To establish whether one set is of a larger cardinality, we try to establish a one-to-one correspondence between the members of the set.
For example, I have a very large dinner party and I don’t want to count up all the forks and spoons that I’ll need for the guests. So, instead of counting, everytime I place a fork on the table I also place a spoon. If I can match the two, they must be an equal number (whatever that number is).
So let’s start with one $1 bill. We’ll match it with one $100 bill. Let’s add a second $1 bill and match it with another $100 bill. Ad infinitum. For each $1 bill there is a corresponding $100 bill. So there is the same number of bills (the two infinite sets have the same cardinality).
You likely can see the point I’m making now; there are just as many $1 bills as there are $100 bills, but each $100 bill is worth more.
You could make an argument that infinite $100 bills are more valuable for their ease of use or convenience, but infinite $100 bills and infinite $1 bills are equivalent amounts of money. Don’t think of infinity as a number, it isn’t one, it’s infinity. You can map 1000 one dollar bills to every single 100 dollar bill and never run out, even in the limit, and therefore conclude (equally incorrectly) that the infinite $1 bills are worth more, because infinity isn’t a number. Uncountable infinities are bigger than countable ones, but every countable infinity is the same.
Another thing that seems unintuitive but might make the concept in general make more sense is that you cannot add or do any other arithmetic on infinity. Infinity + infinity =/= 2(infinity). It’s just infinity. 10 stacks of infinite bills are equivalent to one stack of infinite bills. You could add them all together; you don’t have any more than the original stack. You could divide each stack by any number, and you still have infinity in each divided stack. Infinity is not a number, you cannot do arithmetic on it.
100 stacks of infinite $1 bills are not more than one stack of infinite $1 bills, so neither is infinite $100 bills.
You can map 1000 one dollar bills to every single 100 dollar bill and never run out, even in the limit, and therefore conclude (equally incorrectly) that the infinite $1 bills are worth more, because infinity isn’t a number.
Yes, the mapping that you’re describing isn’t useful; but that doesn’t invalidate the simple test that we can do to prove that two infinite sets are the same. And the test is pretty intuitive in some cases. If for every fork there is a spoon, then they must be an equal number. And if for every positive whole number (e.g “2”) there is a negative whole number (e.g. “-2”), then the set of positive whole numbers and the set of negative whole numbers must be the same.
Another thing that seems unintuitive but might make the concept in general make more sense is that you cannot add or do any other arithmetic on infinity.
I agree with you that adding infinity to itself just gets you the same number. But now we’re starting to ask: just what is infinity? We could think of infinity as a collection of things or we could think of infinity like we do numbers (yes, I know infinity is not technically among the real numbers). In the latter sense we could have a negative infinity {-1…-2…-3…etc.} that is quantitatively “worth less” than a countable positive infinity. On the other hand, if we think of infinity as a collection of stuff, then you couldn’t have a negative infinity because you can’t have less than zero members in the set.
I’ll admit that I’m getting out of my depth here since I know this stuff from philosophical study rather than maths proper. As with anything, I’m happy to be proven wrong, but I’m quite sure about the 1-1 correspondence bit.
Your 1-1 relationship makes sense intuitively with a finite set but it breaks down with the mathematical concept of infinity. Here’s a good article explaining it, but DreamButt’s point of every set of countable infinite sets are equal holds true because you can map them. Take a set of all positive integers and a set of all positive, even integers. At first glance it seems like the second set is half as big right? But you can map them like this:
Set 1 | Set 2
1|2
2|4
3|6
4|8
5|10
6|12
If you added the numbers up on the two sets you would get 21 and 42 respectively. Set 2 isn’t bigger, the numbers just increased twice as fast because we had half as many to count. When you continue the series infinitely they’re the same size. The same applies for $1 vs $100 bills.
$1|$100
$2|$200
$3|$300
In this case the $1 bills are every integer while the $100 bills is the set of all 100’s instead of all even integers, but the same rule applies. Set two is increasing 100x faster but that’s because they’re skipping all the numbers in between.
