Jeff's Lunchbreak: Does the Bible Really Say Pi = 3

I spend much more time on this site debunking religious arguments than atheist arguments, but I've just been reminded of one of the stupider arguments that some atheists use, so I thought I'd deal with it. Obviously, if you've read the rest of this blog, you know I'm an atheist myself, but I think that stupid arguments are bad no matter who's making them.

In 1 Kings 7:23, discussing Solomon's Temple, the Bible describes some of the furnishings thusly:

He made the Sea of cast metal, circular in shape, measuring ten cubits from rim to rim and five cubits high. It took a line of thirty cubits to measure around it.

Now, as everyone should remember from elementary school, circumference and diameter are related by the formula:

Circumference = Pi * Diameter

Or, to rearrange that equation a bit to solve for Pi:

Pi = Circumference / Diameter

Using the passage, we could then calculate Pi as follows:

Pi = 30 / 10
or

Pi = 3

Again, thinking back to elementary school days, everybody should at least know a 3 digit approximation of Pi as 3.14. And so the argument goes, since the Bible gives such an erroneous value for Pi, it obviously can't be the inspired word of God. Here's one example of someone trying to use this argument, but I've seen it many other places.

In short, I think this is a rather stupid argument.

Pi is an irrational number. In other words, it doesn't matter how many decimal places you want to carry it out to, you'll only ever be able to write it as an approximation, and never an exact value. If you're still not following what that means, if you say that Pi is approximately 3.14, I could say - true, but it's really a bit closer to 3.142. But if you use 3.142, then I could say it's actually a bit closer to 3.1416. But if you use 3.1416, I could counter with 3.14159, and on and on forever. There's just no way to write pi as an exact value*. What this also means, is that even if you know the diameter exactly, you won't be able to write the circumference exactly, and vice versa.

So, when a scribe was describing Solomon's Temple, and wanted to give measurements of furnishings, there's no possible way he could have given exact values for the circumference and diameter of circular objects. It wasn't a limitation because the ancients didn't know enough. Even today, we couldn't do it. It's just a physical impossibility. So, the scribe rounded off his numbers.

Some people might still want to argue that the Bible would at least have been more accurate if it had used 31 cubits for the circumference of a 10 cubit diameter circle. I say - who cares? It's necessarily an approximation, so the scribe only used a single significant figure. Besides, there are plenty of sillier passages from the Bible, such as Genesis 30:37-43 or Judges 1:19, that skeptics can use in these types of arguments.

*This reminds me of the nerd obsession with knowing as many digits of Pi as possible. While this is certainly interesting for a variety of reasons, it's not really terribly practical. For example, if you use an approximation of Pi out to 10 decimal places (3.141 592 653 6), for a sphere the size of the Earth (diameter = 7917.5 miles), your calculation of the circumference would be off by less than 0.006 inches. And that's assuming you knew the diameter exactly. In reality, the uncertainty in your measurement would swamp the discrepancy from using your approximation of Pi.

Comments

I think it's just an approximation as well, but I still count that as an error. It obviously can't be both 30 cubits around and 10 cubits across. It mentions that it's a handbreath thick, which is a much smaller unit of measurement, showing that they weren't limited by only measuring things in cubits.It also mentions some wheel like things a few lines later as being one and a half cubits so they also aren't limited to not using fractions. Why didn't they say that the wheels were one or two cubits instead of one and a half? It tells the dimensions of the temple in such oddly specific details, but why? Then it rounds off some numbers so that it looks better when read? I think it's a very reasonable thing for a scribe a few thousand years ago to do, but I don't think it's something that an inerrant bible would do.If people are going to treat the book like it has been written by an all knowing all powerful god, then it should be held to a higher standard. I think it's a very minor error, and it's also not a technical book giving you blueprints to build something with, but still an error.

I was challenged by a religious friend to find just one error that could be proven in the bible and I mentioned this one. He told me that it wasn't an error and that if god wanted pi to be an even three, then that's what it was. Since I wasn't able to measure it and I wasn't there, then I couldn't prove that it wasn't 30 around and 10 across! There really are other crazy parts to the bible, and some really messed up things in it morally, but when people choose to believe, then it doesn't matter what errors it has.

Posted by: Eric T. Jones | January 20, 2011 1:42 PM

Good point. I made the mistake of ignoring the context of the quote. Considering the level of precision of the other measurements given in the surrounding text, you'd expect that this one would have been more accurate.

Thankfully, not everybody's like your friend. I do know a few people like that myself, but I also know many others that could be swayed with enough evidence. Plus, it's not like most people will make such a big change after one night's dinner conversation, but it can start them on the path.

Posted by: Jeff | January 21, 2011 12:38 PM

I do agree that it is over used and it's not a definitive mathematical proof that says the bible is fake. Saying that would be silly. There are also so many other good reasons to doubt it.

Yes, it's good that most people aren't that narrow minded. Most people are much more reasonable. I hope that I've sent some people on the right path, and not just wasted my breath, but lately I've been feeling very ambivalent towards religion as a whole.

Posted by: Eric T. Jones | January 22, 2011 7:50 AM

Oops, I meant to make a funny joke about you being a quote miner :-)

Posted by: Eric T. Jones | January 22, 2011 7:52 AM

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