Thread: Southern Cross
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Old 11-07-2020, 02:46 PM
precessed (John welch)
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Southern Cross

Hullo from a newbie

I'm interested in medieval history and am looking for any unexpected ideas as leads for inquiry. Ptolemy in 2nd century drew the Southern Cross as the rear feet of Centaur and pointers as front feet. At latitude 30deg N the Crux was not of great magnitude and with precession went south from Alexandria Egypt about 5-8 deg by 1300. In 1304-1321 the poet Dante wrote "Divine Comedy" about a boat going to hell in Antarctica. He was an ambassador to Venice which imported Indonesian spice through Alexandria and in those days Java had 300ft ships ( James Cook crossed the Antarctic Circle in a 110ft ship) and Indonesia traded with Madagascar Africa from 8th cent. Europeans didn't reach Java until 1505 so Dante possibly learned about Antarctica 2 centuries earlier from Arabs in Egypt who had sailed to Indonesia.

Ptolemy's faint Crux became Dante's "flames of heaven" :Goder pareva ’l ciel di lor fiammelle: oh settentrional vedovo sito, poi che privato se’ di mirar quelle! (Purg. 1.22-27)."Heaven appeared to revel in their flames: o northern hemisphere, because you were denied that sight, you are a widower!"This must be from a later date when someone travelled to the Tropics. Maybe Arabs or Marco Polo saw the Cross as a full constellation . However Dante wrote Tutte le stelle gią de l ' altro polo vedea la notte , e'l nostro tanto basso, che non surgėa fuor del marin suolo. "night showed stars of the other pole and ours was so low it didn't rise above the sea." (Inferno 26).

Polaris was visible about lat. 16deg S in Ptolemy's day , the centre of Madagascar and visible about 6deg S in Dante's time. Kochab was near polar and is about 16 degrees today.

Dante also wrote of the empty southern seas and a boat reaching a mountain at the south pole , which contrasts with the Arctic pole. A question is : at low elevations is the Cross so dim that it does not have the visual strength to be called a constellation? Would Polaris be invisible south from lat. 6deg S in 1300? Do you have comments on other aspects which I could follow up?

Last edited by precessed; 11-07-2020 at 07:30 PM.
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