Acting alone, gravity would cause stars to collapse completely, but as long as energy is produced at their centers by nuclear fusion (the joining of atomic nuclei to form new elements, as in a hydrogen bomb), the star is heated and puffed up.

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This project, a collaboration between America, Russia, Japan and Europe, is intended to create sustained nuclear fusion by squeezing gases so hard that their atomic nuclei fuse together and give off more energy than was needed to squeeze them.

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The energy released by the fusion reactions then heats the surrounding fuel, within which atomic nuclei may further begin to fuse.

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Until recently he was Director of the United Kingdom Atomic Energy Authority (UKAEA) Culham, with responsibility for the UK fusion programme and operation of the Joint European Torus (JET).

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The idea of the fusion torch attracted a lot of attention, and won its inventors an award from America's Atomic Energy Commission.

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After the Soviet Union broke America's atomic monopoly in 1949, several prominent scientists and politicians favoured the development of the hydrogen bomb, a fusion weapon hundreds of times more powerful than the bombs that the Manhattan Project had built.

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