Spark Science Podcast
Science on the Screen: The Man Who Knew Infinity
Jordan Baker: Here we go!
[♪ Blackalicious rapping Chemical Calisthenics ♪]
♪ Neutron, proton, mass defect, lyrical oxidation, yo irrelevant
♪ Mass spectrograph, pure electron volt, atomic energy erupting
♪ As I get all open on betatron, gamma rays thermo cracking
♪ Cyclotron and any and every mic
♪ You’re on trans iridium, if you’re always uranium
♪ Molecules, spontaneous combustion, pow
♪ Law of de-fi-nite pro-por-tion, gain-ing weight
♪ I’m every element around
[♪Blackalicious rapping Chemical Calisthenics ♪]
Regina Barber DeGraaff: Welcome to Spark Science where we explore stories of human curiosity. I’m Regina Barber DeGraaff and I teach physics and astronomy at Western Washington University. I was invited to speak at Pickford Film Center and it’s an independent theatre, here in Bellingham, Washington. They invited me to talk before the movie, The Man Who Knew Infinity.
I interviewed Dr. Sarkar who was on the episode “Math History.” I also interview another mathematician from Western Washington University, Dr. Stephanie Treneer. Please enjoy our panel discussion before the film, The Man who Knew Infinity where we discuss the work of brilliant mathematician, Ramanujan.
Lindsey: Thank you for joining us this evening. My name is Lindsey, I am the marketing manager for the Pickford. I would like to welcome you to this very special evening. It is a part of Science on Screen. Science on Screen is a program funded by the Alfred P. Sloan Foundation and administered by the Coolidge Corner Theatre in Massachusetts. It partners with independent cinemas across the country to present series of films, classic cult films, documentaries that are somehow partnered creatively with science. And so, we’ve been working on our series. This is the first year that we applied and we won the grant, so this is our first year to do this.
[Audience applause.]
Audience: Yay!
Lindsey: Yeah! Regina has been a huge help and we’re featuring a lot of Wes Anderson films and this is one that has been . . . tonight’s is not a Wes Anderson film, but it has been approved by the Sloan Foundation as one of their newest films to be added to the catalogue, so we’re excited to show this sneak preview before it opens to the public.
The final Science on Screen series film is going to be The Royal Tenenbaums. That’s on June 4th, featuring a lecture on family relationships by Dr. Janet Ferrol. She’s a clinical instructor at the University of Washington Department of Psychology and Behavioral Sciences. So that’s a Saturday afternoon, June 4th. It’s our last one. You can pick tickets up on your way out or any time before the screening at the box office.
OK, I’m going to give a little short introduction, to set the scene about what you’re about to hear and then introduce our guests. Tonight’s program features the discussion of the work of Srinivasa Ramanujan, a self-taught Indian mathematician who produced a huge volume of ground-breaking work before his untimely death.
Nearly 100 years later, the influence of his work is still shaping mathematics. As we strive to understand some of his most surprising results, Western Washington University colleagues, Dr. Regina Barber DeGraaff, Dr. Amites Sarkar, and Dr. Stephanie Treneer will discuss his contributions to mathematics, his collaboration with GH Hardy at Trinity College, Cambridge, and what it means to do research in mathematics.
So please join me in giving them a warm welcome and I hope you enjoy tonight. Thank you!
[Applause.]
Regina Barber DeGraaff: So, what was your name as you’re walking away?
Lindsey: Oh, Lindsey.
Regina Barber DeGraaff: Lindsey! As Lindsey said, we all work at Western. I teach physics and astronomy at Western Washington University and my colleagues here, Amites and Stephanie teach math. The reason I’m here, I know a little bit about math. Not that much. They know way more about this than I do, but the reason I’m here is I’m also the host of Spark Science, which is a science talk show where we try to basically humanize science, try to make people not so scared of it. I’m going to be able, or try to kind of guide the discussion and ask questions. One of the questions I ask on my show all the time is “how did somebody get into science, what sparked their interest into science.” So before we even get into this, I’m going to try to humanize us.
So I’m going to talk about why we kind of got into science and I’m going to let them go first. I like space. That’s why I got into science. So I’m going to let them go. I’m going to ask Stephanie first. So, why did you pick math?
Dr. Stephanie Trenner: Um, I guess I sort of felt like I didn’t have a choice. It was always my favorite subject from when I was sort of “yay-high.”
Regina Barber DeGraaff: What was that – 5?
Dr. Stephanie Trenner: Well, I don’t really know. Certainly elementary school. It was always what I was kind of best at. And then I sort of . . . when I got to college, I thought, well, I should try other things, so I took general chemistry and really, really hated labs.
Regina Barber DeGraaff: So offense to our chemistry colleagues.
Dr. Stephanie Trenner: Yeah, no offense to chemists, but I was not a chemist. So I thought, well I’m just going to keep on with the math. And then I sort of fell in love with number theory in college.
Regina Barber DeGraaff: Wow.
Dr. Stephanie Trenner: And then went on to study it in grad school.
Regina Barber DeGraaff: And what did you study, real quick?
Dr. Stephanie Trenner: Yeah, so actually, I went to the University of Illinois for grad school which as a long tradition of number theory research and I sort of landed in sort of a hot bed of Ramanujan study, because Bruce Barron, he was one of the long-time professors there, he’s retired now, was one of the preeminent Ramanujan-scholars and he actually spent most of his academic career publishing volumes of work based on Ramanujan’s notebooks.
So Ramanujan was famous for keeping these notebooks where he recorded all these amazing results but not really proving anything. We’ll talk about that maybe a little bit later. And so Bruce, together with many collaborators, has, you know, many mathematicians since that time have been working on proving all of these results and remarkably most of them are actually true. And so he has been compiling these volumes of sort of line by line, the notebooks with justification for all of the work.
Regina Barber DeGraaff: That’s amazing. And when you were “this high,” you were in Seattle?
Dr. Stephanie Trenner: Yes, I grew up in Seattle?
Regina Barber DeGraaff: So you’re a Washingtonian?
Dr. Stephanie Trenner: Oh yeah.
