The constellations flow.
And the axis of the world beneath inscribes a circle in the sky a thousand
generations round, bestowing briefly as it passes by the honour of The
Pole on certain favoured stars.
Fragments of Berossus, Vega
Though the ancients conceived of the celestial sphere as eternal, unchangeable and perfect — and so were greatly disturbed by the appearances of "new stars" (novas and supernovas) and other "meteorological" phenomena (so called because they were "lofty" or "atmospheric") such as comets — that the heavens are not immutable is now common knowledge.
The so-called fixed stars move with respect to the solar system as they and we orbit the centre of the galaxy at different distances and varied speeds, and wander through space with our own peculiar, local motions; but such proper motions are not discernible by the human eye in the course of a single lifetime. What we may notice however is the precession of the equinoxes — the slow circling of the pole.
The precession of the equinoxes is the visible effect of the rotation of the Earth's axis — not the rotation of the Earth about its axis but the slow movement of the axis itself, as shown below. The cause is gyroscopic precession caused primarily by the moon's gravitational pull on a somewhat-less-than truly spherical Earth, but since there are other forces acting on the Earth (such as the Sun's gravity) and the Earth itself is not completely rigid, the motion of the pole illustrated above is neither a perfect circle nor perfectly periodic (every time a major earthquake redistributes the Earth's mass, the pole shifts by a microscopic but measurable amount).
With modern instruments we have been able to measure directly the stately progress of individual stars across the sky, but the precession of the equinoxes, through the slow progression of the sun against the background stars, has been recognised for thousands of years.
However, whilst Hipparchus (after whom the European Space Agency's stellar distance and proper motion measuring satellite Hipparcos satellite was named) is usually credited with discovering equinoctial precession, there is the fascinating possibility that human knowledge of the phenomenon is vastly older.
Given that the pole moves approximately half a degree (the apparent angular diameter of both the sun and moon, about the width of the little-finger nail at arms length) in about 36 years, anyone who carefully observed the sun's movements would have surely noticed its slow drift. The question is, how significant would such observations have been? Would ancient peoples have attached any importance to the slow motion of the equinoxes? Could they have deliberately observed them for calendrical (ritual or agricultural or other) purposes? [Of course, in referring to ritual or agricultural purposes the two were in all probability intimately related — though the timing of the seasons may have been mechanical, spirits or deities would have been the inferred motive forces behind the movemts... and independently responsible for the timely arrival of the rains, the sun or other concomitants of fertility.]
But, although one speaks of the "precession of the equinoxes," the days on which day and night are of equal length, as Clive Ruggles nicely states in his Encyclopedia of Cosmologies and Myth1
It is far easier to discern the movement of the solstices than the equinoxes; in the course of the year the point at which the sun appears at the horizon each day slowly drifts north (or south) then seems to stand still and then reverse course, heading south (or north) again until the other solstice, then beginning the cycle again. (The English word "solstice" is from the Latin solstitum, meaning the sun stands still.)
But whether one notices the movement of the equinoxes or the solstices, the precessional effect that causes the sky to turn is readily apparent; however, if one observes the sky for only a relatively limited period, it would be quite easy to think not that the sky was turning, but that it was slowly falling to one side.
Given the ubiquity of mythology concerning the ends of ages — particularly associated with the falling of sky-bridges, the diversion of sky-rivers, the general disconnection of pathways to and from the sky, etc. — and our increasing appreciation of the astronomical alignments of ancient monuments (Stonehenge, Egyptian pyramids, etc.), the idea that mankind has known about, if not understood, the long, slow movement of the heavens for several thousand of years rather than the mere two thousand since the time of Hipparchus, is not only not implausible, it has a certain appealing logic — though seeking to identify threads of astronomical knowledge in traditions whose histories may have been purely oral far longer than they have been written down can be complex and controversial.
The idea that much of the world's mythology might encode in memorably epic style arcane knowledge of the skies was most famously2 set out in Hamlet's Mill3 in 1969 by Giorgio de Santillana and Hertha von Dechend. In Hamlet's Mill, the authors peer deeply into world mythology, finding numerous parallels that are difficult to explain other than by reference to common astronomical knowledge. Of course, under the cumulative effects of the accretion of later history onto potentially primordial myths, progressive changes in language and culture, and the steady erosion of texts and traditions, it can be difficult to tell when, or whether, one has found a genuine thread of antiquity; but the breadth and depth of the study is impressive and persuasive — although, alas, it is also not infrequently in need of decryption in its own right, such is the density of the text in places.
The precession of the equinoxes is the visible effect of the rotation of the Earth's axis — not the rotation of the Earth about its axis but the slow movement of the axis itself, as shown below. The cause is gyroscopic precession caused primarily by the moon's gravitational pull on a somewhat-less-than truly spherical Earth, but since there are other forces acting on the Earth (such as the Sun's gravity) and the Earth itself is not completely rigid, the motion of the pole illustrated above is neither a perfect circle nor perfectly periodic (every time a major earthquake redistributes the Earth's mass, the pole shifts by a microscopic but measurable amount).
With modern instruments we have been able to measure directly the stately progress of individual stars across the sky, but the precession of the equinoxes, through the slow progression of the sun against the background stars, has been recognised for thousands of years.
