There have been a number of Scientific discoveries that seemed to be purely scientific curiosities that later turned out to be incredibly useful. Hertz famously commented about the discovery of radio waves: “I do not think that the wireless waves I have discovered will have any practical application.”
Are there examples like this in math as well? What is the most interesting “pure math” discovery that proved to be useful in solving a real-world problem?
Non-Euclidean geometry was developed by pure mathematicians who were trying to prove the parallel line postulate as a theorem. They realized that all of the classic geometry theorems are all different if you start changing that postulate.
This led to Riemannian geometry in 1854, which back then was a pure math exercise.
Some 60 years later, in 1915, Albert Einstein published the theory of general relativity, of which the core mathematics is all Riemannian geometry.
This won’t make any sense to any of you right now, but: E = md3
Oh god, the cringe.
I work with a guy who is a math whiz and loves to talk. Yesterday while I was invoicing clients, he was telling me how origami is much more effective for solving geometry than a compass and a straight edge.
I’ll ask him this question.
My disclaimer: I don’t know what any of this means, but it might give you a direction to start your research.
First thing he came up with is Number Theory, and how they’ve been working on that for centuries, but they never would have imagined that it would be the basis of modern encryption. Multiplying a HUGE prime number with any other numbers is incredibly easy, but factoring the result into those same numbers is near impossible (within reasonable time constraints.)
He said something about knot theory and bacterial proteins, but it was too far above my head to even try to relay how that’s relevant.
Tell him I would like to subscribe to his blog
The following aren’t necessarily answers to your question, but he also mentioned these, and they are way too funny to not share:
The Hairy Ball theorem
Cox Ring
Tits Alternative
Wiener Measure
The Cox-Zucker machine (although this was in the 70s and it’s rumored that Cox did most of the work and chose his partner ONLY for the name. 😂)
Based Cox.
I am pretty sure that the first thing you mentioned (multiplying being easy and factoring being hard) is the basis of public key cryptography which is how HTTPS works.
Somewhat related fun fact: One of the most concrete applications for quantum computers so far is breaking some encryption algorithms.
Origami can be used as a basis for geometry:
http://origametry.net/omfiles/geoconst.html
IIRC, you can do things that are impossible in standard Euclidean construction, such as squaring the circle. It also has more axioms than Euclidean construction, so maybe it’s not a completely fair comparison.
Does this count? Because it really is wtf.
Doom absolutely counts!
Quake, not Doom. Doom didn’t use true 3D rendering and had almost no dynamic lighting.
Oops. I thought that weird approximated constant was somewhere in the doom sources… Thanks I guess for correcting me.
Here’s some math-related Doom content for you: John Romero accidentally coded in the wrong digit of pi in the 10th position, and this guy explores how the game rendering changes when pi is increasingly wrong
The exact example I also thought of from the question! Well done
Don’t put that cursed shit on mathematicians, lol.
A brain teaser about visiting all islands connected by bridges without crossing the same bridge twice is now the basis of all internet routing. (Graph theory)
freaking freaky little Russian outpost that one is. Bridges galore
It’s imaginary numbers. Full stop. No debate about it. The idea of them is so wild that they were literally named imaginary numbers to demonstrate how silly they were, and yet they can be used to describe real things in nature.
I’m studying EE in university, and have been surprised by just how much imaginary numbers are used
EE is absolutely fascinating for applications of calculus in general.
I didn’t give a shit about calculus and then EE just kept blowing my mind.
From what I’ve seen that’s one example where you could totally just use trig and pairs of numbers, though. I might be missing something, because I’m not an electrical engineer.
You can, they map, but complex numbers are much much easier to deal with
In quantum mechanics, there are times you divide two different complex numbers, and complex multiplication/division is the thing two real numbers can’t really replicate. That’s how the Bloch 2-sphere in 3D space is constructed from two complex dimensions (which maps to 4 real ones).
It’s peripheral, though. Nothing in the guts of the theory needs it AFAIK - the Bloch sphere doesn’t generalise much and is more of a visualisation. So, jury’s still out on if it’s us or if it’s nature that likes seeing it that way.
I mean, quaternions are the weirder version of complex numbers, and they’re used for calculating 3D rotations in a lot of production code.
There’s also the octonions and (much inferior) Clifford algebras beyond that, but I don’t know about applications.
