Earth's Obliquity

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Earth's Obliquity

Postby dragonsteeth » Sun 05 Sep 2021 9:34 am

One of the arguments made by Velikovsky in Worlds in Collision was that either the Obliquity of the Earth changed in Historical times or else the geographical latitude of Thebes was lower for part of the 18th Dynasty in Ancient Egypt.

A water Clock has survived from the time of Tutankhamun's grandfather Pharaoh Amenhotep III which is marked with seasonal hours (See Worlds in Collision p. 320). With most modern clocks all our hours are of equal length sixty minutes long. The ancient system for seasonal hours was a bit different. In Ancient Egypt the time between sun up and sun set would have been divided into 12 equal intervals. This meant the mid Winter hours of sun up in Thebes would have been shorter than the 12 hours of sun up at the Summer Solstice. This meant that if the clock was constructed for Thebes latitude 26.5 degrees North the hour interval markings on the clock should provide an indication of the angle of the Earth's obliquity at the time when it was made.

Velikovsky questioned whether there had been a pole shift but did not follow up the question of a change of Obliquity as carefully as he could have. Many of ancient records particularly those linked to traditions relating to Ursa Major (aka: the Plough, the Wain, the great Dipper, the Foreleg of the Bull, or the Egyptian Hoe of Anubis) suggest that the constellations star Dubhe was the Pole Star in antiquity. But this would have required a substantially higher angle of Obliquity of more than 35 degrees. This conflicts with the evidence of the Water Clock of Amenhotep III which suggests a lower Obliquity nearer 10 degrees than the modern 23.5 degrees.

My interest here is not to check if the Earth's obliquity changed in the Bronze Age but to investigate what effect such changes would have on the Earth's climate.

From a geographical point of view a higher obliquity of more than 30 degrees should have catastrophic consequence for areas like the Mediterranean with even hotter Summers but further North warmer Summers, with substantially longer hours of Sunshine, would enable a wider range of cereals to be grown with more success. On the other hand a smaller increase of the angle of obliquity of between 25 and 30 degrees might have overall beneficial influence on the climate.

I don't have special knowledge for climate modelling but I think that the consequences with a lower Obliquity would be dire for Northern climes from France to Scandinavia. The Summer months would be much cooler and the hours of Summer sunshine would be dramatically reduced so that the upper limit for growing different cereal crops would shift well to the South. Slightly milder winters would probably fail to compensate for the lack of Summer heat plunging areas like Scandinavia into a long Norse 'Fimbulwinter' causing mass migration amongst Northern populations. With an obliquity of 16 degrees the Sun would rise no higher in Mid Summer than it does now for the end of April.

The historical evidence with regard any shift is mixed. One of the earliest British monuments is the New Grange mound in Southern Ireland. Built around 3,000 BCE the entrance shaft today aligns very closely with the Winter Solstice sunrise. On the other hand in Assyria and Babylonian throughout the 2nd Millenium BCE their astronomers had adopted a Summer Solstice ratio of 2 : 1 which they continued to use until around 750 BCE. This 2 : 1 ratio is better suited for a location like Seattle latitude 48 N rather than Babylon at 32.5 degrees North.

However to repeat here I am more interested in the question what effect different obliquities would have on the climate. For instance it has been suggested that the new geological Meghalayan Age started around 2,150 BCE and coincided with a series of World wide mega droughts. Could an increase to the angel of obliquity produce such droughts?

Biblical scholars like William Whiston proposed that before the 'fall of man' the Earth had a more accommodating (but improbable) zero angle of Obliquity but I believe the present angle of 23 degrees to be far more beneficial. We know that this current figure can move up and down from about 23 to 24 degrees, a movement which might be one of the contributing factor towards the cycle of Ice Ages. Could a slightly higher obliquity banish Ice Ages? Is there evidence for changes to the Earth's angle of Obliquity in more remote early geological eras?
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