I understand that both sets are equally infinite (same cardinality). And I do see the plausibility in your argument that, in each case, since there’s an infinite number of bills their value should be equally infinite. If your argument is correct, then I should revise my understanding of infinity. So maybe you can help me make sense of the following two examples.
First, the number of rational numbers between 0 and 1 is countably infinite. That is, we can establish a 1-1 correspondence between the infinite set of fractions between 0-1 and the infinite set of positive integers. So the number of numbers is the same. But clearly, if we add up all the infinite fractions between 0 and 1, they would add up to 1. Whereas, adding up the set of positive integers will get us infinity.
Second, there are equally many positive integers as there are negative integers. If we add up the positive integers we get positive infinity and if we add up all the negative integers we get negative infinity. Clearly, the positive is greater than the negative.
In these two cases, we see that a distinction needs to be made between the infinite number of members in the set and the value of each member. The same arguably applies in the case of the dollar bills.
But clearly, if we add up all the infinite fractions between 0 and 1, they would add up to 1.
0.9 and 0.8 are in that set, so they would add up to at least 1.7. In fact if you give me any positive number I can give you a (finite!) set of (distinct) fractions less than 1 which sum to more than that number. In other words, the sum is infinite.
I meant to say that we can infinitely divide the numbers between 0 and 1 and then match each with an integer. But I realized that the former wouldn’t be rational numbers, they would be real numbers.
That aside, I see now that the original idea behind the meme was mistaken.
I meant to say that we can infinitely divide the numbers between 0 and 1 and then match each with an integer. But I realized that the former wouldn’t be rational numbers, they would be real numbers.
That aside, I see now that the original idea behind the meme was mistaken.
You’re right that we don’t need to, but mathematicians can use this method to prove that two infinite sets are the same size. This is how we know that the infinite set of whole numbers is the same size as the infinite set of integers. We can also prove that the set of real numbers is larger than the set of whole numbers.
I’m not quite sure how else to explain it, so I’ll link a Numberphile video where they do the demonstration on paper: https://www.youtube.com/watch?v=elvOZm0d4H0&t=19s . Here you can see why it’s useful to try to establish this 1-1 correspondence. If you can’t do so, then the size of the two infinite sets are not equal.
I think you’re misunderstanding the math a bit here. Let me give an example.
If you took a list of all the natural numbers, and a list off all multiples of 100, then you’ll find they have a 1 to 1 correspondence.
Now you might think “Ok, that means if we add up all the multiples of 100, we’ll have a bigger infinity than if we add up all the natural numbers. See, because when we add 1 for natural numbers, we add 100 in the list of multiples of 100. The same goes for 2 and 200, 3 and 300, and so on.”
But then you’ll notice a problem. The list of natural numbers already contains every multiple of 100 within it. Therefore, the list of natural numbers should be bigger because you’re adding more numbers. So now paradoxically, both sets seem like they should be bigger than the other.
The only resolution to this paradox is that both sets are exactly equal. I’m not smart enough to give a full mathematical proof of that, but hopefully that at least clears it up a bit.
Adding up 100 dollar bills infinitely and adding up 1 dollar bills infinitely is functionally exactly the same as adding up the natural numbers and all the multiples of 100.
The only way to have a larger infinity that I know of us to be uncountably infinite, because it is impossible to have a 1 to 1 correspondence of a countably infinite set, and an uncountably infinite set.
Infinity is a concept that can’t be reached so it can’t be counted up fully. Its not a hard number so you can’t get a full value from it since there is always another number to reach. Therefore you only peak at ∞ in any individual moment. You can never actually count it.
If you’re responding to the part about countable infinity and uncountable infinity, it’s a bit of a misnomer, but it is the proper term.
Countably infinite is when you can pick any number in the set and know what comes next.
Uncountably infinite is when it’s physically impossible to do that, such as with a set of all irrational numbers. You can pick any number you want, but it’s impossible to count what came before or after it because you could just make the decimal even more precise, infinitely.
The bizarre thing about this property is that even if you paired every number in a uncountably infinite set (such as a set of all irrational numbers) with a countably infinite set (such as a set of all natural numbers) then no matter how you paired them, you would always find a number from the uncountably infinite set you forgot. Infinitely many in fact.
