Metals in the Movies: Raiders of the Lost Ark

Raiders of the Lost Ark
The Raiders of the Lost Ark is an amazing movie. One of my personal favorites, to be sure. Harrison Ford is great, there are fantastic fight scenes and hilariously anticlimactic sword fights. There are iconic lines and famous boulder scenes, and lots of Nazis get their faces melted off. What’s not to like? In the office though, we’ve come to an agreement that like the Star Trek movies, only the odd-numbered Indiana Jones films are any good.

The only redeeming thing about Indiana Jones and the Kingdom of the Crystal Skull is that Shia LaBeouf was in it.

You had a point to make about metals?
That’s right, I did!

Let’s apply an overly detailed eye towards the use of metals in The Raiders of the Lost Ark.

There isn’t a whole lot to work with here. Most of the metal we see is in the form of guns, U-Boats, and cool airplanes that propeller Nazi faces off. Considering the film is set in the 1930s, the guns are alloy steel, as are the U-Boats. Airplanes of the interwar period are mostly a mix of steel and an aluminum alloyed with copper for extra strength. Nothing super exciting there. Although I can never get enough about airplanes, but that’s neither here nor there.

But… one thing that really stands out is the “switching the golden idol head with a bag of sand” scene.

Sand for Gold?

The trick that Indy uses seems to be a reasonable one. That is, unless you know a lot about metals and have a weird brain. Fortunately, I do.

OK – the idol head looks to be about 9 inches high by 3 inches by 3 inches, or a total of 81 cubic inches. For the purposes of this example, let’s assume that the idol is solid gold, not hollow. From our friends at Matweb, we learn that 14k gold has a density of 0.6980 pounds per cubic inch. This gives us a weight of 56 pounds.

Now, dry sand has a density of .0643 pounds per cubic inch. Doing some fancy multiplication, a bag of sand approximately the same size will weigh 5.2 pounds. Of course the whole scheme is going to fail and trigger the giant stone ball of death! You’d need a bag of sand at least 10 times as large as the idol in order not to trigger the trap underneath the idol’s head! But, we can forgive Indy a bit.

After all, he’s an archaeologist, not a mathematician.