Today, let's ask what meters really measure. The
University of Houston's College of Engineering
presents this series about the machines that make
our civilization run, and the people whose
ingenuity created them.
When the Greek philosopher,
Protagoras said, "Man is the measure of all
things," he was closer to literal truth than we
realize. The gauges and meters we use to measure
things usually begin by copying our own senses. You
can see that by looking at our weights and
measures, which largely reflect what we see and
feel.
For example, a pound or even a kilogram is roughly
the mass of any fairly dense material -- like a
rock or a piece of metal -- that we can hold
comfortably in our hand. The inch, foot, yard, and
meter all correspond roughly with various body
parts.
The mile and kilometer also have a meaning that's
made clear in parts of rural America, where people
talk about the distance of a see. Ask someone in
eastern Kentucky how far it is into town, and he
might say, "Oh, 'bout two sees." He means you
should look down the road as far as you can see.
Where your vision runs out, you spot -- say -- an
oak tree. You walk to it, and look again. There in
the distance, is the town -- just two "sees" away.
And how far is a see? Of course it varies; but even
in flat terrain, our ability to make things out
usually ends after about a mile or a kilometer.
We divide our thermometers into degrees Fahrenheit
or Celsius, and these are roughly the smallest
increments of temperature we can feel. We usually
know if we have a one-degree fever. We can sense
about one volt with our tongue; our ears are
sensitive to about one pound per square inch of
pressure change; and so on.
The kilowatt and horsepower are roughly the power
that most of us can produce in a short sprint --
like running upstairs. By the way, when James Watt
specified the unit of a horsepower, he made it less
than the work of a real horse so his engines would
seem more powerful. Not only is the kilowatt or
horsepower close to the maximum power you or I can
produce; it's also the most power we can tangle
with without being hurt -- the rate the sun pours
energy on us if we tan ourselves on the beach, or
the rate we consume energy when we take a hot
shower.
Since we're the basis for most of our measuring
devices, our science reflects the world in human
terms. But that's not really so bad. Scientists
realize that science isn't ultimate truth. It's
something we construct to make our experiences
predictable. Our science-based engineering
obviously serves us by mirroring human needs and
nature. And so does science itself.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
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