It’s often demonstrated by drawing up a chart of all rational numbers, and pairing each with an irrational number. Even if you did it perfectly, you could change the first digit of the irrational number paired with one, change the second digit of the irrational number paired with two, and so on. Once you were done, you’d put all the new digits together in order, and now you have a new number that appears nowhere on your infinite list.
It’ll be at least one digit off from every single number you have, because you just went through and changed those digits.
Because of that property, uncountably infinite sets are often said to be larger than countably infinite sets. I suppose depending on your definition that’s true, but I think of it as just a different type of infinity.
Sure if you’re talking about a concept like money, but we’re talking about dollar bills and 100 dollar bills, physical objects. And if you’re talking about physical objects you have to consider material reality, if you’re choosing one or the other the 100 dollar bills are more convinient. Therefore they have more utility, which makes them have a higher value.
I was actually discussing this with my wife earlier and her position is that the 1 dollar bills are better because it’s tough to find somebody who’ll split a 100, and 100s don’t work in vending machines.
I thought the hundreds would be better because you could just deposit them in the bank and use your card, and banks often have limits on how many individual bills you can deposit at once, so hundreds are way better for that.
~~I was thinking that, bill for bill, the $100 bill will always be greater value. But I can see the plausibility in your argument that, when we’re counting both the value of the members of each set, the value of the $100 bill pile can always be found somewhere in the series of $1 bills. The latter will always “catch up” so to speak. But, if this line of reasoning is true, it should apply to other countably infinite sets as well. Consider the following two examples.
First, the number of rational numbers between 0 and 1 is countably infinite. That is, we can establish a 1-1 correspondence between the infinite set of fractions between 0-1 and the infinite set of positive integers. So the number of numbers is the same. But clearly, if we add up all the infinite fractions between 0 and 1, they would add up to 1. Whereas, adding up the set of positive integers will get us infinity.
Second, there are equally many positive integers as there are negative integers. There is a 1-1 correspondence such that the number of numbers is the same. However, if we add up the positive integers we get positive infinity and if we add up all the negative integers we get negative infinity. Clearly, the positive is quantitatively greater than the negative.
In these two cases, we see that a distinction needs to be made between the infinite number of members in the set and the value of each member. The same arguably applies in the case of the dollar bills.~~
Ah but you see if you take into consideration it’s talking about bills and not money in an account you have to take into consideration the material reality. A person who receives more 100s would have an easier time depositing and spending the money therefore they have higher utility, therefore they are worth more than the 1s.
Sure they may have the same amount of numbers (and 1, 2,3… May even be larger because you’ll eventually repeat in the 1:1 examile) but in reality the one with the 100s will have an easier time using their objects (100 dollar bills) than the ones who pick the 1 dollar bills
You’re right that they’re the same size but you’re mistaken when you try to assign a total value to the stack. Consider breaking each $100 bill into 100 $1 bills. The value is the same, clearly. So for each pair, you have a $1 bill and a small stack of 100 $1 bills. Now combine all singles back together in an infinite stack. Then combine all stacks of 100 into an infinite stack.
And you know what? Both infinite stacks are identical. They have the same value.
But the creation of each additional bill devalues the currency. At some point the value of all this paper money is negative because it’s not worth keeping and storing. The point at which they cross from positive to negative value would give them zero value, and they’d be equal.
You likely can see the point I’m making now; there are just as many $1 bills as there are $100 bills, but each $100 bill is worth more.
But the monetary value of the bills in each stack still adds up to infinity for both. It’s like having an uncapped Internet connection at 56 KBit/s versus 100 MBit/s: You can download all the things with both, but that alone doesn’t make them equal.
To establish whether one set is of a larger cardinality, we try to establish a one-to-one correspondence between the members of the set.
For example, I have a very large dinner party and I don’t want to count up all the forks and spoons that I’ll need for the guests. So, instead of counting, everytime I place a fork on the table I also place a spoon. If I can match the two, they must be an equal number (whatever that number is).
