Find your birthday (or any other number) in pi ...

http://www.angio.net/pi/piquery

by RiderOfGiraffes • 16 years ago

42 36 16 years ago

angio.net

RiderOfGiraffes4• 16 years ago

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

MattF• 16 years ago

Mine's at 177,322,565

RevRal• 16 years ago

Position 21,786,098

Who can get closest to zero?

m_eiman• 16 years ago

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…

nuclear_eclipse• 16 years ago

The string 19850427 occurs at position 5,438,413

naish• 16 years ago

I'm at 1,251,501 if I exclude the century (19); otherwise, my DOB is not to be found.

dkokelley2• 16 years ago

I lose: The string 19880316 occurs at position 59,056,088

atlbeer• 16 years ago

The string 31182 occurs at position 118,017 counting from the first digit after the decimal point. The 3. is not counted.

3-11-82

pingswept• 16 years ago

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?

brown9-2• 16 years ago

DeusExMachina• 16 years ago

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• 16 years ago

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

alphaBetaGamma• 16 years ago

The statement (infinite && not periodic) ==> (any finite sequence is in it) is not true. \a number could have a decimal expansion that is not periodic but does not include certain digits. E.g: write Pi in binary and consider the same sequence of 0's and 1's as a number in decimal

Oatmeat• 16 years ago

It is conjectured that pi is normal: http://en.wikipedia.org/wiki/Normal_number

If the conjecture is true then any finite sequence of numbers can be found in the digits of pi. As others have noted, infinite sequences are not guaranteed or even likely to appear. As zackattack points out, for example, the decimal expansion of 1/9 does not appear in the digits of pi.

pook• 16 years ago

RMS's birthday is today.

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

david927• 16 years ago

happy birthday, rms!

dkokelley2• 16 years ago

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

mcantor• 16 years ago

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!

RiderOfGiraffes4• 16 years ago

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)

ilitirit• 16 years ago

> although 355/133 is close and you can get as close as you like by using bigger numbers

355/113

RiderOfGiraffes4• 16 years ago

Corrected - thanks.

philh• 16 years ago

>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

RiderOfGiraffes4• 16 years ago

Corrections made - thanks.

araneae• 16 years ago

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

I'm so sad.

kmano8• 16 years ago

Also doesn't have my bday.. 04221986

daten• 16 years ago

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?

python_kiss• 16 years ago

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

arethuza• 16 years ago

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

eru• 16 years ago

Depends on how much leeway you allow in encoding..

tocomment• 16 years ago

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?

huhtenberg• 16 years ago

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

Why am I not surprised? :)

tel• 16 years ago

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.

frankus• 16 years ago

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

Find your birthday (or any other number) in pi ...

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