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.