So let’s start with one $1 bill. We’ll match it with one $100 bill. Let’s add a second $1 bill and match it with another $100 bill. Ad infinitum. For each $1 bill there is a corresponding $100 bill. So there is the same number of bills (the two infinite sets have the same cardinality).
You likely can see the point I’m making now; there are just as many $1 bills as there are $100 bills, but each $100 bill is worth more.
You could make an argument that infinite $100 bills are more valuable for their ease of use or convenience, but infinite $100 bills and infinite $1 bills are equivalent amounts of money. Don’t think of infinity as a number, it isn’t one, it’s infinity. You can map 1000 one dollar bills to every single 100 dollar bill and never run out, even in the limit, and therefore conclude (equally incorrectly) that the infinite $1 bills are worth more, because infinity isn’t a number. Uncountable infinities are bigger than countable ones, but every countable infinity is the same.
Another thing that seems unintuitive but might make the concept in general make more sense is that you cannot add or do any other arithmetic on infinity. Infinity + infinity =/= 2(infinity). It’s just infinity. 10 stacks of infinite bills are equivalent to one stack of infinite bills. You could add them all together; you don’t have any more than the original stack. You could divide each stack by any number, and you still have infinity in each divided stack. Infinity is not a number, you cannot do arithmetic on it.
100 stacks of infinite $1 bills are not more than one stack of infinite $1 bills, so neither is infinite $100 bills.
Yes, the mapping that you’re describing isn’t useful; but that doesn’t invalidate the simple test that we can do to prove that two infinite sets are the same. And the test is pretty intuitive in some cases. If for every fork there is a spoon, then they must be an equal number. And if for every positive whole number (e.g “2”) there is a negative whole number (e.g. “-2”), then the set of positive whole numbers and the set of negative whole numbers must be the same.
I agree with you that adding infinity to itself just gets you the same number. But now we’re starting to ask: just what is infinity? We could think of infinity as a collection of things or we could think of infinity like we do numbers (yes, I know infinity is not technically among the real numbers). In the latter sense we could have a negative infinity {-1…-2…-3…etc.} that is quantitatively “worth less” than a countable positive infinity. On the other hand, if we think of infinity as a collection of stuff, then you couldn’t have a negative infinity because you can’t have less than zero members in the set.
I’ll admit that I’m getting out of my depth here since I know this stuff from philosophical study rather than maths proper. As with anything, I’m happy to be proven wrong, but I’m quite sure about the 1-1 correspondence bit.
Your 1-1 relationship makes sense intuitively with a finite set but it breaks down with the mathematical concept of infinity. Here’s a good article explaining it, but DreamButt’s point of every set of countable infinite sets are equal holds true because you can map them. Take a set of all positive integers and a set of all positive, even integers. At first glance it seems like the second set is half as big right? But you can map them like this:
Set 1 | Set 2
1|2
2|4
3|6
4|8
5|10
6|12
If you added the numbers up on the two sets you would get 21 and 42 respectively. Set 2 isn’t bigger, the numbers just increased twice as fast because we had half as many to count. When you continue the series infinitely they’re the same size. The same applies for $1 vs $100 bills.
$1|$100
$2|$200
$3|$300
In this case the $1 bills are every integer while the $100 bills is the set of all 100’s instead of all even integers, but the same rule applies. Set two is increasing 100x faster but that’s because they’re skipping all the numbers in between.
I understand that both sets are equally infinite (same cardinality). And I do see the plausibility in your argument that, in each case, since there’s an infinite number of bills their value should be equally infinite. If your argument is correct, then I should revise my understanding of infinity. So maybe you can help me make sense of the following two examples.
First, the number of rational numbers between 0 and 1 is countably infinite. That is, we can establish a 1-1 correspondence between the infinite set of fractions between 0-1 and the infinite set of positive integers. So the number of numbers is the same. But clearly, if we add up all the infinite fractions between 0 and 1, they would add up to 1. Whereas, adding up the set of positive integers will get us infinity.
