Well, maybe you have - but I hadn't, not until an idle online search for articles on pinhole cameras led me to an excellent essay by British physicist-cum-YouTube star Jim Al-Khalili.
Why search on "pinhole camera" (besides an impulse to see the surprisingly detailed photos that artists have taken with little more than a cardboard box)? Because we're using these simple devices in Room A302 to make first contact with image formation and human vision. For it turns out that if you carefully study the images formed by a pinhole camera, you may well rediscover a fundamental law governing the propagation of light through a uniform medium.
That law will seem obvious, in retrospect, to anyone who has seen shafts of sunlight poke through holes in the clouds: light rays remain straight until bent by changes in the medium through which they travel. One of my students realized, seconds before the bell today, that this had to be the case if images in pinhole cameras always are upside-down (and she just had determined that they are).
What she may not have realized was that she was following in the footsteps of Abu Ali al-Hasan ibn al-Hasan ibn al-Haytham - a 10th-century Islamic scholar; a man who was born in Basra (then part of the Persian empire) and spent much of his life in Cairo; a man who formulated the now-hallowed steps of the scientific method; a man who experimented extensively with lenses, mirrors, and human vision; a man who realized, centuries before Galileo or Newton, that heavenly bodies had to obey the same physical laws that governed the motions of everyday objects.
A mere month ago, I would've said that my student was channeling Galileo, Newton, or one of their European contemporaries when she reached her perceptive conclusion. But these luminaries labored half a millennium after a prodigiously productive age of Islamic scholarship, an age that saw the development of algebra, the genesis of scientific chemistry, and a Google-like ambition to gather all of human knowledge and translate it into Arabic.
How do I know? Because I have been pulling late nights watching Professor Al-Khalili's marvelous BBC miniseries on science in the Islamic world. Concerns about copyright violation aside, I feel no small debt of gratitude to those who took the trouble to post the series' four episodes (in 10-minute chunks) on the ever-growing audiovisual archive known as YouTube. For it has been several years since I last had the opportunity to deeply peruse the gifts that Islamic scholars bequeathed our technological generation. (The last opportunity came when I had the good fortune to edit an article on Islamic astronomy for Sky & Telescope Magazine.)
They say that "history is written by the winners," and perhaps that explains why modern, Western overviews of the origins of physics generally begin with Galileo (with a cameo appearance by an ancient Greek or two, straw men inserted parenthetically into the story in order to be debunked). And at first glance scholarship would appear to be an unaffordable luxury in today's war-torn Basra (where al-Haytham was born) and Baghdad (an unparalleled center of learning while much of Europe languished in darkness).
But history teaches us that no society can forever keep its place - real or imagined - at the head of the geopolitical pack. History also has plenty to teach us about the sometimes invisible intellectual currents that flow between cultures and across the ages, currents that enrich our material and spiritual lives even when made anonymously, even when we fail to trace them back to their sources.
Copyright 2009 Joshua Roth.