First, I start moving people to hotel rooms…
The first one, because people will die at a slower rate.
The second one, because the density will cause the trolley to slow down sooner, versus the first one where it will be able to pick up speed again between each person. Also, more time to save people down the rail with my handy rope cutting knife.
I think it was numberphile, or maybe vsauce, who did a video on infinities. It was really interesting. I learnt a lot, then forgot it all.
Ah yes, I remember my eyes glazing over as things got too complicated to fit through my thick skull
Is there a way to take both routes?
Hit the hand brake and drift that sucker.
Running in the 90s intensifies
with my knack for drifting i’ll miss both and hit something else entirely even within this imaginary scenario
You dont have to since the set of all positive integers belongs to the set of all real numbers, you actually hit both tracks by just taking the lower track.
never doubt my ability to mess up the unmessable. i just might stumble into disabling clipping and end up falling forever.
I mean, the bottom. The trolley simply would stop, get gunked up by all the guts and the sheer amount of bodies so close together. Checkmate tolley.
How do we know it’s an accurate illustration? They might have jacked up the trolley with monster truck wheels or something.
The illustration can’t be accurate - you can’t picture an infinite number of people between each pair of people, but the description is clear. The trolly can’t progress because it can’t get from the first person to the second due to the infinite people between them, and the infinite people between each of those between them, etc.
Like in the second infinity you can’t count to one, you can’t count from 0 to 1*10^(-1000)
I mean, maybe, but I can only go off what I see here.
Top case is not the smallest infinite; going for prime number would save a lot of time for a lot of people before they die
The set of all primes is the same size infinity as the set of all positive integers because you could create a way to map one to the other aka you can count to the nth prime. Reals are different in that there are an infinite number of real between any two reals which means there’s no possible way to map them.
The set of primes and the set of integers have the same size, you can map a prime to every integer.
depends on what you mean by “smallest”
I thought that the correct answer to these was making a loop on the right, merging the lines.
The answer is multi track drifting
Unfortunately it’s hard to join the tag end of one infinity to the tag end of another infinity to allow traversing both completely
I don’t really think it’s even sensible to talk about the tag end of an infinity. The bitten/bitter end is at 1, the tag end at infinity in this mental model. I feel that is the correct way to use rope terms for imagined embodied infinities as the small end is clearly bitten to (tied to) zero while the other end is free
No, we need a second trolley.
Good to know there are roughly 6 real numbers for every integer
If there are child real numbers then you can fit more.
Some infinities are bigger than other infinities
Is this actually true?
Many eons ago when I was in college, I worked with a guy who was a math major. He was a bit of a show boat know it all and I honestly think he believed that he was never wrong. This post reminded me of him because he and I had a debate / discussion on this topic and I came away from that feeling like he he was right and I was too dumb to understand why he was right.
He was arguing that if two sets are both infinite, then they are the same size (i.e. infinity, infinite). From a strictly logical perspective, it seemed to me that even if two sets were infinite, it seems like one could still be larger than the other (or maybe the better way of phrasing it was that one grew faster than the other) and I used the example of even integers versus all integers. He called me an idiot and honestly, I’ve always just assumed I was wrong – he was a math major at a mid-ranked state school after all, how could he be wrong?
Thoughts?
Two sets with infinitely many things are the same size when you can describe a one to one mapping from one set to the other.
For example, the counting numbers are the same size as the counting numbers except for 7. To go from the former set to the latter set, we can map 1-6 to themselves, and then for every counting number 7 or larger, add one. To reverse, just do the opposite.
Likewise, we can map the counting numbers to only the even counting numbers by doubling the value or each one as our mapping. There is a first even number, and a 73rd even number, and a 123,456,789,012th even number.
By contrast, imagine I claim to have a map from the counting numbers to all the real numbers between 0 and 1 (including 0 but not 1). You can find a number that isn’t in my mapping. Line all the numbers in my mapping up in the order they map from the counting numbers, so there’s a first real number, a second, a third, and so on. To find a number that doesn’t appear in my mapping anywhere, take the first digit to the right of the decimal from the first number, the second digit from the second number, the third digit from the third number, and so on. Once you have assembled this new (infinitely long) number, change every single digit to something different. You could add 1 to each digit, or change them at random, or anything else.
