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Posidonius calculated the Earth's circumference by reference to the position of the star Canopus.As explained by Cleomedes, Posidonius observed Canopus on but never above the horizon at Rhodes, while at Alexandria he saw it ascend as far as 7 + 1 ⁄ 2 degrees above the horizon (the meridian arc between the latitude of the two locales is actually 5 degrees 14 minutes).
Taking the Earth as spherical, the Earth's circumference would be fifty times the distance between Alexandria and Syene, that is 250,000 stadia. Since 1 Egyptian stadium is equal to 157.5 metres, the result is 39,375 km, which is 1.4% less than the real number, 39,941 km.
Approximate sizes of the planets relative to each other. Outward from the Sun, the planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Jupiter's diameter is about 11 times that of the Earth's and the Sun's diameter is about 10 times Jupiter's. The planets are not shown at the appropriate distance from the Sun.
Proposition 6 states that the Moon moves [in an orbit] lower than [that of] the Sun, and, when it is halved, is distant less than a quadrant from the Sun (Heath 1913:372). Proposition 7 states that the distance of the Sun from the Earth is greater than 18 times, but less than 20 times, the distance of the Moon from the Earth (Heath 1913:377 ...
The second book contains his calculation of the circumference of the Earth. This is where, according to Pliny, "The world was grasped." Here Eratosthenes described his famous story of the well in Syene, wherein at noon each summer solstice, the Sun's rays shone straight down into the city-center well. [ 22 ]
Size of Jupiter compared to Earth and Earth's Moon. Jupiter is about ten times larger than Earth (11.209 R 🜨) and smaller than the Sun (0.102 76 R ☉). Jupiter's mass is 318 times that of Earth; [2] 2.5 times that of all the other planets in the Solar System combined.
He was the first to calculate the Earth's circumference (within 0.5 percent accuracy). [28] His great achievement in the field of cartography was the use of a new technique of charting with meridians , his imaginary north–south lines, and parallels , his imaginary west–east lines. [ 29 ]
The Jupiter radius or Jovian radius (R J or R Jup) has a value of 71,492 km (44,423 mi), or 11.2 Earth radii (R 🜨) [2] (one Earth radius equals 0.08921 R J). The Jupiter radius is a unit of length used in astronomy to describe the radii of gas giants and some exoplanets. It is also used in describing brown dwarfs.