http://www.nature.com/nature/fow/001116.html
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"lose the race; you lose your car"
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"lose the race; you lose your car"
pyramid precccccision
- Thread starter spidergoolash
- Start date
It said feature of the week..I don't want it to disappear from the link
Pyramid precision
All nine of the famous pyramids at Giza are closely aligned to true north, and the debate on how this was achieved rages on. Solar methods can be excluded as insufficiently accurate, leaving stellar alignment as the likely explanation. But details are lacking and existing theories also fail to account for the varying inaccuracy in the pyramids’ alignment throughout the epoch.
Writing in Nature this week, Kate Spence presents an astronomical explanation that is not only practical given the available technology, but also connects the deviation in alignment with time, allowing the pyramids’ construction to be accurately dated.
If one takes a long-exposure photograph of the northerly night sky, the stars will appear as arcs centred on a common point — true north. Currently, this point is occupied (to within one degree or so) by the star Polaris. However, the earth’s axis is not fixed; it precesses so that the north celestial pole moves in a small circle on the sky with a 26,000-year period. When the Egyptians were constructing their tombs, there was no visible pole star within two degrees of true north, yet they were able to achieve an accuracy of just three arc minutes (one twentieth of a degree). A more sophisticated explanation is clearly needed.
Spence identifies this method as the observation of two stars in simultaneous transit — that is, two stars on exact opposite sides of true north which appear to rotate around it. When they are in vertical alignment, as judged by a plumb line, their direction can be taken to be true north with a high accuracy. By running computer simulations of the night sky back to the time of the Egyptian kingdoms, she has also identified the stars that were most probably used — z-Ursae Majoris and g-Ursae Minoris — one each from the constellations of The Great and The Little Bear, which had simultaneous transits in 2467 BC.
Because of the precession of the Earth’s axis, these two stars would have simultaneous transits only for a year or so. One would therefore expect errors in alignments to increase with time away from 2467 BC. This is exactly what is seen — plotting the estimated construction date of the pyramids against their error in orientation produces a remarkably straight line, with those built before 2467 BC pointing slightly east and those built afterwards pointing slightly west. Two pyramids, Khafre and Ashure, do not fall near the straight line, but even this can be explained by assuming that the measurement was made when the two key stars were the other way up in the sky, reversing the deviation.
Obtaining such a strong correlation confirms Spence’s theory, and the plot can also be used in reverse, as a tool to refine the estimates of construction dates. Thus, Spence calculates that the Great Pyramid (Khufu) was set out in 2478 BC ± 5 years. Historians currently place the beginning of King Khufu’s reign at 2554 BC at the latest, so the result may trigger a rethink of the chronology of the ancient Egyptian kings.
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"I will gather myself around my faith, for light does the darkness most fear." - Jewel
Pyramid precision
All nine of the famous pyramids at Giza are closely aligned to true north, and the debate on how this was achieved rages on. Solar methods can be excluded as insufficiently accurate, leaving stellar alignment as the likely explanation. But details are lacking and existing theories also fail to account for the varying inaccuracy in the pyramids’ alignment throughout the epoch.
Writing in Nature this week, Kate Spence presents an astronomical explanation that is not only practical given the available technology, but also connects the deviation in alignment with time, allowing the pyramids’ construction to be accurately dated.
If one takes a long-exposure photograph of the northerly night sky, the stars will appear as arcs centred on a common point — true north. Currently, this point is occupied (to within one degree or so) by the star Polaris. However, the earth’s axis is not fixed; it precesses so that the north celestial pole moves in a small circle on the sky with a 26,000-year period. When the Egyptians were constructing their tombs, there was no visible pole star within two degrees of true north, yet they were able to achieve an accuracy of just three arc minutes (one twentieth of a degree). A more sophisticated explanation is clearly needed.
Spence identifies this method as the observation of two stars in simultaneous transit — that is, two stars on exact opposite sides of true north which appear to rotate around it. When they are in vertical alignment, as judged by a plumb line, their direction can be taken to be true north with a high accuracy. By running computer simulations of the night sky back to the time of the Egyptian kingdoms, she has also identified the stars that were most probably used — z-Ursae Majoris and g-Ursae Minoris — one each from the constellations of The Great and The Little Bear, which had simultaneous transits in 2467 BC.
Because of the precession of the Earth’s axis, these two stars would have simultaneous transits only for a year or so. One would therefore expect errors in alignments to increase with time away from 2467 BC. This is exactly what is seen — plotting the estimated construction date of the pyramids against their error in orientation produces a remarkably straight line, with those built before 2467 BC pointing slightly east and those built afterwards pointing slightly west. Two pyramids, Khafre and Ashure, do not fall near the straight line, but even this can be explained by assuming that the measurement was made when the two key stars were the other way up in the sky, reversing the deviation.
Obtaining such a strong correlation confirms Spence’s theory, and the plot can also be used in reverse, as a tool to refine the estimates of construction dates. Thus, Spence calculates that the Great Pyramid (Khufu) was set out in 2478 BC ± 5 years. Historians currently place the beginning of King Khufu’s reign at 2554 BC at the latest, so the result may trigger a rethink of the chronology of the ancient Egyptian kings.
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"I will gather myself around my faith, for light does the darkness most fear." - Jewel