In it, Hesiod gives us a picture of early Greek astronomy where celestial phenomena are treated from a practical point of view. Like the Mesopotamian farmers of a millennium or two earlier, his interest is in the stars as useful indicators of the course of the agricultural year. Throughout the poem, the various characteristic phenomena surrounding stars or groups of stars are taken to be indicators of certain agricultural tasks to be performed (the data are correct for Greece around 700 BCE):
| Object | Phenomenon | Time | Task | Lines |
|---|---|---|---|---|
| Pleiades | Heliacal rising | Early May | Harvest | 383–71 |
| Pleiades | Heliacal setting | Late March | Sharpening | 383–71 |
| Pleiades/Hyades | Cosmical setting | Early November | Ploughing | 383–71, 614–72 |
| Sirius | Culmination | Late September | Wood felling | 414–223 |
| Arcturus | Acronychal rising | Late February | Vine pruning | 564–704 |
| Orion | Heliacal rising | Early July | Winnowing | 597–95 |
| Arcturus | Heliacal rising | Mid September | Vintage | 609–116 |
Aside from these practical considerations we also learn (586–7)7 that during the time of the heliacal rising of Sirius (late July) women are at their most lustful and men at their least virile, a state of affairs which seems to encapsulate Hesiod’s somewhat gloomy view of life.
This outlook is reinforced by other advice (479–82):8
But if you plough the good ground at the solstice,With regard to the timing of astronomical phenomena Hesiod also notes (as mentioned above) the acronychal rising of Arcturus two months after the winter solstice (564‒7):4
You will reap sitting, grasping a thin crop in your hand,
Binding the sheaves awry, dust-covered, not glad at all,
And you will bring it home in a basket, and few will admire you.
When sixty wintry days after the solstice,Since the winter solstice in 700 BCE occurred on 27th December, this would put the acronychal rising of Arcturus on 24th February by Hesiod's (inclusive) reckoning, and in fact this is correct to within a day or two. He also states that Pleiades are invisible for forty days and nights (385–6)1 which means from their heliacal setting at the end of March to their heliacal rising in early May, and again this is correct.
Zeus has finished his work, then the star Arcturus
Leaves the holy stream of Okeanos,
And first rises brilliant at dusk.
After him the shrilly wailing daughter of Pandion,
The swallow, appears to men when spring is just beginning.
Before she comes, prune the vines, for it is best so.
Rather timidly, he recommends a short sailing season beginning in early autumn rather then the more usual early summer (663‒8):9
Fifty days after the solstice,Hesiod also has something to say about the size of the cosmos. In the Theogony (720‒25)10 we have the following interesting passage:
When the season of tiring heat has ended,
Then is the right time for men to go sailing, and you will not wreck
Your ship, nor will the sea drown the sailors,
Unless Poseidon, the Earth-Shaker, intends it,
Or Zeus, king of the deathless gods, wish to destroy them.
As far beneath the earth as heaven is above earth;Now this is clearly meant to create a poetic impression of the size of the universe as then conceived and is not supposed to be taken literally. However, somewhat mischievously, we can use this to calculate the size of Hesiod's cosmos.
So far is it from earth to Tartaros.
For a bronze anvil falling down from heaven nine days and nights
Would reach the earth upon the tenth; and again,
A bronze anvil falling from earth nine days and nights
Would reach Tartaros upon the tenth.
Hesiod states that the anvil will take 9 complete days to fall to Earth from Heaven, that is 216 hours (= 9 × 24) which is 777,600 seconds. In this time a body will accelerate from a state of rest under the influence of gravity at a rate of 9.81 metres per second per second to reach a terminal velocity of 7,628,256 ( = 9.81 × 777,600) metres per second (ignoring air resistance) which is 27,461,722 kilometres per hour. Furthermore, in this time it will have traversed a distance of 2,965,865,932,800 metres (= ½ × 9.81 × 7776002) or nearly 3 billion kilometres.
However, we really do need to factor in air resistance since Hesiod can have had no notion of empty space (Homer, for example, tells us that aer and aither filled the space between Earth and Heaven), and in this case the fall will be slower, much slower, and so the distance traversed will be considerably less. We'll make a few assumptions: that the acceleration due to gravity is the constant g = 9.81 m s–2; that the cross sectional area of the anvil is given by A = 0.16 m2 (equivalent to a 40 cm cube); that the mean density of the air from the top of the atmosphere to sea level is given by ρ = 0.6 kg m–3; that the mass of the anvil is given by m = 512 kg (roughly equivalent to a 40 cm cube of bronze); that the drag coefficient is given by Cd = 0.8 (roughly equivalent to an angled cube). Using these assunptions in the formula for terminal velocity, which is given by:
Vt = ( 2 mg / ρACd ) ½and, further assuming that the fall is vertical and that the terminal velocity is reached quickly and thereafter remains constant, we arrive at a figure of 362 metres per second. Consequently, the length of the fall to Earth from Heaven will be 281,229,014 metres ( = 362 × 776,200) or roughly 280,000 km. Since this is half the distance from Heaven to Tartaros, the effective size of Hesiod's cosmos is thus 560,000 km from top to bottom, or a little over two thirds the size of the Earth–Moon system.
Lunar crater: Hesiodus (diameter 43 km).
