http://www.archive.org/stream/throughspaceandt031585mbp/throughspaceandt031585mbp_djvu.txt wrote:
THROUGH SPACE & TIME (1934)
BY SIR JAMES JEANS
Aratus and star-signs
<<The Greeks and Egyptians had very similar names for many of the constellations of the Zodiac, but the Chinese Zodiac is named after twelve quite different animals. In place of our Ram, Bull, Twins and Crab, they have Dog, Cock, Ape, Ram, and so on. The remainder of the sky has also been divided into constellations, some of which are mentioned by very ancient writers. Orion and the Great Bear are mentioned both in Homer and in the Book of Job, while the Little Bear was described by Thales in the seventh century before Christ. Many of the constellations also are common to many languages and peoples. The Orion constellation, for instance, is often associated with a hunter or hero, and the Taurus constellation with a fierce animal.
All the constellations which could be seen from ancient Greece were drawn on a globe by the astronomer Eudoxus, a pupil of Plato, in the fourth century before Christ, and subsequently described in verse by Aratus. Most of them are associated in some way or other with the legends or fairy tales of long ago either of ancient Greece or of some still earlier civilisation. Thus we read of Helice and Cynosura, the Great Bear and the Little Bear, the latter being a hunter who was changed into a bear so that he should not kill his mother, whom Juno had already changed into a bear out of jealousy; or again of Hercules (whom Aratus describes merely as "The kneeling man") and the dragon; or best story of all, a real thriller of Perseus arriving in the nick of time to rescue Andromeda who was chained to a rock in the sea while Cetus, the sea-monster, was coming to devour her. He made Cetus look at the Medusa's head, which turned everyone to stone who saw it, but escaped this fate himself by looking at it in a mirror.
I have heard it suggested that our more modern nursery rhyme, which describes the cow jumping over the moon, was inspired by the sight of the moon moving through, or perhaps under, the constellation Taurus. The little dog who laughed to see such fun would no doubt be Canis Minor, the next constellation. There is also a dish (Crater) in the sky to run away with the spoon.
The Greeks were not great travellers, so that there were parts of the sky south of the equator which they did not see at all, and so could not divide into constellations. It was a pity, for the moderns who named the constellations in this part of the sky did not always maintain the dignity and simplicity of the older names. We find such constellations appearing as the Printer's Workshop, the Painter's Easel, the Engraver's Pen, the Chemical Furnace, and, even more ridiculous, the Honours of Frederick, the Harp of the Georges, the Oak-tree of Charles I. Even more recently a French astronomer, Lalande, tried to insert a cat into heaven. He wrote : * * I love cats ; I adore cats ; I may be pardoned for placing one in the sky after sixty years of arduous labours". But it has since disappeared, perhaps because it did not enjoy the society of its neighbours, Canis Major, Canis Minor, and Canes Venatici.
As Greece lies about 40 degrees north of the equator, the parts of the sky which the ancient Greeks could not see would be those which lay within 40 degrees of the South Pole. We might then reasonably expect that all the constellations with modern names would lie inside a circle 40 degrees in radius, having the South Pole as centre. Broadly speaking, we find that they all lie within a circle of 40 degrees radius, but its centre is not the South Pole. The reason for this is both interesting and informative.
The earth spins in space like a spinning top, but its axis does not always point in the same direction. The bulge round the earth's equator is continually being pulled by the sun's gravitational pull, and as this pull twists the earth's axis round in space, the earth top wobbles, rather as the ordinary schoolboy's top does when it is "dying".
It is found that the earth's axis wobbles round in a complete small circle once every 26,000 years. At the present moment the axis points to the tip of the tail of the Little Bear, but 4000 years ago it pointed to the Bear's left ear, and 5000 years ago to the tip of its nose. And 13,000 years ago the whole Little Bear was well down in the northern sky, while earth's axis pointed near Vega, which is now well down in the sky. Because the spinning top on which we live is rolling about in space, the inhabitants of Greece must have seen different parts of the sky at different epochs just as, when we live on a rolling ship, we see different sights through the porthole of our cabin. This goes some way to wards explaining why many southern constellations, such as the Centaur, have Greek names ; those parts of the sky are not visible from Greece now, but they were 4000 years ago, when people believed in Centaurs.
The constellations which Aratus mentioned in his poem are not even those which the Greeks were able to see at the time of Aratus; they are, broadly speaking, those which had been visible from the latitude of Greece about 2500 years earlier, or about 2800 years before Christ. Thus it seems likely that Aratus merely described constellations which had been named in the first instance by people who resided in the same latitude as Greece, at the period of about 2800 B.C. This points very strongly to the Babylonians, especially as there is other evidence that some at least of the principal constellations had been known to the Babylonians at an even earlier date.>>
