Today, Benjamin Franklin thinks about theoretical
and applied science. 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.
The French economist Turgot
said about his contemporary, Ben Franklin, "He
snatched lightning from the skies and the sceptre
from tyrants." That's about as close as you can get
to putting Franklin in a nutshell. Franklin's
breadth and intelligence were dazzling by any
measure. His life spelled out the progress of the
American Revolution -- from intellectual
adventurism in the early 18th century all the way
to an established new nation.
When he was only 23 Franklin turned his omnivorous
curiosity on heat radiation. He belonged to a
scientific club that eventually became the American
Philosophical Society. Franklin cooked up an
experiment and another member helped him. They laid
colored cloth patches -- and a pane of glass -- on
the snow one sunny winter day. Then they noted how
deeply each melted into the snow. The white cloth
hardly sank at all. The darker each patch was, the
deeper it sank. The black cloth and the glass pane
sank deepest.
Franklin didn't publish these results until much
later. By then he'd added a twist: he also focused
a burning glass on both white and black paper. The
white paper absorbed less heat, so it took longer
to catch fire than the dark paper.
Franklin brought out issues that weren't explained
until the 20th century. The explanation goes like
this: black cloth is black because it absorbs
light. White cloth reflects light. Heat radiation
is a lot like light, but not entirely so. Some
surfaces respond differently to light and heat --
skin, for example. Black skin absorbs light. But it
reflects heat just the way white skin does. If it
didn't, Nigerians would all have to live in
Stockholm. Ben Franklin's pane of glass made a
similar point. Light goes right through glass. But
it absorbs the heat carried in sunlight. Glass is
black to heat radiation.
The young Franklin concluded by saying, "What
signifies Philosophy that it does not apply to some
Use?" And he went on to say what his tests
suggested about dressing for cold and warm
climates.
Years later, an aging Franklin watched an early
balloon ascent in Paris. The man next to him said,
"What good is it?" and Franklin replied, "What good
is a newborn baby!" The older Franklin was
answering the younger Franklin's question, "What
signifies Philosophy that it does not apply to some
Use."
Early-20th-century physicists eventually showed us
the newborn baby in the young Franklin's
experiments. His simple tests exposed behavior that
couldn't be explained until we'd completely
rewritten the laws of nature. Their value lay far
beyond the obvious utility of choosing the right
clothes for a sunny day.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
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