The Longitude The Longitude QuestionQuestion

1490-19451490-1945►European exploration and colonial European exploration and colonial

expansion is at its heightexpansion is at its height►British maintain worldwide dominanceBritish maintain worldwide dominance►British Royal Navy dominates the seasBritish Royal Navy dominates the seas

Lands at any timepart of the Brittish Empireshown in red.http://www.regiments.org/nations/

Latitude is easily determined by Latitude is easily determined by looking at the sun’s angle at noon.looking at the sun’s angle at noon.

Using a sextant, navigators Using a sextant, navigators could precisely measure the could precisely measure the angle of the sun above the angle of the sun above the horizon at local high noon. horizon at local high noon. This angle could be used to This angle could be used to determine ones determine ones latitudelatitude..

The sextant could also be used The sextant could also be used to take lunar measurements to to take lunar measurements to find longitude but the find longitude but the calculations were too difficult calculations were too difficult for most to perform.for most to perform.

http://en.wikipedia.org/wiki/Sextant

During cloudy days and nights, looking to During cloudy days and nights, looking to the “heavens” for guidance was fruitless.the “heavens” for guidance was fruitless.

Sailing for a few days in cloudy weather Sailing for a few days in cloudy weather degraded information about the ship’s degraded information about the ship’s position.position.

Land sightings, current, and weather Land sightings, current, and weather changes were used to guide ships.changes were used to guide ships.

Galileo’s method of using the location of Galileo’s method of using the location of Jupiter’s moons was impossible if the ship Jupiter’s moons was impossible if the ship pitched and rolled.pitched and rolled.

In 1707, five British ships In 1707, five British ships sink within minutes after sink within minutes after running onto the rocks of running onto the rocks of

the Scilly Islesthe Scilly Isles

► 1647 sailors die1647 sailors die►Multiple treasure Multiple treasure

chests of great chests of great monetary value monetary value lost.lost.

Scilly Isles

Wreck was due to the difficulty Wreck was due to the difficulty of determining longitude at seaof determining longitude at sea

► A sailor and unofficial A sailor and unofficial navigator on board navigator on board warned Admiral Shovell warned Admiral Shovell of the ships’ proximity of the ships’ proximity to the Scilly Isles.to the Scilly Isles.

► For questioning the For questioning the Admiral the sailor was Admiral the sailor was hanged, according to hanged, according to some reports.some reports.

Sir Clowdisley Shovell Admiral of the Associationhttp://www.geocities.com

In 1714 the British government In 1714 the British government passes the Longitude Act which:passes the Longitude Act which:

►Offers a prize ofOffers a prize of £ 20,000 to anyone £ 20,000 to anyone who can come up with a solution to find who can come up with a solution to find longitude at sea within ½ degree (35 longitude at sea within ½ degree (35 miles at the equator).miles at the equator).

►Creates a Longitude Board to evaluate Creates a Longitude Board to evaluate solutions.solutions.

►The Longitude Board is comprised The Longitude Board is comprised primarily of astronomers and primarily of astronomers and mathematicians.mathematicians.

John Harrison - John Harrison - Clock Maker ExtraordinaireClock Maker Extraordinaire

► Son of a CarpenterSon of a Carpenter► No formal educationNo formal education► Carpenter and Carpenter and

Mechanic by tradeMechanic by trade► Keen understanding of Keen understanding of

materials, i.e. metals materials, i.e. metals and woodsand woods

► Interested in creating a Interested in creating a chronometer to solve chronometer to solve the longitude problem.the longitude problem.

https://eee.uci.edu

Early Achievements of Early Achievements of HarrisonHarrison

► Built a clock entirely out of Built a clock entirely out of wood at the age of 20. A wood at the age of 20. A self lubricating clock, where self lubricating clock, where lubricants bleed out of the lubricants bleed out of the woods.woods.

► Invented the Gridiron Invented the Gridiron Pendulum. This was a Pendulum. This was a pendulum constructed of pendulum constructed of alternating dissimilar alternating dissimilar metals. The thermal metals. The thermal expansions of the two expansions of the two metals cancelled out, thus metals cancelled out, thus maintaining a constant maintaining a constant pendulum length.pendulum length.

Brass and Iron Rodshttp://physics.kenyon.edu/

What is a chronometer?What is a chronometer?

