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.

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 Imperial Rome, they were all a like in

the

matter of wheel spacing.

The United States standard railroad gauge of 4 feet, 8.5 inches, then, 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 ass.

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

So what horse's ass can we blame kts on?