E=mc2 (4 page)

m Is for mass
4

For a long time the concept of "mass" had been like the concept of energy before Faraday and the other nineteenth-century scientists did their work. There were a lot of different material substances around—ice and rock and rusted metal—but it was not clear how they related to each other, if they did at all.

What helped researchers believe that there had to be some grand links was that in the 1600s, Isaac Newton had shown that all the planets and moons and comets we see could be described as being cranked along inside an immense, God-created machine. The only problem was that this majestic vision seemed far away from the nitty-gritty of dusty, solid substances down here on earth.

To find out if Newton's vision really did apply on Earth—to find out, that is, if the separate types of substance around us really were interconnected in detail—it would take a person with a great sense of finicky precision; someone willing to spend time measuring even tiny shifts in weight or size. This person would also have to be romantic enough to be motivated by Newton's grand vision—for otherwise, why bother to hunt for these dimly suspected links between all matter?

This odd mix—an accountant with a soul that could soar—might have been a character portrait of Antoine-Laurent Lavoisier. He, as much as anyone else, was the man who first showed that all the seemingly diverse bits of tree and rock and iron on earth—all the "mass" there is—really were parts of a single connected whole.

It turned out to be a good marriage, despite the difference in age, and despite the fact that soon after the handsome twenty-eight-year-old Lavoisier rescued Marie Anne, he shifted back to being immersed in the stupendously boring accountancy work he did for Paulze, within the organization called the "General Farm."

This was not a real farm, but rather an organization with a near monopoly on collecting taxes for Louis XVI's government. Anything extra, the Farm's owners could keep for themselves. It was exceptionally lucrative, but also exceptionally corrupt, and for years had attracted old men wealthy enough to buy their way in, but unable to do any detailed accounting or administration. It was Lavoisier's job to keep this vast tax-churning device in operation.

He did that, head down, working long hours, six days a week on average for the next twenty years. Only in his spare time—an hour or two in the morning, and then one full day each week—did he focus on his science. But he called that single day his "jour de bonheur"—his "day of happiness."

Perhaps not everyone would comprehend why this was such a "bonheur." The experiments often resembled Lavoisier's ordinary accounting, only dragged out even longer. Yet the moment came when Antoine, in that irrational exuberance young lovers are known for, said his bride could now help him with a truly major experiment. He was going to watch a piece of metal slowly burn, or maybe just rust. He wanted to find out whether it would weigh more or less than it did before.

(Before going on, the reader might wish to actually guess: Let a piece of metal rust—think of an old fender or underbody panel on your car—and it ends up weighing

They put various substances in their drawing room apparatus, sealed it tight, and applied heat or started an actual burn to speed up the rusting. Once everything had cooled down, they took out the mangled or rusty or otherwise burned-up metal and weighed it, and also carefully measured how much air may have been lost.

Each time they got the same result. What they found, in modern terms, was that a rusted sample does not weigh less. It doesn't even weigh the same. It weighs
more.

This was unexpected. The additional weight was not from dust or metal shards left around in the weighing apparatus—he and his wife had been very careful. Rather, air has parts: there are different gases within the vapor we breathe. Some of the gases must have flown down and stuck to the metal. That was the extra weight he had found.

What was really happening? There was the same amount of stuff overall, yet now the oxygen that had been in the gases floating above was no longer in the air.
But it had not disappeared.
It had simply stuck on to the metal. Measure the air, and you would see it had lost some weight. Measure the chunk of metal, and you would see it had been enhanced—by exactly that same amount of weight the air had lost.

With his fussily meticulous weighing machine, Lavoisier had shown that matter can move around from one form to another, yet it will not burst in and out of existence. This was one of the prime discoveries of the 1700s—on a level with Faraday's realizations about energy in the basement of the Royal Institution a half century later. Here too, it was as if God had created a universe, and then said, I am going to put a fixed amount of mass in my domain, I will let stars grow and explode, I will let mountains form and collide and be weathered away by wind and
ice;
I will let metals rust and crumble. Yet throughout this the total amount of mass in my universe will never alter; not even to the millionth of an ounce; not even if you wait for all eternity. If a city were to be weighed, and then broken by siege, and its buildings burned by fire—if all the smoke and ash and broken ramparts and bricks were collected and weighed, there would be no change in the original weight. Nothing would have truly vanished, not even the weight of the smallest speck of dust.

To say that all physical objects have a property called their "mass," which affects how they move,
is
impressive, yet Newton had done it in the late 1600s. But to get enough detail to show exactly how their parts can combine or separate? That is the further step Lavoisier had now achieved.

Whenever France's scientists make discoveries at this level, they're brought close to the government. It happened with Lavoisier. Could this oxygen he'd helped clarify be used to produce a better blast furnace? Lavoisier had been a member of the Academy of Sciences and now was given funds to help find out. Could the hydrogen he was teasing out from the air with his careful measurements be useful in supplying a flotilla of balloons, capable of competing with Britain for supremacy in the air? He got grants and contracts for that as well.

In any other period this would have guaranteed the Lavoisiers an easy life. But all these grants and honors and awards were coming from the king, Louis XVI, and in a few years Louis would be murdered, along with his wife and many of his ministers and wealthy supporters.

