On a remote atoll in the Pacific Ocean, the United States successfully detonates Mike, the world's first hydrogen bomb. The 10.4-megaton thermonuclear device, built upon the Teller-Ulam principles of staged radiation implosion, instantly vaporized an entire island and left behind a crater more than a mile wide. The incredible explosive force of Mike was also apparent from the magnitude of its mushroom cloud--within 90 seconds the mushroom cloud climbed to 57,000 feet and entered the stratosphere. One minute later, it reached 108,000 feet, eventually stabilizing at a ceiling of 120,000 feet. Half an hour after the test, the mushroom stretched 60 miles across, with the base of the head joining the stem at 45,000 feet. Its explosive power was more than 800 times that of the atomic bomb that destroyed Hiroshima in 1945. In 1955, the Soviet Union detonated a hydrogen bomb on the same principle of radiation implosion, and the world started to live under the threat of thermonuclear war for the first time in history.