What is nuclear fusion?
Nuclear fusion is the process in which light atomic nuclei, such as hydrogen, combine to form a heavier nucleus, releasing enormous energy. It is what powers the Sun and other stars.
In the Sun's core, temperatures of about 15 million degrees Celsius and immense pressure force hydrogen nuclei together to form helium. A tiny amount of mass is converted into a huge amount of energy, as described by Einstein's equation E = mc². Every second, the Sun fuses about 600 million tonnes of hydrogen.
Fusion is different from fission, which splits heavy atoms like uranium and is used in today's nuclear power plants. Fusion produces no long-lived radioactive waste and uses fuel that can be extracted from seawater, making it an attractive future energy source.
Fusion on Earth
Recreating fusion on Earth is extremely difficult because the fuel must be heated to over 100 million degrees and contained. In December 2022, the US National Ignition Facility achieved ignition, producing more energy from fusion than the laser energy used to trigger it. The international ITER project in France is building a giant reactor to test fusion at scale.
Did You Know?
Hydrogen bombs, or thermonuclear weapons, use fusion and are far more powerful than the atomic bombs used in World War II, which used fission.