Lavoisier might have avoided being caught up with the other victims. The Revolution was only at its most lethal phases for a few months, and many of Louis' closest supporters simply lived out those periods in quiet. But Lavoisier could never drop the attitude of careful measuring. It was part of his personality as an accountant; it was the essence of his discoveries in science.

Now it would kill him.

The first mistake seemed innocuous enough. Outsiders constantly bothered members of the Academy of Sciences, and long before the Revolution, one of them, a Swiss-born doctor, had insisted that only the renowned Lavoisier would be wise enough, and understanding enough, to judge his new invention. The device was something of an early infrared scope, allowing the doctor to detect the shimmering heat waves rising from the top of a candle, or of a cannonball, or even—on one proud occasion, when he'd lured the American representative to his chambers—from the top of Benjamin Franklin's bald head. But Lavoisier and the Academy turned him down. From what Lavoisier had heard, the heat patterns that the doctor was searching for couldn't be measured with precision, and to Lavoisier that was anathema. But the Swiss-born hopeful—Dr. Jean-Paul Marat—never forgot.

The next mistake was even more closely linked to Lavoisier's obsession with measurement. Louis XVI was helping America fund its revolutionary war against the British, an alliance that Benjamin Franklin had been central in sustaining. There were no bond markets, so to get the money Louis had to turn to the General Farm. But taxes already were high. Where could they go to get more?

In every period of incompetent administration France has suffered—and Louis's successors in the 1930s would have given him a good run—there almost always has been a small group of technocrats who've decided that since no one who was officially in power was going to take charge, then they would have to do it themselves. Lavoisier had an idea. Think of the measuring apparatus in his drawing room, the one where he and Marie Anne had been able to keep exact track of everything going in and out. Why not enlarge it, wider and wider, so that it encompassed all of Paris? If you could track the
city's
incomings and outgoings, he realized, you could tax them.

There once had been a physical wall around Paris, but it dated from medieval times, and had long since become nearly useless for taxation. Tollgates were crumbling, and many areas were so broken that smugglers could just walk in.

Lavoisier decided to build another wall, a massive one, where everyone could be stopped, searched, and forced to pay tax. It cost the equivalent, in today's currency, of several hundred million dollars; it was the Berlin Wall of its time. It was six feet high, of heavy masonry, with dozens of solid tollgates and patrol roads for armed guards.

Parisians hated it, and when the Revolution began, it was the first large structure they attacked, two days before the storming of the Bastille: they tore at it with firebrands and axes and bare hands till it was almost entirely gone. The culprit was known, as an antiroyalist broadsheet declared: "Everybody confirms that M. Lavoisier, of the Academy of Sciences, is the 'beneficent patriot' to whom we owe the . . . invention of imprisoning the French capital. . . ."

Even this he might have survived. A mob's passions are brief, and Lavoisier hurriedly tried to show he was on their side. He personally directed the gunpowder mills that supplied the Revolutionary Armies; he tried to have the Academy of Sciences show new, reformist credentials by getting rid of the grand tapestries in its Louvre offices. He even seemed to be succeeding—until one never-forgiving figure from his past emerged.

By 1793, Jean-Paul Marat was head of a leading faction in the National Assembly. He'd suffered years of poverty because of Lavoisier's rejection: his skin was withered from an untreated disease, his chin unshaven, his hair neglected. Lavoisier by contrast was still handsome: his skin was smooth; his build was strong.

Marat didn't kill him immediately. Instead, he made sure Paris's citizens were constantly reminded of the wall, this living, large-scale summary of everything Marat hated about the class-smug Academy. He was a magnificent speaker—along with Danton and, in recent history, Pierre Mendes-France, among the finest France has produced. ("I am the anger, the just anger, of the people and that is why they listen to me and believe in me.") The only sign of Marat's tension—barely visible to listeners watching his confident posture, right hand on his hip, left arm casually extended on the desk in front of him—was a slight nervous tapping of one foot on the ground. When Marat denounced Lavoisier, he embodied the very principle that Lavoisier had demonstrated. For was it not true that everything balances? If you seem to destroy something in one place, it's not really destroyed. It just appears somewhere else.

In November 1793 Lavoisier got word he was going to be arrested. He tried hiding in the abandoned parts of the Louvre, roaming through the Academy's empty offices there, but after four days he gave up, and walked— with Marie Anne's father—to the Port Libre prison.

If he looked out his window of the Port Libre ("Our address is: first floor hall, number 23, room at the end"), he could see the great classical dome of the Observatory, a landmark over one century old, and now closed by Revolutionary orders. At least at night, when the guards ordered candles blown out in Lavoisier's prison, the stars were visible above its dome.

There were transfers to other prisons; the trial itself was on May 8. A few prisoners tried to speak, but the judges laughed at them. Marat's bust was on a shelf looking down on the accused. That afternoon, twenty-
eight of
the onetime millionaires from the General Farm were taken to what's now the Place de la Concorde. Their hands were tied behind their backs. It was a steep climb up to the working level of Dr. Guillotin's instrument. Most seem to have been quiet, though one of the older men "was led to the scaffold in a pitiful state." Paulze was third; Lavoisier was fourth. There was about a minute after each beheading: not to clean the blade, but to clear away the headless bodies.