The genius of the race being what it was, the Greeks must from the earliest times have been in the habit of scanning the heavens, and, as might be expected, we find the beginnings of astronomical knowledge in the earliest Greek literature.
In the Homeric poems and in Hesiod the earth is a flat circular disc; round this disc runs the river Oceanus, encircling the earth and flowing back into itself. The flat earth has above it the vault of heaven, like a sort of hemispherical dome exactly covering it; this vault remains for ever in one position; the sun, moon and stars move round under it, rising from Oceanus in the east and plunging into it again in the west.
Homer mentions, in addition to the sun and moon, the Morning Star, the Evening Star, the Pleiades, the Hyades, Orion, the Great Bear (“which is also called by the name of the Wain”), Sirius, the late-setting Boötes (the ploughman driving the Wain), i.e. Arcturus, as it was first called by Hesiod. Of the Great Bear Homer says that it turns round on the same spot and watches Orion; it alone is without lot in Oceanus’s bath (i.e. it never sets). With regard to the last statement it is to be noted that some of the principal stars of the Great Bear do now set in the Mediterranean, e.g. in places further south than Rhodes (lat. 36°), γ, the hind foot, and η, the tip of the tail, and at Alexandria all the seven stars except α, the head. It might be supposed that here was a case of Homer “nodding”. But no; the old poet was perfectly right; the difference between the facts as observed by him and as seen by us respectively is due to the Precession of the Equinoxes, the gradual movement of the fixed stars themselves about the pole of the ecliptic, which was discovered by Hipparchus (second century B.C.). We know from the original writings of the Greek astronomers that in Eudoxus’s time (say 380 B.C.) the whole of the Great Bear remained always well above the horizon, while in the time of Proclus (say A.D. 460) the Great Bear “grazed” the horizon.
In Homer astronomical phenomena are only vaguely used for such purposes as fixing localities or marking times of day or night. Sometimes constellations are used in giving sailing directions, as when Calypso directs Odysseus to sail in such a way as always to keep the Great Bear on his left.