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.
Ben Franklin's breadth and
intelligence were dazzling by any measure. His life
embodies the entire shape of the American Revolution, all
the way from intellectual adventurism in the early
eighteenth century to an established new nation.
Franklin devoted his life to understanding and harnessing
the forces and fluxes around him -- electricity, music,
politics -- it hardly mattered, for he was omnivorous.
Historian I.B. Cohen tells how, when Franklin was
twenty-three, he worked with a scientific club that
eventually became the American Philosophical Society.
Franklin and a friend named Breintnal contrived an
experiment. One sunny winter day, they laid colored cloth
patches and a pane of glass out on the snow and noted how
deeply each eventually sank into the melting snow below
it. 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.
Breintnal published those results eight years later.
Then, 32 years afterward, Franklin wrote about them,
adding yet another twist. He also focused a burning glass
on both white and black paper. White paper absorbed less
heat, and it took longer to catch fire than dark paper.
Those results wouldn't be entirely clear until much
later. Anything black absorbs light, while anything white
reflects it. The catch is that some surfaces respond
differently to light and heat. Take skin, for example:
Equatorial peoples have dark skin whose pigment protects
them from sunburn. You might think dark skin would absorb
heat and make life miserable in hot countries. But the
sun's rays carry more infrared heat than light. Dark skin
reflects heat just as 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 glass absorbs the heat
radiated by the sun -- stops it in its tracks. In that
sense, glass is opaque. It is black to infrared (or heat)
radiation.
Franklin finished by saying:
"What signifies Philosophy that it does not apply to some Use?" Then he went on to
say what his tests suggested about dressing for cold and
warm climates. Many years later, Franklin made his famous
remark, "What good is a new-born baby?" That was an older
and wiser Franklin offering a subtle answer to the
younger Franklin's question, "What signifies Philosophy that it does not apply to some Use."
The questions raised by Franklin and Breintnal were not
entirely new. They'd undoubtedly read older speculations
by Boyle, Boerhaave and Newton on the action of heat and
light. I admire Franklin for the way he always brought
his wide-ranging curiosity back to the hard earth, but
rooted in the hard earth is not where these young
students of nature (and of government) started out.
I'm John Lienhard, at the University of Houston, where
we're interested in the way inventive minds work.
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