Making time

What the public clock can, and cannot, tell us about why Europe grew rich

Take a look at the main square of almost any old European town. Somewhere above it – on a church tower or a town hall – there is a clock. It has hung there for centuries, striking the hour for everyone within earshot: the merchant, the apprentice, the magistrate, the beggar. Except for the most exquisite ones, we barely notice it now. Yet that public, shared, freely available timepiece is one of the foundations of the modern economy.

Now travel back to eleventh-century China. Around 1088 the official Su Song built a wondrous astronomical clock tower at Kaifeng: twelve metres tall, water-driven, with an escapement-like mechanism that turned a celestial globe while small figures emerged to mark the hours. It was centuries ahead of anything in Europe. And it changed almost nothing. As the economic historian David Landes told the story, timekeeping in China was an imperial secret, bound up with astrology and the emperor’s heavenly mandate, shut away inside the palace. When invaders sacked Kaifeng in 1127 the clock was carried off, no one could rebuild it, and the knowledge died with its handful of court specialists.

The puzzle Landes left us is why the same machine could be a curiosity in one place and a turning point in another.