# Do irrational numbers contain everything infinitely times?

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#1
I have a question about irrational numbers.
If I start writing a number of n digits does this sequence of numbers exist on every irrational number infinitely many times for all nΕΝ?
So for example if myself is nothing more than a really really large number (total information of myself) and every 10^10^10 numbers of pi is another universe (total information of the universe) do I have infinite replicas of myself ?
I guess that this happens for a completely random number, so is my question equivalent to 'Are irrational numbers completely random?'?
Is there any proof for this?
I'm a high school student ,don't expect any further knowledge from me.
0
5 years ago
#2
No. A counterexample is the irrational number , which only contains the digits 1 and 0, so doesn't contain the digit sequence 2.

You could construct a number that satisfies your property. List every one digit sequence, then every two digit sequence, then three digit, then one digit, then two digit, three, four, one, two, three, four, five, one, ....

It's not yet known whether pi has this property.
2
5 years ago
#3
Another (more general) counter example is constructing an irrational number where and are any two digits you like.
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5 years ago
#4
(Original post by Quantum boy)
I have a question about irrational numbers.
If I start writing a number of n digits does this sequence of numbers exist on every irrational number infinitely many times for all nΕΝ?
So for example if myself is nothing more than a really really large number (total information of myself) and every 10^10^10 numbers of pi is another universe (total information of the universe) do I have infinite replicas of myself ?
I guess that this happens for a completely random number, so is my question equivalent to 'Are irrational numbers completely random?'?
Is there any proof for this?
I'm a high school student ,don't expect any further knowledge from me.
In addition to the counter-examples other folk have already posted, you might like to have a look at the notion of a normal number, the requirements for which are a bit stronger than those you advance. But you might find it amusing!
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#5
(Original post by Zacken)
Another (more general) counter example is constructing an irrational number where and are any two digits you like.
I was talking about the 'natural' irrational numbers: pi, e, nth roots of integers. Do they all have these properties?

(Original post by morgan8002)
You could construct a number that satisfies your property. List every one digit sequence, then every two digit sequence, then three digit, then one digit, then two digit, three, four, one, two, three, four, five, one, ....
What if you just list every 1 digit sequence, then 2,3,4,5,....
The n digit sequences will contain every sequence of 1,2,...,n-1 in them.
Doesn't this mean every sequence will be repeated infinitely?

So irrational numbers don't necessarily carry infinite information, but do pi for example satisfy this?

(Original post by Gregorius)
In addition to the counter-examples other folk have already posted, you might like to have a look at the notion of a normal number, the requirements for which are a bit stronger than those you advance. But you might find it amusing!
So normal numbers are completely random (No digit or sequence is "favored"). I got the general idea ,but what is natural density anyway?
0
5 years ago
#6
(Original post by Quantum boy)
I was talking about the 'natural' irrational numbers: pi, e, nth roots of integers. Do they all have these properties?
Literally no clue what you're going on about...

What makes those examples you've given any more "natural" than my counter-example.

Also, nth root of integers aren't always irrational, e.g: for some .
0
5 years ago
#7
(Original post by Quantum boy)
I was talking about the 'natural' irrational numbers: pi, e, nth roots of integers. Do they all have these properties?
If you take a number like the answer is that we simply do not know if every finite sequence of digits occurs somewhere. This sort of question is, in general, very hard.

So normal numbers are completely random (No digit or sequence is "favored". I got the general idea ,but what is natural density anyway?
Calculate the proportion of digits having some property (for example "equal to seven" or "even" up to some large number of digits N. The natural density is x if, as N gets larger and larger, this proportion gets closer and closer to x.
0
5 years ago
#8
(Original post by Quantum boy)
I was talking about the 'natural' irrational numbers: pi, e, nth roots of integers. Do they all have these properties?
and e (transcendentals) are a different class of irrationals to irrational roots

No idea what you mean by natural irrationals...
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5 years ago
#9
(Original post by Johann von Gauss)
No idea what you mean by natural irrationals...
It is a term used informally in analytic number theory to describe those irrational numbers that just keep popping up everywhere!
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5 years ago
#10
(Original post by Gregorius)
It is a term used informally in analytic number theory to describe those irrational numbers that just keep popping up everywhere!
Is there a rigorous definition?
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#11
(Original post by Johann von Gauss)
and e (transcendentals) are a different class of irrationals to irrational roots

No idea what you mean by natural irrationals...
(Original post by Zacken)
Literally no clue what you're going on about...

