Caution: We Brake for Newton

By Dennis Overbye

Big people drive big cars. If one generalization seems safe in modern America, it is that the richer or more important you are, the more tons of steel and tinted glass you ride around in. Little people, if they drive at all, drive little cars, and you know without getting out your high school physics book what happens when big cars hit little cars. Perhaps it is fitting in some Darwinian way; we lowly ones in our eggshells offer minimal resistance as the Trumps and Keatings crunch over us, car phones in hand, on the way to their bankruptcy hearings and leveraged buyouts. Indeed, it seems part of the American Dream to become rich enough to wrap oneself in so much tanklike armor that one barely feels the bump of the riffraff undertire. But now that dream is under attack, according to an organization calling itself the Coalition for Vehicle Choice. According to the coalition, a collection of the usual well- meaning but misguided dupes, liberals, Congressmen, pessimists and wimps is threatening to make us all drive weenie cars by raising the required gas mileage of new autos.

The point was made bluntly with a full-page ad in the New York Times that featured a photograph of a large car demolishing a smaller one. A headline blared in big black type, THE LAWS OF PHYSICS CANNOT BE LEGISLATED AWAY. The occasion for this uplifting lesson is the debate on George Bush's energy plan, which emphasizes domestic energy production to the exclusion of conservation. Environmentalists point out that raising fuel-economy standards from 27.5 m.p.g. to 34 (Honda and Toyota just announced they would start selling some cars with engines that do twice as well) would save more oil than expedited drilling in Alaska could provide. The carmakers clearly wanted to nip that idea in the bud. Efficient cars are smaller cars, and therefore fuel economy, they say, is dangerous to your health.

As a science writer, I have to commend the coalition for this attempt to introduce physics into the national discourse, which surely needs an intellectual lift, but there are problems. Big cars are safer only for the people who happen to be riding in them at the time, much the way that Uzis are safer only for the people holding them. The National Highway Traffic Safety Administration doesn't count the number of lungs damaged by ozone from automobile exhaust. The birds and seals suffering and dying along whatever pristine coast an oil tanker chooses to run aground on don't make the tally. But they are traffic victims, as surely as are pedestrians run over in a crosswalk.

The coalition didn't specify what laws of physics it had in mind. Colliding cars remind us of Newton's laws, which say in effect that the heavier and faster a thing is, the harder it is to stop. That's a fine analysis for a pair of billiard balls, but the world is more complicated than that. There are more laws of physics, such as those that govern the greenhouse effect. Nature has to obey them all. The art of science consists partly of figuring out which laws are the most important in a given situation. This is where the coalition failed. We need a better metaphor than the two-body-crunch, winner-loser model of society. And there is one. I suspect that even the poet-physicists in the Coalition for Vehicle Choice have heard of the second law of thermodynamics, one of the most far-reaching commandments of physics and one of the few to have escaped from science into the popular culture. At its most vulgar, the second law can be summarized as "Things get worse." Not an inspiring slogan.

Thermodynamics originated as the study of heat and steam engines but has been generalized to include subjects as diverse as computers, biology and cosmology. There are three laws of thermodynamics. The first law says you can't create energy. The second law says you always squander some. The third law says you can't cool anything to absolute zero. Cynical students often put them thus: 1) You can't win; 2) You can't break even; 3) You can't get out of the game. The second law defines a quantity called entropy, which is a measure of waste and disorder, and which tends to increase over time inside the beating cylinder of an automobile engine, for example, or inside the universe. A little energy always gets wasted, which is why automobile exhaust is always hot and why you can't build a perpetual-motion machine. The melting of an ice cube, the gradual disarray of a closet and typos in this magazine are all triumphs of the second law.

Picture an ad with a giant photograph of an idling exhaust pipe, seen end on, a faint stream of God-knows-what wafting lazily out on its way to the ozone layer or to your lungs. In this context those "laws of physics" mean something very different. The more and bigger machines we build, the more hot mystery exhaust we produce. What cannot be legislated away is the tendency for it to disperse and for oil to gush out of broken boats. The laws of physics say you can never put Alaska back together again once you have dismantled it for its minerals. As a point of national discourse, thermodynamics would be a reminder of mortality and humility. Left to themselves, things do get worse. Engineers will never build the perfect car or the foolproof missile-defense system, regardless of what you read in the glossy science magazines. The burden of saving the planet belongs not to technologists but to the rest of us. Sure we can always make better machines, but they will not save us; it is we who have to save them.

Accidents are of course entropy, as is the slow wear of tire treads or the blur of alcoholic vision that suddenly turns all your raging horsepower and tons of steel from an asset into a trap. Too much entropy can deliver you back into Newton's dread realm after all. It was a big, black American sedan that skidded up the mountain road where I live on Memorial Day night, climbed a guy wire and broke the telephone pole. The way the car came to rest -- lights blazing, leaning against the opposite side of the pole from where it hit, the driver dead in the backseat -- and the location of every last splinter of glass in the woods were perfectly explicable by the laws of physics.