Yeah but aren’t quaternions basically just a weird subgroup of 2x2 complex matrices?
Would that make it less true? Complex numbers can be seen as a weird subgroup of the 2x2 real matrices. (And you can “stack” the two representations to get 4x4 real quaternions)
Furthermore, octonions are non-associative, and so can’t be a subgroup of anything (although you can do a similar thing using an alternate matrix multiplication rule). They still show up in a lot of the same pure math contexts, though.
I just think complex vector spaces are a great place to stop your abstraction
Stopping while we’re ahead? Never!
/s, but also I’m sort of in this picture.
Well who wants constraints anyway? The most inconvenient constraints in the wrong place can make certain things much more complicated to deal with… Now a nice, sensible normal Hilbert space, isn’t that lovely?
I don’t really get 'em. It seems like people often use them as “a pair of numbers.” So why not just use a pair of numbers then?
They also have a defined multiplication operation consistent with how it works on ordinary numbers. And it’s not just multiplying each number separately.
A lot of math works better on them. For example, all n-degree polynomials have exactly n roots, and all smooth complex functions have a polynomial approximation at every point. Neither is true on the reals.
Quantum mechanics could possibly work with pairs of real numbers, but it would be unclear what each one means on their own. Treating a probability amplitude as a single number is more satisfying in a lot of ways.
That they don’t exist is still a position you could take, but so is the opposite.
Because the second number has special rules and a unit. It’s not just a pair of numbers, though it can be represented through a pair of numbers (really helpful for computing).
I totally get your point, and sometimes it seems like that. Why not just use a coordinate system? Because in some applications the complex roots of equations is relevant.
If you square an imaginary number, it’s no longer an imaginary number. Now it’s a real number! That’s not something you can accomplish with something like a pair of numbers alone.
IIRC quaternions were considered pretty useless until we started doing 3D stuff on computers and now they’re used everywhere
This talk by Freya Holmer on Quarternions is awesome and worth anybody’s time that like computer graphics, computer science, or just math.
That was a cool watch. Thanks.
I wonder if complex numbers predate the discovery of electromagnetism
Yes, mathematicians first encountered equations which could only be solved with complex numbers in the 16th century.
Complex numbers. Also known as imaginary numbers. The imaginary number
iis the solution to√-1. And it is really used in quantum mechanics and I think general relativity as well.It’s used extensively in electronic circuit design (where it’s called “j”, as "i’ already meant electronic current).
Also signal processing has i or j all over it.
I’m the akshually guy here, but complex numbers are the combination of a real number and an imaginary number. Agree with you, just being pedantic.
Sure, but 1 is a real number. 😜
Yes, and 1 is also a complex number.
Of course, but 1 is the loneliest number.
2 is as bad as 1: it’s the loneliest number since the number 1.
Electromagnetics as well.
A complex number is just two real numbers stitched together. It’s used in many areas, such as the Fourier transform which is common in computer science is often represented with complex numbers because it deals with waves and waves are two-dimensional, and so rather than needing two different equations you can represent it with a single equation where the two-dimensional behavior occurs on the complex-plane.
In principle you can always just split a complex number into two real numbers and carry on the calculation that way. In fact, if we couldn’t, then no one would use complex numbers, because computers can’t process imaginary numbers directly. Every computer program that deals with complex numbers, behind the scenes, is decomposing it into two real-valued floating point numbers.
That’s not quite accurate because the two numbers have a relationship with each other. i^2 = - 1, so any time you square a complex number or multiply two complex numbers, some of the value jumps from one dimension to the other.
It’s like a vector, where sure, certain operations can be treated as if the dimensions of the vector are distinct, like a translation or scale. But other operations can have one dimension affecting the other, like rotation.
uh… broski… you do realize a vector of two real numbers can be rotated… right? Please give me a single example for a supposed impossible operation to do on a vector of two real numbers that you can do on complex numbers. I can just define v² where v is a vector (a,b) as (a,b)²=(a²-b²,2ab). Okay, now I’ve succeeded in reproducing your supposedly mathematically impossible operation. Give me another one.
