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A university lecture hall, with a large whiteboard in the centre. To one side, a desk and an overhead projector; to the other side, a door and a portable lectern. On the wall close to the door is a telephone.
AL stands next to the desk with his back to the audience. RUTH enters. She writes ā1, 2, 3, 4, 5ā on the whiteboard.
RUTH: (Nervous.) Good evening ladies and gentlemen. Iād like to go through one or two very basic mathematical ideas that are integral to this evening so that the recurrent mathematical themes become clear to you all.
Right, OK. (Beat.) Letās consider these sets of numbers. (She writes them up as she speaks.) 2, 4, 6, 8, 10ā¦2, 3, 5, 7, 11ā¦1, 2, 4, 8, 16⦠These are known as sequences, and they have two characteristics. The terms can go on forever and they have a pattern, which helps you to continue the sequence. Some patterns are more obvious than others. With these numbers (Indicates the first sequence.) the pattern is very clear. But in this sequence, (Indicates the second sequence.) the primes, the pattern is less obvious. Is there a pattern at all? To find the hidden pattern you sometimes need to look at them in a new way. If we add together the terms of a sequence, we would have what is known in mathematics as a series. (She writes four ā+ās between the numbers.)
So, 1+2+4+8+16 is a finite series with 5 terms, with the sum of 31. If we allow the series to continue forever, it would become an infinite series. And it is clear that the sum of: 1+2+4+8+16 and so on to infinity is itself infinite, making it a divergent series. That is to say it diverges from zero, that is to say the difference between the sum and zero widens infinitely.
(She writes the maths up as she speaks.) I can also express the above series as the sum of integral powers of 2. 2 to the power of 0 plus 2 to the power of 1 plus 2 squared plus 2 cubed plus 2 to the power of 4 plus⦠Or using the sigma notation of a sum we can write it another way: āthe sum from r equals zero to infinity of 2 to the power of r.ā
I would like to show you another divergent series, perhaps the simplest of all: 1+2+3+4+ā¦and so on to infinity equals infinity. All of this is very logical. Now Iām going to do something very strange. Iām going to disrupt our sense of logic and Iām going to show you something really thrilling.
1+2+3+4+5+ and so on to infinity equals minus one twelfth. (Beat.) āHow can this be?ā And youād be right to think so! But let me show you how one can obtain this anomalous result using the Functional Equation of the Riemann Zeta Function. And this is how it goesā¦
RUTH begins to write out the Functional Equation of the Riemann Zeta Function (see Appendix). The maths gets quicker and more complicated.
2 to the power of 1 minus Z, times the gamma of Z, times the zeta of Z, times the cosine of a half pi Z, is equal to pi to the power of Z, times the zeta of 1 minus Z. This is only true for complex values of z. Where z equals x plus i y, where i is the square root of minus 1 ā our imaginary number.
The gamma of z is a very well known definition. The gamma of z is equal to the integral from 0 to infinity of e to the minus t times t to the power of z minus 1 with respect to t. For complex z this is equal to z minus 1 factorial.
Enter ANINDA RAO. He watches RUTH.
The zeta of z equals the sum from n equals 1 to infinity of 1 over n to the power of z. Iām going to put the value 2 into this equation (For which, remember, it is not defined) and then I will show you what happens.
2 to the power of 1 minus 2, times the gamma of 2, times the zeta of 2, times the cosine of a half pi times 2. A half of 2 is 1 so we have the cosine of just pi is equal to pi squared, times the zeta of 1 minus 2ā¦RUTH continues to lecture, oblivious, as ANINDA addresses the audience.
ANINDA: (In an Indian accent.) Youāre probably wondering at this point if this is the entire show. Iām Aninda, this is Al and this is Ruth. (Pause. His accent changes.) Actually, thatās a lie. Iām an actor playing Aninda, heās an actor playing Al and sheās an actress playing Ruth. But the mathematics is real. Itās terrifying, but itās real.
When I was a child I had a real problem with mathematics. I remember I had a chart on the back of my door. It went, ā1 ā One Tractorā. ā2 ā Two Pineapplesā. And, for a reason that nobody could explain, there were three medicine bottles. Then, four pearsā¦and five oranges. Of course when they added one plus two equals three, I tried to understand how one tractor plus two pineapples could make three medicine bottles. (Beat.) Theyād talk about five oranges, which was fine, but when they took away the oranges, thatās when the problems began. As I got older they replaced the numbers with letters ā a, b, cā¦x, y, z. So just to walk into a maths class would bring me out in a cold sweat. Thatās when I thought I had a problem with abstract thinking, but I had no problem with other imaginary ideas. In the school playground I would pretend to be the headmaster of my primary school, Mr Stoddart. Iād do this (He strikes a silly pose.) and the other children would laugh. Of course, I wasnāt really Mr Stoddart, I was PRETENDING to be Mr Stoddart. (Beat.) But I still had a problem with the idea that this (Indicates the maths.) is real. In fact we could say that this is the only real thing here.
(He approaches RUTH, who is still lecturing.) Just to prove to you that we are in the imaginary world of the theatre, Iāll take her glasses. (He lifts the glasses off her face, puts his fingers through the eye holes.) Thereās no glass in there! Bloody useless! Even her voice can be changedā¦all I have to do is this. (He fiddles with an imaginary dial and RUTHās voice becomes ridiculously high-pitched.) Now the maths is even more mystifying! Of course Iām not actually doing this, itās the sound man up there. (He indicates the box atthe back of the auditorium.) Everything is fake BUT the mathematics. (He picks up a phone, attached to the wall.) This phone for example⦠āHello mum?ā⦠no mum, no ring tone! (He pushes the door open.) This door doesnāt lead anywhere! I can push these walls right off! (He pushes the wall which gracefully slides offstage. The other walls do likewise. A dark void is revealed behind. A MUSICIAN walks onstage and takes a seat with his tablas to one side.) This is Hiren Chate. He is real and he will really play the real tablas.
And now, I can do what I could never do at...