NOTES
1. πληιάδων Ἀτλαγενέων ἐπιτελλομενάων / ἄρχεσθ᾽ ἀμήτου, ἀρότοιο δὲ δυσομενάων. αἳ δή τοι νύκτας τε καὶ ἤματα τεσσαράκοντα / κεκρύφαται, αὖτις δὲ περιπλομένου ἐνιαυτοῦ / φαίνονται τὰ πρῶτα χαρασσομένοιο σιδήρου.
2. δῶρα Διωνύσου πολυγηθέος. αὐτὰρ ἐπὴν δὴ / Πληιάδες θ᾽ Ὑάδες τε τό τε σθένος Ὠαρίωνος / δύνωσιν, τότ᾽ ἔπειτ᾽ ἀρότου μεμνημένος εἶναι / ὡραίου: πλειὼν δὲ κατὰ χθονὸς ἄρμενος εἶσιν.
3. ἦμος δὴ λήγει μένος ὀξέος ἠελίοιο / καύματος ἰδαλίμου, μετοπωρινὸν ὀμβρήσαντος / Ζηνὸς ἐρισθενέος, μετὰ δὲ τρέπεται βρότεος χρὼς / πολλὸν ἐλαφρότερος: δὴ γὰρ τότε Σείριος ἀστὴρ / βαιὸν ὑπὲρ κεφαλῆς κηριτρεφέων ἀνθρώπων / ἔρχεται ἠμάτιος, πλεῖον δέ τε νυκτὸς ἐπαυρεῖ: / τῆμος ἀδηκτοτάτη πέλεται τμηθεῖσα σιδήρῳ / ὕλη, φύλλα δ᾽ ἔραζε χέει, πτόρθοιό τε λήγει: / τῆμος ἄρ᾽ ὑλοτομεῖν μεμνημένος ὥρια ἔργα.
4. εὖτ᾽ ἂν δ᾽ ἑξήκοντα μετὰ τροπὰς ἠελίοιο / χειμέρι᾽ ἐκτελέσῃ Ζεὺς ἤματα, δή ῥα τότ᾽ ἀστὴρ / Ἀρκτοῦρος προλιπὼν ἱερὸν ῥόον Ὠκεανοῖο / πρῶτον παμφαίνων ἐπιτέλλεται ἀκροκνέφαιος. / τὸν δὲ μέτ᾽ ὀρθογόη Πανδιονὶς ὦρτο χελιδὼν / ἐς φάος ἀνθρώποις, ἔαρος νέον ἱσταμένοιο. / τὴν φθάμενος οἴνας περταμνέμεν: ὣς γὰρ ἄμεινον.
5. δμωσὶ δ᾽ ἐποτρύνειν Δημήτερος ἱερὸν ἀκτὴν / δινέμεν, εὖτ᾽ ἂν πρῶτα φανῇ σθένος Ὠαρίωνος, / χώρῳ ἐν εὐαέι καὶ ἐυτροχάλῳ ἐν ἀλωῇ.
6. εὖτ᾽ ἂν δ᾽ Ὠαρίων καὶ Σείριος ἐς μέσον ἔλθῃ / οὐρανόν, Ἀρκτοῦρον δ᾽ ἐσίδῃ ῥοδοδάκτυλος Ηώς, / ὦ Πέρση, τότε πάντας ἀποδρέπεν οἴκαδε βότρυς:
7. μαχλόταται δὲ γυναῖκες, ἀφαυρότατοι δέ τοι ἄνδρες / εἰσίν, ἐπεὶ κεφαλὴν καὶ γούνατα Σείριος ἄζει,
8. εἰ δέ κεν ἠελίοιο τροπῇς ἀρόῳς χθόνα δῖαν, / ἥμενος ἀμήσεις ὀλίγον περὶ χειρὸς ἐέργων, / ἀντία δεσμεύων κεκονιμένος, οὐ μάλα χαίρων, / οἴσεις δ᾽ ἐν φορμῷ: παῦροι δέ σε θηήσονται.
9. ἤματα πεντήκοντα μετὰ τροπὰς ἠελίοιο, / ἐς τέλος ἐλθόντος θέρεος καματώδεος ὥρης, / ὡραῖος πέλεται θνητοῖς πλόος: οὔτε κε νῆα / καυάξαις οὔτ᾽ ἄνδρας ἀποφθείσειε θάλασσα, / εἰ δὴ μὴ πρόφρων γε Ποσειδάων ἐνοσίχθων / ἢ Ζεὺς ἀθανάτων βασιλεὺς ἐθέλῃσιν ὀλέσσαι:
10. τόσσον ἔνερθ᾽ ὑπὸ γῆς, ὅσον οὐρανός ἐστ᾽ ἀπὸ γαίης: / τόσσον γάρ τ᾽ ἀπὸ γῆς ἐς Τάρταρον ἠερόεντα. / ἐννέα γὰρ νύκτας τε καὶ ἤματα χάλκεος ἄκμων / οὐρανόθεν κατιὼν δεκάτῃ κ᾽ ἐς γαῖαν ἵκοιτο: / ἐννέα δ᾽ αὖ νύκτας τε καὶ ἤματα χάλκεος ἄκμων / ἐκ γαίης κατιὼν δεκάτῃ κ᾽ ἐς Τάρταρον ἵκοι.
Last updated 14/05/20
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