What makes those examples you've given any more "natural" than my counter-example.

Also, nth root of integers aren't always irrational, e.g: for some .
Sorry guys for this expression, I made it up.
I meant the ones which have occured naturally : they were found in an application (ratio of length of circle to diameter, a number e so that (e^x)'=e^x,... ). The 0.deedeeeeeddddededde example is a random number generator ,it has little or no meaning.
Anyway, sorry for the misunderstanding.
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5 years ago
#12
Actually a very interesting question.

Certainly not every irrational number does, but it would be interesting if there were a proof that a particular one has this property.
0
5 years ago
#13
(Original post by Quantum boy)
Sorry guys for this expression, I made it up.
I meant the ones which have occured naturally : they were found in an application (ratio of length of circle to diameter, a number e so that (e^x)'=e^x,... ). The 0.deedeeeeeddddededde example is a random number generator ,it has little or no meaning.
Anyway, sorry for the misunderstanding.
But you could say 0.dedeedeeedeeeed... is the simplest irrational where only 2 digits occur in the decimal expansion...

And what about the physical constants like the speed of light in a vacuum, etc.

You can't really prove anything about something unless it is rigorously defined, so its tough to say if what you are asking about is true or not.
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5 years ago
#14
(Original post by Johann von Gauss)
Is there a rigorous definition?
Nope.
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#15
(Original post by Johann von Gauss)
But you could say 0.dedeedeeedeeeed... is the simplest irrational where only 2 digits occur in the decimal expansion...

You can't really prove anything about something unless it is rigorously defined, so its tough to say if what you are asking about is true or not.
Ok let's make it more specific. They might be many natural irrational numbers, but the ones I know are pi,e,nth roots (ok not all of them).
0
5 years ago
#16
What about Sum(x=1 -> inf): 10^(-x^2)? isn't that a pretty 'simple' and 'natural-looking' irrational number that obviously doesn't contain every sequence of n digits?

[I have no idea how to insert equations!]
0
5 years ago
#17
Yes

Spoiler:
Show
... in binary

More seriously your statement is not known whether you restrict to algebraic irrationals, transcendental, or what you are calling "natural" irrationals (including π, e, √2)
0
#18
(Original post by Forum User)
What about Sum(x=1 -> inf): 10^(-x^2)? isn't that a pretty 'simple' and 'natural-looking' irrational number that obviously doesn't contain every sequence of n digits?

[I have no idea how to insert equations!]
(Original post by Lord of the Flies)
Yes
Spoiler:
Show
... in binary

More seriously your statement is not known whether you restrict to algebraic irrationals, transcendental, or what you are calling "natural" irrationals (including π, e, √2)
Since there is no strict definition there is really no point in discussing this I guess.
0
5 years ago
#19
There must be an infinite amount of irrational numbers that have this property, but determining whether a number, like pi or e, does have it must be impossible.
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#20
(Original post by Johann von Gauss)
But you could say 0.dedeedeeedeeeed... is the simplest irrational where only 2 digits occur in the decimal expansion...

And what about the physical constants like the speed of light in a vacuum, etc.

You can't really prove anything about something unless it is rigorously defined, so its tough to say if what you are asking about is true or not.
I think the physical constants satisfy my conditions ,because they are completely random .
They are in the form 'write any number from 0 to 9 randomly' .
But perhaps they are not even irrational numbers.
0
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