However, whilst Hipparchus (after whom the European Space Agency's stellar distance and proper motion measuring satellite Hipparcos satellite was named) is usually credited with discovering equinoctial precession, there is the fascinating possibility that human knowledge of the phenomenon is vastly older.Given that the pole moves approximately half a degree (the apparent angular diameter of both the sun and moon, about the width of the little-finger nail at arms length) in about 36 years, anyone who carefully observed the sun's movements would have surely noticed its slow drift. The question is, how significant would such observations have been? Would ancient peoples have attached any importance to the slow motion of the equinoxes? Could they have deliberately observed them for calendrical (ritual or agricultural or other) purposes? [Of course, in referring to ritual or agricultural purposes the two were in all probability intimately related — though the timing of the seasons may have been mechanical, spirits or deities would have been the inferred motive forces behind the movemts... and independently responsible for the timely arrival of the rains, the sun or other concomitants of fertility.]
But, although one speaks of the "precession of the equinoxes," the days on which day and night are of equal length, as Clive Ruggles nicely states in his Encyclopedia of Cosmologies and Myth1
The word equinox is generally taken to refer to the days when, at every point on the earth, day and night are of equal length. But this definition of the equinox is a bit misleading... [and] In practice, one cannot determine the equinox by measuring the length of time between sunrise and sunset [p148]due to effects of latitude, atmosphere and the local horizon.
It is far easier to discern the movement of the solstices than the equinoxes; in the course of the year the point at which the sun appears at the horizon each day slowly drifts north (or south) then seems to stand still and then reverse course, heading south (or north) again until the other solstice, then beginning the cycle again. (The English word "solstice" is from the Latin solstitum, meaning the sun stands still.)
But whether one notices the movement of the equinoxes or the solstices, the precessional effect that causes the sky to turn is readily apparent; however, if one observes the sky for only a relatively limited period, it would be quite easy to think not that the sky was turning, but that it was slowly falling to one side.
Given the ubiquity of mythology concerning the ends of ages — particularly associated with the falling of sky-bridges, the diversion of sky-rivers, the general disconnection of pathways to and from the sky, etc. — and our increasing appreciation of the astronomical alignments of ancient monuments (Stonehenge, Egyptian pyramids, etc.), the idea that mankind has known about, if not understood, the long, slow movement of the heavens for several thousand of years rather than the mere two thousand since the time of Hipparchus, is not only not implausible, it has a certain appealing logic — though seeking to identify threads of astronomical knowledge in traditions whose histories may have been purely oral far longer than they have been written down can be complex and controversial.
The idea that much of the world's mythology might encode in memorably epic style arcane knowledge of the skies was most famously2 set out in Hamlet's Mill3 in 1969 by Giorgio de Santillana and Hertha von Dechend. In Hamlet's Mill, the authors peer deeply into world mythology, finding numerous parallels that are difficult to explain other than by reference to common astronomical knowledge. Of course, under the cumulative effects of the accretion of later history onto potentially primordial myths, progressive changes in language and culture, and the steady erosion of texts and traditions, it can be difficult to tell when, or whether, one has found a genuine thread of antiquity; but the breadth and depth of the study is impressive and persuasive — although, alas, it is also not infrequently in need of decryption in its own right, such is the density of the text in places.
Having studied a very wide range of astronomical mythological (archaeoastronomical and ethnoastronomincal) materials in the course of researching the star-myths for Fragments of Berossus, I think it is fair to say that there are indeed mysterious correlations between astronomical mythologies around the world at times when, conventionally, there should have been no significant contact between widely separated peoples. Either significant knowledge of the stars was disseminated around the world many thousands of years ago, or many peoples have independently observed the same phenomena and taken the same approach to recording it for posterity... if the myths are indeed, genuinely astronomical.
But whether genuine astronomical phenomena were observed and woven into myth or not, the mythologies of the heavens are a continual fascination; they encode, at the very least, some of mankind's oldest perceptions of itself, its place in the world, and the powers that shape its existence.
1 Ruggles, Clive L. N. Ancient astronomy : an encyclopedia of cosmologies and myth / (Santa Barbara, Calif. ; Oxford. : ABC Clio, c2005.) British Library Shelfmarks Q520.9303, YC.2007.b.740, HLR 520.93; ISBN 1851094776
2 But see also Wood, Florence. Homer's secret Iliad : the epic of the night skies decoded / (London : John Murray, 1999.) British Library Shelfmarks 99/39045, YK.1999.a.4587; ISBN 0719557801
3 The version I have is: De Santillana, Giorgio, Hamlet's mill : an essay on myth and the frame of time / (Boston [Mass.] : Godine, 1977, c1969. British Library Shelfmark X.950/13423; ISBN 0879232153 (Paperback). A generally favourable but balanced overview of and commentary on Hamlet's Mill by John Major Jenkins can be found here.)
But whether genuine astronomical phenomena were observed and woven into myth or not, the mythologies of the heavens are a continual fascination; they encode, at the very least, some of mankind's oldest perceptions of itself, its place in the world, and the powers that shape its existence.
1 Ruggles, Clive L. N. Ancient astronomy : an encyclopedia of cosmologies and myth / (Santa Barbara, Calif. ; Oxford. : ABC Clio, c2005.) British Library Shelfmarks Q520.9303, YC.2007.b.740, HLR 520.93; ISBN 1851094776
2 But see also Wood, Florence. Homer's secret Iliad : the epic of the night skies decoded / (London : John Murray, 1999.) British Library Shelfmarks 99/39045, YK.1999.a.4587; ISBN 0719557801
3 The version I have is: De Santillana, Giorgio, Hamlet's mill : an essay on myth and the frame of time / (Boston [Mass.] : Godine, 1977, c1969. British Library Shelfmark X.950/13423; ISBN 0879232153 (Paperback). A generally favourable but balanced overview of and commentary on Hamlet's Mill by John Major Jenkins can be found here.)
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