'Don’t rock the boat.' 'We’ve always done it that way!' 'If it isn’t broken, don’t fix it.' Do these statements ring any bells? Here’s an example of how we tend to lock ourselves into old ways of thinking.
The U.S. standard railroad gauge (the distance between the rails) is 4 feet 8.5 inches — an exceedingly odd number. How did the railroad builders determine that gauge? That’s the way they built them in England, and English expatriates built the first U.S. railroads. Why did the English build them like that?
The first rail lines were built by the same people who built the pre-railroad tramways, and that was the gauge they used. Why did they use that gauge? The people who built the tramways used the same jigs and tools that they used for building wagons, which used the same wheel spacing.
Why did the wagons have that particular, odd wheel spacing? Well, if they tried to use any other spacing, the wagon wheels would break on some of the old, long-distance roads in England, because that was the spacing of the wheel ruts. So who built those old, rutted roads?
Imperial Rome built the first long-distance roads in Europe and England for their legions. Some of the roads are still in use. And the ruts in the roads? Roman war chariots formed the initial ruts, which everyone else had to match for fear of destroying their wagon wheels. Since the chariots were made for (or by) Imperial Rome, they all had the same wheel spacing.
Specifications and bureaucracies live forever. The U.S. standard railroad gauge of 4 feet 8.5 inches has its origins in the specifications for an Imperial Roman war chariot. The chariots were made just wide enough to accommodate the back ends of two war horses. So the next time you see an odd specification and wonder what horse’s derriere came up with it, you might be exactly right.
Here’s the twist to the story:
When a space shuttle is on its launch pad, it has two big booster rockets attached to the sides of the main fuel tank. These are solid rocket boosters (SRBs).
Thiokol Propulsion makes the SRBs at its factory in Utah. The engineers who designed them would’ve made them a bit fatter, but the SRBs travel from the factory to the launch site by train. The railroad line from the factory runs through a tunnel in the mountains. The SRBs had to fit through that tunnel. The tunnel is slightly wider than the railroad track, and the railroad track is just wide enough to accommodate two horses’ behinds.
So a major design feature of what is arguably the world’s most advanced transportation system was determined more than 2,000 years go — by the width of a horse’s derriere!