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Because he knew the value which Hipparchus eventually gave for the distance to the Moon (71 Earth radii) and the rough region of the eclipse, Toomer was able to determine that Hipparchus used the solar eclipse of March 14, 190 BC. This eclipse fits all the mathematical parameters very well, and also makes sense from a historical point of view.
Hipparchus's solution was to place the Earth not at the center of the Sun's motion, but at some distance from the center. This model described the apparent motion of the Sun fairly well. It is known today that the planets , including the Earth, move in approximate ellipses around the Sun, but this was not discovered until Johannes Kepler ...
Around 200 BCE Eratosthenes determines that the radius of the Earth is roughly 6,400 km. [43] Circa 150 BCE Hipparchus uses parallax to determine that the distance to the Moon is roughly 380,000 km. [44] The work of Hipparchus about the Earth-Moon system was so accurate that he could forecast solar and lunar eclipses for the next six centuries.
Depending on the distance that van Helden assumes Aristarchus used for the distance to the Moon, his calculated distance to the Sun would fall between 380 and 1520 Earth radii. [29] Hipparchus gave an estimate of the distance of Earth from the Sun, quoted by Pappus as equal to 490 Earth radii.
In contrast, the Lunar distance (LD or ), or Earth–Moon characteristic distance, is a unit of measure in astronomy. More technically, it is the semi-major axis of the geocentric lunar orbit . The lunar distance is on average approximately 385,000 km (239,000 mi), or 1.28 light-seconds ; this is roughly 30 times Earth's diameter or 9.5 times ...
Eratosthenes (c. 276 – c. 194/195 BC), a Greek mathematician who calculated the circumference of the Earth and also the distance from the Earth to the Sun. Hipparchus (c. 190 – c. 120 BC), a Greek mathematician who measured the radii of the Sun and the Moon as well as their distances from the Earth. On the Sizes and Distances
Shortly afterwards, Eratosthenes calculated the size of the Earth, providing a value for the Earth radii which 252,000 stades, which may be equivalent to 39,690 kilometers, rather close to the true figure of 40,120 kilometers. [16] Hipparchus wrote another book On the Sizes and Distances of the Sun and Moon, which has not survived. Both ...
On Sizes and Distances, by Hipparchus (c. 190 – c. 120 BC Topics referred to by the same term This disambiguation page lists articles associated with the title On Sizes and Distances .