Railroads and Horses' Behinds
 

The US standard railroad gauge (distance between the rails) 
is 4 feet, 8.5 inches. That's an exceedingly odd number.

Why was that gauge used?
Because that's 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's 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 that 
wheel spacing.

Why did the wagons have that particular odd wheel spacing?
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.

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 Imperial Rome, they were all
alike in the matter of wheel spacing.
The United States standard railroad gauge of 4 feet, 8.5 inches
is derived from the original specifications for an Imperial
Roman war chariot. And bureaucracies live forever.
So the next time you are handed a spec and ! told we have always
done it that way and wonder what horse's ass came up with that,
you may be exactly right, 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...
When you see a Space Shuttle sitting on its launch pad, there are
two big booster rockets attached to the sides 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 would 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, as you now know, is about as wide as two horses' behinds.
So, a major Space Shuttle 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.

And you thought being a horse's behind wasn't important ??

--- Original source is unknown.