The Sciences


Air Conditioning America, the National Building Museum, Washington, D.C.

By Scott KimAug 1, 1999 5:00 AM


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Air-conditioning blew into residential use in the late 1940s, eventually giving rise to the ranch house--and the computer revolution. Courtesy Carrier Corporation If man has the intelligence to heat his house in the wintertime, why does he not cool it in the summer?" asked Alexander Graham Bell in 1918. Blame the second law of thermodynamics, which says that heat can't pass from a cooler object to a hotter object. Instead, the hot body will warm up the cool one (see, for example, Casablanca or Some Like It Hot). That makes it hard to bring the indoor temperature down to a comfortable 68 degrees Fahrenheit when outside it's 99 in the shade.

By the nineteenth century, however, a few sweaty visionaries had already found a loophole that enabled them to invent chilling machines. When a substance expands, spreading its heat over more volume, its temperature drops. Similarly, compressing a substance crowds the heat into a smaller space, bringing the temperature up. In a window air conditioner, refrigerants expand into coils, lowering their temperature. Fans blow warm, indoor air over the cold coils, cooling the air and heating the refrigerants, which then pass to a compression unit and are squeezed into a tiny volume. The temperature of the refrigerants shoots up above that of the hot, outdoor air, which can then carry away the excess heat. Got it?

If not, a visit to "Stay Cool! Air Conditioning America" at the National Building Museum in Washington, D.C., won't necessarily help. A genial engineer addresses visitors from video screens mounted on decorative ducts, but he doesn't explain much about how the technology works. The exhibit does a far better job of conveying how air-conditioning profoundly altered manufacturing, architecture, medicine, entertainment, the population size of the southern states, even cooking. The information revolution would never have happened without it, because early computers succumbed easily to overheating. Candy wrappers, infantwear, drug bottles, and other objects hanging from the exhibit area's ceiling remind visitors that the production of many staples relies on strict temperature, humidity, and dust control. Without AC, chocolate would leach ugly gray fat onto its surface, and pasta would spoil, thread would snap.

The exhibit leads visitors on a historical tour from the movie palaces of the 1910s and 1920s (where the public first encountered air-conditioning) to the ultimate in climate control: the space shuttle. Home cooling didn't become common until after World War II. A bank of telephones plays tapes of consumers' reactions: "Now that we have air-conditioning, we've sold our summer house," comments one 1954 survey respondent. Postwar architecture reflects these changes. Gone are the wide eaves, deep porches, thick walls, and high ceilings that once defended home owners and office workers from the worst of the heat; instead, low ranch houses face the sun, and sealed glass office towers shut out the world.

The air in the exhibit is a uniform 70 degrees and 50 percent humidity. "It would have been fun to play with the climate," explains Chrysanthe Broikos, one of the exhibit's cocurators. "But we had to keep the temperature and humidity steady to preserve the artifacts." She gestures toward a wall of air conditioners. One, a familiar brown box, is a 1970 Fedders model on loan from Sam and Wilma Broikos--Chrysanthe's parents. Another, a York console model the size of a small harpsichord, sports elegant mahogany veneer. Such objects, however, are rare in the exhibit, which relies a little too much on photos and graphics, such as time lines that look like giant thermometers. Still, if you find yourself in Washington on a sweltering August day, it's a pleasant way to spend an hour. And it's air-conditioned. --Polly ShulmanStay Cool! Air Conditioning America

TelevisionThe Life of Birds A ten-part series airing on public broadcasting stations from July 20 to September 28.

Birds and their followers: After three years of shooting, the good knight Attenborough is bringing his feathered friends to the small screen. Courtesy BBC

One night, coming home from a long weekend, I heard a rustling in the chimney. I pointed a flashlight into the blackness, and eyes blinked back at me. I retreated to the kitchen, hoping the animal would leave, but when I returned a great horned owl had taken possession of my coffee table. He stood there, more than two feet high, looking about the room with a mixture of poise and panic. Then he gracefully launched himself up--and crashed into the ceiling. In the end I had to enlist the help of a neighbor; we threw a sheet over him and carried him out.

Every day, birds flit through our world but only occasionally do they make themselves known to us in intimate ways. I never understood how my owl had flown straight down into the chimney. Had he fallen? Had he been pushed by a jealous rival? But now I know what probably happened, thanks to Sir David Attenborough and his ten-part series on PBS entitled The Life of Birds.

