Lunar Eclipses Lunar Distances Longitude by Time
Centuries ago it was realised that knowing your longitude at sea was a pearl beyond price and that the choice was between designing and building an accurate clock which would work afloat, or looking to the heavens to find the time.
People searched long and hard for other solutions. Henry Bond, in the 17th century, reckoned magnetic dip was the answer and said so in his book Longitude Found. Others suggested lines of anchored ships across the oceans, flashing lights onto clouds, measuring the height of tides, or inducing dogs to bark.
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