Railroad tracks, a horses ass... and rockets! [Long] The US standard railroad gauge (the distance between two rails) is 4 feet 8.5 inches... an exceedingly odd number. Why was that gauge used? Because a number of the early railroad lines in the US were built to fit standard-gauge locomotives manufactured by English railroad pioneer George Stephenson. The English expatriates who immigrated to America built them to the same dimension they had built them in England. 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 thats the same gauge they used. Why did ""they"" use the gauge for tramways then? Because the people who built the tramwys used the same jigs and tools that they used for building wagons, which also used that wheel spacing. OK! 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 the old long-distance roads in England, because that's the spacing of those wheel ruts. If you wheel spacing didn't match the old ruts, your wheels would quickly self-destruct. So who built those old rutted roads? Imperial Rome built the first long-distance roads in Europe and in England for legions. Those roads have been in use 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 Imperial Rome, they were all made exactly alike in their wheel spacing. Every Imperial Roman war chariot was made just wide enough to accommodate the back ends of two Roman war horses. Those Roman chariots carved their deep ruts through England, Europe and the Middle East for several centuries thus establishing a well-worn precedent that has lasted for two thousand years. Providing how much bureaucracy can last forever. Thus the U.S. standard railroad gauge of 4 feet 8.5 inches is derived from the original specifications for an Imperial Roman war chariot designed to accommodate the width of two equitine buttocks. So the next time you're handed a specification and wondered what horse's ass came up with that one, perhaps you'll pause and think about just how right you might be. _____ An ironic addendum ot this story is that the solid rocket boosters (SRBs) used on the NASA space shuttles were manufactured by Thiokol Corp in Ogden, Utah, then shipped to Florida by rail-car for final assembly at the Cape Canaveral launch site. The rail lines pass through several narrow railroad tunnels hand carved through the Rocky Mountains back in the 1800's. The booster pieces thus had to be built small enough to fit through these narrow tunnel bores. Thus our story concludes the width of one of the most advanced vehicles ever constructed by man was determined in part by the width of one of our most ancient vehicles... and a horse's ass!