Not long ago, trying and failing to fall asleep, I suddenly became aware of a surfeit of lights staring at me out of the darkness: the moonlight peaking, Fraunhofer-line like, through the slits between the Venetian blinds; the fluorescent hour and minute hands of my watch, glowing green as they slowly, slowly marked the passing minutes and hours; the pale light slinking under the bedroom door from another room; the glowing red on/off button on the power strip plugged in the wall; and the two pinpoint yellow lights where the power cord mated with my computer. All, all suddenly conspired, or so my sleep-deprived mind perceived, to illuminate my bedroom.
Illuminate is probably not the right word to describe this sensation: the total number of lumens emitted by these light sources barely signified. But the mind plays funny tricks at three in the morning. Most babies, and many adults, find night-lights comforting. There is even a psychological disorder, nyctophobia, characterized by a severe fear of the dark.
I am the opposite of a nyctophobe. I require darkness to sleep, and the darker the better.
During World War II night fighter pilots would sit in a dark room before flying off on a mission, allowing the retina’s rods to become super-sensitive. Rods are responsible for night vision, and dark-adapted vision is optimal after 30 minutes or more of darkness. So sensitive are these dark-adopted rods that, some evidence suggests, under ideal conditions their photoreceptors can be activated by a single photon. My rods had turned minuscule points of light into searchlights, high-intensity beams pointed at my reticular activating system. Restless, I got up and went out on my back porch.
The nights in Palo Alto are generally clear, and one can see a plethora of stars. Not as many as I saw in my youth, lying on my back in a field in central Wisconsin; there are too many city lights for that beautiful brilliance.
I wonder if this is how astronomy, that oldest of the sciences, began: some Mesopotamian insomniac looks up at the night sky and notices that the stars resolve themselves into the false order of constellations, and how they trek through the night sky, and track through the seasons. He uses cutting-edge cuneiform technology to note down his findings, becomes Ur’s or Babylon’s temple priest for his efforts (astrology and astronomy being close kin, and academia then as now dependent on government funding). Science is born. Or not. But it is a pretty thought to think at 3 A.M.
These night lights tell stories. Some I am sure you know, some perhaps are less familiar. Start with the fluorescent watch hands. In the early twentieth century there was a radiation craze, and one fall-out of the public passion for being irradiated was the development of radioluminescent watches whose hands were painted with radium. For the first time in history an insomniac knew exactly how much sleep he was missing, a minor advance in the march of human progress. The watches were very popular in their day.
The painters -- usually women -- used delicate camel hair paintbrushes, which they twisted to a fine point using their lips and tongues. They received, for their efforts, about 27 cents per dial, adjusted for inflation, and were expected to paint 250 dials per day. Here they are at work:
Day after day, year-in and year-out, they painted their lips with radium. And then, predictably -- predictable to us, but those were more innocent, or at least more reckless, times -- they developed osteonecrosis of the jaw, anemia, and oropharyngeal cancers. The company denied responsibility, though its chemists carefully used lead screens, masks, and tongs.
As occupational diseases go, it was unique, and of course one never sees these patients today. They were already an epidemiologic legend when I was a fellow three decades ago. But I have seen osteonecrosis of the jaw, and it is ugly: bones turning to mush, chronic infections, long periods with an oral surgeon, and chronic pain.
Those lethal watches had long-term legal consequences: the public outcry over lawsuits against the U.S Radium Company (the watches’ manufacturer) by the so-called “Radium Girls” ultimately led to the enactment of occupational disease labor laws. The employees themselves received a $10,000 payout and a $600 annual annuity. Radium paint was still in use as late as the 1960’s.
Radium poisoning had a popular culture afterlife. Nothing Sacred, a delightful 1930’s screwball comedy, starred Carol Lombard as a woman allegedly dying of radium poisoning. Allegedly, because radium poisoning was a misdiagnosis by her drunkard physician, allowing the lovely Ms. Lombard’s character to live and fall in love. Hollywood can make even environmental carcinogenesis a matter of sport: her character cheerfully states, “You know, I’m not going to bed until I have convulsions and my teeth start falling out.”
The current fluorescence of the minute and hour hands of my watch does not involve radium: today’s phosphorescent paints are either silver-activated zinc sulfide or doped strontium aluminate. I can not sleep soundly knowing that I am not contributing to the deaths of watchmakers.
But there is another radiation source in my bedroom, and it is associated with one of those night lights: the smoke detector. It uses the radioactive isotope americium-241 to emit alpha particles into an ionization chamber. If smoke particles enter the ionization chamber the ions are less capable of carrying a current, and the current drop sounds an alarm.
The light in my particular smoke detector is powered by a battery, not the americium-241, but it still manages to help keep me awake. Given the isotope’s 432-year half-life, this could be a long night. But at least I don’t have to worry about alpha particles, with their low penetrative power.
The stars, the ultimate night lights, tell so many stories that one hardly knows where to start, or end. The constellations each have their own stories, stories that charmed me as a Boy Scout: I still thrill to see Orion’s belt on a cold, clear winter night. Orion, the hunter, banished to the skies by Gaia for threatening to kill all the animals.
But my favorite story is scientific, not mythological: the story of Olbers’ paradox, named after Heinrich Olbers, a 19th century Dutch astronomer (though Johannes Kepler had, even earlier, considered the problem). Assume that the universe is infinite, and that the stars are evenly distributed throughout. Our line of sight should then, in every direction, be filled with stars. Hence Olbers’ paradox: why is the sky dark at night? Why is night not as bright as the day?
The first approach to a right answer (there is more than one right answer, it turns out) came, not from a scientist, but from a writer: Edgar Allen Poe, he of “Nevermore” and “The Pit and the Pendulum.” Poe reasoned:
“Were the succession of stars endless, then the background of the sky would present us a uniform luminosity, like that displayed by the Galaxy – since there could be absolutely no point, in all that background, at which would not exist a star. The only mode, therefore, in which, under such a state of affairs, we could comprehend the voids which our telescopes find in innumerable directions, would be by supposing the distance of the invisible background so immense that no ray from it has yet been able to reach us at all.”
A good enough answer, I would have thought, but there’s another. The Big Bang, some 13.7 billion years ago, was associated with intense heat and, the astronomers say, light brighter than the sun. But most of that radiation has now redshifted to microwave wavelengths. Have you ever seen a microwave when you pop up some Orville Redenbacher? Me neither: my rods and cones aren’t built for them.
If you want to see a brief, nifty explanation of Olbers’ Paradox, go to this YouTube video: http://www.youtube.com/watch?v=gxJ4M7tyLRE
Olbers’ Paradox is resolved by Edgar Allen Poe and Orville Redenbacher popcorn, which I for one find a deeply satisfying outcome. It would be even more troubling if the sky was bright all night long: I would never sleep.