The World Ahead Globe IconThe action is shifting from the public to the private sectorIllustration: Science Photo LibraryBy Geoffrey Carr, Senior editor, Science & technology, The EconomistTwo 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 fus...