Nuclear fusion — it’s the same reaction that powers the sun and the stars, and it could redefine our future on Earth. At MIT and Commonwealth Fusion Systems, scientists are building SPARC, a revolutionary fusion reactor designed to generate more energy than it consumes. Unlike fission, which splits heavy atoms, fusion joins light atoms together, releasing enormous energy with no meltdown risk or long-lived radioactive waste. But to make it work, they must control plasma hotter than the surface o