By Geoffrey Carr, Senior editor, Science & technology, The Economist

Two developments in the coming year will mark a decisive shift from the public to the private sector in the decades-old quest to generate cheap and abundant power from nuclear fusion. The first will be the opening towards the end of 2025, by a private firm, of a machine called SPARC. This will be the first fusion reactor, public or private, designed to operate at near-commercial scale, with an eventual output of about 140 megawatts (MW). The second will be the non-opening of ITER, the flagship of intergovernmental fusion collaboration, which was scheduled to be ready in 2025. In a hurried announcement in July, that date was postponed.