I don’t think this is really an accurate way of thinking about them. Yes, they can be mapped to a 2d plane, so you can represent them with their two real-numbered coordinates along the real and imaginary axes, but certain operations with them (eg. multiplication) can be done easily with complex numbers but are not obvious how to carry out with just grid points. (3,4) * (5,6) isn’t well-defined, but (3+4i) * (5+6i) is.
I am having genuine difficulty imagining in your head how you think you made a point here. It seems you’re claiming that given if two vectors have the same symbols between them, they should have identical output, such as (a,b) * (c,d) should have the same mathematical definition as (a+bi) * (c+di), or complex numbers are not reducible to real numbers.
You realize mathematical symbols are just conventions, right? They were not handed down to us from Zeus almighty. They are entirely human creations. I can happily define the meaning of (a,b) * (c,d) to be (ac-bd,ad+bc) and now it is mathematically well-defined and gives identical results.
Right, but you need to specify that additional definition. Imaginary numbers are useful because they come pre-loaded with all those additional definitions about how to handle operations that use them.
I also find your hostile confusion unwarranted, given two other commenters have pointed out the same flaw in your argument that I have.
Because your arguments are just bizarre. Imaginary numbers do not have a priori definitions. Humans have to define imaginary number and define the mathematical operations on them. There is no “hostile confusion” or “flaw,” there is you making the equivalent of flat-earth arguments but for mathematics. You keep claiming things that are objectively false and so obviously false it is bizarre how anyone could even make such a claim. I do not even know how to approach it, how on earth do you come to believe that complex numbers have a priori definitions and they aren’t just humans defining them like any other mathematical operation? There are no pre-given definitions for complex numbers, their properties are all explicitly defined by human beings, and you can also define the properties on vectors. You at first claim that supposedly you can only do certain operations on complex numbers that you cannot on vectors, I point out this is obviously false and you can’t give a single counter-example, so now you switch to claiming somehow the operations on complex numbers are all “pre-given.” Makes zero sense. You have not pointed out a “flaw,” you just ramble and declare victory, throwing personal attacks calling me “confused” like this is some sort of competition or something when you have not even made a single coherent point. Attacking me and downvoting all my posts isn’t going to somehow going to prove that you cannot decompose any complex-valued operations into real numbers, nor is it going to prove that complex numbers somehow don’t have to have their properties and operations on them postulated just like real numbers.
I’m being combative because I don’t get how you don’t understand our argument, and because I view claims like “You keep claiming things that are objectively false” to be hostile when they stem from a misunderstanding rather than a fault on my part.
Let me restate my main point: complex numbers can be defined as vectors with the necessary rules to define various operations, such as multiplication over them and how they relate to sqrt(-1). Those additional rules are just as important to their definition as their appearance as two real-numbered values is. Both vectors and complex numbers are defined by humans, but we have chosen to give them separate definitions, because each definition includes the rules defining these operations and relationships, and they are different between the two types of mathematical object.
And, for the record, I downvoted your posts that were hostile (not all of them) and responded in kind. It’s a separate effort than trying to prove my point here.
What point is there to “prove”? Your argument now is just that we defined them differently therefore they are different. Which suggests a straw man to my original point as I never once implied or suggested that in mathematics, real and complex numbers don’t have different definitions, that’s not relevant to anything.
As far as I know, matrices were a “pure math” thing when they were first discovered and seemed pretty useless. Then physicists discovered them and used them for all sorts of shit and now they’re one of the most important tools in in science, engineering and programming.
Huge in 3d graphics and AI.
The invention of the number 0, the discovery of irrational numbers, or l the realization that base 60 math makes sense for anything round, including timekeeping.
60 was chosen by the Ancient Sumerians specifically because of its divisibility by 2, 3, 4, and 5. Today, 60 is considered a superior highly composite number but that bit of theory wouldn’t have been as important to the Sumerians and Babylonians as the simple ability to divide 60 by many commonly used factors (2, 3, 4, 5, 6, 10, 12, 15) without any remainders or fractions to worry about.
12 is the most based number in that respect IMO.
But then…hey, we use that for hours!
and in parts of the world for inches to a foot. pretty useful for carpentry for example
If I recall correctly, one mathematician in the 1800s solved a very difficult line integral, and the first application of it was in early computer speech synthesis.
the man you’re thinking of is, I believe, George Boole, the inventor of Boolean algebra.
Non-linear equations have entered the chat.
