How did ancient sailors sail against the wind? Here is an answer.
“Every day a great number of ships gathered on each side to bring provisions, and no wind could blow without them having a favorable course from a certain direction,” Caesar later wrote in his book “The War civil”.
The reason for all this redundant planning had to do with a problem that has plagued Mediterranean sailors for at least 3,000 years. In summer, the prevailing westerly winds severely hampered the movement of sailing ships laden with crops and other cargo from the east to Rome.
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Yet the flow of food and supplies to the Italian peninsula continued unabated. Historians have wondered for decades how ancient sailors achieved this.
An Israeli researcher wanted an answer. So first he did what any academic could do: he studied wind patterns and ancient weather texts. And then he did something more unusual. He and a team of experts built a replica of a 5th century BC boat and sailed it across part of the Mediterranean to test his theory.
Researcher David Gal, a doctoral student at the University of Haifa, published the results of his study this summer in the Journal of Archaeological Method and Theory.
“We started with a trivial question: how did Roman ships visiting the Levant return to Rome?” Gal said. “It just looks like, ‘Oh, they turned them around and sailed the other way.’ However, a windward voyage was impractical in the type of ships they were using, so how did they accomplish these voyages?
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Gal believes these retired sailors took advantage of brief wind reversals to sail to Rome and other western destinations. Moreover, by examining Roman and Greek texts on weather, he discovered that these breeze cycles are virtually unchanged over the past three millennia.
Gal said sailors’ lives depended on anticipating weather conditions, so they knew when to start a voyage and when to find a safe port. They often waited days before catching the right wind to start or resume their journey.
“There’s an ancient story of two friends leaving and going in opposite directions,” Gal said. “The blessing they give each other is, ‘May the gods grant fair winds to both of us’, which is a contradiction. Waiting for favorable winds was a big part of ancient navigation.
To understand how sailors managed to make their way across the Mediterranean, Gal and other researchers undertook a two-step process. First, they built a replica of a typical ship that sailed the sea between Europe and Africa three millennia ago, which they named Maagan Mikhael II. Its design was based on a wreck discovered off the coast of Israel in 1983. Rigged with a square sail, the new version was built by a team of experts led by Yaacov Kahanov, professor emeritus in the Department of Maritime Civilizations of the University of Haifa. .
“It’s an exact replica of a 2,400-year-old ship,” Gal said. “We learned a lot sailing it, including the difficulties of sailing upwind.” They sailed from Israel to Cyprus with a crew of six in 74 hours in 2018.
The second phase of the study was to understand the weather. As well as reading 3,000-year-old texts, Gal reviewed modern records of winds and waves around the Mediterranean. It collected data points from 7,000 different locations, taken hourly over the past 15 years. He compared these results with the old data and made a startling discovery.
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“Wind and wave oscillations are the same as 3,000 years ago,” he said. “Once we could establish that modern winds are equal to ancient winds, we could use the data to analyze sail mobility. We were able to examine the routes taken by ships carrying grain from Alexandria to Egypt, and found that in July and August they first had to sail northeast to Turkey instead of west to Rome.
Gal found that ancient ships were able to locate brief westerly blowing breezes that typically occurred in the early morning and late evening. These light air currents would allow ships to sail for a short time to Rome. Once the winds died down, the crews dropped anchor and waited to sail away.
Gal cited the biblical example of the apostle Paul. The New Testament records how he was transported from the city of Caesarea in Judea to Rome to stand trial by Emperor Nero for sedition. The Acts of the Apostles record a long voyage involving several ships.
“It could take weeks to make the trip from the Levant to Rome,” Gal said. “The sailors expected a lot at that time.”
Using computers, Gal calculated all the numbers – old and new – to run cruise simulations. He uncovered hundreds of possible trade routes that ancient sailors might have taken to sail the eastern Mediterranean during the summer months when the winds were unfavorable.
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Modern sailors can tack into the wind by setting the sails at sharp angles. This was not feasible 2,400 years ago because the sails were repaired then.
Gal spent 20 years as a pilot in the Israeli Air Force before becoming interested in sailing and meteorology. He said the research offers new insight into the intricacies of sailing in ancient times and the impressive knowledge base of sailors who plied these waters.
“In the summer they had no choice but to crawl across the Mediterranean and then start moving very slowly west,” he said. “Coastal navigation was difficult and dangerous. You could sit for 10 days waiting for a favorable breeze. It took tremendous expertise to do what they were doing back then.