Pliny on Astronomy

By Philip Matyszak

Given that the Greeks and Romans had only intelligence and the naked
eye to make guesses about the cosmos, it is not surprising that they were sometimes wildly inaccurate, but sometimes they were often amazingly right

On the existence of other worlds

‘It is madness to harass the mind, as some have done, with attempts to measure the world, and to publish these attempts; or, like others, to argue from their conclusions that there are innumerable other worlds, and … if only one nature produced the whole, there will be so many suns and so many moons, and that each of them will have immense trains of other heavenly bodies.’ (Natural History 2.1)

The size of the sun

‘It is immeasurably huge. This you can tell from the following observation. Trees which are planted at the far limits of East and West, nevertheless cast shadows of the same proportions – though these trees are miles and miles apart, the sun appears in the same place, as though centred on either one’. (Natural History 2.45)

The moon and planets

Pliny was well aware that the world is round, and that it rotates on its axis every twenty four hours. However he believed that the planets rotated around the earth, from Saturn (the outermost) to Jupiter then Mars and finally – beneath the sun – the erratic and wandering Venus and tiny Mercury.

The moon, according Pliny, is 126,000 stades away. This is about 15,000 miles – an error of about 235,000 miles. Perhaps Pliny should have paid more attention to Posidonus, whose estimate of two (2) million stades he quotes in his work. Two million stades is a quarter of a million miles – and is pretty near spot on.

Professor Philip Matyszak, author of The Classical Compendium: A Miscellany of Scandalous Gossip, Bawdy Jokes, Peculiar Facts, and Bad Behavior from the Ancient Greeks and Romans, has a doctorate in Roman history from St John’s College, Oxford. Presently he is teaching and preparing courses for the eLearning program at Cambridge university’s Institute of Continuing Education at Madingley Hall. The author of many other books, learn more about Professor Matyszak, click here.

IMAGE: A 19th century portrait of Pliny the elder