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Overview
Nuclear fusion occurs when light atomic nuclei combine to form heavier nuclei. Fusion powers the Sun and other stars. It can release large amounts of energy because the final nucleus can be more tightly bound than the original nuclei.
Joining Light Nuclei
Fusion combines light nuclei such as hydrogen isotopes. To fuse, nuclei must come close enough for the strong nuclear force to overcome electric repulsion.
Coulomb Barrier
Positively charged nuclei repel each other electrically. High temperature and pressure help nuclei approach closely enough for fusion to occur.
Fusion in Stars
Stars produce energy through fusion in their cores. Hydrogen fusion is the main energy source for stars like the Sun.
Energy Release
Fusion releases energy when the final products have less mass-energy than the initial particles, with the difference appearing as energy.
Fusion Reactors
Controlled fusion research attempts to create useful energy on Earth using plasmas, magnetic confinement, inertial confinement, or other methods.
Plasma
Fusion conditions often require plasma, a hot ionized state of matter where electrons and nuclei are separated.
Advantages and Challenges
Fusion fuel can be abundant and fusion reactions can produce high energy, but maintaining stable, controlled fusion conditions is technically difficult.
Common Mistakes
A common mistake is thinking fusion is simply ordinary burning. Fusion is a nuclear process, not a chemical combustion process.
Why This Matters in Physics
Fusion connects nuclear physics, stars, plasma physics, energy research, mass-energy equivalence, and the origin of elements.