How did ancient seafarers sail against the wind? Here’s an answer.

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In the year 48 BC BC Julius Caesar and Pompey the Great were locked in a desperate battle. The two generals led vast armies against each other in a civil war to decide the fate of the Roman Republic.

At Dyrrhachium in present-day Albania, Caesar attacked Pompey’s supply base on the Adriatic coast. Due to the vagaries of the wind, Caesar sent supply ships to several destinations in the Mediterranean to ensure his own troops could be fed and equipped for the coming campaign.

“For every day a great number of ships were assembling from every direction bringing up provisions, and no wind could blow unless they had a favorable course from some direction,” Caesar later wrote in his book The Civil War.

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 the summer, the prevailing westerly winds severely hampered the movement of sailing ships laden with grain and other goods from the east back to Rome.

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However, the influx of food and supplies into the Italian peninsula continued unabated. Historians have wondered for decades how ancient seafarers made it.

An Israeli researcher wanted an answer. So first he did what any academic would do: study wind patterns and ancient texts about the weather. And then he did something more unusual. He and a team of experts built a replica of a boat from the 5th century BC. and sailed it across part of the Mediterranean Sea to test his theory.

Researcher David Gal, a PhD student at the University of Haifa, published the results of his study this summer in the Journal of Archaeological Method and Theory.

“We began with a trivial question: How did Roman ships visiting the Levant return to Rome?” said Gal. “You would just say, ‘Oh, they flipped her and sailed the other way.’ However, sailing upwind was not practical with the type of ships that used them. So how did you manage those trips?”

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Gal believes these aging sailors took advantage of short shifts in the wind to sail to Rome and other western destinations. Furthermore, in examining Roman and Greek texts on weather, he discovered that these wind cycles have remained virtually unchanged for the past three millennia.

Gal said seafarers’ lives depended on anticipating weather patterns so they knew when to start a voyage and when to find safe haven. They often waited days before catching the right winds to begin or continue the journey.

“There’s an old tale of two friends who set off and went in opposite directions,” Gal said. “The blessing they give each other is, ‘May the gods grant us both favorable winds,’ which is a contradiction. Waiting for favorable winds was a big part of ancient seafaring.”

To understand how seafarers managed to cross the Mediterranean Sea, Gal and other researchers undertook a two-step process. First they built and named a replica of a typical boat that sailed the seas between Europe and Africa three millennia ago Ma’agan Mikhail II. Its design was based on a shipwreck discovered off the coast of Israel in 1983. The square-rigged new version was built by a team of experts led by Yaacov Kahanov, Professor Emeritus at the Department of Maritime Civilizations at the University of Haifa.

“It’s an exact replica of a 2,400-year-old ship,” Gal said. “We learned a lot from sailing, including the difficulties of sailing upwind.” They sailed from Israel to Cyprus in 74 hours in 2018 with a crew of six.

The second phase of the study was about understanding the weather. In addition to reading 3,000-year-old texts, Gal also reviewed modern records of winds and waves around the Mediterranean. It has collected hourly data points from 7,000 different locations for the past 15 years. He compared these findings with the old data and made a surprising discovery.

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“The wind and wave vibrations are the same as they were 3,000 years ago,” he said. “Once we could determine that modern winds corresponded to ancient winds, we could use the data to analyze sail mobility. We were able to look at the routes taken by ships carrying grain from Alexandria in Egypt and found that in July and August they had to sail northeast towards Turkey first, rather than west towards Rome.”

Gal found that old ships were able to locate short winds from the west, typically in the early morning and late evening. These light air currents would allow the ships to sail to Rome for a short time. As soon as the wind died down, the crews dropped anchor and waited before starting again.

Gal quoted the biblical example of Paul the apostle. The New Testament tells how he was transported from the city of Caesarea in Judea to Rome to be tried by Emperor Nero for sedition. Acts tells of a lengthy voyage involving several ships.

“The journey from the Levant to Rome could take weeks,” Gal said. “Back then, seafarers waited a lot.”

Using computers, Gal processed all the numbers – old and new – to run cruise simulations. He uncovered hundreds of possible trade routes that ancient navigators might have used to cross the eastern Mediterranean during the summer months when the winds were unfavorable.

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Modern sailors can tack against the wind by setting the sails at acute angles. This was not feasible 2,400 years ago because sails were attached at the time.

Gal spent 20 years as a pilot in the Israel Air Force before turning to sailing and meteorology. He said this research offers new insights into the complexities of sailing in ancient times and the impressive knowledge base of the sailors who have plied these waters.

“In the summer they had no choice but to crawl across the Mediterranean Sea and then move west very slowly,” he said. “Coastal sailing was difficult and dangerous. You could sit 10 days waiting for a favorable breeze. It took tremendous expertise to do what they were doing back then.”

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