Regina Barber DeGraaff: Alright. Amita, want to tell me why you got into math?
Dr. Amita Sarkar: I was actually inspired by the books written by two of the characters in this movie. So, just in order to explain, I can also explain something about the setting of the movie, because it ties in with how I got into it. So that’s Ramanujan.
And then on the next slide, you can see Trinity College, Cambridge, this famous and amazing place. And the bottom slide is a photograph from about the year 2000. The top right is from about the year 1900 and the top left is an engraving from 1798.
Regina Barber DeGraaff: And for our listeners, I’m going to take this audio for our show later, but for our listeners, there is really no difference between any of these pictures. And when Amites told me — and we saw the movie a little earlier than you, I’m sorry — and we saw that it didn’t change at all, and he kept saying “this looks exactly the same.”
Dr. Amites Sarkar: Yeah, you could almost spot the difference. I noticed a couple earlier. They have a saying in Trinity, which is that “change is good and no change is better.” [Laughing.] That’s an example of that. That famous movie, Chariots of Fire, I don’t know if many of you have seen this movie, Chariots of Fire, about two sprinters. A key scene, the great court run is set in Trinity, but it wasn’t filmed in Trinity, they didn’t have permission. But they did have permission to shoot this movie.
And probably the most famous alumnus of Trinity, Cambridge was to Sir Isaac Newton and his law of gravitation, his laws of motion really absolutely ground-breaking work, set the stage for modern science in the late 17th century with his book, Principia Mathematica. And besides discovering the laws of motion and gravitation, from which he derived laws of motion, and showed the effects of the moon on the earth’s tides and other things. He also discovered calculus, discovered or invented calculus.
And at the same time, in Germany, Gottfried Wilhelm Leibniz also discovered calculus. And later on, this led to a bit of a dispute between the two men and their followers, between Newton and England and the followers of Newton and Leibniz in Germany and the followers of Leibniz.
And one of the consequences of this was that English mathematics was cut off from the continent from around 200 years. England had some great physicists, like Maxwell, who also went to Trinity in that time, but mathematically, relatively speaking, it was isolated and that continued for 200 years until these two guys came on the scene around 1910.
They had a famous collaboration, which was the stuff of legend, really.
Regina Barber DeGraaff: And for our listeners it’s Hardy and Littlewood.
Dr. Amita Sarkar: GH Hardy, yes.
Regina Barber DeGraaff: These two guys.
Dr. Amites Sarkar: GH Hardy and J Littlewood. They also went to Trinity. They wrote 93 papers together, incredibly influential. People still mime them for ideas. At the time, it was unusual to collaborate in mathematics. One of the interesting things is that now it’s the norm, then it was rare, and this was probably the first famous one in mathematics.
And not only did they collaborate, they also maintained correspondences with mathematicians from other countries, so in Denmark and France and Germany, and also in America. So really, they put mathematics, or put England and Cambridge back on the mathematical map in a big way.
Towards the end of their lives, they both wrote books emphasizing the aesthetic component of mathematics as opposed to its practical applications. And Hardy’s book, which I really recommend, is called A Mathematician’s Apology. It makes the case for, you know, the artistic side. Two famous quotations from this book are, “A mathematician, like a painter or a poet, is a maker of patterns.” And “beauty is the first test. There is no permanent place in the world for ugly mathematics.” It’s a very poetic book actually. It’s a justification of his life’s work, it’s slightly depressing.
Littlewood’s book — for reasons you should read it and see why — Littlewood’s book is a little more uplifting. It’s called A Mathematicians Miscellany and it ranges from anecdotes to longer essays. There’s a beautiful one about the discovery of Neptune. But these are two books and both of them I recommend to you, if you’re interested in this.
Regina Barber DeGraaff: And when did you read them? How old were you?
Dr. Amites Sarkar: Well, I was a teenager. I was 15 when I read them. That was the first time I heard about Ramanujan. I didn’t know that there were any Indian mathematicians, actually.
Regina Barber DeGraaff: At all?
Dr. Amites Sarkar: Yeah, I was incredibly ignorant. And Ramanujan is an Indian mathematician, maybe I could be a mathematician. And then later, just by coincidence, later that year, we had a family trip to India and I begged my parents, can we go to Madras, I want to see where this guy grew up and lived and everything. And eventually they said yes and so me and my dad and brother traveled to Madras…
Regina Barber DeGraaff: You’re 15 when this happened?
Dr. Amites Sarkar: I was 16 at the time. I think my dad made some interesting phone calls, because we were hosted by Professor Rangachari of the University of Madras. And he drove us around and he took us to the library, where I held Ramanujan’s notebook in my hand, three red books. And then also he drove us to meet Ramanujan’s wife. So I met Ramanujan’s wife, who is in this movie. She was 90 at the time. She lived in a small two-room house. One of the rooms was a shrine to her husband. And that was a life-changing experience for me.
A few months later, I applied to Trinity College, Cambridge, and was lucky enough to get in. So that’s I guess my second connection with the movie. It was a longer answer.
Regina Barber DeGraaff: No, I love that story. That’s wonderful. So I mean, the reason I ask these questions, I don’t have an awesome story like that so that’s why I just said “I like science and I like space.” But the reason I ask that is because once we know the stories of these scientists, and that’s what this movie is about, once we humanize these scientists, science becomes less frightening.
[♪ Janelle Monae singing Wondaland ♪]
Regina Barber DeGraaff: Now that we kind of got a grasp of kind of the history of what’s going on with Trinity, I want to kind of give it over to Stephanie and she’s going to kind of take us through the math that’s happening in this movie, which is really interesting and groundbreaking.
Dr. Stephanie Trenner: Yeah, so I wanted to talk a little bit about the math that happens that you’ll actually see in the movie, they’re working on in the movie, and then also talk a little bit about how it has influenced mathematics since that time, because it’s really had a very profound influence. And what you see in the movie is just mostly working on one or two problems that Hardy and Ramanujan worked on during their time at Cambridge, but actually they did a large volume of work. You mentioned how many papers they published together.
And so I wanted to give an idea of sort of Ramanujan’s work is still influencing mathematics today. So here’s a definition. So they make this definition in the movie, but it goes by really fast, so I thought we would spend a minute and think about it here, because actually the origins of this problem that they’re going to be working on are pretty easy to state and start thinking about. It starts with this definition and so you guys know what a positive integer is? Right? 1, 2, 3, 4, 5, 157, 6,924,000,000, positive integers.
Regina Barber DeGraaff: That’s my favorite right there.
Dr. Stephanie Trenner: That one there? So we can think about how we might take a positive integer, like say 4, and write it as a sum of other positive integers. Pretty simple.
Regina Barber DeGraaff: So a sum being addition.
Dr. Stephanie Trenner: Yeah, so like 3 + 2 = 5. So that’s one way to write 5 as a sum of two positive integers. And then we’re just going to count all the ways to do it.
So one of those ways of writing it is a “partition.” So 3 + 2 is a partition of 5, and then we want to just count all of the ways that we can do that.
Regina Barber DeGraaff: Which they actually go through in the movie, right?
Dr. Stephanie Trenner: Everyone talking partitions uses this example, pretty much. I have seen this example about 100 times. So here are the partitions of 4. So you have 4, and 3 + 1, and 2 + 2, and 2 + 1 + 1, and 1 + 1 + 1 + 1. So notice that I haven’t written 1 + 2 + 1 up here, because I’m not going to count that as a different partition than 2 + 1 + 1. So for the purposes of what we’re doing here, we think if we rearrange the terms in a given partition, that doesn’t make it different. OK?
So we count this as 5 partitions of 4. And so, well, mathematicians like patterns, right? So, we have this definition. We can play around with it. We could compute this number, this partition number, for a number of small integers N and see what we come up with. But before too long, we’re going to start asking ourselves, because we like patterns, “Well, can we find some nice formula for P of N, the number of partitions of an arbitrary integer, N?”
Well, we can sort of start with simple examples. So can you guys all agree that P of 1 is 1? There is only 1 way to write 1 as a sum of a positive integers, because it’s just 1 itself. So what’s P of 2? 2. Good. And what about P of 3?
Audience Member: 3.
Dr. Stephanie Trenner: Are you sure about it? So what are there? There’s . . .
Audience Member: 2 + 1.
Dr. Stephanie Trenner: 2 + 1, what else?
Audience Member: 1 + 1 + 1.
Dr. Stephanie Trenner: 1 + 1 + 1. And what else? Just 3 itself, that counts too. So there’s 3 of them.
OK, and then we already looked at P of 4. That’s 5. Oh, what about P of 5?
Regina Barber DeGraaff: Do you want to let them discuss amongst themselves?
Dr. Stephanie Trenner: Oh, yeah.
Regina Barber DeGraaff: Just like in class! Talk to your neighbor. See, this isn’t scary! This is fun!
Dr. Amita Sarkar: It’s scary for me! [Laughing.]
Regina Barber DeGraaff: Who wants to guess?
Audience Member: If it’s Fibonacci, it’s going to be 8.
Regina Barber DeGraaff: If it’s Fibonacci, it’s going to be 8.
Dr. Stephanie Trenner: Oh, we have a guess at a pattern already! So you’re guessing that the numbers are going to continue, like the Fibonacci sequence.
Regina Barber DeGraaff: I want different — somebody who doesn’t think 8.
Dr. Stephanie Trenner: Who doesn’t think 8 is next?
Regina Barber DeGraaff: Any number that isn’t 8? Yeah?
Audience Member: 6.
Dr. Stephanie Trenner: 6. Did anybody get a different number other than 8 and 6?
Audience Member: 7.
Dr. Stephanie Trenner: 7. How many people got 7?
Regina Barber DeGraaff: That was a hint already! You were like, “How many people?”
Dr. Stephanie Trenner: I know, I telegraphed that one. OK, so now can we guess at a pattern? What do you think P of 6 is going to be, without trying to work it out, but just guess.
Regina Barber DeGraaff: Yeah, let’s just guess.
Someone says 9.
Dr. Stephanie Trenner: 9, alright.
Regina Barber DeGraaff: Ooh!! That pain is learning! That’s what that struggle is. That’s what I tell my students! Struggle and learning, like working out.
Dr. Stephanie Trenner: Alright, so is it P of 7? Yeah, what do you think?
13? Hmm… Oooh. So they’re not Fibonacci numbers and they’re not even prime numbers anymore.
Regina Barber DeGraaff: ut-oh! That’s why this question was hard!
Dr. Stephanie Trenner: Yeah, it gets hard. So this is actually why this function is interesting, because it actually doesn’t have a really nice, obvious pattern. So they’re not even all odd. And they get kind of big kind of fast and already at this point I wouldn’t want to sit down and work out all of them by hand.
So P of 10 is 42. What is your guess about sort of order of magnitude, like how big would P of 200 be? I mean, I know this is based on nothing but pure guess, but just guess.
[Inaudible responses in background.]
I heard 2,000, I heard 600. 5,000. So kind of on the order of the thousands, that many? Do you guys all kind of think that? It’s a reasonable guess. I haven’t given you that much data to go on.
[Audience exclaiming.]
Dr. Stephanie Trenner: Yeah.
Regina Barber DeGraaff: And this number, remember this, and you’re going to all feel very, very smart as you’re watching this movie.
Dr. Stephanie Trenner: You will see this number in the movie and you’ll be, “Ah-ha! I know where that is, I know where that comes from.” So 3, is that 3 trillion something? Do I have my zeros? 3.9 trillion. So huge numbers, right? So how do you think they calculated that? They certainly didn’t just write down all of the partitions of 200, because they would never, I mean, even if they had enough time, and I mean, who could make sure that you actually got all of them, because there are just so many.
So, we would like some sort of a formula, or people that were thinking about this at the time, would like some sort of formula for P of N, but it doesn’t obviously follow any nice patterns, so it’s actually turns out to be sort of a hard problem to find a nice, general formula for P of N.