Second, there are equally many positive integers as there are negative integers. If we add up the positive integers we get positive infinity and if we add up all the negative integers we get negative infinity. Clearly, the positive is greater than the negative.
In these two cases, we see that a distinction needs to be made between the infinite number of members in the set and the value of each member. The same arguably applies in the case of the dollar bills.
EDIT: I see now that I was mistaken.
0.9 and 0.8 are in that set, so they would add up to at least 1.7. In fact if you give me any positive number I can give you a (finite!) set of (distinct) fractions less than 1 which sum to more than that number. In other words, the sum is infinite.
I meant to say that we can infinitely divide the numbers between 0 and 1 and then match each with an integer. But I realized that the former wouldn’t be rational numbers, they would be real numbers.
That aside, I see now that the original idea behind the meme was mistaken.
Um no? 3/4 + 5/6 > 1
If you mean the series 1/2 + 1/3 + 1/4 + … that also tends to infinity
I meant to say that we can infinitely divide the numbers between 0 and 1 and then match each with an integer. But I realized that the former wouldn’t be rational numbers, they would be real numbers.
That aside, I see now that the original idea behind the meme was mistaken.
I don’t see what you are trying to say. You can also match 200 $1 bills with each $100 bill. The correspondence does not need to be one-to-one.
You’re right that we don’t need to, but mathematicians can use this method to prove that two infinite sets are the same size. This is how we know that the infinite set of whole numbers is the same size as the infinite set of integers. We can also prove that the set of real numbers is larger than the set of whole numbers.
I’m not quite sure how else to explain it, so I’ll link a Numberphile video where they do the demonstration on paper: https://www.youtube.com/watch?v=elvOZm0d4H0&t=19s . Here you can see why it’s useful to try to establish this 1-1 correspondence. If you can’t do so, then the size of the two infinite sets are not equal.
The video shows that rational numbers (aka fractions) are countable (or listable). Did you mean real numbers?
Good catch, I’ll edit that sentence
But the meme doesn’t talk about the value of each $100 bill; it talks about the value of the bills collectively.
I think you’re misunderstanding the math a bit here. Let me give an example.
If you took a list of all the natural numbers, and a list off all multiples of 100, then you’ll find they have a 1 to 1 correspondence.
Now you might think “Ok, that means if we add up all the multiples of 100, we’ll have a bigger infinity than if we add up all the natural numbers. See, because when we add 1 for natural numbers, we add 100 in the list of multiples of 100. The same goes for 2 and 200, 3 and 300, and so on.”
But then you’ll notice a problem. The list of natural numbers already contains every multiple of 100 within it. Therefore, the list of natural numbers should be bigger because you’re adding more numbers. So now paradoxically, both sets seem like they should be bigger than the other.
The only resolution to this paradox is that both sets are exactly equal. I’m not smart enough to give a full mathematical proof of that, but hopefully that at least clears it up a bit.
Adding up 100 dollar bills infinitely and adding up 1 dollar bills infinitely is functionally exactly the same as adding up the natural numbers and all the multiples of 100.
The only way to have a larger infinity that I know of us to be uncountably infinite, because it is impossible to have a 1 to 1 correspondence of a countably infinite set, and an uncountably infinite set.
Infinity is a concept that can’t be reached so it can’t be counted up fully. Its not a hard number so you can’t get a full value from it since there is always another number to reach. Therefore you only peak at ∞ in any individual moment. You can never actually count it.
If you’re responding to the part about countable infinity and uncountable infinity, it’s a bit of a misnomer, but it is the proper term.
Countably infinite is when you can pick any number in the set and know what comes next.
Uncountably infinite is when it’s physically impossible to do that, such as with a set of all irrational numbers. You can pick any number you want, but it’s impossible to count what came before or after it because you could just make the decimal even more precise, infinitely.
The bizarre thing about this property is that even if you paired every number in a uncountably infinite set (such as a set of all irrational numbers) with a countably infinite set (such as a set of all natural numbers) then no matter how you paired them, you would always find a number from the uncountably infinite set you forgot. Infinitely many in fact.
