Quote: Original post by BitMasterQuote: Original post by Hodgman
I'm assuming that "1/inf" is the smallest value that is still greater than zero.
Such a value does not exist. Whenever you believe you have found such a value x, then x/2 is smaller, positive and not zero either (this works regardless of whether we are working with real or rational numbers).
In actual textbook math (not school-math, university-level math) there are preciously few points were an "infinity" can be. There are some more specialized branches of mathematics which allow actually using infinity as a more regular symbol, but even there you have to be extremely careful what you are allowed to do with it. There is a Wikipedia article about that.
The rest of the post kinda dies with that.
Maybe I should not have skimmed the thread like that but so far it seems arguments are on the "drawing sketches, waving hands"-level largely.
The only proper definition for the convergence of a sequence S(n) to the limit C I know is
and I don't think I have seen anyone trying to apply this to the problem. That would of course first require us to put the happy sketch into an actual formula you can work with but I feel a bit lazy today.
My personal guess is the result will be that the happy sketch idea simply does not converge because for every finite value the circumference is 4 while the limit would have to be pi. So even for it's not possible to find an as required.
Exactly, you can't define an infinitesimal as the smallest number that is still greater than zero, because you can always generate a real number between that number and zero, and so on. The set (0,n) is open on the lower bound. It makes no sense to ask what the 'first' element of the set is.
You can however define different types of infinities. You can construct ordinal numbers by defining them in terms of sets. We start with defining zero as the empty set. Where the number x is the set that contains all subsets corresponding to the numbers less then x.Then you can define omega as the set that contains all finite ordinals (It's bigger than any finite ordinal number). However now you are able to construct omega+1 which is bigger than that all the way to 2*omega ... omega^2 ...
Similarly you can define an infinitesimal as 1/omega. Its larger than zero but smaller than any 1/n where n is a finite ordinal. But now you can construct 1/omega+1 ... 1/2*omega ... 1/omega^2 ...
This type of infinity is different than a cardinal infinity, such as the 'amount' of things we have in a set. Aleph Null is defined to be the size of a countable set(Natural numbers, Integers, Rationals) The infinity of the continuum (The real numbers) is uncountable and larger than Alpha Null (The continuum hypothesis says that it is Aleph One) You can always create a larger cardinal by taking the power set of a set (The set that contains all of the subsets of the specified set)
Things then can get really weird from here on out as you can define 'large cardinals' that are inaccessible by a succession of Alephs or even a limit of Alephs. Then you can create hyper-inaccessible cardinals, then hyper-hyper-inaccessible cardinals ...
Sorry I get carried away.