►A precision time piece that keeps the A precision time piece that keeps the time at a fixed location. This time acts time at a fixed location. This time acts as a reference point for determining as a reference point for determining longitude.longitude.

►Knowing local noon at sea and the time Knowing local noon at sea and the time at Greenwich England, navigators could at Greenwich England, navigators could determine how many minutes or miles determine how many minutes or miles they were from Greenwich, England.they were from Greenwich, England.

Chronometers had to keep time Chronometers had to keep time even when the ship tipped, even when the ship tipped,

pitched and yawed.pitched and yawed.

1810 Chronometer mounted on Gimbelshttp://www.stedmundsbury.gov.uk

Precision Pendulum Clocks failed Precision Pendulum Clocks failed at Seaat Sea► Accurate time is kept Accurate time is kept

by the oscillations of by the oscillations of the pendulum.the pendulum.

► Frequency (cycles/sec) Frequency (cycles/sec) are determined by the are determined by the length of the pendulum length of the pendulum and force of gravityand force of gravity

► f = (1/2f = (1/2) * √(g/L)) * √(g/L) ► Pendulum clocks Pendulum clocks

require a constant require a constant gravitational force, in gravitational force, in other words- other words- stable stable groundground

John Harrison’s H1John Harrison’s H1Completed when he was 42Completed when he was 42

This took seven years for Harrison to build.(Courtesy National Maritime Museum, London)

Two independentPendulums

The Board doubts a mechanical The Board doubts a mechanical instrument can solve the instrument can solve the

longitude problemlongitude problem

►Board demands a sea trial Board demands a sea trial of H1of H1

►Board grants Harrison £ Board grants Harrison £ 500 to improve H1500 to improve H1

►Eventually Harrison Eventually Harrison develops a small timepiece, develops a small timepiece, the H4 at the age of 68the H4 at the age of 68

The H4

Multiple trialsMultiple trials

►H4 goes to Jamaica and measures H4 goes to Jamaica and measures longitude to within 2 miles.longitude to within 2 miles.

►Board claims result was “luck”Board claims result was “luck”►H4 goes for a second trial, and H4 goes for a second trial, and

measures location of Barbados within measures location of Barbados within 10 miles.10 miles.

►Board awards Harrison £ 10,000 but Board awards Harrison £ 10,000 but demands more testing and detailed demands more testing and detailed plans so that device can be reproduced plans so that device can be reproduced by other clockmakers.by other clockmakers.

Foul PlayFoul Play

► Nevil Maskelyne was appointed Nevil Maskelyne was appointed Astronomer Royal and sits on the Astronomer Royal and sits on the Board of LongitudeBoard of Longitude

►Maskelyne develops a less accurate Maskelyne develops a less accurate solution (barely within the Longitude solution (barely within the Longitude Act’s limits) based on the lunar Act’s limits) based on the lunar distance method, which requires distance method, which requires many calculations from viewing the many calculations from viewing the moon against the stars.moon against the stars. Conflict of InterestConflict of Interest

►Maskelyne claims Harrison’s H4 is Maskelyne claims Harrison’s H4 is inaccurate and results are just luck.inaccurate and results are just luck.

Wikipedia

Royal InterventionRoyal Intervention

►King George III finally intervenes on King George III finally intervenes on Harrison’s behalf and has him Harrison’s behalf and has him “righted”.“righted”.

► In 1773, when he was 80 years old, In 1773, when he was 80 years old, Harrison received £ 20,000 from Harrison received £ 20,000 from Parliament for his achievements, but Parliament for his achievements, but he never received the official award he never received the official award (which was never awarded to anyone). (which was never awarded to anyone).

►Harrison struggled with the Board for Harrison struggled with the Board for over 38 years.over 38 years.

Timepieces TodayTimepieces Today

►Quartz clocks – use an electronic Quartz clocks – use an electronic oscillator that is made from a quartz oscillator that is made from a quartz crystal. Accurate to 10 seconds/year.crystal. Accurate to 10 seconds/year.

►Atomic clocks – uses the resonant Atomic clocks – uses the resonant frequency of atoms. Accurate to frequency of atoms. Accurate to 11s/years/year

Some sources:Some sources:

TV Movie - Longitude

http://www.youtube.com/watch?v=ROz0-4ymuXQYou Tube – John Harrison His Clock and theLongitude Problem