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More or Less puts the Chinese Market Crash in context. Tim Harford asks how big the market is, how many investors does it have and does it tell us anything about the wider Chinese economy? He also looks at a fascinating piece of research showing that world class runners don’t actually move their legs faster than the average park runner!

´óÏó´«Ã½ Trending asks should we be allowed to delete our tweets. It follows Twitter’s action in banning a website which flagged up MPs deleted tweets. And Trending also talks to a 19 year old Dutchman who’s been mapping the Syrian conflict – from his bedroom.

In The Why Factor, Mike Williams looks at the history of encryption – from the Roman Caesar Cipher to modern day computer encryption. We use encryption every day – in our bank transfers, on our mobile phones and whenever we buy anything online. Why is it so important?

(Image: An investory looks at a stock information board. Credit: Reuters.)