So that was people starting thinking about. So, this is a formula. It’s a recursive formula, which means that it defines P of N for a particular N in terms of the partition number for smaller values of N. And this falls from work of Oiler [sp?] in the 1700s and so, let’s see P of N is P of N minus 1. It’s sort of the sum of two numbers, minus two more numbers, plus two more numbers, and this actually is a pattern here that continues. Does anyone happen to know what these numbers are: 1, 2, 5, 7, 12, 15?
That’s kind of tricky.
Regina Barber DeGraaff: I mean, they’re so similar to the ones we had up there before, the partition numbers.
Dr. Stephanie Trenner: Well, yeah, except 12 wasn’t a partition number, so they are actually something called generalize pentagonal numbers. Whooo!
Regina Barber DeGraaff: I have no idea what those are.
Dr. Stephanie Trenner: Yeah, I’m not going to spend time explaining what those are now, but there is a pattern to these numbers. So, let me say one more thing about this formula, because it’s a little funny. The formula goes on and on and on, but if you notice, if you do this for a particular N, like we’ll do it for N = 11 in a minute, pretty soon the numbers inside those Ps drop to be below 0. So, we just agree that P of a negative number is 0. So in that way, the sum just ends after some number of terms.
So, for example, for P of 11, it’s just four terms: P of 10 plus P of 9 minus P of 6 minus P of 4, and those are values we already saw. We plug them in and we get 56. So, this is one way to calculate partition numbers that’s better than just running down all the partitions. Certainly better, although it’s still kind of tedious for big numbers.
So it’s actually maybe surprising that someone actually had the patience to crank through this formula for fairly big numbers. In fact, all the way up to 200. So that is what this guy did.
So a Major Percy McMann, so you’re actually going to see him in the movie too, and you’ll know it’s him because he’s played by the same guy who played Jack Sparrow’s first mate in The Pirates of the Caribbean movies.
Regina Barber DeGraaff: Yeah. When Stephanie pointed that out, I was like, “Oh my god!”
Dr. Stephanie Trenner: Regina was like, “Who’s that guy, who’s that guy?” And then all of the sudden, half way through the movie, I was like, “Oh, I know who it is!”
Regina Barber DeGraaff: Yes. It was amazing.
Dr. Stephanie Trenner: It was cool. Anyways, so he was a major in the British army and then he retired and devoted himself to mathematics and became a fellow of the Royal Society of London. And so he was really interested in sort of commentarial things, counting problems, and so he cranked through that recursive formula by hand and calculated tables of partition numbers all the way up to 200. And those were actually very valuable for people like Ramanujan looking at those tables of values later and trying to figure out patterns in the partition mbiras.
So he did this by hand, but still you can imagine that was pretty tedious, and so there was still this desire to find some type of better formula for P of N. So, this is one of the big contributes that Hardy and Ramanujan made together. Ramanujan had proposed this formula for P of N and then he was actually able to formally prove it with Hardy during their time at Cambridge. So it’s actually an asymptotic formula for P of N, which means it’s not an exact formula, but roughly speaking it means that these two functions, P of N, and this funny function on the right sort of grow at the same rate as N gets really, really big.
And you’ll notice there’s really sort of interesting things in that formula on the right. There are square roots and there is pi up there and there’s E, which is another famous mathematical constant. And it’s really sort of surprising that that formula would have anything to do with integers, because if you plug in an integer N to that formula, you’re certainly not going to get integers, but it turns out that it actually is a good asymptotic formula for P of N.
Regina Barber DeGraaff: Well, and once he got this, when it has natural numbers like E and pi, that seems like it means, something right? For like a mathematician, that’s really awesome.
Dr. Stephanie Trenner: Absolutely. When you’re a mathematician and you come up with a formula that sort of has these really beautiful constants in it that are important, you sort of figure that you got it right somehow.
Regina Barber DeGraaff: Right.
Dr. Stephanie Trenner: Yeah, that’s kind of the goal, is to find something that feels right and something this beautiful probably felt right to Ramanujan.
Dr. Amites Sarkar: It’s also mysterious, right? I mean like, what do these numbers even do? Those circle and everything.
Dr. Stephanie Trenner: Yeah, so one of the important things about this formula was not just that they were able to prove it, but to prove it, they had to develop this new method called the “circle method,” which ended up having widespread applications to various other problems in analytic number theory. And so throughout kind of the early part of the 20th century, this method was used to prove a lot of other results besides this one.
Regina Barber DeGraaff: Can either of you kind of give just a very brief explanation on why pi is so important to circles and stuff? Super brief, but it’s . . .
Dr. Amites Sarkar: I mean, it’s defined in terms of circles and it shows up in, in you know, the volume of a sphere. But the surprising thing is that it also shows up here in a completely different context. I mean, I defy anyone to explain to me intuitively why pi should appear here, or E for that matter, or square roots. So that’s the surprising that, that you can have something from branch of mathematics. It shows up in a completely different place. And it’s very much against my intuition.
[♪ Janelle Monae singing Wondaland ♪]
♪ Early late at night
♪ I wander off into a land
♪ You can go, but you mustn’t tell a soul
♪ There’s a world inside
♪ Where dreamers meet each other
♪ Once you go, it’s hard to come back
♪ Let me paint your canvas as you dance
♪ Dance in the trees
♪ Paint mysteries
♪ The magnificent droid plays there.]
Dr. Stephanie Trenner: So, go on now and talk a little bit about some ways that Ramanujan’s work influenced later mathematics. So here are some values of the partition number and these would be kind of like the tables that McMann generated of the partition numbers that Ramanujan studied and he actually noticed a really surprising pattern among these numbers.
So if I highlight these ones, so let’s think about what these are. So in each sort of pair of columns I’ve got N on the left and P of N on the right. So the N that correspond to the red numbers are all numbers 4, 9, 14, 19, 24, 29. So they are numbers that are four more than a multiple of five. Does that make sense?
So, when you have a number N that is four more than a multiple of five, then it turns out that the number of partitions of that number is — well, what do you notice about those numbers in red?
Audience Member: Divisible by 5.
