Ah, the joys of naivety...
Yesterday I wrote about walking to Antiochia, for our noble Embassadors.
Today, I have made some calculations if they took a ship at Constantinopolis. Silly me.
There are about 870 nautical miles (about 1000 miles) from Constantinopolis to the harbor of Antiochia, the town of Seleucia Pieria. A fast merchant ship, could maintain a sustained speed of 4 or 5 knots, and with good, favorable wind, reach 6 knots, while courier ships, basically light galleys, could maintain much higher speeds.
Anyway, considering my familiarity with Mediterranean navigation after writing the adventures of a fleet of 200 Greek trierei (triremes) for The Libyan, I feel confident about the following numbers:
Let's consider our Embassy arrives in Constantinopolis and is assigned or simply gets a fast merchant ship (which is somewhat logical, as an unwanted, unsolicited Embassy wouldn't be favored by a military vessel).
Here's the rough travel plan, in yellow the sea part, in blue the land path, so you can compare. The original picture was taken by the NASA and it's used here with implicit permission. Visit the Wikipedia entry for the original picture if you want.
The first 200 miles are used to get through the Strait of Dardanelos and to enter into the Adriatic Sea. Maintained speed for 10 hours a day, considering the chaotic currents, etc, 4 knots. Partial time: 5 days.
Next we get favorable, North winds that push us in open sea (as we aren't really merchanting anything, we don't have to go to harbors, and so on, except for water or food, which we are carrying in good quantities anyway), we sail the next 400 miles until we get close to Chiprus at an average speed of 5.8 knots for 11 hours per day (even when we could also sail by night, but it's always dangerous!). Partial time: about 4.5 days.
Finally, we move at a very comfortable speed of 5 knots bording the coast of Chiprus and directly until Seleucia Piaria, 250 miles, 11 hours per day. Partial time: 4.5 days.
Total time from Constantinopolis to Seleucia Piaria: 14 days.
Even considering delays, harbor stops, and the like: 20 days.
Definitely, we are going by sea!
Now, how will we return? Will Flavius Iulius Valens Augustus allow us to use the cursus publicus? Will we return by galley (remember, opposing winds this time) and then rush through Thracia, Moesia, and Dacia?