11 Oct '10 16:24>1 edit
Originally posted by wolfgang59You guys still have not convinced me that there is any problem here.
Very elegant. I'm glad I've got an ally!
Originally posted by LemonJelloI propose that the notions of one-to-one-correspondence / union / intersection etc are invalid with infinite sets.
No. The numbering of balls is irrelevant. It doesn't matter if you simply don't number the balls at all. What is relevant is the relationship between the extraction command and the temporal indexing of the balls (in terms of bag age). In the actual problem statement, for the case presented here, the extraction command is stated clearly in reference to ...[text shortened]... ntably infinite set can be placed in one-to-one correspondence with a proper subset of itself.
Originally posted by iamatigerWhy should I think one-to-one correspondence, for example, is "invalid with infinite sets"? One-to-one correspondence basically means there is some bijection, and I think it is trivial to show that such can exist for infinite sets. You are proposing that it is "invalid" in what sense?
I propose that the notions of one-to-one-correspondence / union / intersection etc are invalid with infinite sets.
I further propose that:
The number of elements in the bag tends to infinity if and only if:
For any number of elements X, there is a step at which the number of elements in the bag is greater than X.
In our case it is then simple to pr ...[text shortened]... 1 elements. so the number of elements in the bag tends to infinity with increasing step number.
Originally posted by LemonJelloIt's just that I think we are leaping to conclusions.
Why should I think one-to-one correspondence, for example, is "invalid with infinite sets"? One-to-one correspondence basically means there is some bijection, and I think it is trivial to show that such can exist for infinite sets. You are proposing that it is "invalid" in what sense?
Regarding the rest, I fully grant you that for any such X as you h ...[text shortened]... is the correct answer to the problem posed in the other thread is, I think, much tougher.
Originally posted by mtthwAt every step I put a random ball numbered between 1 and infinity into the bag.
[b]Here's what it probably my final take on the problem.
The argument that the answer cannot be infinite is sound. If there were any balls in the bag at time 0, then it would be possible to name one.
Originally posted by iamatigerDoes the face that every ball is eventually extracted really mean that the number of balls ends up at zero?
It's just that I think we are leaping to conclusions.
Does the face that every ball is eventually extracted really mean that the number of balls ends up at zero? I'm not sure that we can guarantee that, with infinite sets of added and extracted balls. After all, when ball N is being extracted, ball 2N + 2 is being added, this logic seems to completely i at the mapping B->B-1 aligns set B with A, so the two sets have the same number of elements.
Originally posted by iamatigerAt T0, I put my hand in the bag, take one out and tell you the number on it. Easy.
At every step I put a random ball numbered between 1 and infinity into the bag.
Name a ball in the bag at T0
Originally posted by JirakonDo you agree that the sets A={1,2,3,..} and B={2,4,6,...} have the same cardinality?
Say what you will, I can't imagine ever being convinced that the order in which the balls are removed should have any bearing on the amount of balls remaining.
Originally posted by JirakonLOL, it is indeed a mind-boggling problem.
I guess the main disagreement everyone's having is whether the two sets in the problem are ever actually the same size. It just doesn't make sense that two sets start out empty, then start growing, with one growing twice as fast as the other, until they're the same size 😕
In my view, the set of balls removed will always contain half the values in the set ...[text shortened]... ken, nor when each ball is taken out. The alternative is just too much for my finite mind @_@