September 21, 2017

Klaim: Siklus Saros – 101 Kesalahan Flat Earth Indonesia

Respon: Katanya “anda bisa cek di situs resmi NASA”, well….

A Saros series doesn’t last indefinitely because the three lunar months are not perfectly commensurate with one another. In particular, the Moon’s node shifts eastward by about 0.5º with each cycle. A typical Saros series for a solar eclipse begins when new Moon occurs ~18° east of a node. If the first eclipse occurs at the Moon’s descending node, the Moon’s umbral shadow will pass ~3500 km below Earth and a partial eclipse will be visible from the south polar region. On the following return, the umbra will pass ~300 km closer to Earth and a partial eclipse of slightly larger magnitude will result. After ten or eleven Saros cycles (about 200 years), the first central eclipse will occur near the south pole of Earth. Over the course of the next 950 years, a central eclipse occurs every 18.031 years (= Saros) but will be displaced northward by an average of ~300 km. Halfway through this period, eclipses of long duration will occur near the equator. The last central eclipse of the series occurs near the north pole. The next approximately ten eclipses will be partial with successively smaller magnitudes. Finally, the Saros series will end a dozen or more centuries after it began at the opposite pole. Due to the ellipticity of the orbits of Earth and the Moon, the exact duration and number of eclipses in a complete Saros is not constant. A series may last 1226 to 1550 years and is comprised of 69 to 87 eclipses, of which about 40 to 60 are central (i.e., total, hybrid or annular).

For more information, see Saros Series Statistics. Bagian 1.6: Saros Series Statistics

The Saros cycle itself isn’t perfect; the various lunar cycles don’t quite mesh up perfectly. For this reason, successive eclipses in a Saros series are shifted slightly either north or south (depending on the particular Saros) from each other. This means that a Saros series is actually of limited duration — about 70 to 85 eclipses over 1,200 to 1,500 years. Each series starts with a small partial eclipse in either the north or south polar regions; as the shadows of the successive eclipses move farther into the Earth, the first total eclipse will be seen near the polar regions. The eclipses of the series then march down or up the Earth, until the last total eclipse, and then a series of diminishing partial eclipses, occurs at the opposite pole to where the series started; and then it ends.The fact that the length of a Saros has an odd third of a day means that successive eclipses don’t occur in the same part of the world; since the Earth has rotated by an additional third between eclipses. This gives rise to an even longer cycle, the Triple Saros, in which eclipses occur in the same part of the world every 54 years and 32 or 33 days (depending on leap years).

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