Tuesday, August 4, 2009

Proving Infinity

I'm going to put on my pedant hat again today and talk about a concept that we all know and love...or maybe not so much love depending on your math skills.

Let's have some personal background to this logical exercise first:

A year ago this September 19th, the Society of Non-Theists at Purdue University SONTAPU, lol held a sort of mock-evangelical rally for the Flying Spaghetti Monster* to try to convey a message. This message was: "Unverifiable claims aren't true just because you cannot disprove them.

Throughout the day, we drew larger and larger crowds. The various people were eliciting emotions ranging the gamut from "lol" to "Alright!" to "What on Earth are they doing?" to "OH LAWD BABEH JEEBUS HELP ME!!!1!1!eleven"

In the corner, however stood two people. One was holding a video camera and the other was talking, perhaps if narrating.

After I read a chapter of the Gospel of the Flying Spaghetti Monster in my best "Preacher Voice" I went to go get some water and was stopped by these guys to talk.

It became clear very quickly that these people were not here to get the poop on what we were doing and why we were doing it, but I talked to them civilly. They asked me how I felt about God and what I, myself believed.

I told them. As a scientist and, much more specifically, a Math major, education classes be damned, I had very specific ideas of what I would need to be persuaded to the side of the believers. That is to say, PROOF. Logic. In order for me to stand up and say "There exists a higher power." I need to see a written proof with QED at the end (although now, I think I'd also accept the heavens parting and having God himself send me on a quest a-la Monty Python).

"How about infinity?" was the response. "Can you prove infinity?"

"Well...prove infinity itself? Hmm...I'm not sure I, myself know how to do that. I suppose you could go through the route proving that the integers have no upper bound and are therefore infinite."

This, of course, didn't help. Eventually, they moved away from Math onto subjects that they were more properly coached on and that I didn't have enough real training in to properly bullshit mine their arguments. I made eye contact with other people from our group in the traditional, "Shit, shit, help me! They won't stop throwing bullshit at me!" fashion, allowed someone else to get caught up in the argument and then bowed out claiming various excuses.

But, it got to me. Infinity. What does infinity mean? We use it in math all the time, don't we? Calculus is basically built around the concept of infinity, isn't it? Differentials...integrals, Reimann sums...The infinite and the infinitesmal are all around...well...sort of.

Infinity is a somewhat wooly concept...and by somewhat wooly, I mean completely incomprehensible. To have an infinite quantity of something is physically impossible. It's a contradiction of terms, really. If you have a quantity, you have quantified it. How can you quantify something that is, by definition, inquantifiable? Well, that's precisely it. You can't.

Infinity is not a thing. It is not a measurement. It is not, really, even a state of mind.

Infinity is, in all senses, the impossible we can never and WERE NEVER MEANT TO reach simply by the very nature of the concept! It's not even a benchmark that is merely set too high.

"But, Mark," You say. "There are so many other concepts that we can't actually see that we use all the time, too!"

"Well, yeah. Sorta."

"I mean, you have imaginary numbers, transendental numbers, even, perhaps, NEGATIVE numbers are also abstract concepts that we are surrounded by in math that we don't actually argue with."

This is very true. You probably couldn't find -1 apple, or 2i dollars in your wallet...and I'd love to see someone come up with exactly pi of something.

However, in each of these situations, regardless of their abstractness, we use them because they appear in nature. Even imaginary numbers have a very useful practical application that translates into something tangible. Just ask your friendly neighborhood electrical engineer. I'm sure he'd be glad to point you in the right direction.**

The point is that infinity is really the only one of these that doesn't get a real, practical analog because it doesn't exist on its own.

Infinity is a tool, certainly, but not something that can be proven.

*Yes, they're bowing down to me. It seems that, on the same day, there was a flash mob. They were going through and taking showers and brushing their teeth in all the fountains on campus. There is a small fountain right by where we were holding our event.

**Just make sure he's bathed recently.***

***I'm just kidding. I love you all. Please don't kill me with your trebuchets.


  1. Infinity is an obvious extrapolation of something that does exist in nature: large numbers. There's no such thing as a perfect circle, either; all actual 'circles' are a bit off.

  2. Also, what exactly is meant by "prove infinity"? Prove that it exists? Because it doesn't, not really—it's an abstract concept. It's a fairly useful concept, though.

  3. That's the whole point. Unlike other abstract concepts such as negative numbers or imaginary numbers, infinity does not, in itself "exist." Assuming you have a perfect compass and a

    There is nothing large enough such that you would ever be able to construct "infinity."

    There is no infinity. There is only talk and discussion of infinity. You could say, "Well, mathematically, this happens at infinity...but that's, in the end, pipe dreaming. We can never travel to the land beyond infinity where x/(x+1) converges to equal 1. It doesn't ever equal 1. You can get close because as x increases, x/(x+1) decreases asymptotically to 1...but there will always be some egregious trailing decimal that will still be there after calculators and super computers have long since given up. You could run a program for years and years and years, have someone sitting doing long division for his entire life trying to get the largest number he can think of and still never obtain 1.

    Infinity is, indeed, an obvious extrapolation of incredibly large numbers...but no matter how big those numbers get, you will always have to hop into the interpolative hyper jet to get you to the land of infinity.

  4. But what I'm saying is that no abstract concept exists. I don't see how infinity is different than imaginary numbers in this respect. Heck, even regular numbers: '5' doesn't exist in and of itself either. It's a more familiar concept to most people than 'infinity', but not in any way 'real'. There's nothing odd about infinity; it's just a relatively difficult to understand concept.

  5. But, I think, that's the point. I'm not saying that it isn't a completely formed concept but rather that it is not constructible unlike, say, 5 or -2 or (2i+e) which are, indeed, and I agree 100 percent, equally abstract in just those terms.

    So many people think of infinity as an actual THING that can be put down on paper. When encountering limits for the first time and you're taking the limit to infinity you are taught that it is a destination.

    What I'm saying is that the concept is not a landing point but a vehicle to obtain an otherwise incomprehensible answer.

    Your answer should never be infinity because infinity, in itself, is meaningless beyond its use as a mathematical tool.

    I suppose I was being hasty for not including some of this in the post itself but I've been (and still am) packing all week and I'm tired.

    I also think I wanted to, at some point, go back to the whole creationists trying to use infinity to prove the existence of a god...I really should start posting when I actually have the time to make sure they're complete.

    Thanks for pointing all of this stuff out. I appreciate it!

  6. CANTOR sets ;)

    aleph naught and other levels of infinity...

    I dunno. I'm with Nathaniel... they are all equally abstract in math, and hey why not say "infinity" has a realizable analog just as good as any of the other concepts do? Set it either before the big bang or after the heat death of the universe take your pick.

    Besides, you really can't talk about pi even without some idea of infinity because it is irrational. That in itself I think encompasses an "existence" of infinity for pi to even be a decent concept.

    But yeah, cantor sets are far more interesting to talk about than exactly what is the line between "real abstract" and "abstract abstract"