Easy as Pi

Have you ever noticed how ridiculously specific the Bible is when describing the structures that were built in the worship of God? Cubits, acacia wood, pitched within and without, cherubim, ox blood… There’s a lot of detail. Which is why this verse describing the molten sea in Solomon’s temple is surprising:

Then he made the sea of cast metal. It was round, ten cubits from brim to brim, and five cubits high, and a line of thirty cubits measured its circumference. -1 Kings 7:23 (ESV)

That pool’s dimensions are given again in 2 Chronicles:

Then he made the sea of cast metal. It was round, ten cubits from brim to brim, and five cubits high, and a line of thirty cubits measured its circumference. -2 Chronicles 2:4 (ESV)

The surprising part is that the math doesn’t work out. Mathematicians have used the Greek letter pi to represent the ratio of a circle’s circumference to its diameter. Simply put: π = circumference / diameter.

The Bible clearly states that this pool was circular, that its diameter was 10 cubits, and its circumference was 30 cubits. Here’s the math:

That just doesn’t make sense. Every seventh grader can tell you that pi is approximately 3.14. Most seventh graders can tell you that the circumference of this pool should have been 31.4 cubits. So is the Bible wrong?

Some, while trying to defend the Bible’s creditability, have stated that the figures are merely estimates. This seems very unlikely considering the detail in the descriptions surrounding these two passages. Some have speculated that the pool was not completely circular but elliptical. This is problematic because the passages only give one measurement across. An oval shape would have been wider one direction than the other. I would have expected both measurements to have been given.

I believe the solution is much, much simpler. A few verses later, we are given a little more of a physical description of the pool.

Its thickness was a handbreadth, and its brim was made like the brim of a cup, like the flower of a lily. It held two thousand baths. -1 Kings 7:26 (ESV)

This handbreadth-wide brim may be the missing piece to the formula. It is possible that the two measurements were measuring two different circles. One circle (ten cubits from brim to brim) at the edge of the pool and the other (thirty cubits measured its circumference) at the edge of the water.

So, in order to do the math, I converted the units to inches using my own arm and hand. I’m going with an even 18 inches per cubit and 4 inches per handbreadth.

Once we subtract four inches from each side of the circle, we have an inner circle with a diameter of 14.33 feet and a Biblically stated circumference of 45 feet.

That looks about right to me.

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About Jeff Postlewaite

high school principal since '07, father since '04, teacher since '03, husband since '03, sound tech since '96, UVA fan since '92, gadget junkie since '89, Christian since '88, Giants fan since '84, golfer since '83, brother since '83, human since '81

Posted on March 23, 2012, in Biblical Thought, Math and tagged , , . Bookmark the permalink. Leave a comment.

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