Random and Pseudorandom

In Our Time: Science

BBC

History

4.5 • 1.4K Ratings

🗓️ 13 January 2011

⏱️ 42 minutes

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Summary

Melvyn Bragg and his guests discuss randomness and pseudorandomness.Randomness is the mathematics of the unpredictable. Dice and roulette wheels produce random numbers: those which are unpredictable and display no pattern. But mathematicians also talk of 'pseudorandom' numbers - those which appear to be random but are not. In the last century random numbers have become enormously useful to statisticians, computer scientists and cryptographers. But true randomness is difficult to find, and mathematicians have devised many ingenious solutions to harness or simulate it. These range from the Premium Bonds computer ERNIE (whose name stands for Electronic Random Number Indicator Equipment) to new methods involving quantum physics.Digital computers are incapable of behaving in a truly random fashion - so instead mathematicians have taught them how to harness pseudorandomness. This technique is used daily by weather forecasters, statisticians, and computer chip designers - and it's thanks to pseudorandomness that secure credit card transactions are possible.With:Marcus du SautoyProfessor of Mathematics at the University of OxfordColva Roney-DougalSenior Lecturer in Pure Mathematics at the University of St AndrewsTimothy GowersRoyal Society Research Professor in Mathematics at the University of CambridgeProducer: Thomas Morris.

Transcript

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0:00.0	Thanks for downloading the In Our Time podcast. For more details about In Our Time and for our terms of use, please go to BBC.co.uk.
0:09.0	I hope you enjoy the program.
0:12.0	Hello, a little earlier today I rolled a single dye ten times.
0:16.0	This is what I got.
0:18.0	Six, one, three, four, four, four, four, four, one, 1, 2, 1 4.
0:27.0	That's a sequence of random numbers between 1 and 6.
0:30.4	Random because there's no pattern to them.
0:32.2	It's impossible to predict the next
0:34.0	number in the sequence. Randomness will be familiar to anybody who's bought a
0:37.8	lottery ticket or shoveled a pack of cards. A key feature of randomness is
0:41.9	that what you do one time has no effect on what you do the next time.
0:46.0	But there's also a phenomenon known as pseudo-randomness, numbers which look random but aren't.
0:51.0	Pseudo-random numbers are essential in statistics. Drug
0:54.4	trial, trials, medical trials generally and opinion polls would be all but
0:59.1	impossible without them. Cryptography and electrical engineering are just a couple of the many other fields where pseudo-randomness
1:05.6	is highly valued.
1:07.4	With me to discuss randomness and pseudo-randomness are, Marcus Usotoi, professor of Mathematics at the University of Oxford and
1:14.2	Simony Professor of Public Understanding of Science,
1:17.1	Colver Roney Dougal, Senior Lecturer in Pure Mathematics at the University of St Andrews,
1:21.8	and Timothy Gowers, Royal Society Research Professor in Mathematics
1:25.6	at the University of Cambridge.
1:27.6	Marcus Gisoto I've just meant throwing a dye, but can you give us another example of
	...

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