The Weight of Mystery

In the popular 1981 action film, Raiders of the Lost Ark, Indiana Jones battled Nazis seeking the lost Ark of the Covenant. As described in the Bible, the Ark was a gold-covered box of acacia wood with a lid of solid gold, built as a container for two stone tablets on which were written the Ten Commandments. It was carried ahead of the people during the days in the wilderness when the Hebrews were en-route from Egypt to Canaan. But when it wasn’t in-transit, it sat in the inner sanctum of the Tabernacle and, later, the Temple in Jerusalem.

A Seemingly Simple Question

The instructions for how the Ark was to be constructed are provided in Exodus 25:10-22. A few weeks ago I was reading a commentary on Exodus and, thinking about the slab of gold forming the lid and all the other gold used in its construction, I had a very simple question: How much would it have weighed? Could it have been easily carried by four men?

It seems like it should be easy to calculate an answer. We know the density of acacia wood (0.54 g/cm³) and gold (19.3 g/cm³). Exodus 25:10-22 provides dimensions for the Ark’s length (2.5 cubits), width and height (both 1.5 cubits). But how long is a cubit?

A cubit is the distance between elbow and fingertips and the definition varies in different cultures and time periods (anywhere from 17.5 to 20.8 inches). A commonly-cited value is 18 inches (45.7 cm).

My thinking is that the Hebrew artisans who built the Ark for Moses would have learned their craft in Egypt. We know the length of the ancient Egyptian cubit from measuring rods discovered in New Kingdom tombs that are roughly contemporary to the time the Exodus is supposed to have taken place. The Egyptian cubit is about 52.4 cm so I’ll use that as the base measurement. This gives me 131 cm (51.6”) for the length and 79 cm (31”) for the width and height.

I am now able to calculate the surface area but to calculate the volume I’ll need to know the thickness of the wooden walls and Exodus doesn’t provide that measurement. Neither does it tells us the thickness of the solid gold lid nor the dimensions of the cherubim atop the lid.

Scene from Raiders of the Lost Ark. You can actually purchase a kit (http://goldenarmor.com/arkhomepage/) that allows you to build a replica of the prop from the movie

Feast of the Assumptions

What have others come up with in estimating the missing dimensions? A simple Google search for “how heavy was the ark of the covenant” returned wildly varying answers.

WarrenMyers is one of the first results that pops up in Google, which is unfortunate because his assumptions are unsupported and his math is questionable. For example, he assumes the walls are 2” thick but calculates the wooden part of the Ark weighs only 25 lbs (based on Myers’ assumptions my math says the wood should weigh over 240 lbs). He estimates 104 lbs for the cherubim and guesses 1/32 inch (0.8 mm) for the thickness of the gold plating, eventually determining a total weight of 615 lbs.

Another of the top hits, JacquesGauvin uses some ridiculous assumptions. He assumes 3” thick walls, making the wood portion 413 lbs. His carrying poles are 6” diameter, more like fence posts. His cherubim are 1000 lbs. He guesses 0.125” (3.2 mm) for the thickness of the gold plating. His Ark finally weighs in at a whopping 4763 lbs. That’s more than twice the weight of all the gold Exodus 38:24 says was used in construction of the entire Tabernacle!

These two examples illustrate a couple of points: 1) unconstrained assumptions can vary wildly and 2) gold is the major determining factor in the weight. In Gauvin’s example, even if the weight of the acacia wood is reduced to almost nothing, you would still have an Ark weighing in excess of two tons due simply to the amount of gold used in his estimates.

Scientific Wild-Ass Guesses

A more thoughtful exercise is taken by ElihuSchatz. I found his Jewish Bible Quarterly article well after I had already started working through the issues on my own and was pleasantly surprised to see that Schatz had also identified gold as the key factor. Schatz’s Ark weighs in at 183 lbs mainly because his gold overlay is only 0.2 mm thick. But unlike the wild guesses of Myers and Gauvin, Schatz arrived at this thickness through deduction.

Exodus 38:24 tells us that 29 talents and 730 shekels of gold were used in the construction of the Tabernacle. This includes not only the Ark, but also an incense altar, table, lampstand, and the walls of the Tabernacle.A talent was 3000 shekels and archaeological evidence tells us a shekel weighed 11.3 g. In modern measures, 994 kg (2187 lbs) of gold were used for all the items in the Tabernacle.

