Is Pi Truly Infinite and Nonrepetitive?

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Discussion Overview

The discussion revolves around the nature of pi, specifically whether it is truly infinite and nonrepetitive, and the implications of these properties regarding the presence of all possible number combinations within its decimal expansion. Participants explore concepts related to normality, periodicity, and the existence of finite sequences within pi.

Discussion Character

  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants propose that if pi is infinite and nonrepetitive, it could contain every number combination, including itself, which would imply periodicity.
  • Others argue that if pi is "normal in base ten," then every finite sequence of decimal digits should appear somewhere in its expansion, but this is not proven.
  • It is noted that there are uncountably many non-terminating decimal expansions, while only countably many can be found in pi, suggesting that not all can appear.
  • Some participants assert that pi is not periodic and cannot be rational, which would contradict it containing itself in a non-trivial sense.
  • There is a discussion about the existence of a number n such that a specific mathematical condition involving pi holds, with some participants questioning the validity of such a condition.
  • One participant mentions a specific string of digits found in pi, but this does not address the broader question of whether all combinations exist within pi.

Areas of Agreement / Disagreement

Participants express differing views on whether pi contains every finite number combination and whether it is normal in base ten. The discussion remains unresolved, with multiple competing perspectives presented.

Contextual Notes

Limitations include the lack of proof regarding the normality of pi and the implications of periodicity. The discussion also highlights the complexity of defining and proving properties related to infinite sequences and rationality.

Edi
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If pi is infinite and nonrepetive and every number combination is in pi, somewhere, does that mean pi itself is in pi somewhere.. ? (that would make it periodic)
 
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Yes, it is, starting at the first digit :)
 
Edi said:
If pi is infinite and nonrepetive and every number combination is in pi, somewhere, does that mean pi itself is in pi somewhere.. ? (that would make it periodic)

If pi is "normal in base ten" then that would mean that every _finite_ sequence of decimal digits occurs somewhere in the decimal expansion of pi.

There can only be countably many non-terminating decimal expansions found in consecutive digits in the decimal expansion of pi -- the one starting at the first digit, the one starting at the second digit, the one starting at the third digit, etc.

Since there are uncountably many non-terminating decimal expansions, it is certain that not all of them appear.
 
If pi is infinite and nonrepetive and every number combination is in pi, somewhere, does that mean pi itself is in pi somewhere.. ? (that would make it periodic)
Is there any proof that every (finite) number combination is in pi?
 
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Dead Boss said:
Is there any proof that every (finite) number combination is in pi?

It is not known whether pi is normal in base 10.
 
[itex]\pi[/itex] is not periodic. If it were it would be in [itex]\mathbb{Q}[/itex] which it isn't.
 
telecomguy said:
The string 31415926 occurs at position 50,366,472 counting from the first digit after the decimal point.

http://www.angio.net/pi/bigpi.cgi
Interesting but does not answer the question which was about the entire countable string. On the other hand, Edi seems to be under the impression that we could have entire string, then additional digits which is not possible.

Edi, it is NOT known whether "every number combination is in pi" is true or not.
 
You are looking for a number n such that 10^n*pi-pi is an integer. Call this integer q.
Then (10^n-1)*pi = q
pi = q/(10^n-1)
To find such an n, pi would have to be a rational number, which is isn't.
So, no, pi cannot repeat or contain itself.
 
  • #10
Khashishi said:
You are looking for a number n such that 10^n*pi-pi is an integer. Call this integer q.

As has been pointed out, n=0, q=0 satisfies this criterion. Pi contains itself -- in a trivial sense.

Then (10^n-1)*pi = q

Yes
pi = q/(10^n-1)

pi = 0/0 ?
 
  • #11
you know what I meant.
 
  • #12
Khashishi said:
You are looking for a number n > 0 such that 10^n*pi-pi is an integer.

Happy?
 
  • #13
Well, I could be even more picky and take n = 0.1200175... and q = 1.
 
  • #14
jbriggs444 said:
Well, I could be even more picky and take n = 0.1200175... and q = 1.

Please stop hijacking this thread. We all know what Khashishi meant.
 

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