: 28/08/2008 19:26:33 »
Any and all patterns will occur somewhere in pi. It might take a while to find them.

• Neilep Level Member
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##### Why Calculate Pi to So Many Decimal Places ?
« Reply #10 on: 28/08/2008 19:54:04 »
The book, 'The Life of Pi' is much more interesting. The first few chapters are dull but then....wow! it is brilliant.

Sheepy, I think 7 decimal places is enough for anyone but I guess you can't have too much of a good thing.

#### syhprum

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##### Why Calculate Pi to So Many Decimal Places ?
« Reply #11 on: 29/08/2008 17:08:59 »
Parraleling the hunt for evermore digits of Pi the hunt for the 45th Mersenne number seems to have succeeded as reported in the Scientific American this when verified will earn a \$100,000 prize

#### Glenn

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##### Why Calculate Pi to So Many Decimal Places ?
« Reply #12 on: 16/09/2008 09:30:00 »
Though I too am fascinated by the trillion digits of pi so far calculated, it's more important to know HOW to calculate it. For example, this continued fraction will do nicely:

4    1^2   2^2   3^2   4^2        k^2
pi = ---- ----- ----- ------ ----- ... ------- ...
1+    3+     5+     7+     9+        2k+1+

While other methods converge to pi more quickly, this is the easiest-working.
« Last Edit: 17/09/2008 08:04:21 by Glenn »

#### neilep

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##### Why Calculate Pi to So Many Decimal Places ?
« Reply #13 on: 16/09/2008 13:40:03 »
Is it even possible to display a trillion digits ?

#### Chemistry4me

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##### Why Calculate Pi to So Many Decimal Places ?
« Reply #14 on: 31/12/2008 03:10:23 »
Though I too am fascinated by the trillion digits of pi so far calculated, it's more important to know HOW to calculate it. For example, this continued fraction will do nicely:

4    1^2   2^2   3^2   4^2        k^2
pi = ---- ----- ----- ------ ----- ... ------- ...
1+    3+    5+    7+    9+        2k+1+

While other methods converge to pi more quickly, this is the easiest-working.
How does that method work? I'm no maths wizz, actually I'm mathamatically dyslexic, but its not that uncommon, 436 people out of 34 have it... mwhahahaha

#### Mr. Scientist

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##### Why Calculate Pi to So Many Decimal Places ?
« Reply #15 on: 31/12/2008 04:22:59 »
Though I too am fascinated by the trillion digits of pi so far calculated, it's more important to know HOW to calculate it. For example, this continued fraction will do nicely:

4    1^2   2^2   3^2   4^2        k^2
pi = ---- ----- ----- ------ ----- ... ------- ...
1+    3+    5+    7+    9+        2k+1+

While other methods converge to pi more quickly, this is the easiest-working.
How does that method work? I'm no maths wizz, actually I'm mathamatically dyslexic, but its not that uncommon, 436 people out of 34 have it... mwhahahaha

They've used what is called a Infinite Series.

#### Chemistry4me

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##### Why Calculate Pi to So Many Decimal Places ?
« Reply #16 on: 31/12/2008 04:49:53 »
So can somebody demonstrate for me how its done? How does this Infinite Series work? As I said, my maths isn't exactly out of this world... [:I] [:I]

#### Mr. Scientist

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##### Why Calculate Pi to So Many Decimal Places ?
« Reply #17 on: 31/12/2008 04:57:18 »
So can somebody demonstrate for me how its done? How does this Infinite Series work? As I said, my maths isn't exactly out of this world... [:I] [:I]

well, i only glanced very quickly at the math, but generally speaking, if you want to calculate something large, then it goes through a series.

#### Chemistry4me

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##### Why Calculate Pi to So Many Decimal Places ?
« Reply #18 on: 31/12/2008 04:59:38 »
Um... forgive me for saying this Mr. Scientist, but you are still talking in riddles. [:I] [:I]

#### Mr. Scientist

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##### Why Calculate Pi to So Many Decimal Places ?
« Reply #19 on: 31/12/2008 05:04:19 »
Um... forgive me for saying this Mr. Scientist, but you are still talking in riddles. [:I] [:I]

Do you know calculus? Or would you like me to hopefully explain this in some effecient way for you to understand?

#### Mr. Scientist

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##### Why Calculate Pi to So Many Decimal Places ?
« Reply #20 on: 31/12/2008 05:05:29 »
Even better,  here is a link

Series (mathematics) - Wikipedia, the free encyclopedia
A series may be ... However, infinite series of nonzero terms can also converge, ... The idea of an infinite series expansion of a function was ...
en.wikipedia.org/wiki/Series_(mathematics) - 73k - Cached

#### Chemistry4me

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##### Why Calculate Pi to So Many Decimal Places ?
« Reply #21 on: 31/12/2008 05:13:00 »
Do you know calculus? Or would you like me to hopefully explain this in some effecient way for you to understand?
I know a little bit of calculus [:I] If you can explain how that Infinite Series works to solve π I would be very greatful

#### Mr. Scientist

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##### Why Calculate Pi to So Many Decimal Places ?
« Reply #22 on: 31/12/2008 05:23:17 »
Do you know calculus? Or would you like me to hopefully explain this in some effecient way for you to understand?
I know a little bit of calculus [:I] If you can explain how that Infinite Series works to solve π I would be very greatful

It will take me about 20 mins then to type it out. Hold on. :)

#### Chemistry4me

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##### Why Calculate Pi to So Many Decimal Places ?
« Reply #23 on: 31/12/2008 05:27:09 »
WOW! Must be some complicated stuff , never mind, I can wait... the mystery of pi shall be explained. Umm... pie...

#### Mr. Scientist

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##### Why Calculate Pi to So Many Decimal Places ?
« Reply #24 on: 31/12/2008 05:36:52 »
Right, first contemplate what is a string or a sequence of numbers:

1, 1/2, 1/3, 1/4, 1/5

if we dot it at the end like so,

1, 1/2, 1/3, 1/4, 1/5...

It means, ''and so on,'' in this particular pattern. We can now say that the n^th number is a_n, then one can evaluate that a_1 is 1, and a_2 is 1/2, so that implies that a_n=1/n. An infinite series of numbers will look something like this:

∑ = 1 + 1/2 + 1/4 + 1/8 + ...

Where again, the (+ ...) means an infinite continuation of the numerical processes. Since we can't add all of infinite numbers, we can however add the first lot of ''n'' terms like

∑_1 = 1
∑_2 = 1 + 1/2 = 3/2
∑_3 = 1 + 1/2 + 1/4 = 7/4

where ∑ just means the 'sum of.'

Does that help?

#### The Naked Scientists Forum

##### Why Calculate Pi to So Many Decimal Places ?
« Reply #24 on: 31/12/2008 05:36:52 »