Few will have seen a sky like it. Yet this extraordinary-looking cloud formation wasn't photographed in exotic climes, but in St Albans, Hertfordshire, on a recent August evening. What is it and how did it form?

Number one seed Roger Federer begins the defence of his Wimbledon title with a straight-sets win against Dominik Hrbaty on Centre Court.

How Justine Henin-Hardenne's straight sets win over Daniela Hantuchova on Centre Court unfolded.

Bonnie was the most studied hurricane ever - data from space show it had a central cloud tower twice the height of Mt Everest.

Aviation scientists are testing new type of radar system which would probably have prevented the sort of air turbulence incident which killed a passenger and injured dozens more on a flight over the Pacific.