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Here is a bad photo ( colors dont show) of a watercolor I finished today. It is a painting of Athena. It is 22 x 30 on Fabriano paper. Athena is the goddess of wisdom.
ne will work. It is pencil and watercolor on 22 x 30 Arches paper.
Eratosthenes knew that on the summer solstice at local noon in the Ancient Egyptian city of Swenet (known in Greek as Syene) on the Tropic of Cancer, the sun would appear at the zenith, directly overhead. He also knew, from measurement, that in his hometown of Alexandria, the angle of elevation of the Sun would be 1/50 of a full circle (7°12') south of the zenith at the same time. Assuming that Alexandria was due north of Syene he concluded that the distance from Alexandria to Syene must be 1/50 of the total circumference of the Earth. His estimated distance between the cities was 5000 stadia (about 500 geographical miles or 950 km). He rounded the result to a final value of 700 stadia per degree, which implies a circumference of 252,000 stadia. The exact size of the stadion he used is frequently argued. The common Attic stadion was about 185 m, which would imply a circumference of 46,620 km, i.e. 16.3% too large. However, if we assume that Eratosthenes used the "Egyptian stadion"[1] of about 157.5 m, his measurement turns out to be 39,690 km, an error of less than 1%.[2]
Although Eratosthenes' method was well founded, the accuracy of his calculation was inherently limited. The accuracy of Eratosthenes' measurement would have been reduced by the fact that Syene is slightly north of the Tropic of Cancer, is not directly south of Alexandria, and the Sun appears as a disk located at a finite distance from the Earth instead of as a point source of light at an infinite distance. There are other sources of experimental error: the greatest limitation to Eratosthenes' method was that, in antiquity, overland distance measurements were not reliable, especially for travel along the non-linear Nile which was traveled primarily by boat. So the accuracy of Eratosthenes' size of the earth is surprising.
Eratosthenes' experiment was highly regarded at the time, and his estimate of the Earth’s size was accepted for hundreds of years afterwards. His method was used by Posidonius about 150 years later.
Very hot in the morning. In the afternoon sudden thunder-storm & very heavy rain. About 50 yards from the gate the road & pavement flooded a foot deep after only 1 1/2 hours rain.
Blackberries beginning to redden.
( I missed a few days on his journal so I am catching up)
This morning all surfaces, even indoors, damp as a result of mist. A curious deposit all over my snuff-box, evidently residue of moisture acting on lacquer.
Very hot, but rain in afternoon.
Am told the men caught another snake this morning – definitely a grass snake this time. The man who saw them said they had tied a string round its neck & were trying to cut out its tongue with a knife, the idea being that after this it could not “sting.”¹
The first Beauty of Bath apples today.