Noah's Ark: Sea Trials

by Brian Dunning
October 11, 2011

Today we're going to have a bit of fun and shine the light of science on an ancient story. It is said that a gigantic wooden ship once carried a family and two of every kind of animal to safety, when the entire world was flooded. Noah's Ark sailed for five months, then rested aground, sheltering its multitudinous crew for more than a year.

The elephant in the room here is that it's virtually impossible to do an episode on this subject without having it sound like an attack on Christianity. I argue that it's not at all; the majority of Christians, when you combine the numerous denominations, don't insist that the Noah story is a literal true account. And, as has been pointed out many times, the Bible is hardly the only place where various versions of the Noah story are found. The most famous parallel, of course, is the Epic of Gilgamesh, wherein one of the many Babylonian gods charged the man Utnapishtim to build an ark, in a story that parallels Noah's in all the major details and most of the minor ones. It is perfectly plausible that all such stories stem from an actual event, the details of which are lost to history, but that might well account for the stories we have today of a boat and a flood. But regardless, in this episode I'm not going to address any issues of faith, but only of science. We want to look at the engineering plausibility of Noah's great ship.

Noah's Ark was a great rectangular box of gopherwood, or perhaps some combination of other woods colloquially referred to as gopherwood. Its dimensions are given as 137 meters long, 23 meters wide, and 14 meters high. This is very, very big; it would have been the longest wooden ship ever built. These dimensions rank it as one of history's greatest engineering achievements; but they also mark the start of our sea trials, our test of whether or not it's possible for this ship to have ever sailed, or indeed, been built at all.

Would it have been possible to find enough material to build Noah's Ark? When another early supership was built, the Great Michael (completed in Scotland in 1511) it was said to have consumed "all the woods of Fife". Fife was a county in Scotland famous for its shipbuilding. The Great Michael's timber had to be purchased and imported not only from other parts of Scotland, but also from France, the Baltic Sea, and from a large number of cargo ships from Norway. Yet at 73 meters, she was only about half the length of Noah's Ark. Clearly a ship twice the length of the Great Michael, and larger in all other dimensions, would have required many times as much timber. It's never been clearly stated exactly where Noah's Ark is said to have been built, but it would have been somewhere in Mesopotamia, probably along either the Tigris or Euphrates rivers. This area is now Iraq, which has never been known for its abundance of shipbuilding timber.

In 2003, a doctoral candidate at the Georgia Institute of Technology, Jose Solis, created a proposal to build the Ark for Noah based on sound naval architecture. He proposed a dead weight — the weight of the wooden structure alone minus cargo and ballast — as 3,676 tons. Fully loaded, it would have displaced 13,000 tons, as compared to the Great Michael's 1,000 that consumed "all the wood of Fife". Where would all that wood have come from? In his proposal, Solis simply skipped this detail, and assumed the wood was commercially available at a cost of $16,472,040 in 2003 dollars. Tens of thousands of massive timber-quality trees would have to have been imported into the middle of what's now Iraq. Did Noah have the resources to import from France, Norway, or anywhere else?

But if the Ark did get built, it would be necessary to overcome its extraordinary fragility. If you pick up a toy Hot Wheels car, you can squeeze it as hard as you want but you can't break it. However, if you were a giant and reached down to pick up a normal passenger car, your fingers would crush it before creating sufficient friction to lift it. If you even lifted it by one corner, you would warp its structure noticeably. When we extend this to even larger vessels, their fragility is magnified. Recall that when the Titanic sank, that massive steel structure tore completely in half simply because one end was heavier than the other. Just that difference in weight was sufficient to tear open many decks of reinforced steel that had been engineered to the day's toughest standards. Were Titanic a wooden box instead of rigid steel, you (as a giant) could destroy it just by swishing your finger in the water next to it.

