Does the expression, "We've
always done it that way!" ring any bells? The US standard
railroad gauge (distance between the rails) is 4 feet, 8.5
inches. That is an exceedingly odd number. Why was that gauge
used? Because that is the way they built them in England, and English
expatriates built the US railroads. Why did the English build them
like that? Because the first rail lines were built by the same people
who built the pre-railroad tramways, and that is the gauge they used.
Why did "they" use that gauge then? Because the people who
built the tramways used the same jigs and tools that they used for
building wagons, which used the same wheel spacing. Okay! 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's 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. The roads have been used ever since. 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. Therefore, the United States standard
railroad gauge of 4 feet, 8.5 inches is derived 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 behind came up with it, you may
be exactly right. This is because the Imperial Roman war
chariots were made just wide enough
to accommodate the back ends of two war-horses. Now, the twist to the
story...
There is an interesting extension to the story about railroad gauges
and horses' behinds. When we see a Space Shuttle sitting on its launch
pad, there are two big booster rockets attached to the sides of the
main tank. These are solid rocket boosters, or SRBs.
Thiokol makes the SRBs at their factory at 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 happens to run 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 about as wide as two horses' behinds.
So, a major design feature of what is arguably the world's most
advanced transportation system was determined over two thousand years
ago by the width of a horse's behind.
Your devoted disciple and adoring fan.