This new number can’t be the first number in my mapping because the first digit won’t match anymore. Nor can it be the second number, because the second digit doesn’t match the second number. It can’t be the third or the fourth, or any of them, because it is always different somewhere. You may also notice that this isn’t just one number you’ve constructed that isn’t anywhere in the mapping - in fact it’s a whole infinite family of numbers that are still missing, no matter what order I put any of the numbers in, and no matter how clever my mapping seems.
The set of real numbers between 0 and 1 truly is bigger than the set of counting numbers, and it isn’t close, despite both being infinitely large.
It’s pretty well settled mathematics that infinities are “the same size” if you can draw any kind of 1-to-1 mapping function between the two sets. If it’s 1-to-1, then every member of set A is paired off with a member of B, and there are no elements left over on either side.
In the example with even integers y versus all integers x, you can define the relation x <–> y = 2*x. So the two sets “have the same size”.
But the real numbers are provably larger than any of the integer sets. Meaning every possible mapping function leaves some reals leftover.
Weeeell… not really. It’s pretty well settled mathematics that “cardinality” and “amount” happen to coinciden when it comes to finite sets and we use it interchangeably but that’s because we know they’re not the same thing. When speaking with the regular folk, saying “some infinities are bigger than others” is kinda misleading. Would be like saying “Did you know squares are circles?” and then constructing a metric space with the taxi metric. Sure it’s “true” but it’s still bullshit.
It is true! Someone much more studied on this than me could provide a better explanation, but instead of “size” it’s called cardinality. From what I understand your example of even integers versus all integers would still be the same size, since they can both be mapped to the natural numbers and are therefore countable, but something like real numbers would have a higher cardinality than integers, as real numbers are uncountable and infinite. I think you can have different cardinalities within uncountable infinities too, but that’s where my knowledge stops.
Hilbert’s Paradox of the Grand Hotel seems to be the thought experiment with which you were engaged with your math associate. There are countable and uncountable infinities. Integers and skip counted integers are both countable and infinite. Real numbers are uncountable and infinite. There are sets that are more uncountable than others. That uncountability is denoted by aleph number. Uncountable means can’t be mapped to the natural numbers (1, 2, 3…). Infinite means a list with all the elements can’t be created.
Change the numbers to rubber balls with pictures of ducks or trains and different iconography. You can now intuit that both sets are the same size.
I side with you, though the experts call me stupid for it too.
if for all n < infinity, one set is double the size of another then it is still double the size at n = infinity.
You’re not stupid for it. Since it makes sense.
However, due to the way we “calculate” the sizes of infinite sets, you are wrong.
Even integers and all integers are the same infinity.
But reals are “bigger” than integers.
I know it seems intuitive but assuming that a property holds for n=infinity because it holds for all n<infinity would literally break math and it really doesn’t make much sense when you think about it more than a minute. Here’s an easy counterexample: n is finite.
fossilesque you’re one of my fav posters
ilu2 :)
You’ve misunderstood “some infinities are bigger than others.” Both of these infinities are the same size. You can show this since each person on the bottom track can be assigned a person from the top track at 1 to 1 ratio. An example of infinities that are different sizes are all whole numbers and all decimal numbers. You cannot assign a whole number to every decimal number.
Matt parker does a good video on this. I can’t remember the exact title but if you search “is infinite $20 notes worth more than infinite $1 notes” you should find it.
There are more reals than naturals, they do not match up 1 to 1, for exactly the reason you mentioned. Maybe you misread the meme?
By assigning a person to a decimal value and implying that every decimal has an assigned person the meme is essentially counting all the decimals. This is impossible, the decimals are an uncountable infinity. It’s like saying. Would you rather the number of people the trolley hits to be 7 or be dog.
What the meme has done is define the decimals to be a countable infinity bigger than another countable infinity. They’re both the same infinity.
Yeah, but if you can line up the elements of a set as shown in the bottom track, then they’re, at most, aleph 0.
