The Reason For Measuring Lunar Distances
In celestial navigation, precise knowledge of the time at Greenwich and the positions of one or more celestial objects are combined with careful observations to calculate latitude and longitude. Reliable marine chronometers were unavailable until the late 18th century and not affordable until the 19th century. For approximately one hundred years (from about 1767 until about 1850) mariners lacking a chronometer used the method of lunar distances to determine Greenwich time, an important step in finding their longitude. A mariner with a chronometer could check and correct its reading using a lunar determination of Greenwich time.
Read more about this topic: Lunar Distance (navigation)
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“We have not strength enough to follow our reason so far as it would carry us.”
—François, Duc De La Rochefoucauld (1613–1680)
“We recognize caste in dogs because we rank ourselves by the familiar dog system, a ladderlike social arrangement wherein one individual outranks all others, the next outranks all but the first, and so on down the hierarchy. But the cat system is more like a wheel, with a high-ranking cat at the hub and the others arranged around the rim, all reluctantly acknowledging the superiority of the despot but not necessarily measuring themselves against one another.”
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“A bird half wakened in the lunar noon
Sang halfway through its little inborn tune.”
—Robert Frost (1874–1963)
“We then entered another swamp, at a necessarily slow pace, where the walking was worse than ever, not only on account of the water, but the fallen timber, which often obliterated the indistinct trail entirely. The fallen trees were so numerous, that for long distances the route was through a succession of small yards, where we climbed over fences as high as our heads, down into water often up to our knees, and then over another fence into a second yard, and so on.”
—Henry David Thoreau (1817–1862)