The problem is, overcoming the forces that cause nuclei to repel each other requires a massive amount of energy, and so far, scientists haven't been able to figure out a way to get more energy out of a reaction than they put in. Physicists and engineers have been at work on this thorny question for decades – during which time most laypeople have either forgotten about fusion or dismissed it as a thing of the distant future.

Scientists are making progress. They point to the fact that the rate at which they've increased fusion energy output is greater than that of Moore's Law, the famed predictor of computing power. They also cite Iter, an enormous, internationally-funded fusion reactor currently under construction in southern France; when completed, it will theoretically produce 10 times as much energy as it needs to run. Designed according to the most well-established fusion science, Iter is widely seen as the surest way to fusion power – its name is even a play on the Latin for “the way,” singular – and the project correspondingly receives much of the world's government fusion funding. But even supporters bemoan the bureaucracy of the seven-entity collaboration; Iter is billions over budget and years behind schedule, with the first reactor experiments not expected until at least 2025.

Enter the Bruce Waynes of the world. The approaches that people like Bezos and Allen are backing are long shots compared with Iter, prioritising engineering simplicity over scientific certainty. But with high risk comes the potential for high reward: an economical, scalable design for a fusion reactor is the kind of globe-altering idea that could earn an investor a lot of money – and, perhaps even more valuable amid Silicon Valley's boom and bust, an enduring legacy.