# Set Theory to Show Transcendental Numbers Exists

1. May 9, 2007

### ashnicholls

Does anyone know how Cantor showed the existence of Transcendental numbers. How can he say that most numbers are transcendental????????

Is that why everyone critised it?

Cheers Ash

2. May 9, 2007

### matt grime

The algebraic numbers are a countable set.

3. May 9, 2007

### ashnicholls

Yes sorry I should have said I undestand that, but how does he go on to say most numbers are transcendental, only a few are surely???????

4. May 9, 2007

### ashnicholls

Does he mean though, if a number is not countable, its non algebraic so its transcendental?????

Is that the gist of it?

Cheers

5. May 9, 2007

### fopc

I believe the existence of transcendental numbers was established before Cantor was born.

As already stated, the algebraic numbers are countable.
Since the real numbers are uncountable, what does that tell you about the set of transcendental numbers?

6. May 9, 2007

### matt grime

Countable pertains to sets, not real numbers. The SET of algebraic numbers is countable. The set of real numbers is uncountable. Thus the set of algebraic numbers is 'almost none' of the totality of real numbers.

7. May 9, 2007

### ashnicholls

yes sorry I know he didnt prove there existence, he just made a method to show other number were transcendental.

eerrrrrrrrrrrrrrrrrrr of course, all real are uncountable, so most are transcendental, obvious, thanks.

How do all of you know all of this????

Cheers Ash

8. May 9, 2007

### ashnicholls

sorry that has gone straight over my head, group/set theory is not a strength of mine.

Cheers

9. May 9, 2007

### matt grime

Then what do you think countable/uncountable means if you don't know your set theory. Please, let us know what you think 'countable' means.

10. May 9, 2007

### ashnicholls

No I understand countable, ie The sets has a 1-1 correspondence with N.

But dont really get what you mean:

Countable pertains to sets, not real numbers. The SET of algebraic numbers is countable. The set of real numbers is uncountable. Thus the set of algebraic numbers is 'almost none' of the totality of real numbers.

Can you explain this any simpler?

11. May 9, 2007

### ashnicholls

And I have found some where in my notes that:

The of Cardinality of A, the set of algebraic numbers, is aleph null, which is correct, A is countable, algebraic numbers are not transendental but it then says on the same line, so there are many transcendentals, how can you come to that conclusion by sayin algebraic numbers are not transendental???????????????

12. May 9, 2007

### ashnicholls

Right, I thought I had it but I have lost lost it now.

Am i right in thinking that he said if a set is countable, then it does not contain transendental numbers. So as the set of real numbers is not countable it contains transendental numbers,

Is that the logic behind it???????

If so how did he work that out, how can he say that a number is transendental or not on whether you can count the set that it is in is countable or not?

Or am I completly of line with whats is going on?

Cheers Ash

13. May 9, 2007

### matt grime

The set of real numbers is not countable. The set of real numbers is the union of the algebraic numbers and the transcendentals. The algebraic numbers are a countable set, thus the transcendental numbers must be an uncountable set (or the reals would be the union of two countable sets, hence countable which would be a contradiction).

When we say 'thus almost all of the real numbers are transcendental' we are saying that countable sets are, in some sense, a lot smaller than uncountable sets. In fact, if you were to pick a number uniformly at random from the interval [0,1] then it would be transcendental with probability 1.

Last edited: May 9, 2007
14. May 9, 2007

### ashnicholls

ok thanks for your help, I will run with that thought now.

Hopefully that is all I need.

15. May 9, 2007

### ashnicholls

Oh there is one more thing why did people critise this method????

16. May 9, 2007

### matt grime

Because they thought it nonsense to have 'different sizes of infinity', perhaps.

It is possible to edit your posts, rather than having consecutive 1 line posts.

17. May 9, 2007

### ashnicholls

Yes ok sorry, I was just being lazy.

What is the proof that you cant count the set of real numbers?

18. May 9, 2007

### matt grime

Cantor's diagonal argument, amongst others.

19. May 9, 2007

### EnumaElish

20. May 9, 2007

### ashnicholls

Cheers,

Is what I have written here correct?

"With these proofs he could then go onto show that any real number that is not in the set of algebraic numbers is a transendental number. And he also showed that because the set of real numbers is far larger than the set of integers, and because the set of algebraic numbers has the same cardinality as the set of integers because it is countable, this implies that the set of real numbers is far greater than the set of integers. This also implied that the number of transendental numbers is larger than the set of intergers and that most numbers can be considered as transendental numbers."