It was generated at the Relativistic Heavy Ion Collider (RHIC) in New York, US, which smashes beams of gold nuclei together at near light speeds.

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Neutrons ejected from a watery surface move much more slowly than those from a rocky one, because the hydrogen nuclei in water are light enough for an exiting neutron to knock around much like one billiard ball hitting another a process that slows the neutron down.

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But in Dr Rostoker's reactor, the helium nuclei created by the process of light fission would be speedy enough to escape from the ends of the ellipsoid, where the magnetic field is weakest.

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