I don’t think we should take the visuals of the hypothetical shit post literally.
If they say there’s one guy for every real number, let them
Ah I see why they worded it the way they did. I would argue that’s just the limitation of the illustration, considering the text words the premise correctly, but fair!
One person for every decimal isn’t possible even with infinite people. That is the point I’m making.
Neither is assigning a person to every natural number, so I’m not sure what point you’re trying to make?
But you actually can assign a unique person to every number, you just need an infinite number of people. You literally mathematically can’t do that for uncountable infinities.
Really? Isn’t the point that when you assign a natural number to every real number you can always generate a “new” real number you haven’t “counted” yet, meaning the set of real numbers is larger which is also is the point of the image.
It’s just an illustration… how else would you draw it?
My argument applies to the text of the post too. You literally can’t assign people (count) the decimals.
Diagonally
The bottom rail represents the real numbers, which are “every decimal number”.
No it’s doesn’t because the bottom rail is a countable infinity, the decimals are an uncountable infinity. Go watch the video it explains it.
I know it is drawn countably infinite, but it represents the reals, also wise guy, i studied basic logic in university, it covers this topic.
By assigning people to it it becomes countable. You can’t assign uncountable numbers like that. It’s both in the text of the meme and in the illustration
i don’t know why you’re trying so hard to away explain why the meme doesn’t work, but sure.
the real numbers on the bottom rail include all decimals, no?
Natural numbers < whole numbers < rational numbers < real numbers
Okay, to clarify, I mean the “is partial set of” instead of “is smaller than”.
Your saying it would be correct for “whole numbers” and “decimal numbers”. But that’s exactly what OP said “natural” and “real”
actually you can show that the naturals, integers and rationals all have the the same size.
for example, to show that there are as many naturals as integers (which you do by making a 1-to-1 mapping (more specifically a bijection, i.e. every natural maps to a unique integer and every integer maps to a unique natural) between them), you can say that every natural, n, maps to (n+1)/2 if it is odd and -n/2 if it is even. so 0 and 1 map to themselves, 2 maps to -1, 3 maps to 2, 4 maps to -2, and so on. this maps every natural number to an integer, and vice-versa. therefore, the cardinality (size) of the naturals and the integers are the same.you can do something similar for the rationals (if you want to try your hand at proving this yourself, it can be made a lot easier by noting that if you can find a function that maps every natural to a unique rational (an injection), and another function that maps every rational to a unique natural, you can use those construct a bijection between the naturals and rationals. this is called the schröder-bernstein theorem).
it turns out that you cannot do this kind of mapping between the naturals (or any other set of that cardinality) and the reals. i won’t recite it here, but cantor’s diagonal argument is a quite elegant proof of this fact.
now, this raises a question: is there anything between the naturals (and friends) and the reals? it turns out that we don’t actually know. this is called the continuum hypothesis
I clarified my above comment
You can’t count the decimals, op is counting the decimals and insisting that they are more of those counted decimals than in the integers. This inherently doesn’t make sense and is improper use of what infinities are and what they can represent.
An example of infinities that are different sizes are all whole numbers and all decimal numbers.
not sure what you mean by this, if you mean fractions you are wrong. Rational numbers and natural numbers can have a 1 on 1 assignment, look up cantors diagonalization. If you meant real numbers then you are right.
Decimals are how you represent numbers, not the numbers themselves.
I’m not talking about fractions, I’m talking about the reals because that it what op referred to
- I lay some extra track so the train runs over the perverts that come up with these “dilemmas” instead. Problem solved. 👍
This hypothetical post is a thought crime!
Getting killed by a train is apparently just an inevitability in this universe. Either choice is just the grand conductors plan.
An infinite amount of people on the track implies that the track is infinitely long. If that is not the case and the track is a normal length then the sudden addition of all that bio-mass in a finite space will cause a gravitational collapse. But will the collapse start on the first track or the second? Either way I hope you saved your game because you might lose your progress.
The mass of dead bodies is what replenishes the new living ones on the finite track.
The infamious theory of infinitly-expanding train track in porportion with train-travelled distence sequared by prof. buttnugget
Q.E.D.
