Fusion (noun, “FYEW-zhun”)
Fusion occurs when pairs of atomic nuclei slam into each other and meld, or fuse, together. This process leads to new atoms of a different element and releases lots of energy. Fusion is the physical reaction that powers the sun and other stars.
Fusing atoms requires squeezing them together under immense heat and pressure. Inside stars, these conditions fuse hydrogen atoms into helium atoms. The mass of each newborn helium atom is less than the total mass of the hydrogen atoms that formed it. The remaining mass transforms into energy, making stars shine.
Scientists and engineers are trying to mimic that fusion process on Earth inside machines called reactors. If they succeed, fusion could provide an abundant source of clean energy. The hydrogen fuel needed for fusion is plentiful on Earth. And it gives off nearly 4 million times as much energy as burning fossil fuels. What’s more, fusion does not give off the climate-warming gases that come from burning fossil fuels. And fusion does not generate all the radioactive waste that nuclear fission does. (Fission is the physical reaction that powers today’s nuclear power plants.)
The trouble is that creating the heat and pressure needed to fuse atoms together is very, very difficult. So, fusion energy is not yet a practical power source.
In a sentence
Nuclear fusion could provide more abundant, cleaner energy than the currently used form of nuclear power, fission.