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From today's featured article

Beaufighter, a common platform for AI Mk. IV radar
Beaufighter, a common platform for AI Mk. IV radar

Airborne Interception radar, Mark IV, was the first successful air-to-air radar system, used in Britain's Bristol Beaufighter heavy fighters by early 1941 in the Second World War. Early development of the Mk. IV was prompted by a 1936 memo from the inventor Henry Tizard to Robert Watt, director of the radar research efforts, who agreed to allow physicist Taffy Bowen to form a team to study the problem of air interception. The team had a test bed system in flights later that year, but progress was delayed for four years by emergency relocations, three abandoned production designs, and Bowen's increasingly adversarial relationship with Watt's replacement, Albert Percival Rowe. The Mk. IV had many limitations, including displays that were difficult to interpret, a maximum range that decreased with the aircraft's altitude, and a minimum range that was barely close enough to allow the pilot to see the target. Nevertheless, the Mk. IV played a role in the Royal Air Force's increasingly effective response to The Blitz, the Luftwaffe‍‍ '​‍s night bombing campaign. The Mk. VIII largely relegated the Mk. IV to second-line duties by 1943. (Full article...)

Did you know...

William M. Mitchell
William M. Mitchell

In the news

Former Indian President, A. P. J. Abdul Kalam
A. P. J. Abdul Kalam

On this day...

July 31: Tu B'Av (Judaism, 2015); Feast day of Saint Ignatius of Loyola; Ka Hae Hawai'i Day (Flag Day) in Hawaii

Bush and Gorbachev sign the START I treaty.
Bush and Gorbachev sign the START I treaty.

From today's featured list

BBC Sports Personality of the Year Award
BBC Sports Personality of the Year Award

The BBC Sports Personality of the Year Award is the main award of the BBC Sports Personality of the Year ceremony, which takes place each December. The winner is the sportsperson, judged by a public vote from a pre-determined shortlist, to have achieved the most that year. The recipient must either be British or reside and play a significant amount of their sport in the United Kingdom. Sports Personality of the Year was created by Paul Fox, who thought of the idea while he was editor of the magazine show Sportsview. The first award ceremony took place in 1954 as part of Sportsview, and was presented by Peter Dimmock. Approximately 14,500 votes were cast by postcard, and Christopher Chataway beat Roger Bannister to win the inaugural BBC Sportsview's Personality of the Year Award. Three people have won the award more than once: boxer Henry Cooper and the Formula One racing drivers Nigel Mansell and Damon Hill have each won twice. The most recent award winner is Formula One driver Lewis Hamilton, who won in 2014. (Full list...)

Today's featured picture

Long-tailed broadbill

The long-tailed broadbill (Psarisomus dalhousiae) is a species of broadbill found in the Himalayas. This insectivore is very sociable and normally travels in large, noisy parties. It can be identified by its shrill call.

Photograph: JJ Harrison

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