Perhaps we take the earth's coordinate grid system, if we think about it all, for granted. But not so fast. Calculating latitude, the distance of a position north or south of the equator, involves trigonometry and calculating longitude, distance east or west of the prime meridian, demands an accurate clock.
A clock? Yes, a clock which tells the time at the prime meridian, the sun's set "starting point" as it moves across the sky, and your position on the earth. Long story very short, if it's Noon at the prime meridian and 2.00 pm at your position, you're at longitude 30° east. Why? Because the sun crosses the sky at a rate of 15° per hour, given 24 hours in a day and 360° in a circle (360° ÷ 24 hours = 15° per hour).
Simple enough math but how do you make the calculation without a good clock? Tricky, which is why Parliament offered an immense prize of £20,000 in 1714, over £2 million today, to anyone who could come up with such a device. John Harrison did so and accurate navigation became possible. But here's the thing.
Back in 1966, science prof John Habgood re-examined the Piri Reis map, compiled from ancient maps by the Turkish admiral of the same name in 1513. Hapgood discovered what he believed were accurate measures of longitude and latitude. If true, this is remarkable.
It means that the ancient maps used by Reis were made by people who understood trigonometry and had some kind of reliable clock. The first supposition is understandable, the 2nd century BC Greek mathematician, Hipparchus, is held to have invented trigonometry.
So Greek cartographers were able, at least in theory, to calculate latitude. But longitude? That takes a good clock and we all know these weren't invented until the 18th century. Or were they.
It means that the ancient maps used by Reis were made by people who understood trigonometry and had some kind of reliable clock. The first supposition is understandable, the 2nd century BC Greek mathematician, Hipparchus, is held to have invented trigonometry.
So Greek cartographers were able, at least in theory, to calculate latitude. But longitude? That takes a good clock and we all know these weren't invented until the 18th century. Or were they.
Here's Harrison's prototype clock:
A clock? Or something very like it, dating from the first or second century BC. Food for thought. Hapgood's suggestion in Maps of the Ancient Sea Kings is that there must have been a civilization prior to the Greeks who were skilled mathematicians and able to tell time to the degree required to calculate longitude. I find that fascinating.
Speaking of time, the Government's been shut down for a very long time and everyone seems a lot happier. Was there an advanced civilization before our own? I'd have thought that obvious.
Mercator,
LSP
