Circumference: Chapter 1

Athens herself by the mid-third century had already been supplanted by Rhodes as the leading mercantile democracy in the Aegean.

After a few days afloat, a different sort of star would have appeared near the southern horizon: a steady gleam that would shine day and night, never setting but rising subtly as the vessel neared shore. At the sight of it most of those aboard would have begun their obeisances to the gods who had secured their safe passage.

To be sure, the Ptolemies did commission massive new temples in the ancient style, largely to help the Macedonian rulers ingratiate themselves with their native subjects.

Approaching from the north, Eratosthenes’s ship would likely have made for the mouth of the eastern or Great Harbor, which was bound by Pharos Island on the west and on the east by the promontory of Lochias.

The inspections at the Emporion had their pecuniary purpose, of course. Much of the state’s revenue was derived not from direct taxation, but from duties placed on goods moving in and out of the port.

The king’s Asian empire, alas, proved
even more ephemeral than Alexander’s: within six months all his
appointed governors were deposed, and Seleucus II was crowned in Babylon.

It is, in any case, another reason to extol, not begrudge, the fundamental innovativeness of the Ptolemaic state.

Below a certain age, kids don’t have enough guile to filter what their parents tell them in private. From them, you get a peek into what’s in the hearts of the grown-ups, buried under all the emotions and rationalizations that come with adult concerns.

And what of the city’s old topography? General subsidence of the waterfront, combined with a rise in elevation inland, have erased the city’s original outlines. The broad sweep of the harbors remains, but the quays where Eratosthenes landed are now underwater.

A fine mist of pulverized concrete seems to cover everything, and the once salubrious climate is overwhelmed by smog.

The voyage of Nearchus, who was commissioned by Alexander in 325 to reconnoiter a possible sea route for the invasion of Africa, taught the Greeks much about the coastal regions of the Arabian Sea and the Persian Gulf.

It was not long after this that a certain Greek polymath named Eratosthenes of Cyrene (c. 285–204 BCE) calculated the circumference of our planet.

But like many innovations, the solution is remarkable not
for its inherent difficulty, but because it took
one remarkable mind
to apprehend its power.

In some cases, we will find that Eratosthenes was prescient in his thinking; in others, that he was sloppy or mistaken, but that his errors had the fortuitous effect of canceling each other out.

In some cases, we will find that Eratosthenes was prescient in his thinking; in others, that he was sloppy or mistaken, but that his errors had the fortuitous effect of canceling each other out.