Everybody knows Isaac Asimov, author of Foundation and I, Robot and Nightfall and The Caves of Steel. What most people don't remember about him today is that all the great books I listed were written prior to 1955. For most of the 1960s, Asimov made his name as a pop historian and science writer. 1972's The Gods Themselves is a return to hard-SF form: three linked novellas around a single fascinating breakthrough.

The Electron Pump is the source of clean energy for a devastated and demoralized Earth. Discovered by accident, it involves an interdimensional exchange of Tungsten for Plutonium. The accidental discoverer of the Electron Pump, Dr. Hallam is a scientific thug, jealous of his power and privilege, and unwilling to see the exact mechanisms of the pump investigated, because that might reveal that he was a mere conduit for the aliens. Worse, long-term use of the pump would change the workings of the strong nuclear force, causing the sun to go nova in decades. Hallam, and the comfortable people of Earth, refuse to stop the pump, despite concerning messages from the intelligent para-Universal beings on the other side.

The second section of the book concerns those para-Universal beings, an imaginatively constructed three-sexed species. The Soft Ones are divided into Rationals, Emotionals, and Parentals, with each mated triplet needing one of each. Photosynthetic Soft Ones flow like smoke, and can meld and penetrate each other and physical objects. Hard Ones are enigmatic, long-lived, the true power on their dying world. With the sun dying, they have invented the Electron Pump, first to exchange energy with humans, and then to borrow energy from a sun gone nova.

The third section takes place on the moon, following Dennison, the disgraced co-discoverer of the Electron Pump as he adapts to lunar society with the help of the beautiful (and Intuitive, with a capital I) tour guide Selene. They enjoy lunar sports like the melee and slope gliding, and Dennison invents a counter to the Electron Pump, that draws from a universe with a weaker Strong Force, general energy while preserving the balance of forces around Earth.

There's a lot to like here. The depiction of a senior scientist not as a genius, but as a grasping and jealous politician, is one area where Asimov's life experience as a professor and science writer paid off. I wonder if Hallam was based on anyone specific. Maybe Edward Teller or James Watson, or just a particularly obstinate department head. The alien Soft Ones are a fascinating species that is, I think, just on the limits of reliability. The third section, with lunar life, is weaker and a retread of ideas better developed by Heinlein, but the overall themes of sustainability, the long-term safety of technologies our civilization depend on, is quite well-developed. Not the best Asimov, but a good book regardless.