All about Wonderful Greenwich and its many attractions is here ⇐.
One of the and most significant and greatest endeavours of human history has been the pursuit of navigational method at sea. It required the accurate measurement of astronomical observations and the development of a marine chronometer. The later being particularly difficult.
The Meridian Courtyard
The Meridian Courtyard is just in front of Flamsteed House, with the The Time Ball ⇒ on top. Here you can stand on the worlds east/west divide at 0 degrees longitude. Admission to Royal Observatory, Flamsteed House and the Meridian Courtyard is here ⇒.
However you can stand on the meridian for free where the red meridian line crosses an intersection in the paths in the park on the tourist map here ⇒.
The Meridian Line
There is usually a queue to stand astride the Meridian Line. This where the journey to east or west begins.
Inside Flamsteed House
Initially ones position, to the east or west of a starting point, could only be determined by dead-reckoning. That is, by measuring the distance traveled. At sea that meant measuring ones speed through the water. It was done by throwing a log overboard attached to a rope. The rope had knots at fixed intervals and the number of knots that were drawn out were counted for a fixed period of time using a sand glass. It was contrived so that one Knot was equal to one nautical mile per hour. A term that is still used today.
The dead reckoning method was woefully inadequate for long distances, no use for creating accurate charts and led to many disasters.
A better method required an accurate seagoing timekeeper. Such a timekeeper could be set to keep the time at a meridian. Greenwich was adopted and the time as Greenwich Mean Time (GMT). Wherever the ship was it would have the time at Greenwich. Therefore if at local noon the GMT timekeeper showed one o’clock the ship must be 1/24 of the way around the world. If the clock showed two o’clock then the ship must be 2/24 around the world etc and with every second that passed a smaller division. A fuller explanation and an extensive history of navigation can be found here ⇐.
After many years of effort John Harrison created the first maritime chronometer that would keep accurate time even on board a rolling ship.
The project began with H1 which was not accurate enough.
Neither was H2.
Neither was H3.
In 1759, after near 30 years of effort, Harrison created H4. This device had the advantage of advances in metallurgy, temperature compensation and the important realisation that a smaller/faster movement would be less effected by a ships movement.
There are more Antique Timepieces at the London Science Museum⇐.
Mechanical Marine Chronometers can be as accurate as 5 secs gain or loss in fifteen days.
The first quartz clock was created in 1927 and worked by counting the electrically induced vibration of a piece of quartz. By 1969 a miniature version could be worn on ones wrist. Quartz chronometers can be as accurate as 0.7 seconds gain of or loss in 15 days.
A cesium (atomic) clock operates by exposing cesium atoms to microwaves until they vibrate at one of their resonant frequencies. They are accurate to within one second in 1,400,000 years.
The next generation of atomic clocks will keep time to one second in 15 billion years. At last the perfect boiled egg.
Back to some of the artifacts in Flamsteed House.
If you would like to know more about the development of navigation and its importance to our evolution it is here ⇐.
And, thank you for visiting Freed From Time (which isn’t as much of an anomaly as it sounds, probably 🙂 ).