# eby / tags / mathematics

## Tagged with “mathematics” (6)

1. ### Random and Pseudorandom - In Our Time

13th January 2010

Melvyn Bragg and guests discuss random and pseudorandom numbers. Randomness will be familiar to anybody who’s bought a lottery ticket or shuffled a pack of cards. But there’s also a phenomenon known as pseudo-randomness –numbers which look random but aren’t. So why are these numbers useful and how can they be generated? Melvyn is joined by Marcus du Sautoy, Professor of Mathematics at the University of Oxford; Colva Roney-Dougal, Senior Lecturer in Pure Mathematics at the University of St Andrews; and Timothy Gowers, Royal Society Research Professor in Mathematics at the University of Cambridge.

2. ### 6 Degrees of Separation

Episode three of A Further Five Numbers, the BBC radio series presented by Simon Singh.

Six is often treated as 2x3, but has many characteristics of its own. Six is also the "pivot" of its divisors (1+2+3=6=1x2x3) and also the centre of the first five even numbers: 2, 4, 6, 8, 10. Six seems to have a pivoting action both mathematically and socially. How is it that everyone in the world can be linked through just six social ties? As Simon discovers, the concept of “six degrees of separation” emerged from a huge postal experiment conducted by the social psychologist Stanley Milgram in 1967. Milgram asked volunteers to send a package by mail to one of a hundred people chosen at random. But they could only send mail to people they knew on first name terms.

3. ### 6.67 x 10^-11 – The Number That Defines the Universe.

Episode four of A Further Five Numbers, the BBC radio series presented by Simon Singh.

Newton’s equation of gravity included a number G, which indicates the strength of gravitation. It took 100 years before the shy Englishman Henry Cavendish (he left notes for his maids because he was too shy to talk to women) measured G to be 6.67 x 10^-11 Nm²/Kg². It allowed him to weigh the Earth itself. There has been an ever-greater desire to measure this number with accuracy, which even implied an antigravity at times. How did we measure this tiny number and what does it mean for the universe? The Astronomer Royal Martin Rees explains that a large value for G would mean that stars would burn too quickly and a low value would mean that the stars would not form in the first place, so is G perfectly tuned for life? Is God a mathematician?

4. ### 1729 — The First Taxicab Number

Episode five of A Further Five Numbers, the BBC radio series presented by Simon Singh.

Curious properties sometimes lurk within seemingly undistinguished numbers. 1729 sparked one of maths most famous anecdotes: a young Indian, Srinivasa Ramanujan, lay dying of TB in a London hospital. G.H. Hardy, the leading mathematician in England, visited him there. "I came over in cab number 1729," Hardy told Ramanujan. "That seems a rather dull number to me."

"Oh, no!" Ramanujan exclaimed. "1729 is the smallest number you can write as the sum of two cubes, in two different ways." Most of us would use a computer to figure out that 1³ + 12³ = 9³ + 10³ = 1729. Ramanujan did it from his sickbed without blinking.

5. ### A Countdown to Zero

Episode one of Five Numbers, the BBC radio series presented by Simon Singh.

What’s 2 minus 2? The answer is obvious, right? But not if you wore a tunic, no socks and lived in Ancient Greece. For strange as it sounds, ‘nothing’ had to be invented, and then it took thousands of years to catch on.

6. ### Nassim Nicholas Taleb and Benoit Mandelbrot on the financial crisis

As the financial sector shifts, so does the reach of the jolt to economic structures around the world. Economist Nassim Nicholas Taleb and his mentor, mathematician Benoit Mandelbrot, speak with Paul Solman about chain reactions and predicting the financial crisis.