Brass Monkey: Differences in Metal Expansion

Be careful what you accept as truth!

In typical web-surfing fashion, I stumbled upon something interesting today. I have recently acquired a cast metal puzzle called "NEWS" by Hanayama.

Although it is rated as one of their toughest puzzles, I was able to solve it last night in just a few hours. To be fair, I could tell just by looking at it how it might be solved, because I've seen other puzzles that use the same mechanic. This one, however, *does* have it's own special trick.

But back to the main point. So I was browsing around looking for additional puzzles of this type. I found one that looked like a small brass cannon. Googling for the best price led me to an article about "brass monkeys" and cannon balls. I read it out of curiosity and it was quite interesting.

Being quite interested in etymology, I always find the historical origin of phrases to be extremely entertaining reading. I almost always come away with a feeling of "wow, I just uncovered something I never knew". This experience was no different.

Although I only have a very cursory knowledge of the phrase "freezing the balls off a brass monkey", it was still interesting to learn of its origin. Apparently stacks of cannon balls on sailing ships were stored in pyramids contained and bordered by a brass square with indentations for the outermost balls. This metal square, apparently called a "monkey", would allow the stack to be built and prevent its collapse.

The cannon balls were made of iron and the "monkey" was made of brass. In the article, it was explained the the difference in the coefficient of linear expansion between iron and brass caused the brass to shrink more than the iron in very cold weather. So much so that the cannon balls could pop out of the brass bracket, causing the stack to collapse and cannon balls to go rolling about.

After reading this I felt, "wow, I now have some new knowledge." I was prepared to accept this information as outright fact for two reasons:

1. It seemed to make sense. I have a good understanding of physics and the properties of matter. I have experience with shrinking and expanding metal with respect to temperature.
2. I happen to know that a huge number of common (and uncommon) phrases in the English language have nautical origins. This merely seemed like another one in the library.

Shortly after reading the "brass monkey" article, I was thankful to learn that if I had chosen to believe this story I would have been absolutely wrong. This is the link that saved me from the all too common folly of believing what we read without question.

I looked up the coefficient of linear expansion and found similar numbers as those given in the link above. The coefficient for brass appears to be 10.4 x 10^-6 inches per degree Fahrenheit. The coefficient for iron appears to be 6 x 10^-6 inches per degree Fahrenheit. If the temperature dropped 100 degrees Fahrenheit, the difference in expansion of the metals is something like 1 hundredth of an inch at most.

So please, even if something "seems right", it may not be. If you want to have true knowledge, you really need to verify the claims for yourself to the best of your ability We need to focus more on teaching our children HOW to think rather than WHAT to think. Critical thinking is the goal.