Bikini atomic test is still a grave wonder, 50 years on

The obliteration of the South Pacific island of Bikini by an American hydrogen bomb 50 years ago today marks a watershed in modern history.

Resulting fear of the destructive power of the bomb spurred a global race for nuclear weapons, divided scientific communities and led to movements ranging from peace to conservation.

Yet the bomb known as Bravo was not the first the American scientists had produced deriving a large part of its energy from hydrogen. Nor was it the most destructive weapon humankind could produce.

The blast came 81/2 years after hundreds of thousands of Japanese were killed when the United States ended the war in the Pacific by dropping atomic bombs on the cities of Nagasaki and Hiroshima. A month earlier the first nuclear test was carried out in the US state of New Mexico.

Just 169 people were displaced from the islands of Bikini Atoll, part of the US-administered Marshall Islands, to allow the test to go ahead. The ferocity of the blast overwhelmed scientists' measuring instruments and obliterated one of the islands. A mushroom cloud at least 160km wide rose up, dropping back to earth a shower of nuclear fallout in the form of white ash.

The radioactive material fell on Rongelap Island, where some of the Bikinians had been relocated. The Marshall Islands government estimates that 840 Bikini Atoll residents have died of health problems caused by nuclear tests carried out by the US between 1946 and 1958.

Also affected by Bravo were hundreds of Japanese fishermen who were not told of the test.