Chaos and non-linear dynamics were treated as a toy or curiosity for a pretty long time, probably in no small part due to the complexity involved. It’s almost certainly no accident that the first serious explorations of it after Poincare happen after the advent of computers.
So, one place where non-linear dynamics ended up having applications was in medicine. As I recall it from James Gleick’s book Chaos, inspired by recent discussion of Chaotic behavior in non-linear systems, medical doctors came up with the idea of electrical defibrillation- a way to reset the heart to a ground state and silence chaotic activity in lethal dysrhythmias that prevented the heart from functioning correctly.
Fractals also inspired some file compression algorithms, as I recall, and they also provide a useful means of estimating the perimeters of irregular shapes.
Also, there’s always work being done on turbulence, especially in the field of nuclear fusion as plasma turbulence seems to have a non-trivial impact on how efficiently a reactor can fuse plasma.
A good friend of mine from high school got his physics PhD at University of Texas and went on to work in the high energy plasma physics lab there with the Texas Petawatt laser, and a lot of the experiments it was used for involved plasma turbulence and determining what path energetic particles would take in a hypothetical fusion reactor.
Be honest, how many unofficial experiments were there?
You ever just start lasering shit for kicks?
Probably not as many as we’d like to think. I recently got to run a few days of tests at Lawrence Livermore National Labs with an absurdly massive laser. At one point we needed to bring in a small speaker for an audio test. It took the lab techs and managers about two hours and a couple phone calls to some higher ups to make sure it was ok and wouldn’t damage anything. There’s so much red tape and procedure in the way that I don’t think there’s an opportunity to just fuck around. The laser has irreplaceable parts that people aren’t willing to jeopardize. Newer or smaller lasers are going to be more relaxed. This one is old enough to be my father, and it’s LLNL’s second biggest single laser iirc. And they are the lab using lasers for fusion, so they have big lasers.
Reminds me of that scene from Ali G
Having watched all the veritasium math videos I feel like all the major breakthroughs in math were due to mathemicians playing around with numbers or brain teasers out of curiosity without a concrete use case in mind.
I’ve read that all modern cryptography is based on an area (number theory?) that was once only considered “useful” for party tricks.
Donuts were basis of the math that would enable a planned economy to be more efficient than a market economy (which is a very hard linear algebra problem).
Basically using that, your smart phone is powerful enough to run a planned economy with 30 million unique products and services. An average desktop computer would be powerful enough to run a planned economy with 400 million unique products and services.
Odd that knowledge about it has been actively suppressed since it was discovered in the 1970s but actively used mega-corporations ever since…
I’d like to read up on this if you have sources
Look up Wassily Wassilyevich Leontief
Are you talking about the input-output thing? It assumes each sector produces exactly one thing, and is agnostic of growth, change and multiple non-equal possibilities existing. I’m skeptical.
It’s not really covered up, either.
That’s pretty interesting. Do you happen to have any introductory material to that topic?
I mean, it might even have applications outside of running a techno-communist nation state. For example, for designing economic simulation game mechanics.
Well Wassily Wassilyevich Leontief won a Nobel prize in economics for his work on this subject that might help you get started
There’s no such thing as a Nobel Prize in economics. Economists got salty about this and came up with the Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel, and rely on the media shortening it to something that gets confused with real Nobel Prizes.
Fair point
I mean, it’s endorsed by the same people. He has a page on their website and everything.
The same site says things like:
Between 1901 and 2024, the Nobel Prizes and the Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel were awarded 627 times to 1,012 people and organisations.
which pretty clearly makes a distinction between the Nobel Prizes and the Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel.
Yeah, you’re not wrong about the history. It just still seems like it counts.
It’s funny that you’re saying this is “actively suppressed” while not naming this field or providing links for further readings.
Donut mathematics is the name of the field; I literally named it. The writings on it are dense and only available in Russian and Mandarin Chinese. Further I provided the name of an author on the subject.
What would you call the purposeful prevention of English/French/German/etc translations of the material?
The phrase “donut mathematics” was not in your earlier comment. You literally did not name it.
Maybe they’re scared that project Cybersyn would actually work
Imaginary numbers probably, they’re useful for a lot of stuff in math and even physics (I’ve heard turbulent flow calculations can use them?) but they seem useless at first
