

Find your birthday (or any other number) in pi ... - RiderOfGiraffes
http://www.angio.net/pi/piquery

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RiderOfGiraffes
For those who are interested:

It is conjectured that pi is "normal" in the sense that the digits occur with
equal liklihood. Making that statement precise is exceedingly hard, and not
very enlightening.

EDIT: philh points out that the full definition of "normal" says that every
block occurs equally often (a concept that needs care to make formally
correct) and that _does_ imply that every finite sequence does occur.

pi is known to be transcendental. It is not only not rational (cannot be
expressed as the ratio or integers (although 355/113 is close and you can get
as close as you like by using bigger numbers)) but it is also not the root of
any polynomial with integer coefficients (rationals being a special case).

The digits of pi cannot become periodic.

None of the above is enough to show that every finite number occurs
"eventually". As an example, consider the number:

0.123 112233 111222333 111122223333 111112222233333 ...

Here the digits 1 through 3 occur equally often, it never becomes periodic, it
is transcendental, and yet the sequence 321 will never occur. Now instead of
using 1 through 3, generalise to using 1 through 9.

It is generally believed that the digits are "effectively random" which means
any finite sequence will occur with probability 1, but the observations made
above are not enough to ensure that. (EDIT: although the full definition of
"normal" does, rather thanthe limited version I originally put - thanks to
philh for the correction).

(edited a typo 133 -> 113 : thank you for the correction)

~~~
philh
>It is conjectured that pi is "normal" in the sense that the digits occur with
equal liklihood.

That's only part of it. You need that every block occurs as often as every
other block of equal length. So every digit occurs as often as every other
digit; every pair of digits occurs as often as every other pair; every triple
occurs as often as every other triple; and so on. So the number you give is
not normal in base 3.

A consequence of normality is that every finite sequence of digits eventually
appears.

<http://en.wikipedia.org/wiki/Normal_number>

~~~
RiderOfGiraffes
Corrections made - thanks.

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mcantor
Page is worth it for this nugget:

Be warned that 50 million digits of pi takes up 50 megabytes. This can take up
to _4 hours_ to download with a 28.8k modem!

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pook
RMS's birthday is today.

"The string 03161953 occurs at position 30,263,003 counting from the first
digit after the decimal point."

~~~
dkokelley
Seriously?! We share a birthday then (shifted by about 35 years though). Happy
birthday, birthday buddy.

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daten
Weird. If I "See 10 digits starting at position 186,557,264", the result is:
8912345678

But if I search for that result, it doesn't find it.

If I search for 12345678 it finds it and you can see 89 before it. Why can't I
search for that number?

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tocomment
I always find it weird to think that I'm in pi somewhere. The exact position
of every atom in my body at every moment of my life.

Maybe I'm getting the math wrong though?

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pingswept
This isn't true in a strict sense, is it? The digits of pi aren't random, and
for numbers of arbitrary size, it seems that you could just keep asking for a
longer numbers until you can't find a match any more.

Ah, we know that none of the numbers of the form pi + x can found in pi.

But I still wonder whether there exist numbers of finite length that can't be
found within the digits of pi. Any hardcore mathematicians in the house?

~~~
DeusExMachina
I'm not a mathematician, but I read a lot of time ago that since pi is
infinite but not periodic, you shold be able to find in it any sequence you
want, given infinite time to search in it.

This is what I remember, but I could be wrong.

~~~
zackattack
You can't find 1/9 in pi. 1/9 precludes the possibility of any other sequence.

~~~
staticshock
I think the parent was talking about sequences of digits, i.e. integers, not
just "any rational number"

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huhtenberg
_The string 718281828 did not occur in the first 200000000 digits of pi after
position 0._

Why am I not surprised? :)

~~~
tel
There's almost a 1 in 10 chance of seeing any 9 digit string (according to the
website), so it might be a little bit surprising at least.

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arethuza
I wonder where the first item of "intellectual property" exists in pi
(suitably encoded, of course)?

~~~
eru
Depends on how much leeway you allow in encoding..

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araneae
pi doesn't have my phone number (in the first 200000000 digits)

I'm so sad.

~~~
kmano8
Also doesn't have my bday.. 04221986

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python_kiss
I created a version of my own: <http://jawadonweb.com/projects/pi>

:)

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frankus
It couldn't find "help I'm trapped in a universe factory" in the first two
million digits.

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RiderOfGiraffes
My birthday occurs at position 157,396,201, using the ISO date format.

~~~
RevRal
Position 21,786,098

Who can get closest to zero?

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m_eiman
Writing a bit of code that'll find the first valid ISO date should be easy
enough, then we'll just need to find someone who was born that day…

~~~
jonp
29021960 appears starting at digit 713.

Wikipedia lists Khaled, Algerian raï musician; Richard Ramirez, American
serial killer; Tony Robbins, American motivational speaker as being born on 29
February 1960.

Oddly searching for 29021960 doesn't return a result. But searching for
2902196 does and shows there's a zero after it.

~~~
gjm11
ISO format is yyyymmdd, not ddmmyyyy. First recent ISO date in pi is 19530921
at the 417th decimal place. All Wikipedia has for that date is the birth of a
musician and recording engineer called Andy Heermans.