Schatz writes (p. 116), “I calculated the total weight of the gold for all the vessels [in the tabernacle], and had to use a thickness for the gold overlay of 0.02 centimeters in order to approximate the value.” He cites the calculations made in his commentary (in Hebrew) on the book of Exodus, so I’m not able to see how he arrived at his conclusion but independently I had run some numbers on my own and arrived at the same figure. I originally was concerned that it might be too thin and would scrape off, but subsequent research told me that 0.02 cm (0.2 mm) is twice the thickness of the side of an aluminum can, so it seems that a gold overlay of that thickness would be durable.

I do have quibbles about some of Schatz’s other assumptions. For example, he estimates the walls of the Ark were 1.0 cm thick. This seems too flimsy and 2.0 cm would be more realistic. An article from the Metropolitan Museum of Art references (p. 130) an ancient Egyptian royal coffin from 2680 BCE “made of plywood, the six layers arranged with the grain running in alternate directions for strength and to prevent warping.” Each of the six layers was an eighth of an inch thick, giving a total thickness of ¾” (1.9 cm).

Also questionable is Schatz’s assertion that a 1-mm layer of gold for the cover “would have sufficient structural strength” (p. 117) to hold up his 25-kg (55 lb) cherubim. Gold has about the same elasticity of aluminum. A 1-mm piece of gold the size of a stick of chewing gum could be easily bent in your hands, so I have my doubts about its structural integrity. The inner coffin in King Tut’s tomb is made of solid gold with a thickness of 2.5-3.0 mm. My reasoning is that the ancient Egyptian goldsmiths knew what they were doing, so 3 mm seems a more realistic estimate for the thickness of the Ark’s cover.

On the bright side, I consider Schatz’s estimate of 25 kg for the two cherubim realistic. I base this on the fact that King Tut’s famous gold mask is 54 cm tall and 39 cm wide and weighs 10 kg. For comparison, the angels on the Raiders prop are 16.5” (42 cm) long and 8.75” (22 cm) tall. I think the cherubim may have been standing figures instead of crouching as in the angels from Raiders. The cherubim may also have been bigger than what the moviemakers had in mind. No one knows. But I think an estimate of 25 kg for the two cherubim puts us in the right neighborhood.

Multiple views of King Tut's gold death mask.

Putting it All Together

To arrive at an estimate for the weight of the Ark, I need to determine the weight of the acacia wood used to construct the chest, add the weight of the gold overlay, then the estimates for the solid-gold cover and cherubim. There’s also supposed to be a gold molding around the edges and rings to hold the carrying poles, but those comprise only a minor fraction of the total weight. Considering all the estimations and approximations, we can only hope to be in ballpark range for the total weight anyway.

The weight of the acacia wood using my preferred 2-cm thickness comes out to be 47 kg and the gold overlay of 0.2-mm thickness is 33 kg. The weight of the solid gold lid is 60 kg and the cherubim 25 kg. Almost half the weight is in the chest and the other half in its cover. The center of gravity would be around the point where the lid comes in contact with the chest.

The total weight using my estimations is 165 kg (362 lbs) and more than 70% of that weight (118 kg) comes from the gold. Four men could lift it but couldn’t be expected to carry it very far for very long.

Using a shorter cubit (such as the 18” cubit) dramatically reduces the estimate to 131 kg (289 lbs). Decreasing the thickness of the gold overlay to 0.1 mm further reduces the weight to 119 kg (261 lbs). Using 2.5 mm for the thickness of the cover marginally reduces the estimated weight to 111 kg (244 lbs).

As you can see, small changes in the variables can increase or decrease the estimated weight by 33% or more. You can come up with various reasons to tweak the numbers to get the weight of the Ark (and its contents) down to 180 lbs, and it might work if you only consider the Ark in isolation, but any of these tweaks will affect how much gold you end up using for all the Tabernacle items. Reducing the length of the cubit, for example, reduces the surface area of not only the Ark but all the other Tabernacle items and the amount of gold that would be needed to cover them.

Now that I have an idea how much the Ark could have weighed, in my next article I will discuss some observations I drew from this analysis and examine the question as to whether the Ark ever existed at all.

What is Gopher Wood?

In northern Kentucky, the Creation Museum is building a full-size replica of Noah’s Ark, based on the specifications provided in Genesis 6:14-16:

Make yourself an ark of gopher wood; make rooms in the ark, and cover it inside and out with pitch. This is how you are to make it: the length of the ark three hundred cubits, its breadth fifty cubits, and its height thirty cubits. Make a roof for the ark, and finish it to a cubit above; and set the door of the ark in its side; make it with lower, second, and third decks. (RSV)

There’s not a whole lot of detail and it allows plenty of room for imagination. The Creation Museum ended up with a vaguely Egyptian-looking design. The Bible doesn’t define the length of a cubit but it is the length from the elbow to the tip of the fingers. If the standard measure is 18 inches, the dimensions of the ark would be 450 x 75 x 45 feet. The Creation Museum chose an Egyptian cubit of 20.4 inches, so that makes their Ark 510 feet long. By contrast, the Titanic was 850 feet long, but was made of steel. Noah’s Ark would have been bigger than any wooden ship that has ever been constructed.

