Or how a horse's butt (behind if you prefer) determined size of the the
Moon Shot's booster rockets (and maybe a whole lot more!)
Railroad tracks: The U.S. standard railroad gauge (distance between the
rails) is 4 feet, 8.5 inches That is an exceptionally odd number!
Why was that gauge used?
Because that's the way they built them in England, and the U.S. railroads were built by English expatriates. Why did the English build them that
way?
Because the first rail lines were built by the same people who built the pre-railroad tramways, and that's the gauge they used. Why did "they" use that gauge then?
Because the people that built the tramways used the same jigs and tools that they used for building wagons, which used that wheel spacing. So why did the wagons have that particular odd
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's the spacing of the wheel ruts. So, who built those old rutted roads? The first long distance roads in Europe (and England) were built by Imperial Rome for their legions. The roads have been used ever since. And the ruts in the roads? The ruts in the roads, which everyone had to match for fear of destroying their wagon wheels, were first formed by Roman war chariots. Since the chariots were made for (or by) Imperial Rome, they were all alike in the matter of wheel spacing. The U.S. standard railroad gauge of 4 feet, 8.5 inches derives from the original specification for an Imperial Roman war chariot. Specifications and bureaucracies live forever.
So the next time you are handed a specification, and wonder what horse's butt came up with it, you may be exactly right, because the Imperial Roman war
chariots were made wide enough to accommodate the back end of two war horses. Thus we have the answer to the original question.
Now a twist to the story... When we see a space shuttle sitting on its launching pad, there are two booster rockets attached to the side of the
main fuel tank. These are solid rocket boosters, or SRBs. The SRBs are made by Thiokol, at their factory in Utah. The engineers, who designed the SRBs, might have preferred to make
them a bit fatter, but the SRBs had to be shipped by train, from the factory to the launch site. The railroad line from the factory had to run through a tunnel in the mountains. The tunnel
is slightly wider than the railroad track, and the railroad track is about as wide as
two horses' behinds. So, the major design feature of what is arguably the worlds' most advanced transportation system, was determined over two thousand years ago, by the width of a horses'
butt!
Don't you just love engineering?