It’s often demonstrated by drawing up a chart of all rational numbers, and pairing each with an irrational number. Even if you did it perfectly, you could change the first digit of the irrational number paired with one, change the second digit of the irrational number paired with two, and so on. Once you were done, you’d put all the new digits together in order, and now you have a new number that appears nowhere on your infinite list.
It’ll be at least one digit off from every single number you have, because you just went through and changed those digits.
Because of that property, uncountably infinite sets are often said to be larger than countably infinite sets. I suppose depending on your definition that’s true, but I think of it as just a different type of infinity.
Sure if you’re talking about a concept like money, but we’re talking about dollar bills and 100 dollar bills, physical objects. And if you’re talking about physical objects you have to consider material reality, if you’re choosing one or the other the 100 dollar bills are more convinient. Therefore they have more utility, which makes them have a higher value.
I agree. I’m just being a math nerd.
I was actually discussing this with my wife earlier and her position is that the 1 dollar bills are better because it’s tough to find somebody who’ll split a 100, and 100s don’t work in vending machines.
I thought the hundreds would be better because you could just deposit them in the bank and use your card, and banks often have limits on how many individual bills you can deposit at once, so hundreds are way better for that.
If you’re considering material reality then you can’t have an infinite amount of it.
That’s a concession of the premise, you obviously can’t have infinite anything, but if you could then the 100s would bring more utility
But the utility is not the issue in the premise.
“Would you rather have an infinite number of $1 or $100 bills?” Obviously $100 bills, but they are worth the same amount.
If utility isn’t the reason why you’re picking 100s then why would you if they’re the same amount?
Nah. We’re taking the singles and hitting up the strip club boiii.
Only valid retort
~~I was thinking that, bill for bill, the $100 bill will always be greater value. But I can see the plausibility in your argument that, when we’re counting both the value of the members of each set, the value of the $100 bill pile can always be found somewhere in the series of $1 bills. The latter will always “catch up” so to speak. But, if this line of reasoning is true, it should apply to other countably infinite sets as well. Consider the following two examples.
First, the number of rational numbers between 0 and 1 is countably infinite. That is, we can establish a 1-1 correspondence between the infinite set of fractions between 0-1 and the infinite set of positive integers. So the number of numbers is the same. But clearly, if we add up all the infinite fractions between 0 and 1, they would add up to 1. Whereas, adding up the set of positive integers will get us infinity.
Second, there are equally many positive integers as there are negative integers. There is a 1-1 correspondence such that the number of numbers is the same. However, if we add up the positive integers we get positive infinity and if we add up all the negative integers we get negative infinity. Clearly, the positive is quantitatively greater than the negative.
In these two cases, we see that a distinction needs to be made between the infinite number of members in the set and the value of each member. The same arguably applies in the case of the dollar bills.~~
EDIT: I see now that I was mistaken.
Ah but you see if you take into consideration it’s talking about bills and not money in an account you have to take into consideration the material reality. A person who receives more 100s would have an easier time depositing and spending the money therefore they have higher utility, therefore they are worth more than the 1s.
Sure they may have the same amount of numbers (and 1, 2,3… May even be larger because you’ll eventually repeat in the 1:1 examile) but in reality the one with the 100s will have an easier time using their objects (100 dollar bills) than the ones who pick the 1 dollar bills
You’re right that they’re the same size but you’re mistaken when you try to assign a total value to the stack. Consider breaking each $100 bill into 100 $1 bills. The value is the same, clearly. So for each pair, you have a $1 bill and a small stack of 100 $1 bills. Now combine all singles back together in an infinite stack. Then combine all stacks of 100 into an infinite stack.
And you know what? Both infinite stacks are identical. They have the same value.
But the creation of each additional bill devalues the currency. At some point the value of all this paper money is negative because it’s not worth keeping and storing. The point at which they cross from positive to negative value would give them zero value, and they’d be equal.
But the monetary value of the bills in each stack still adds up to infinity for both. It’s like having an uncapped Internet connection at 56 KBit/s versus 100 MBit/s: You can download all the things with both, but that alone doesn’t make them equal.