GAD! I just can't keep up with reading phys-l. Here's a piece that seems
to be everywhere, so I can't properly attribute it. It deals with units
and burocracy, so I thought it belonged in this group.
I spent some time at school today writing on a piece about work done by
the force of friction. I will eventually finish it and post it. As with
much of what I write many are not going to like it, but it will fuel
debate. I hope I can get back in step.
(A student asked me how to do a problem in Hecht today, one I had not
assigned. It is the last problem in the chapter on energy in the second
edition. It is horribly misconceived! That's the second such problem I
have found with that problem. If brand new, innovative misconceptions are
introduced by textbooks, how can we expect to make progress in teaching
our students? The ones who are sufficiently motivated to work extra
problems encounter these terrible booby traps and we have to repair them.
Evidently textbooks are not bound by the primary ethical canon: "First,
do no harm.")
Leigh
Story follows. I can attest to plausibility but not to accuracy.
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? The first long distance roads in Europe (and
England) were built by Imperial Rome for their legions. The roads have
been used ever since. And the ruts? Roman war chariots first made the
initial ruts, which everyone else had to match for fear of destroying
their wagon wheels and wagons. Since the chariots were made for, or by
Imperial Rome, they were all alike in the matter of wheel spacing.
Thus, we have the answer to the original question. The United States
standard railroad gauge of 4 feet, 8.5 inches derives 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 which horse's rear came up with it, 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. And now,
the twist to the story...There's 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 fuel 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 had 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, the major design feature of what is
arguably the world's most advanced transportation system was determined
by the width of a Horse's ass!
Author unknown