Wednesday, June 23, 2010

Dude, Zero Degrees Longitude

Greenwich, located on the zero degree meridian, is the home base for setting time around the world. We took the short train ride there from London and visited the Maritime Museum and the Royal Observatory, which played an important part in one of the most important discoveries and technological advances in our history: how to calculate with accuracy your longitude position while at sea. Latitude, your distance from the equator, can be determined by measuring the distance of the sun (or the Polar Star) from the horizon at noon. For many centuries sailors had no way to determine longitude, their position East or West from a given point. This led to a lot of costly mistakes in lives, ships, and treasures. In the late 1600s many monarchs began offering fabulous rewards for anyone who could solve this problem.
The Royal Observatory in Greenwich was created by King Charles II, specifically to work on this problem, since a detailed and accurate mapping of stars, planets, and other heavenly objects seemed to be the obvious path to explore. He appointed a young scientist named Flamsteed to be in charge.
It was known that an accurate clock could solve the problem, enabling a navigator to compare the time at his current location to the time at his port of departure. But clocks were not accurate or dependable at the time. Nor were they portable. At sea they would stop working or give incorrect time due to motion, changes in temperature, barometric pressure changes, damage by storms, rust, etc. So most scientist concentrated on mapping the stars, advancing the science of astronomy in a giant way.
An unknown watchmaker named John Harrison built an amazing clock that looked like a Rube Goldberg device. It was made of different metals so that when one piece contracted due to the environmental conditions, it's effect was offset by another piece that expanded. It didn't have a pendulum, and it wasn't affected by motion, and even though it was large, it was far smaller than other clocks. Over the years, he built a second version that had improvements and was smaller, but it still looked like a big two foot cube. He kept working, and years later morphed it into what we know today as a watch, about the size of your hand.
All this took over 40 years, all the while battling important scientists who tried to discredit him as a nobody with no formal training. Finally, as an old man, he collected his prize money and seafaring ships were able to plot their positions accurately. And it was during this project, mapping the stars and the eclipses of the moons of Jupiter, that the speed of light was first discovered.

Walking the zero meridian line at the Royal Observatory in Greenwich, the starting point for East and West. The metal strip goes straight to the telescope in the observatory where Flamsteed and his assistants spent years mapping the stars.

A flower garden at the Royal Observatory.

One of the clocks created by John Harrison. What kind of epiphany did he have to leap from this to a device that looks like a pocket watch you can buy today?

The Royal Observatory from the park grounds. The round ball on the left spire drops to the bottom of the spire at noon every day. Navigators and captains on nearby ships on the Thames could see the observatory on the hill and set their ship clocks to the correct time at noon, before they set out to sea. If your ship's clock is inaccurate by several minutes, your navigation can be off by a hundred miles.