Owls and most other hunting birds can dive straight down; some hawks can even hover, dive, and hover again as they move in on their prey. "The Mastery of Flight," the second episode in the series, follows a snowy-faced barn owl, which flies silently and with great precision, gliding just above the ground at dusk. These birds use their sensitive hearing to guide them, but they are occasionally undone by their weak eyesight. My owl had probably been hunting mice that live in the fireplace, stalking noiselessly as he listened to them move about below the chimney. When he made his move, dive-bombing down, he trapped himself for days.

While Attenborough doesn't film any owls on coffee tables, he does wander the seven continents spying on his subjects and occasionally interfering in their busy lives. He riles a New Zealand saddleback by playing a tape of a hostile neighbor's challenge, only switching off the tape when the feisty victim is thoroughly confused and agitated. Sometimes he can't resist helping. The Japanese shearwater can't take off from the ground--it has to climb a tree and launch itself from a high branch. Attenborough, clearly exhilarated by the stream of shearwaters clambering past him up the trunk, gives one a friendly boost. And only he could sit next to a pair of mating albatrosses and maintain his dignity.

In "Signals and Songs" and "Finding Partners," the sixth and seventh episodes, birds try to impress each other with acrobatics, inflatable neck sacs, fancy tail feathers, even courtship beak whacking. The lyrebird of Australia, however, steals the show. The male with the most songs gets the best mates, so to increase his repertoire, he samples tunes from his neighbors. When the hapless fellow in this segment attracts nothing but female cuckoos, he resorts to more creative sounds, such as the screech of a chain saw, the howl of a car alarm, and the click and whir of a camera with automatic rewind. The sounds are uncanny, and though we don't see him win a female lyrebird, he may have a bright future on the talk-show circuit.

Not only does Attenborough show how birds take off, navigate, fly, land, sing, mate, and fight, but he also provides their evolutionary history. Graceful animated segments in which fossilized bones come to life, acquiring first height, then breadth, and finally scales and feathers, illustrate the link between today's birds and yesterday's dinosaurs. Another segment reveals the artistry of feathers--each filament hooks to its neighbor, and if one comes loose, the bird uses its beak to cinch it back like a zipper, keeping the feather intact so it can beat the air. More animation shows songbirds splitting the air as it streams from their lungs, allowing them to sing two notes at once. Although Attenborough covers hundreds of birds (and bird attributes), it's clear there is much more to learn. And after only one episode, you may never look into the sky again without hoping one of them will skim past, minding its own fascinating business.

--Wendy Marston

The Life of Birds

BooksFearsome Fauna: A Field Guide to the Creatures That Live in You.

Roger M. Knutson. W. H. FREEMAN, MAY1999.

A reader who thinks of himself as a miniature Earth--as much a home for countless organisms as a living being--has the best chance of getting through Roger Knutson's book without a perpetual feeling of creepy crawlies. This rogue's gallery of humankind's inhabitants ranges from protozoans small enough that hundreds fit in a single cell to tapeworms 75 feet long. For all the appalling facts he assembles--such as that the tapeworm has no head and experts can't agree which end to call the front--Knutson nevertheless tries to evoke empathy for parasites.

Courtesy Jan Cobb

After all, they live in some of the most disgusting habitats in the world, including our lower intestine. Their success deserves respect as well: There are even more kinds of parasites than insects. Since it's in the best interest of parasites not to be noticed, most do not cause much harm; humans could learn from them in our treatment of our planet, says Knutson. He also scolds animal rights activists for not putting parasites on their list to be protected and points out that because of their struggle for survival in extremely hostile environments, parasites' unique genetics could be medically useful.

The descriptions of some of our closest companions may put readers off food, except perhaps overcooked vegetables, but Knutson has some practical advice for avoiding most parasites. Don't assume you're safe outside of Third World countries--the brain- and retina-dwelling Toxoplasma protozoan probably infects half the U.S. population. So think twice the next time a swimming pond looks clear and inviting, since it's apt to be full of all kinds of feces and parasites that you'd never notice. If you do dive in, be extra careful not to get any water into your mouth or nose; mucous membranes provide easy entry for many kinds of unwanted guests. As important, he says, is to be lucky. Since no one will ever get away with a totally parasite-free life, hope your tenants are the microscopic equivalent of neighbors who just occasionally play the stereo too loudly.Order from

--Fenella Saunders

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