An illustration of engineering methods from the domain of transportation...

Railway tracks in the US are 4 feet, 8.5 inches apart. This is a particularly bizarre measure.

Why did they use this particular distance?

Because US railways were built the same as in England, by English expat engineers, who thought this would be a good idea, since this way, they could use English train engines.

Why did the English build theirs this way?

Because the first train lines were built by the same engineers who built tramways, and this happened to be the track spacing.

Why did the tramways use this spacing?

Because the people who built the tramways were the same as those who built carriages and chariots, and they were used to this width for axles, and used the same methods and tools.

Okay, so why did the chariots use this width?

Because everywhere in Europe and England, the roads already had ruts, and a different width would have caused the chariot's axles to snap.

So why were the ruts in the road this distance apart?

The first main roads in Europe were built by the Roman Empire, to speed up deployment of the Legions.

Why did the Romans use these dimensions, then?

Because the chariots were Roman war chariots. These were pulled by teams of 2 horses, side by side. The horses had to be far enough apart in order not to get in each others' way. In order to ensure better stability for the chariot, the wheels had to be offset from the tracks made by the horses' hooves, and not be too far apart, to make it easier for two chariots to cross.

So now, we have the answer to our question: The spacing of train tracks in the US (4 feet, 8.5 inches) can be explained because 2000 years earlier, on a different Continent, Roman chariots were built as a function of the size of war horses' arses.

And now, here's the icing on the cake:

When you look at the space shuttle on its launch pad, you can see the two booster rockets on either side of the main fuel tank. The company that makes them is in Utah. The engineers who designed them would have liked to make them a bit wider, but the boosters had to be shipped by train to the launch site. The train line between the factory and Cape Canaveral uses a tunnel through the Rocky Mountains. The boosters had to be able to fit through the tunnel. The tunnel is a little wider than the tracks, and the tracks are about as wide as two horses' arses.

Conclusion: One of the engineering constraints on the most advanced vehicle in the world is the width of a horse's arse.

Specifications and bureaucracy will always be with us. So, next time you have some specs in your hands and are wondering which horse's arse invented them, you'll probably be wondering the right thing...

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