Dr. Stephanie Trenner: They are divisible by 5. They all end in either a 0 or 5, which means they are all divisible by 5. So that’s kind of weird. And it turns out it happens again. If you look at numbers that are five more than a multiple of seven, then the partition numbers for those numbers are all divisible by seven. And again with 11. So, numbers that are six more than a multiple of 11 have partition numbers that are divisible by 11.
And this is kind of a strange pattern. And stranger even more so because it doesn’t really happen again after those three instances. So, here’s a different formulation of what we just saw. So, and Ramanujan actually did prove these results. So this is written in the language of modular arithmetic, but really what it means is the number on the left, P of say 5 N plus 4, that just represents all the partition numbers we’re talking about, partition numbers of all numbers which are four more than a multiple of 5.
And then the bit on the right, that part that says sort of the three lines, “0 mod 5” really just means that that number is divisible by five. And the same for the second line, those numbers are divisible by seven and the third numbers are divisible by 11.
So the remarkable thing is not only did he prove these, but he conjectured that these were the only three congruences — that’s what they call these things, congruences — of this form, of the form where you’re dividing by a prime number, L, and you’re looking at numbers that are some Batum more than a multiple of L.
But, he conjectured this back when he was alive, it wasn’t proved until 2003. He was really sort of ahead of his time in terms of his insight for things. In fact, it was proved at the University of Illinois when I was there by my thesis advisor, Scott Ahlgren, and another post-doc, Matt Boylin. And it used a lot of modern mathematical machinery to prove it.
I saw Ramanujan described as a great anticipator. He really anticipated things that were far ahead of his time in terms of mathematics that took everybody else, you know, decades and decades to build the machinery to be able to prove rigorously.
So here’s another result. So it turns out that although these are the only three congruences of this type, if you relax what you mean by these congruences a little bit, if you generalize a little bit, it turns out there’s a lot more. So, if you keep thinking about dividing these partition numbers by a prime number, but instead you just look at partition numbers of any number of AN plus B, where A doesn’t have to be that same prime L anymore, then there’s actually lots and lots of these among the values of the partition function.
In fact, this says there is infinitely many pairs A and B such that P of AN plus B is divisible by L. So this was actually proved again much, much later in 1999 by Ken Ohno, who is very much involved in the mathematical work of Ramanujan continuing on Ramanujan’s legacy and proving things about the partition function. He was also the math technical advisor on the film.
And I got a chance to talk to Ken a little bit about his time. He actually went to Trinity College when they were filming there and worked on set with these guys, which was really cool. So he said that most of the mathematical writing, I think, that you see in the film, is actually Ken’s writing.
But he said also that the actors, Jeremy Irons who plays Hardy and Dev who played Ramanujan really were interested in understanding the motivation of these characters and really kind of getting the details right in terms of their portrayal of mathematicians, even though they didn’t understand the mathematics very well at all. They were really trying to get at the heart of who these guys were. It was interesting.
Regina Barber DeGraaff: Do you want to go into this?
Dr. Stephanie Trenner: You know, I don’t want to take up all the time. I have a little bit more that I can talk about.
Regina Barber DeGraaff: No, I think we can. Go ahead and talk a little bit more and then I wanted to ask more like how can we talk about math to the public and also pop culture, because that’s what this is.
Dr. Stephanie Trenner: Alright, I’ll just mention a couple more things. One of the ways in which Ramanujan’s work was ahead of his time was that he conjectured all these things or he wrote down all these results that he then didn’t prove that really required the modern machinery of what are called “modular forms” to prove. So these results, these recent results that I mentioned, were proved using the theory of modular forms, which although modular reforms were known to Ramanujan, he thought of them in a different way, and sort of the modern theory of them as really been developed over the last 50 years.
If you’re interested in what a modular form is, I have just a little slide that talks about it. So, most of the functions that we think about when we learn math in high school or college are functions of real numbers. So the input value is a real value and the output number is a real number. So I’m thinking of things like polynomials or trigonometric functions.
Regina Barber DeGraaff: Or F equals MA.
Dr. Stephanie Trenner: Sure. Yes. Exactly.
So modular forms are actually complex valued functions, so you’d plug in complex numbers. You guys have heard of imaginary numbers, like the square root of negative 1? So you can think about in general, complex numbers, which include the real numbers but also many more numbers.
So you plug in complex numbers and you get out complex numbers. That’s sort of a weird type of function. And they are meromorphic, which there’s a little definition up there, but really just that means that they are sort of reasonably well behaved functions.
And they have a lot of symmetry and I’ll say about what symmetry means.
[♪ Janelle Monae singing Wondaland ♪]
♪ Your magic mind
♪ Makes love to mine
♪ I think I’m in love, angel
♪ Take me back to Wondaland
♪ I gotta get back to Wondaland
♪ Take me back to Wondaland
♪ Me thinks she left her underpants
♪ Take me back to Wondaland
♪ I gotta get back to Wondaland
♪ Take me back to Wondaland
♪ Me thinks she left her underpants.]
Dr. Stephanie Trenner: So, here’s the sin function, Sin of X, you may be familiar with it. And if you know a little bit about this function, everything you need to know about this function is contained in an interval of length to pi. In fact, it’s periodic, we say, with period 2 pi. So there’s actually two periods drawn on this graph right here, but if we looked just from the right half, from zero to 2 pi, that contains everything we need to know about that function. That picture just repeats to the right and to the left as many times as we want.
And so, we could sort of say that a fundamental domain for this function has length of 2 pi. It contains all of the necessary information about the function in that interval.
Regina Barber DeGraaff: Does this have anything to do with like . . . what is it called . . . like where like Bracciolini . . . it’s like patterns within patterns . . .
Dr. Amites Sarkar: Like fractals?
Regina Barber DeGraaff: Fractals!
Dr. Stephanie Trenner: Um.
Regina Barber DeGraaff: No. The answer can be “no,” it’s fine.
Dr. Stephanie Trenner: Not really directly, no.
