Aviable nuclear fusion reactor, one that spits out more energy than it consumes, could be here as soon as 2025. If a fusion reactor reaches that milestone, it could pave the way for a massive generation of clean energy.
During fusion, atomic nuclei are forced together to form heavier atoms. When the mass of the resulting atoms is less than the mass of the atoms that went into their creation, the excess mass is converted to energy, liberating an extraordinary amount of light and heat.
Fusion powers the Sun and stars, as the mighty gravity at their hearts fuses hydrogen to create helium. But an enormous amount of energy is needed to force atoms to fuse together, which occurs at temperatures of at least 100 million degrees Celsius. However, such reactions can generate far more energy than they require.