Astronomer in 1543: Copernicus moves the Earth

The scientist who measures the universe, from Babylonian clay tablets to space telescopes, still deciding which flicker in the data is a discovery. Astronomy is the oldest continuously practiced science on Earth. Babylonian scribes kept nightly records of the sky on clay for some seven centuries — the longest unbroken scientific dataset ever produced — and Chinese court astronomers logged eclipses, comets and new stars for two thousand years. For most of that history the astronomer was a priest or court official whose real job was calendars and omens; the separation from astrology was only completed around the eighteenth century.

The modern version bears little resemblance to the robed figure at an eyepiece. The International Astronomical Union counts roughly 12,000 professional members worldwide, and most spend their days writing code, not observing: the world's great telescopes sit on Chilean and Hawaiian mountaintops, mostly operated by queue, with data flowing to researchers who may never visit. No country licenses astronomers — the doctorate is the profession's gate, and permanent posts are far scarcer than the PhDs produced each year.

This page follows the profession from the Babylonian diaries and Hipparchus's catalog through Ulugh Beg's Samarkand, Tycho's island, the Harvard computers and the photographic plate on which Hubble wrote "VAR!" It covers how people actually become astronomers today and what the decade of training costs in different countries, what a night on a summit and a year at a desk involve, eight figures who defined the craft, and how much of the work robotic surveys and machine learning are already taking.