So what does this have to do with partitions? Sort of bringing things full circle. So modular forms themselves have sort of become ubiquitous in mathematics. They have lots of connections to not only number theory and algebra, but even things like mathematical physics. But the connection to partitions is that if you write down what’s called a generating function for the partition numbers, which is right here, so what do I mean by that?
Well, if you think about what all of these terms are, the exponent on Q is like N and then on the coefficient, the number in front of the Q, is the P of N value that corresponds to that N. So like 5q4 means there are five partitions of four. And 11q6 means there are 11 partitions of six.
So you can write down this infinite series. This was known was Euler, but it turns out if you define q in the right way, you essentially get a modular form. So you can use all of the modern machinery of modular forms and what we know about modular forms to prove things about this function, which in turn proved things about the partition numbers.
So it’s this really odd combination of using very analytic methods, things about complex numbers, and really sort of heavy machinery to prove things about this particularly interesting sequence of integers. And you wouldn’t really think think that integers and complex numbers would have much at all to do with each other, but it turns out they’re connected in this really beautiful way.
Regina Barber DeGraaff: So, I mean, that brings me to the point of like, is that another reason by both of you went into math, too, just seeing these connections, seeing this beauty, which is what, like you were saying, those books were talking about?
Dr. Amites Sarkar: Yeah, for me definitely. I mean, it’s the connections that are the surprising things somehow. All the busy work is not interesting at all, right? It’s the surprises, right? Just like with everyday life. It’s the surprises.
Regina Barber DeGraaff: I mean, do you think that is conveyed to the public properly? This idea that math is beautiful and there are these wonderful connections? I think is that done well? I think it’s done well in this movie and sometimes in other pop culture, but do you think it could be done better?
Dr. Amites Sarkar: We’re all trying, too, I think. There are classes, but just a little bit at a time. I think it has its authoritarian image somehow that people try to trip you up as well. It has that image as well, trying to patch you out. Which is the opposite of what we’re trying to do.
Regina Barber DeGraaff: Right.
Dr. Stephanie Trenner: Yeah, I think there is sort of this notion that math is sort of a list of rules that someone has devised that need to be either learned.
Regina Barber DeGraaff: It’s like a TV manual.
Dr. Stephanie Trenner: Yeah, sort of rules to be followed, when actually it’s a much more creative process and people don’t necessarily get a chance to see that if they’re just taking standard courses and not experimenting and playing around with things on their own.
Regina Barber DeGraaff: And that brings me . . . we thought of a couple questions before and I will definitely open it up to the audience to be able to ask a couple of questions too once we get kind of to the core of this. And I think a couple of things is, this is all beautiful and this is great to find these connections, but how does any of these kind . . . how can we spark public interest by maybe relating it to everyday life. Like how do we do that? And how does maybe any of this and any parts of math research relate to everyday life?
Dr. Stephanie Trenner: You had some examples?
Dr. Amites Sarkar: Yeah, I mean, I think the human side is very important. All these names, you know, you read about in books. If you’re a math student, you’ll study mathematics by lots of famous mathematicians like Newton, but the human side of it is interesting. Because sometimes people — often people — have difficulty learning mathematics, but the people who invented it also had difficulty getting the thing right. So there’s the human side of it.
The practical applications are also very important, but they can be unexpected. So my favorite story, I think, GPS receivers, so your smart phone has GPS in it. That wouldn’t work without relativity theory, [inaudible.] And if you don’t include the relativistic corrections, your position fix is off by tens, hundreds of meters.
Relativity wouldn’t work without non-Euclidean geometry, but Einstein wasn’t interested in, you know, Einstein wasn’t interested in GPS. And the people who invented non-Euclidean geometry weren’t interested in relativity; they were trying to prove Euclid’s power postulate, so that goes back 2,000 years. So it’s a series of just unexpected coincidences, where someone did something and then 100 years later, it showed up in some completely different context.
And the use of mathematics is undeniable. I mean, every single . . . everywhere you go you see mathematics in action, often to improve things, rather than to design them. But still, they’re everywhere.
Dr. Stephanie Trenner: Yeah, every credit card transaction you make on the internet is based on number theory.
Regina Barber DeGraaff: Right.
Dr. Stephanie Trenner: The security of those transactions is based on . . .
Regina Barber DeGraaff: Prime numbers, right?
Dr. Stephanie Trenner: Yeah, is based on the difficulty of factoring numbers that have large prime factors.
Regina Barber DeGraaff: Right. My favorite [inaudible] . . . My favorite is Michael Faraday, like when he’s playing around like with moving magnets and seeing that that’s actually going to create current, or the other way around, that changing the magnetic field created current or moving current makes a magnetic field.
I think somebody asked him, like, I think this is a famous quote, right, like someone asked him what good is that? What good is showing that these two things are related? And I think he said, “What good is a newborn babe?” He was a really nice man, though. He really was. [Audience laughing.] Read some stuff about him.
But yeah, I mean, this stuff comes out, you know, we as scientists and mathematicians are very passionate about this work and then like it’s lucky that these things come out too. Or, maybe it’s important. Maybe it’s going to happen anyway.
I want to talk about how . . . I mean, we’re going to see a little bit in the movie about the culture of mathematics. And you talked about it a little bit. Like there wasn’t a lot of collaborations. Newton didn’t collaborate, which is why there was these camps and this thing happening. But how has that changed in the last 100 years? And you kind of talked about it a little bit, but can you elaborate on that more?
Dr. Amites Sarkar: Yeah. Do you want to say something else?
I think people do collaborate a lot. And I think people realize that if you collaborate with someone, you typically complement each other. If you’re working on something by yourself, you make some progress and then you get stuck for a long time, and then you make some more progress and then you get stuck for a long time.
But you get stuck on random things. Someone else will get stuck in different places. So where you would get stuck then they can take over, and where they would get stuck maybe you can take over. And people realize that it really does work and it’s fun. But for a long time, the culture was very different.
If you look in the 19th century, there is very, very few joint papers, and the 18th century.
