Question About Hilbert's Hotel

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Of course I deny that.
Alright. Would you agree that there is a first (positive) odd number, a second odd number, a third, and so forth? Indeed, for any n, could you not find the n-th odd number if they are arranged from least to greatest?
 
Alright. Would you agree that there is a first (positive) odd number, a second odd number, a third, and so forth? Indeed, for any n, could you not find the n-th odd number if they are arranged from least to greatest?
Imagine the whole natural numbers going to infinity, then the odd numbers next to them which of course skipping the even numbers. You are pulling the line of odd numbers and then saying they must be equal to the odd plus even. This is erroneous. Your argument that, for any odd number, you can find a whole natural number only shows that the odd numbers are a part of the whole natural number series. You can line up 3 with 2 instead of with 3 but there is still twice as many in the series of odd plus even. By your method there is no larger infinities, because every infinity goes on forever, and you can keep picking numbers from both infinities and putting them together, but one can still be larger because if I put 1 to 1, 3 to 2, 5 to 3, 7 to 4, and 9 to 5, I’ve ignored 5 numbers in the larger series
 
Imagine the whole natural numbers going to infinity, then the odd numbers next to them which of course skipping the even numbers. You are pulling the line of odd numbers and then saying they must be equal to the odd plus even. This is erroneous. Your argument that, for any odd number, you can find a whole natural number only shows that the odd numbers are a part of the whole natural number series. You can line up 3 with 2 instead of with 3 but there is still twice as many in the series of odd plus even. By your method there is no larger infinities, because every infinity goes on forever, and you can keep picking numbers from both infinities and putting them together, but one can still be larger because if I put 1 to 1, 3 to 2, 5 to 3, 7 to 4, and 9 to 5, I’ve ignored 5 numbers in the larger series
You didn’t answer my question. A simple “yes” or “no” would suffice. Can you or can you not associate with each positive integer n the n-th positive odd number, and conversely, can you not say that each positive odd number is the first, or the second, or third, etc?

If you can, then we have a one-to-one correspondence. Now you can disagree with using the definition of “countable infinity” and say that it’s a stupid distinction to make. You can insist that nothing is gained by distinguishing various infinities in this way (I think you’d be wrong, but whatever). But if we’re using the definition that a set is countable if its members can be placed in one-to-one correspondence with the positive integers, then the odds are definitely countable if the above is admitted. It’s over, there’s nothing left to argue after that. Your disagreement lies with definitions, not the reasoning. 🤷
 
By the definitions of math, nothing times itself equals a negative number. Unless you are saying that rule is not based on anything
By the definitions of mathematics, i * i = -1. That is how i is defined.

Wherever you see i[sup]2[/sup] in an equation you can replace it with -1.

Mathematics is an axiomatic system. As long as the axioms are consistent then you have a great deal of leeway in choosing them.

rossum
 
By the definitions of mathematics, i * i = -1. That is how i is defined.

Wherever you see i[sup]2[/sup] in an equation you can replace it with -1.

Mathematics is an axiomatic system. As long as the axioms are consistent then you have a great deal of leeway in choosing them.

rossum
Are we supposed to be teaching high school math in this thread?
 
You didn’t answer my question. A simple “yes” or “no” would suffice. Can you or can you not associate with each positive integer n the n-th positive odd number, and conversely, can you not say that each positive odd number is the first, or the second, or third, etc?

If you can, then we have a one-to-one correspondence. Now you can disagree with using the definition of “countable infinity” and say that it’s a stupid distinction to make. You can insist that nothing is gained by distinguishing various infinities in this way (I think you’d be wrong, but whatever). But if we’re using the definition that a set is countable if its members can be placed in one-to-one correspondence with the positive integers, then the odds are definitely countable if the above is admitted. It’s over, there’s nothing left to argue after that. Your disagreement lies with definitions, not the reasoning. 🤷
I systematically answered that in post 339. The odd numbers only line up with the odd or even numbers, not both. Bottom line
 
By the definitions of mathematics, i * i = -1. That is how i is defined.

Wherever you see i[sup]2[/sup] in an equation you can replace it with -1.

Mathematics is an axiomatic system. As long as the axioms are consistent then you have a great deal of leeway in choosing them.

rossum
So is the principle “a negative times a negative is a positive” always TRUE or not
 
Are we supposed to be teaching high school math in this thread?
I am more revolutionary than you, willing to admit that something in math these days is wrong. Someday quantum physics, now accepted, may be refuted and brought back to classical physics. “Follow the truth wherever it leads you”
 
That’s beyond what we are discussing. Many people nowadays believe that modern math has solved Zeno’s paradox. I think there is, however, still a mysterious quality about it, something math has never solved. The world hasn’t ended if, as well, Cantor was mistaken and his critics turn out to have been the heroes of the late 19 hundreds and early 20th century
 
thinkamdmull,

Your oft-repeated assertion has been that an infinite number of sets of ten must still have twice as many members as an infinite number of sets of five. But is that really the case? Certainly it is true for any finite number of sets, but you yourself have pointed out that infinity is different.

Yes, according to our friend Mr. Cantor, it is possible to show that some infinite sets are larger than others (though it is strange that you, who reject Cantor’s math, keep returning to that point). Here’s the thing, though: you don’t get from one of those sets to a larger or smaller one by performing ordinary arithmetic. “infinity minus one” is NOT smaller than it was before the subtraction. Infinity cut in half, to the extent that is even a meaningful thing to say, also does not get any smaller. That is why your sets of ten and sets of five are not the decisive disproof you seem to think they are – we cannot say with certainty that when you get to an infinite number of each, the sets of five will still have fewer total members than the sets of ten. Indeed, our method of putting the members in one-to-one correspondence (which you still seem to think is trickery or cheating of some kind) seems to indicate that the two infinite sets do have the same number of members after all.

Usagi
 
Here is a set of letter groups: {nmd, sgqdd, ehud, rdudm, mhmd, dkdudm, sghqsddm, ehesddm, rdudmsddm, … }

The ellipsis at the end indicates that I can extend the set indefinitely; there is no limit on the length of a letter group and I can always generate a new unique letter group. These letter groups can be put into a one-to-one correspondence with the natural numbers:

1 → nmd
2 → sgqdd
3 → ehud
4 → rdudm
5 → mhmd
6 → dkdudm
7 → sghqsddm
8 → ehesddm
9 → rdudmsddm
etc.

I am in possession of a rule which generates those letter groups and which guarantees that they are all unique. Given any letter group, I can always generate a further unique letter group.

Two questions.

First, do you agree that the number of letter groups in my set is the same as the number of natural integers in the set of natural integers?

Second, can you deduce the rule I am using?

Here is a hint, in ROT13: Gur pbzchgre sebz Xhoevpx’f N Fcnpr Bqlffrl.

rossum
 
I systematically answered that in post 339. The odd numbers only line up with the odd or even numbers, not both. Bottom line
There is no “lining up”. We are discussing one-to-one correspondences. Bijections, if you prefer. Am I speaking a foreign language?

Yes or no: If f(n)=2n-1, where n can assume integer values, is f a bijection? It must be, as it is a linear function with non-zero slope. Its range is the set of odd numbers, so there is a one-to-one correspondence between the integers and the odd numbers.

There is no “lining up”, so please stop trying to frame it that way.

Also, you never addressed my argument using the set {x, xyx, xyxyx,…}. How can both the sets of integers and the odds be the same size as this set but not be the same size as each other? Is your notion of cardinality not transitive?
 
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