In 100 AD, Plutarch wrote what would become the first science fiction about the civilisation on the moon, appended to a rigorous scientific analysis of current knowledge about the moon.

Orbital mechanics, optics, atmospheric refraction, lunar geography, planetary and stellar composition, xenobotany, gravitation, heliocentricity, eclipse geometry and more are discussed as the state of the art is unpacked. Often startlingly modern for a work that is two millennia old, it serves as a reminder that science began long, long before norms of the modern scientific era were established.

The first half reads as genuine natural philosophy. Plutarch's speakers debate the nature of the lunar surface, rejecting the notion of a perfect celestial sphere made up of fire and ether in favour of a body with mountains, valleys, and shadow-casting terrain. They examine reflected light, atmospheric optics, and the mechanics of eclipse. One speaker advances a proto-gravitational argument: that 'down' is a local condition, that objects fall toward whatever body they belong to, and that the moon holds its own just as Earth holds ours.
The second half carries that physical moon into mythological territory. A soul narrative describes the lunar surface as a way-station between lives, a realm where mind and spirit undergo staged separation before returning to the cosmos or descending again to Earth. Discussing the voyages taken as the mind separates from the soul in journeys around the moon, it serves as both theological and science-fictional.
Perfect for readers drawn to the history of science and the speculations that arise from it, this book is the first known moment empirical observation and speculative reasoning combined, in what would millennia later be called hard sci fi.