I want to take a moment to thank everyone who’s been hanging with me throughout this little history. I feel like I’ve been telling a year-and-a-half-long joke and I’m just about to get to the punchline.
Since January last year, we discovered how people in the past measured space and measured time. We followed along as travelers ventured further and further from home—traders and explorers became bold enough to make long voyages across the oceans without knowing exactly where they were. To navigate, you need to measure both time and space. Most of the inventions that measure time and space didn’t appear until around the 1500s.
Here’s what you need if you plan to cross an ocean and would like to know where you are going:
1. an accurate map, to know what you’re looking for
2. a compass, to orient the map
3. an astrolabe, to find latitude (how far north or south you are)
4. universal time, to find longitude (how far east or west you are)—Galileo proposed that if you can see the positions of Jupiter’s moons, and you know what time it is locally, you can figure out your longitude. Jupiter’s moons would be a universal clock.
5. an accurate clock, to know local time
The Exploration Age sailors set sail without an accurate map or clock, because those things didn’t exist yet (a pendulum clock doesn’t work on a rocking ship).
Astrolabes or Jupiter’s moons are only useful when the sky is clear. So, even in the 1500s sailors didn’t have all the tools they needed for navigating.
Back to the beginning of The Western Civ User’s Guide to Time & Space