“Entry of the Animals” to Noah’s Ark by Athanasius Kircher (1602-1680)

As you can see, the biblical description leaves a lot of wriggle room. And the dimensions and the description of the door and three decks are the clearest parts. The rest of the passage uses some rare words (that I have emphasized in bold), the meanings of which are much debated.

The Hebrew word translated “ark” is tebah. It is used many times in Genesis 6-9, but outside of the flood narrative, it only occurs in Exodus 2:3, 5 to describe the basket in which baby Moses was placed. (The word translated “ark” in Ark of the Covenant is a completely different Hebrew word.) Tebah is a loan word from the Egyptian language to describe a box or chest. The Vulgate translates it as arca, from which we get the word “ark.” To be consistent, the word should be translated as “box” in both Genesis and Exodus. While tebah does not mean a ship, functionally it serves as a lifeboat in both cases.

Next up, the ark is to be constructed of “gopher wood.” What the heck is gopher wood? “Gopher” is a transliteration of the Hebrew word goper and no one knows for sure what it means, except that it has nothing to do with a burrowing rodent. Many English versions of the Bible (KJV, RSV, NJPS, NAB, NABRE) don’t try to translate it. A few others (NEB, NIV, NRSV) translate it as “cypress” wood, but that is just a guess. Hebrew does have a word for cypress, so if that’s what the Priestly writer wanted to say, he could have used that word.

The problem is that goper only appears here in the entire OT. Such a word is called a hapax legomenon (meaning “said once” in Greek). The most reliable way to translate a word is from its context, but how do you do that when you only have one context in which it occurs? Well, we can look to see how it was translated in ancient versions of the OT. The LXX translates it as “squared timber” and the Vg as “smoothed wood.” Both translations are describing not a particular type of wood, but wood prepared in some certain fashion. Because the LXX and Vg were closer to the time of the biblical writings, they may reflect a knowledge of the word no longer available to us or they may have simply guessed at the meaning of the word.

The Hebrew word translated “rooms” in many English versions (KJV, RSV, NRSV, NAB, NABRE, NJPS, NIV) is qinnim. This word is the plural of qen (“nest”) which elsewhere in the OT appears only in the singular. Since the original Hebrew only contained the consonants with the vowels added later, some scholars have proposed a different set of vowels that would yield the word qanim, “reeds” (NEB, NJB). This would yield a neat parallelism in the translation: “Make yourself an ark of gopher wood, with reeds make the ark.” The implication being that the ark would be constructed of both wood and reeds, perhaps with the reeds helping to seal the gaps between the wooden beams. Reeds were also used in the construction of the boats in the other flood myths like Atrahasis and Gilgamesh, so its use here could reflect an influence from those tales.

The Hebrew word (koper) translated “pitch” only appears here in the OT. It is not a hapax legomenon in the strict sense because the word is used twice in the verse, as verb and noun: “and pitch it on inside and out with pitch.” Koper is only one letter different from the hapax goper, so there is a bit of wordplay here. Pitch, tar, or asphalt are petroleum-based products. This poses something of a problem for Young Earth Creationists because they insist that all petroleum products were formed during the Flood. So where did a pre-Flood Noah get his pitch?

V. 16 gives us another hapax in tzohar, which the Vg translates as fenestra (“window”). Modern translators turn to a similar Arabic word which means the back of a hand or a human back. The logical conclusion is that tzohar was used to refer to the top or roof of the ark. The next part of the verse (“and finish it to one cubit from above”) is somewhat incomprehensible, so it is not clear if a gap between the roof and the sides is being discussed or an overhang of the roof. 

What are we to make of all the rare words? One possible explanation is that those words were in the tradition that the Priestly writer received. Just like if we were retelling the nativity story, we might say something like “the infant Jesus was wrapped in swaddling clothes and laid to rest in a manger.” “Swaddling clothes” and “manger” are not everyday words for most people but those words from the King James translation are such a part of the tradition that we would repeat them as-is. Something similar may be happening here with words like “gopher wood”.

Between the vague specifications and the rare words with contested or unknown meanings, we can only have a general idea of what Noah’s Ark was supposed to have looked like. But if you want to see the Creation Museum’s version, The Ark Encounter is scheduled for a grand opening in the summer of 2016.