Is the Bible wrong about pi?
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1 Kings 7:23 And he made a molten sea, ten cubits from the one brim to the other: it was round all about, and his height was five cubits: and a line of thirty cubits did compass it round about. (see also 2 Chron. 4:2)

Some critics say that the measurements given for the circular bath do not give a proper value for pi. There are a couple of answers to this, one of which we give a link to below, and which is better than the one I have here. The more common answer is that these verses give an estimate of pi that is rounded to the nearest full digit.

Objection: The fact is that 30 cubits is not the correct answer. If you say that 31.4 is not the correct answer either, then I will allege that your 31.4159265 figure is incorrect as well. Following the stream of logic you have set in motion, there is no correct answer, because every answer involves rounding. Any answer would be automatically false.

Of course there is a certain category error here, since the value of pi is (so we are told by the mathematicians) one of those things that we can never provide the "correct" answer for -- it goes on an on and on. So the 1 Kings writer would have either had to estimate or else he would still be writing today.

You are assuming the answer involves rounding without proving as much. The answer is wrong until you can prove it results from rounding. You can't allege it's the result of rounding until I prove it's not.

Despite this, it is well-known and accepted that ancient estimates of distance, length, etc. were not always given down to the levels of our modern measurements (though see below). Thus it is the critics burden to show that rounding is not involved, if anything, since rounding was the norm,

If guesswork is going to be admissible, then many biblical contradictions could be explained away by mere conjecture and theorizing. Nearly every numerical contradiction in the OT, for example, could be lightly dismissed by simple reference to the "rounding" defense.

As we have just noted, however, the "pi" category is of a rather different nature, and rounding was standard procedure in the ancient world. Therefore, this "slippery slope" warning is without substance. I expect accuracy to at least two orders of magnitude, which the ancients understood and depended on themselves, so my demand isn't unreasonable.

The ancients did measure pi more precisely in some cases -- but this is found in places like the Rhynd Papyrus, a book of mathematical equations. The Kings and Chronicles writers were evidently literate, but there is no evidence that they were mathematicians. We would rightly expect accuracy of greater order from specialists in mathematics like the writer of the Rhynd Papyrus, and from Babylonian astrologers. But such an expectation is unreasonable from a non-mathematician.

Put it this way: If we ask how many gallons of fuel a rocket contains, we expect a detailed answer like "4,942,827.78 gallons" from a NASA engineer, if he is involved in a techincal discussion with other engineers. If he's talking to the press, and he is savvy, he'll say "4.9 million gallons" rather than bewilder the scientifically inert with more detail. Your average hobbyist (or even a reporter) will say "5 million gallons".

Are any of them incorrect? No, because there is a semantic contract that correlates the level of precision with the level of expertise. Unless the Bible authors were mathematicians on the level of Archimedes (one of the other few ancients to go this far in looking at pi), then it is unreasonable to expect precision to that level from them.

For more info, here are some interesting sites:

Pi through the ages

History of Pi

For another answer, from my friends at CMI, see here.

Here's an interesting result. Skeptic Sam Gibson wrote in to a person styled "Dr. Math" on this issue, and the results of the correspondence are here. On his own site, Sam argues that rounding off pi equates with "rounding off" books of the Bible and taking, say, Romans 7 out of Romans. That's an apples and oranges equation, as his encounter with Dr. Math shows.

A helpful reader has also made this point:

The Hebrew Rabbi and writer of the earliest known Hebrew geometry textbook (Mishnat ha-Middot,) Nehemiah, states, "Now it is written: And he made the molten sea of ten cubits from brim to brim, round in compass, and yet its circumference is thirty cubits, for it is written: And a line of thirty cubits did compass it round about. What is the meaning of the verse, And a line of thirty cubits, and so forth? Nehemiah says: Since the people of the world say that the circumference of a circle contains three times and one seventh of the thread, take off that one seventh for the thickness of the walls of the sea on the two brims, then there remain, Thirty cubits did compass it round about."

And another has added:

...maybe the circumference actually measured 30.3l213 cubits and the diameter measured 9.64866 cubits. The ancients who perhaps hated fractions as much as school kids do today, simply gave the numbers as 30 and 10 respectively. Why should they not? We do know that they were not into the precision fetish that we are today. Also, if the Bible had to go into as much detail as Skeptics want, I hardly would be carrying it to church. I'd need a wheelbarrow.