Is there any numbers with infinite digits

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    Infinite Numbers
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Discussion Overview

The discussion revolves around the concept of numbers with infinite digits, exploring whether such numbers exist in various forms, including integers, rational numbers, and irrational numbers. Participants examine the nature of infinite decimal representations and the implications for different types of numbers.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants propose that there are infinitely many integers, as one can always add another digit to any given integer.
  • Others discuss the existence of certain types of decimals that can be infinite, such as rational numbers (e.g., 1/3) and irrational numbers (e.g., √2), which have non-terminating decimal expansions.
  • A participant questions the nature of an infinite string of digits, such as 11111..., and whether it can be classified as a natural number, rational number, or something else, noting that Peano Arithmetic does not construct such a number.
  • Another participant argues that there are no integers that require an infinite number of digits in their base 10 representation, emphasizing that rational and irrational numbers also do not have infinite strings of digits before the decimal point.

Areas of Agreement / Disagreement

Participants express differing views on the existence and classification of numbers with infinite digits. There is no consensus on whether an infinite string of digits can be considered a valid number or how it fits into existing number classifications.

Contextual Notes

The discussion highlights limitations in definitions and classifications of numbers, particularly regarding the nature of infinite sequences and their representation in various number systems.

amature83
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Hello,

Is there any number with infinite digits (e.g. 34343329...) or just the decimal representation of a number could be infinite (e.g. 1/9 = .1111...)?

I appreciate your reply.

Thanks
ME
 
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If you mean integers (whole numbers, with no decmal places) then yes there are an infinite number of them. You can see this because any number you give me I can always add another digit on the end.

There are a few types of decimals (real numbers) that also go on for ever.

Rational numbers are those that you can write as a fraction like 1/3

Irrational numbers are those that go on for ever but cannot be written as a shorter fraction. Numbers like the sqrt(2), you can write this as an equation but not a fraction.

Transcendental numbers are the 'most infinite' if you like. Not only do these numbers go on for ever but you cannot write numbers like pi or 'e' as any fraction or equation that isn't infinite.
 
If you mean integers (whole numbers, with no decmal places) then yes there are an infinite number of them. You can see this because any number you give me I can always add another digit on the end.

I think I didn't make the question clear. I am sorry about that..
I ask about the infinite string of digits, say infinite string of 1's: 11111... What is that number? I think it's not natural because the construction of N by successor (using Peano Arithm.) would never get us the "infinite" string. So, could we call it rational? My doubts about calling it rational is that -as far as I understand- in rationals the decimal expansion could be an infinite string strings but not the number itself.

ME
 
No, there are no integers whose expression in base 10 requires an infinite number of digits. Specifically, 10n is an unbounded sequence. That means that, given any integer, a, there exist an integer N so that a< 10N. a has less than N decimal places.

A "rational number" is defined as a number of the form m/n where m and n are integers (and n is not 0) so, no, there are no rational numbers, or even irrational numbers, that have an infinite string of digits in front of the decimal point.
 
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mgb_phys & HallsofIvy: thanks a lot
 

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