The space shuttle is perhaps man's most technologically advanced transportation system - and yet it's basic design was dictated by a horse's ass. Say what? Well, it goes like this:

The basic components of the shuttle include the solid rocket boosters. These are built in Utah and shipped by train from the factory to the launch site. The trains have to travel through a tunnel in a mountain; the width of the tunnel limited the size of the boosters.

The tunnels were built to accomodate the standard railway track gauge -- which is 4 feet 8 and one-half inches between rails. This seemingly arbitrary width was set by early American railroad engineers, many of whom were English -- and that was the standard gauge used in England.

The English used this as the standard railway width to take advantage of the tramways that existed in England before the trains -- and that's the width the trams used.

The tramway builders used this width to utilize the tools and fixtures already extant for building horse-drawn wagons and carriages -- and 4 feet 8 and one-half inches was the standard distance between wagon wheels.

The wagon builders used this width because it was the optimum width for the many rutted roads found throughout England. When they tried to use other sizes they found the wheels broke more often.

Many of these roads dated back to the the days of the Roman Legions. Initially built by Imperial Rome, they had been in use ever since.

The ruts on the roads were first caused by Roman war chariots. The standard Roman war chariot had a wheel base of 4 feet 8 and one-half inches.

The Romans used this width so their chariots could accomodate two warhorses.

In effect, two horse's asses determined the size of the rocket booster on the most advanced transportation system we've ever seen.

So the next time you are handed a specification and wonder what horse's ass came up with it, you may be exactly right -- it really was determined by a horse's ass.

NOTE: This has been around for several years in various forms. I couldn't find the earliest version that I recall seeing, nor can I give accurate attribution.