Fusion: The Ultimate Prize

While fission splits atoms, nuclear fusion joins them. The Sun fuses hydrogen into helium at its core, converting mass to energy at a staggering rate. Fusion would produce far less long-lived radioactive waste than fission, cannot run away like a fission reactor, and can use fuel derived from hydrogen isotopes, with deuterium available from water and tritium bred from lithium. The catch: achieving fusion requires heating fuel to over 100 million degrees Celsius, hotter than the Sun's core, and confining it long enough for reactions to sustain themselves. After decades of research, projects like ITER in France aim to prove key parts of the technology. If it works at scale, fusion could provide a major source of low-carbon energy.