Just how big IS a cubit?

{Don’t take this seriously…it’s just an exercise in how many assumptions have to be made for one story to be true}

This week, I saw that a Texas Congressman cited a story of a flood as an example of non-anthropogenic induced climate change and recalled something I was working on about  20 years ago and set aside. You’ll see why I set it aside in a moment.

I grew up with the understanding that a cubit was about 18 inches, or the length of the forearm from the elbow to the middle finger tip. Now, I’ve come to believe that those estimates are far, far short of the actual length. Indulge me, I respectfully request, as I take a wild stab at determining the length of the cubit…all in good fun…

Repeat: this is just for fun!

Per one popular accounting using a “cubit” as a standard:

6:14 Make thee an ark of gopher wood; rooms shalt thou make in the ark, and shalt pitch it within and without with pitch.
6:15 And this is the fashion which thou shalt make it of: The length of the ark shall be three hundred cubits, the breadth of it fifty cubits, and the height of it thirty cubits.
6:16 A window shalt thou make to the ark, and in a cubit shalt thou finish it above; and the door of the ark shalt thou set in the side thereof; with lower, second, and third stories shalt thou make it.

6:19 And of every living thing of all flesh, two of every sort shalt thou bring into the ark, to keep them alive with thee; they shall be male and female.
6:20 Of fowls after their kind, and of cattle after their kind, of every creeping thing of the earth after his kind, two of every sort shall come unto thee, to keep them alive.
6:21 And take thou unto thee of all food that is eaten, and thou shalt gather it to thee; and it shall be for food for thee, and for them.

First, a few initial assumptions (and I’ll be making many, many more along the way):

  • Only two of each species (yes, the “clean” were supposed to be seven of each, but not going into which are clean and which are not
  • Aquatic mammal, reptiles, birds are negligible percentages of the overall count of species and aquatic environment requirements will be neglected
  • Fish will be excluded, although 18,600 of the approximately 31,300 species of fish live in salt water and would have a challenging time surviving under a layer of fresh water  5.5 miles deep
  • Said depth will have no effect other marine flora and fauna depending on sunlight (lots of enormous assumptions like this)
  • The 7,000 amphibians will just have to tread water, though many actually need to live out of it.
  • No attempt to account for the 813 million extra cubic miles of water that covered “the high hills, that were under the whole heaven” and subsequently disappeared
  • No miraculous suspension of physics, biology, botany will be assumed – no mass hibernations, drastic decreases in metabolisms, etc. However….
  • Some kind of botanical miracle has to be assumed to account for the 400,000+ plant and 1.5 million fungi species that regrew rather quickly

We’ll start by assuming the numbers of species of “every living thing of all flesh” that we’ll be rescuing are

  • 6,000 mammals
  • 10,000 birds
  • 10,000 reptiles
  • 1,000,000 arachnids
  • 10,000,000 (on the very low end) insects

Let’s further assume that 20% of mammals and birds and 70% of reptiles are carnivorous. Why? Just go with it … the real numbers are probably more restrictive, but we’ll have to plan for additional foodstock and the associated foods for them. What do we do about the specific dietary requirements like eucalyptus or bamboo? Live food only? Scavengers? Assume them away, that’s what.

Let’s assume an average volume requirement of 6 square feet of floor space for the mammals (from elephants and bears to moles and shrews). That means we need 36,000 square feet. Further assume a stacking factor of 0.8 for those cages that can be piled up, giving us 29,000 SF space needed. Now for the feedstock, given that we don’t really know how long that particular flood lasted (40 days or 150 days…and then floating seven or ten months), let’s say those carnivores need two times the deck space for sufficient food…probably low, but let’s call it 85,000 total SF needed.

For the reptiles, let’s go with 2 SF floor space and a 0.6 stacking factor. With the carnivore foodstock floor requirements of maybe 50%, that works out to be about 18,000 SF. And for birds, we’ll call it a 0.1 stacking factor with a 0.5 SF requirement. That’s just 500 SF, which sounds too low. Call it 2,000.

For insects and spiders, the wood needed to build 11 million compartments is pretty staggering. Neglecting the time it would take to do that, we’ll assume 100,000 SF of floor space needed.

Plenty of comedians have questioned how a 600 year old guy, his wife, their three sons and three daughters-in-law managed to feed all those animals, but we’ll assume that they could.  And to get rid of their feces and urine, let’s assume that channels out the sides were also built into this massive ark to funnel away the waste that would not be used to fertilize the acres and acres of greenery up on the deck. Yes, that’s another assumption of mine – lots of animals need live plants to survive. And while we can assume that a fresh water source for the first forty days was not a problem, the next six to nine months would need something stored.

So to house these animals we’ll need 200,000 SF of floor space. Still seems really low. Worst case, we’ll need a year’s worth of food (takes time for things to germinate and fruit, right?) stores. Neglecting rot, call it maybe 2 million SF of floor space for granaries and straw storage and fresh water storage – once the rains stopped, the salt water would mix up pretty well. That means each deck would be about 800,000 SF – I’m counting the top deck as an extra. With a 300 by 50 cubit dimension order, that means a cubit is actually 36 feet and not 18 inches long.

That means my ark would be 10,800 feet long, 1,800 feet at the beam and 1,080 feet high. Pretty impressive. Particularly as the largest wooden vessels ever built were less than 400 feet long. The structural engineering would be astounding. And the amount of gopher wood (unknown anywhere in the world, by the way…only referenced in one book) would be on the order of 35 million board feet PLUS the amount need to compartmentalize all those animals. Call it 50 million board feet and you’ve stripped 7,000 redwood sized trees to build this. As I doubt gopher wood was on the order of redwoods, I’m thinking that the Sahara Forest supplied the wood. And they’d need about 25,000 gallons of pitch to seal it up.

So, with more assumptions than anyone would ever want to work with, and forgoing a lot more…

1 cubit is about 36 feet long!

(makes a pretty big temple, too)


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