Allow me to explain. What's known as the square-cube law is pretty familiar: increase an object's dimensions, and its surface area increases by the square of the multiplier, and its weight increases by the cube of the multiplier. But one extension of this law is less familiar. When we scale up an object — take a wooden structural beam as an example — the strength of the beam does not increase as fast as its weight. Applied mechanics and material sciences give us all the tools we need to compute this. In summary, the tensile strength of a beam is a function of its moment and its section modulus. No need to go into the complicated details here — you can look up beam theory on Wikipedia if you want to learn the equations. Scale up a simple wooden beam large enough, the weight will exceed its strength, and it will break from its own weight alone. Scaled up to the immense size of Noah's Ark, a stout wooden box would be unspeakably fragile.

If there was even the gentlest of currents, sufficient pressure would be put on the hull to open its seams. Currents are not a complete, perfectly even flow. They consist of eddies and slow-moving turbulence. This puts uneven pressure on the hull, and Noah's Ark would bend with those eddies like a snake. Even if the water itself was perfectly still, wind would expose the flat-sided Ark's tremendous windage, exerting a shearing force that might well crumple it.

Whether a wooden ship the size of Noah's Ark could be made seaworthy is in grave doubt. At 137 meters (450 feet), Noah's Ark would be the largest wooden vessel ever confirmed to have been built. In recorded history, some dozen or so wooden ships have been constructed over 90 meters; few have been successful. Even so, these wooden ships had a great advantage over Noah's Ark: their curved hull shapes. Stress loads are distributed much more efficiently over three dimensionally curved surfaces than they are over flat surfaces. But even with this advantage, real-world large wooden ships have had severe problems. The sailing ships the 100 meter Wyoming (sunk in 1924) and 99 meter Santiago (sunk in 1918) were so large that they flexed in the water, opening up seams in the hull and leaking. The 102 meter British warships HMS Orlando and HMS Mersey had such bad structural problems that they were scrapped in 1871 and 1875 after only a few years in service. Most of the largest wooden ships were, like Noah's Ark, unpowered barges. Yet even those built in modern times, such as the 103 meter Pretoria in 1901, required substantial amounts of steel reinforcement; and even then needed steam-powered pumps to fight the constant flex-induced leaking.

Even in the world of legend, only two other ships are said to have approached the size claimed for Noah's Ark. One was the Greek trireme Tessarakonteres at 127 meters, the length and existence of which is known only by the accounts of Plutarch and Athenaeus. Plutarch said of her:

But this ship was merely for show; and since she differed little from a stationary edifice on land, being meant for exhibition and not for use, she was moved only with difficulty and danger.

The other example is the largest of the Chinese treasure ships built by the admiral Zheng He in the 15th century, matching Noah's 137 meters, but only in the highest estimates. Many believe the biggest ships Zheng took with him on his seven voyages were no bigger than half that size, and moreover, that they remained behind in rivers and were not suitably seaworthy for ocean travels.

The long and the short of it — no pun intended — is that there's no precedent for a wooden ship the size of Noah's Ark being seaworthy, and plenty of naval engineering experience telling us that it wouldn't be expected to work. Even if pumps had been installed and all hands worked round the clock pumping, the Ark certainly would have leaked catastrophically, filled with water, and capsized.

There's another elephant in the room, too, that is necessary to address. Many of the problems with the Noah story are often answered, by those who regard it as a literal true account, with a special pleading. A special pleading is when any question is answered with "It was done by a higher power that you and I are not qualified to understand or question." Obviously, every point that science might raise regarding the Noah story can be fully answered with a special pleading. Superman, Underdog, and The Jetsons can shown to be literal true accounts if we allow special pleadings to be admissible. If the special pleading of divine intervention did indeed come into play during the Great Flood, then it was the most flagrant Rube Goldberg solution I've ever heard of. If divine intervention was needed to give Noah knowledge of how to build the Ark, or to provide the wood for its construction; then why not just provide an already-completed ark? Why bring the animals on board to be fed for a year or more, when divine intervention could have provided them an island? For that matter, why have the entire flood at all, when divine intervention could have simply struck down the evil humans with a plague? Why construct this most elaborate of all disaster and survival scenarios, some part of which was dependent on divine intervention; when divine intervention could have easily made the entire ordeal unnecessary? Special pleadings dismiss the true sciences that have allowed us to build real ships and conquer the world. Looking at the reality of what's possible and how things are done is always more interesting than imagining what's possible when anything is possible.

By Brian Dunning
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