Today, let's ask what meters 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.
Twenty-five hundred years ago
the Greek philospher Protagoras said, "Man is the
measure of all things." In that, he was closer to
literal truth than we might think. The gages 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. They all reflect, in
some way or another, what we see and feel.
A pound or a kilogram is roughly the mass of any
fairly dense material (like a rock or a piece of
metal) that we can comfortably hold in our hand.
The inch, foot, yard, and meter all correspond with
various body parts.
The mile and kilometer also have a meaning that
comes 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 she
might say, "Oh, 'bout two sees." She 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. 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.
Degrees Fahrenheit or
Celsius are about the smallest increments of
temperature we can feel. (We can usually feel 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.
The kilowatt and horsepower are pretty similar --
roughly the power most people
can produce in a short sprint up the stairs. 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 in a short
burst; it's also the most power we can tangle with
without being hurt. It's close to the rate the sun
pours energy on us when we tan ourselves on the
beach. It's like the rate we consume energy when we
take a hot shower.
So our meters replicate us. Like us, their accuracy
runs out beyond a point. Like us, their range and
scope is limited. Our instrument-based science
rightly claims to be the best means we have for
describing physical reality at any moment. But, as
objective as science tries to be, it's a science
that necessarily carries a human slant. The science
we practice is a science that describes a world
with us in it.
That's why our science and our science-based
engineering ultimately serve us so well. They
mirror human needs and nature just because they're
based on measurements that have never been too far
from human needs, or from our human dimensions.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds