There has been a lot of buzz about fusion in the past few days, after the announcement of “ a dramatic leap forward ” from a collaboration between MIT and a newly formed private company, followed by declarations that “ the world’s energy systems will be transformed .” Bob Mumgaard, CEO of the private company involved—Commonwealth Fusion Systems, which has attracted $50 million in support from an Italian energy company—said: “The aspiration is to have a working power plant in time to combat climate change. We think we have the science, speed, and scale to put carbon-free fusion power on the grid in 15 years .” Such projections may be overly optimistic. The Bulletin of the Atomic Scientists has been examining the commercial exploitation of fusion as an energy source for some time; publishing a story a year ago in these pages about even the desirability of such technology […]