The Chinese stock market may have crashed but was it really 'Black Monday'? Are there really eight million foreigners in Britain and how do we know e-cigs are 95% less harmful.

The Chinese Market Crash in context.

How big is the market, how many investors does it have and does it tell us anything about the wider Chinese economy?

Eight Million Foreigners

Are there really eight million foreigners in the UK?

What does 95% less harmful actually mean?

E-cigarettes are 95% less harmful than ordinary cigarettes according to last week's report by Public Health England. But what does this mean? The number was arrived at using something called 'multi criteria decision analysis' so how does it work – we ask the man who brought it to the UK, Professor Larry Phillips.

Thinking Like an Engineer

Guru Madhavan from America's National Academy of Scientists lifts the lid on how engineers think and argues that those making policy should ask engineers as well as economists about solving social problems.

Sprinters legs

It's may seem strange, but world class runners don't move their legs faster than average park runner. That's the claim anyway – is it true and if so what is it that means athletes like Usain Bolt and Justin Gatlin run so fast?