From the main mine that humans made in the Oklo region, one of the natural reactors is accessible via an offshoot, as illustrated here. The large uranium deposit present underwent nuclear fission on and off for hundreds of thousands of years some ~1.7 billion years ago. The yellow rock is uranium oxide. Oklo data shows that the fine-structure constant, which depends on the electron charge, the speed of light, and Planck’s constant, changes by less than ~0.3 parts in 10 quadrillion (10¹⁶) per year, eliminating the tired-light plus varying fundamental constant scenario. (Credit: Robert D. Loss (Curtin U.); US Dept. of Energy)
Planets can create nuclear power on their own, naturally, without any intelligence or technology. Earth already did: 1.7 billion years ago.
If you were hunting for alien intelligence, looking for a surefire signature from across the Universe of their activity, you’d have a few options.
You could look for an intelligent radio broadcast, like the type humans began emitting in the 20th century.
You could look for examples of planet-wide modifications, like human civilization displays when you view Earth at a high-enough resolution.
You could look for artificial illumination at night, like our cities, towns, and fisheries display, visible from space.
And there are many other options: you can look for a unique chemical “fingerprint” of biological processes in an exoplanet’s atmosphere by performing spectroscopy on the planet’s atmosphere, or rapid long-term evolution of certain chemical species. After all, there’s a tremendous amount you can learn even from a single pixel if you can directly image an Earth-sized exoplanet.
But there are technological achievements that we’ve realized here on Earth as human civilization has…
