Navigation

In the great Scilly disaster of 1707, several British naval ships were destroyed and more than 1400 men lost their lives.  The reason... they did not know their exact location.

Location is determined by 2 co-ordinates: Longitude and Latitude.  Latitude is measured by a series of lines parallel to the Earth's equator.  Longitude runs vertically between the North and South poles.

300 Years ago, sailors only knew how to calculate Latitude.  They did this by measuring the angle of the sun relative to the horizon and comparing it to their charts, charts which showed the angle of the sun at any point on earth relative to the date.  Since the angle changed with the days of the year, one could determine with relative accuracy where they were, latitudinally speaking, on the earth.  Basically they knew how far north or south they were depending where the sun was relative to the horizon.

The problem was they did not know how far east or west they were.  While sailing, with no other points of reference sailors had no idea how far they had gone.  One technique employed was called "Dead Reckoning".  Sailors would though out a rope with knots tied at regular intervals.  How many knots passed through their hands while an hour glass drained they would determine their speed in "knots".  Using regular measurements of their speed they estimated how far they travelled and thus where they were East to West.  How accurate was this?  Well maybe that's why it was called "DEAD" reckoning.

So after the great Scilly Disaster of 1707, the British Government created the Longitude Act of 1714.  Basically they created a contest to find the solution to the longitude problem.  The original X-Prize you might say.  The prize; 20,000 pounds.  In today's dollar thats about a Billion Dollars.  It's probably the biggest prize in the history of, well, modern history.

The greatest scientific minds including Isaac Newton sought solutions to the problem.  The astronomers argued the solution was to be found in the stars.  None were accurate enough or feasible enough.  Enter John Harrison.  He realized that the problem was one of time.  If you knew the time at the home port and the time at the current destination, then you could measure where you were longitudinally speaking.  For example, if your clock on the ship showed 12 noon at the home port, then by measuring where the sun was, you could determine where you were.  So the problem was really about making a clock.  A clock that would tell you accurately when it was 12 noon at the home port.


Easy, right?  Well the clocks at the time used a swinging pendulum like the kind we think of in "Cuckoo Clocks"  Also, they were made of wood.  At sea, with the motion of the waves, the humidity, the differences between heat and cold, and more issues ... well these clocks simply would not work.  So the real challenge was how to make an effective clock that worked at sea.

Harrison spent years making bigger clocks, with more exotic materials, with springs, with hizzits and hoozits... but in the end he could not do it.

Until...

Spoiler Alert...

The solution was to go smaller not bigger.  John Harrison invented... The Pocket Watch!  Well sort of... he actually worked with a watch maker and what was made was actually the H4 Seawatch, or "Marine Chronometer" ... (NOT on display in the Royal Museum at Greenwich.) ... which was used to measure Longitude.

John Harrison was a self educated man.  He was not bogged down by dogma and politics.  He was a quiet inventor who followed his intuition.  The astronomers who mocked him were wrong.  He was right.  Harrison forever changed the world and helped us to navigate the seas.

How can you not love this story.

The video I have attached is one of my favorite episodes of NOVA.  Based on a book by the same name, please enjoy: Lost at Sea, The Search For Longitude.


Well done John Harrison.  Bravo.