Dr. Stephanie Trenner: And sort of the 21st century conclusion of this, or evolution of this, is the poly math project. So there are these massively online math projects now where people like, some really preeminent mathematicians like, I guess Tim Gowers and Terry Towers sort of organizing these group projects online where they pose a question and anyone who wants to can write in and add to the discussion. And they’ve proved results and written papers like this.
Dr. Amites Sarkar: Absolutely. There was a blog post several years ago, Tim Gowers’s blog, “Is Massively Collaborative Mathematics Possible?” And then within days of that, people took it up and then set up sort of a collaboration Wiki and then it really took off. And that removes a sort of geographical barrier, where if you’re interested in mathematics and have an internet connection, you can just sort of contribute your ideas and collaborate with the world’s best mathematicians, if you like. So maybe that’s the future, I don’t know
Regina Barber DeGraaff: And that brings us to the point that’s brought up in the movie a lot, this idea if math and you love science, is formal training necessary. And that’s stuff as a professor that kind of get the brunt of sometime, that frustration that is formal training necessary. I wanted to address that just before we went into the movie, because it’s something that’s all in this movie.
Dr. Stephanie Trenner: Yeah, there’s this tension that you’ll see in the movie between Ramanujan, who was really incredibly intuitive but he didn’t have formal training in sort of particularly, sort of the western mathematics way of verifying your work in a way that that can be explained to other people, so that they can understand why things are true, not just, you know, a formula, but how did you come up with the formula, why is it the way it is?
So there’s this tension between Ramanujan on the one hand wanting to just work with his intuition and Hardy really trying to tell them he has to be able to verify his results and explain them in a way that other people can explain them. It’s sort of this tension throughout the whole movie.
[♪ Janelle Monae singing Wondaland ♪]
♪ The grass grows inside
♪ The music floats you gently on your toes
♪ Touch the nose, he’ll change your clothes to tuxedos
♪ Don’t freak and hide
♪ I’ll be your secret santa, do you mind?
♪ Don’t resist
♪ The fairygods will have a fit
♪ We should dance
♪ Dance in the trees
♪ Paint mysteries
♪ The magnificent droid plays there
♪ Your magic mind
♪ Makes love to mine
♪ I think I’m in love, angel.]
Dr. Amites Sarkar: I think another thing in mathematics there’s this tension between your intuition and being able to really check all the details, and even the best mathematicians, their intuition just leads them astray sometimes, so then you check some more details, you sharpen your intuition and then you go forward with your intuition again and then you check some details.
Even Ramanujan’s guesses were wrong, some of them were wrong, about prime numbers. But he certainly had a much better intuition than basically anybody.
Dr. Stephanie Trenner: Which is another recommendation for collaboration, right? Because if you have to explain your work to somebody else and then they can maybe find some gaps where you didn’t know there were gaps before.
Dr. Amites Sarkar: And you have two different intuitions. So that’s another thing. You’re sure this is true, your collaborator says, “No, it can’t be possibly be true. What are you talking about?” And then you talk about it and then you come to the truth, you know.
Regina Barber DeGraaff: Right. So that’s our answer to all of our students that are like, “Why do I have to show you why this answer is right? It’s right.” It’s because you have to explain.
Dr. Amites Sarkar: Mm-hmm.
Regina Barber DeGraaff: That’s, you know, how somebody can help you, like you were saying.
Dr. Stephanie Trenner: Also, you know, if you want other people to gain anything from your work, they have to be able to understand it. Otherwise it just dies with you if you’re the only one that understands it, then it’s not going to help anybody else.
Regina Barber DeGraaff: Absolutely. And so I’m going to . . . this is my last question, I swear, and then I’ll open it up to the audience. [Laughing.] You’re just gifted with all of these images.
Dr. Amites Sarkar: It humanizes you.
Regina Barber DeGraaff: I’m very human. I think they all know I’m a human.
But one last thing, have portrayals of mathematics gotten better over the years in pop culture? We’ve all seen this movie and maybe there’s A Beautiful Mind and or can you think of ones that are just awful portrayals?
Dr. Stephanie Trenner: Yeah, I don’t know. I think in general, as sort of movie making and TV-making has become more sophisticated, they have started hiring consultants, like Ken Ohno, to get things right, where they didn’t do that before.
I think with math sometimes there’s sort of this kind of cliché of the absent-minded professor or the, you know, mentally ill person who is a genius at math. Those are the stories that are told because I guess they are dramatic and interesting, but it’s not particularly typical of mathematicians.
Regina Barber DeGraaff: With that, I’m going to open it up to questions. Casey, I actually know you. [Laughing.] Ask your question.
Dr. Stephanie Trenner: So the question is “how does the portrayal of math work in the movie relate to our experience of math work in real life?”
So, I think it’s actually fairly good. I mean, you sort of see them working at a chalkboard, sort of arguing about things, basically. I mean, arguing in a nice way, that sort of is what happens. Honestly, it’s a lot of either working at a chalkboard or whiteboard or on paper and pencil and, you know, thinking for a while and writing some stuff and scratching it out and talking to people and sort of arguing your position one way or another. That’s sort of what happens in the movie.
There’s this great — I don’t know if you guys watch The Big Bang Theory, but there’s this great clip from one of the episodes where two of the characters, they are physicists, but still it’s the same type of thing.
Regina Barber DeGraaff: One is an astrophysicist.
Dr. Stephanie Trenner: Right. So they decide, OK, they’re going to work. It’s time to work. It’s just a montage of them staring at a whiteboard while “Eye of the Tiger” plays. I like to think that that’s how I work. [Laughing.]
Regina Barber DeGraaff: Do you have anything to add?
Dr. Amites Sarkar: There are a number of different ways of working. I recently wrote a paper with two people, one in England, one in Japan, and so we were just rotating. So every 8 hours, we could only communicate only in these small time windows. And I never met one of them, in fact. So it actually worked quite well.
So the normal thing is what you described. I think what’s in the movie, that’s the usual thing, but I think there’s all sorts of things possible.
Dr. Stephanie Trenner: You mentioned the one thing where he comes in and throws his paper down.
Regina Barber DeGraaff: Frustration is also possible.
