Diurnal Motion in the Southern Hemisphere

Conflicting Reports

Around 450 B.C., Herodotos wrote in Book IV of his Histories that Phoenician sailors were commissioned by the Egyptian pharoah Neco to circumnavigate the continent of Africa. The ship set out from the Red Sea...

"with orders to sail round and return to Egypt and the Mediterranean by way of the Pillars of Hercules [Straits of Gibraltar]. The Phoenicians sailed from the Red Sea into the southern [Indian] ocean, and every autumn put in where they were on the Libyan [African] coast, sowed a patch of ground, and waited for next year's harvest. Then, having got in their grain, they put to sea again, and after two full years rounded the Pillars of Hercules in the course of the third, and returned to Egypt. These men made a statement which I do not myself believe, though others may, to the effect that as they sailed on a westerly course round the southern end of Libya [Africa], they had the sun on their right--to northward of them. This is how Libya [Africa] was first discovered to be surrounded by sea...."

From the northern hemisphere, as we have seen, the Sun appears to rise in the east, or on one's left, facing south, and Herodotos could not believe that it would appear otherwise from southern latitudes. Was he right?

Samuel Taylor Coleridge expressed no such hesitations, however, when he described, in the Rime of the Ancient Mariner, Part II, how the Sun appeared to move in the sky after a storm blasted the Mariner's ship into far southern seas:

"The Sun now rose upon the right:
Out of the sea came he,
Still hid in mist, and on the left
Went down into the sea..."

Who was correct: Herodotos? Or Coleridge and the Phoenicians?

1. Set the planetarium to display the stars of 35 degrees south latitude (the latitude of Buenos Aires, Argentina; Santiago, Chile; and Sydney, Australia, for example).

   The south celestial pole will appear 35 degrees above the southern horizon.

   There is no counterpart of Polaris, no southern star that nearly coincides with the location of the south celestial pole.

   

   

   Star chart created with Voyager II Software for Macintosh, published by Carina Software. This is just a taste of what Voyager can do! For info on Voyager II software, call Carina Software at (510) 355-1266, write them at 12919 Alcosta Blvd Suite #7, San Ramon, CA 94583, or visit Carina Software's home page and check out Voyager II for yourself.

   

2. Face northward, toward the celestial equator (the path of the Sun on an equinox). Then find Orion.
   • How does Orion appear unusual? Are constellation patterns inverted?
   • Which is higher, Rigel or Bellatrix?

   
   
   

   Star chart created with Voyager II Software for Macintosh, published by Carina Software. This is just a taste of what Voyager can do! For info on Voyager II software, call Carina Software at (510) 355-1266, write them at 12919 Alcosta Blvd Suite #7, San Ramon, CA 94583, or visit Carina Software's home page and check out Voyager II for yourself.

   

3. Watch the constellation Orion as it travels through its daily motion.
   • Does Orion still rise in the east? (Examine chart below.)
   • Does Orion still set in the west?
   • Does the sky seem to turn the other way around?
   • Which direction does the westward diurnal motion go, left or right?

   
   
   

   Star chart created with Voyager II Software for Macintosh, published by Carina Software. This is just a taste of what Voyager can do! For info on Voyager II software, call Carina Software at (510) 355-1266, write them at 12919 Alcosta Blvd Suite #7, San Ramon, CA 94583, or visit Carina Software's home page and check out Voyager II for yourself.

1. Seasonal reversal:

   	Scorpius high	Orion high	Sun high	Sun low
   Northern observers	June	December	June	December
   Southern observers	December	June	December	June