The ups and downs of social networks
Facebook has announced that it now has 500m active users, just six years after it was launched. The site has become the poster child of social networking on the web. While some others have seen growth, MySpace, Flickr and Bebo appear to have declined in the past year, according to these figures from Nielsen. Interesting international variations are seen, both in the amount of time Facebook users spend on the site each month and in the competing networks' popularity in different countries.
Tuesday's devastating attacks in Brussels show IS's European network is still at large, despite a year of intensive efforts by security forces to close it down.
Scientists are debating whether it's possible to harness the power of gravity for interstellar space travel.
The four-year-old boy who has become the centre of a controversy between India and Pakistan - and between his father and mother.
Why, almost 60 years after he first appeared in the Daily Mirror, is a layabout lout from north-east England still so loved around the world?