Dr. Amites Sarkar: Yeah, yeah, so there’s a point where . . . anyway. It can be frustrating doing mathematics because you can sort of, you know, what you think is a great idea just doesn’t work. Or you can just be stuck for a long time.
Regina Barber DeGraaff: That’s realistic in the movie, is what you’re saying?
Dr. Amites Sarkar: Totally.
Regina Barber DeGraaff: Your question over there, glasses guy? Sorry. Murray! Sorry. OK. You know him.
The question is why the title The Man Who Knew Infinity?
Dr. Amites Sarkar: Yeah, there’s a famous book . . . the movie is based on a book by Robert Kanigel, it came out about 25 years ago. Apparently, very good. I haven’t read it, but everybody says it’s a really good book.
Regina Barber DeGraaff: And you have no idea where he got that title?
Dr. Amites Sarkar: Um, no.
Regina Barber DeGraaff: Any other questions? I think we got like four more minutes. Right over here.
Audience Member: How frequently do you find yourself actually working out ideas and trying ideas versus just staring catatonically?
[Laughing.]
Regina Barber DeGraaff: Can you repeat what he just said?
Dr. Stephanie Trenner: Yeah, how often are we actually sort of actively working something out as opposed to being stuck, basically, is the question.
Regina Barber DeGraaff: [Laughing.] Yeah!
Dr. Stephanie Trenner: I guess it kind of depends on what you’re working on and how many people you have to collaborate with.
Regina Barber DeGraaff: And when you’re not teaching and you’re not grading.
Dr. Stephanie Trenner: Yeah, I mean, of course, we balance our research work with teaching work and other commitments with the university. So we sort of find time for research where we can. It kind of depends. It’s sort of one of these things where you can be stuck for a long time and then like have an insight and work like crazy and then kind of get stuck again. It’s hard to say how much of my time is spent in either state.
Dr. Amites Sarkar: One thing that happens quite a lot is you think about a problem for a long time and then you think about it when you’re going to sleep. You make no progress at all. It seems you’re completely stuck. And then you’re about to give up and then suddenly you get an idea. It’s completely unpredictable. Math might be completely logical, but the process by which you discover it, who knows what it is.
Dr. Stephanie Trenner: And also, I mean, in reality you’re also potentially maybe working on a couple different projects at a time that are in varied stages, so maybe you’re sort of in the back of your mind thinking about a problem that you’re kind of stuck on, and that’s sort of happened in the background while actively you’re working on revising a paper that’s in sort of in editing process, and then you’re sort of doing something else with a collaborator. Hopefully you have enough going on that you can kind of pick up different things at various stages. And if you’re stuck on one thing, think about something else for a while.
Regina Barber DeGraaff: I’ve gone whole like weeks without doing anything in grad school and then spent two days straight just working. Those bursts are very realistic.
Way, way in the back.
Audience Member: I worked in the physical sciences and did some theoretical work. I can remember taking long, long walks. Do you do that sort of thing?
Dr. Stephanie Trenner: Um, yeah, actually my husband who is in the audience went to grad school with me, and I would always get annoyed with him because we would be working on a problem and then he’d go for a three hour bike ride and come back and say he solved it! [Laughing.]
Regina Barber DeGraaff: So long walks helped. Bike rides help.
Dr. Amites Sarkar: Had he solved it?
Dr. Stephanie Trenner: Yeah! [Laughing.]
Regina Barber DeGraaff: It was a lie!
Male: I always suggested maybe you should try that!
Dr. Stephanie Trenner: I know. I should have taken you up on it!
Regina Barber DeGraaff: One last question, and you’ve had your hand up a couple of times so I’m going to pick you.
Audience Member: So how has the partition theory changed our modern world?
Regina Barber DeGraaff: So how has the partition theorem changed our modern world?
Dr. Stephanie Trenner: Well in a practical way or in a mathematical way? [Laughing.]
Audience Member: [Inaudible.]
Dr. Stephanie Trenner: Yeah, I mean, I don’t . . . practically, I think the applications are still very theoretical, but it has been sort of that particular module or forum has been a testing ground for developing new theories in mathematics and new techniques that have been applied to other problems. So I think it’s been very powerful in terms of deriving new mathematics.
Regina Barber DeGraaff: Like as a tool for and then out of that will come something.
Dr. Stephanie Trenner: Yeah. You sort of think something is true, try it out with partitions and see what happens, and then you think, “Oh, maybe I can generalize this to a whole class of modular forms,” or something like that.
Regina Barber DeGraaff: Awesome, so I think it is 7 o’clock. Is it? Am I right? Am I good at telling time with my brain? Alright. I want to thank you both for being here. That was super interesting. Some of that stuff, most of it I did not know. I want to thank you and thank you for your questions!
[Applause.]
[♪ Janelle Monae singing Wondaland ♪]
♪ Take me back to Wondaland
♪ I gotta get back to Wondaland
♪ Take me back to Wondaland
♪ Me thinks she left her underpants.]
Regina Barber DeGraaff: Thank you for joining us. This show is entirely volunteer-run and if you want to help us out, click on the “donate” button. If there’s a science idea that you’re curious about, send us an email or post a message on our Facebook page, Spark Science.
Today’s episode was recorded at the Pickford Film Center in Bellingham, Washington. Our editor was Lucas Holger Gertz and our editor and producer was Nathan Miller. Our theme music is “Chemical Calisthenics” by Blackalicious and “Wondaland” by Janelle Monae.
[♪ Janelle Monae singing Wondaland ♪]
♪ Take me back to Wondaland
♪ I gotta get back to Wondaland
♪ Take me back to Wondaland
♪ Me thinks she left her underpants.]
[♪Blackalicious rapping Chemical Calisthenics ♪]
♪ Lead, gold, tin, iron, platinum, zinc, when I rap you think
♪ Iodine nitrate activate
♪ Red geranium, the only difference is I transmit sound
♪ Balance was unbalanced then you add a little talent in
♪ Careful, careful with those ingredients
♪ They could explode and blow up if you drop them
♪ And they hit the ground.]
[End]