Longitude by Sobel

Ref: Sobel (2007). Longitude. Bloomsbury.

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Summary

After centuries of risk in sea travel, the UK issues an act to the general public to discern a method to fix longitude- two primary methods prevail- astronomy with sextants, and time with clocks; the latter as Harrison’s H3 prevails, and ticks to this day.
8 Jul, 1714: The longitude act is issued in England during the reign of Queen Anne who names the prizes as follows: first- determine long to .5° (20,000 pounds), second- determine long to 2/3° (15,000 pounds), third- determine long to 1° (10,000 pounds).-Longitude by Sobel.

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At the equator, where the girth of the Earth is greatest, 15° stretch fully 1000 miles. North or South of that line, however, the mileage value of each degree decreases. One degree of longitude equals 4’ of time the world over, but in terms of distance, 1° shrinks from 68 miles at the equator to virtually nothing at the poles.

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Werner Suggested that astronomers should map the positions of the stars along the moon's path and predict when the moon would brush by each one- on every moonlit night, month to month, for years to come. Also, the relative positions of the sun and moon through the daylight hours should be similarly mapped. Astronomers could then publish tables of all the moons meanderings, with the time of each start meeting predicted for one place- Berlin, perhaps, or Nuremberg- whose longitude would serve as the Z.
I am of the opinion, Kendall told the board, that it would be many years (if ever) before a watch of the same kind with that of Mr Harrison’s could afforded for 200lbs. Meanwhile a seamen could buy a good sextant and a set of lunar distance tables for only a fraction of that sun, about 20lbs.
Nevil Maskelyne, 5th astronomer royal, brought the prime meridian to Greenwich (with his lunar charts)- he also went out of his way to ruin Harrison’s chronometer in favor of his own lunar-star charts.

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The measurement of Longitude meridians is tempered by time. To learn one’s longitude at sea, one needs to know what time it is aboard ship and also the time at the home port or another place of known longitude- at that very same moment. The two clock times enable the navigator to convert the house difference into a geographical separation. Since the Earth takes 24 hours to complete one full revolution of 360°. One hour marks 1/24 of a spin, or 15English clockmaker John Harrison, a mechanical genius who pioneered the science of portable precision timekeeping, devoted his life to this quest. He accomplished what Newton had feared was impossible: He invented a clock that would carry the true time from the home port, like an eternal flame, to any remote corner of the world. With no formal education or apprenticeship to any watchmaker, Harrison nevertheless constructed a series of virtually friction free clocks that required no lubrication and no cleaning, that were made from materials impervious to rust, and that kept their moving parts perfectly balanced in relation to one another, regardless of how the world pitched or tossed about them. He did away with the pendulum and he combined different metals inside his work in such a way that when one component expanded or contracted with changes in temperature, the other counteracted the changes and kept the clock’s rate constant.

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Mesmerized by the to and fro of an oil lamp suspended from the nave ceiling and pushed by drafts, he watched as the sexton stopped the pan to light the wick. Rekindled and released with a shove, the chandelier began to swing again, describing a larger arc this time. Timing the motion of the lamp by his own pulse, Galileo saw that the length of a pendulum determines its rate.

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May- Jun, 1772: Harrison’s H-5 proves accurate to within 1/3 of 1 second per day.-Longitude by Sobel.
8 Jul, 1714: The longitude act is issued in England during the reign of Queen Anne who names the prizes as follows: first- determine long to .5° (20,000 pounds), second- determine long to 2/3° (15,000 pounds), third- determine long to 1° (10,000 pounds).-Longitude by Sobel.

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