The God Particle

by Leon Lederman

  Even so, Mendeleev took a lot of guff in his lifetime. This odd man—he seems to have survived on a diet based on sour milk (he was testing some medical fad)—was subjected by his colleagues to considerable derision for his table. He was also a great supporter of his students at the University of St. Petersburg, and when he stood behind them during a protest late in his career the administration booted him out.

  Without students, he might never have constructed the periodic table. When first appointed to the chair of chemistry in 1867, Mendeleev couldn't find an acceptable text for his classes, so he began writing his own. Mendeleev saw chemistry as "the science of mass"—there's that concern with mass again—and in his textbook he came up with the simple idea of arranging the known elements by the order of their atomic weights.

  He did so by playing cards. He wrote the symbols of the elements with their atomic weights and various properties (for example, sodium: active metal; argon: inert gas) each on a separate note card. Mendeleev enjoyed playing patience, a kind of solitaire. So he played patience with the elements, arranging the cards so that the elements were in order of increasing atomic weights. He then discovered a certain periodicity. Similar chemical properties reappeared in elements spaced eight cards apart; for example, lithium, sodium, and potassium are all chemically active metals, and their positions are 3, 11, and 19. Similarly, hydrogen (1), fluorine (9), and chlorine (17) are active gases. He rearranged the cards so that there were eight vertical columns, with the elements in each column having similar properties.

  Mendeleev did something else that was unorthodox. He felt no compulsion to fill in all the slots in his grid of boxes. Just as in solitaire, he knew that some of the cards were hidden in the deck. He wanted the table to make sense not only reading across the rows but also reading down the columns. If a space called for an element with particular properties and no such element existed, he left it blank rather than trying to force an existing element into the slot. Mendeleev even named the blanks, using the prefix "eka," which is Sanskrit for "one." For example, eka-aluminum and eka-silicon were the gaps in the vertical columns beneath aluminum and silicon, respectively.

  The gaps in the table were one of the reasons Mendeleev was so widely mocked. Yet five years later, in 1875, gallium was discovered and turned out to be eka-aluminum, with all the properties predicted by the periodic table. In 1886 germanium was discovered, which turned out to be eka-silicon. The game of chemical solitaire turned out to be not so nutty.

  One of the factors that made Mendeleev's table possible was that chemists had become more accurate in measuring the atomic weights of the elements. Mendeleev himself had corrected the atomic weights of several elements, which did not win him many friends among those important scientists whose figures were being revised.

  No one understood why the regularities appeared in the periodic table until the discovery in the following century of the nucleus and the quantum atom. In fact, the initial impact of the periodic table was to discourage scientists. There were fifty or more substances called "elements," basic ingredients of the universe that presumably could not be subdivided further—this meant more than fifty different "atoms," and the number was soon to swell to over ninety. This is a long way from an ultimate building block. Looking at the periodic table in the late 1800s should have made scientists tear their hair out. Where's the simple unity we've been seeking for over two millennia? Yet the order that Mendeleev found in this chaos pointed to a deeper simplicity. In retrospect, the organization and regularities of the periodic table cried out for an atom with some structure that repeated itself periodically. Chemists, however, were not ready to abandon the notion that their chemical atoms—hydrogen, oxygen, and so on—were indivisible. A more fruitful attack would come from a different angle.

  Don't blame Mendeleev for the complexity of the periodic table, though. He was simply organizing the confusion as best he could, doing what good scientists do—looking for order in the midst of the complexity. He never was fully appreciated by his peers during his lifetime, never won the Nobel Prize, even though he was alive for several years after the founding of the Prize. At his death in 1907, however; he received the ultimate honor for a teacher. A band of students followed his funeral procession, carrying high above them the periodic table. His legacy is the famous chart of the elements that hangs in every laboratory, every high school chemistry classroom in the world.

  For the final stage in the oscillating development of classical physics we swing from the study of matter and particles back to the study of a force. In this case, electricity. In the nineteenth century, electricity was considered almost a science unto itself.

  It was a mysterious force. And at first appearance, it didn't seem to occur naturally, except in the frightening form of lightning. So researchers had to do an "unnatural" thing to study electricity. They had to "manufacture" this phenomenon before they could analyze it. We have come to realize that electricity is everywhere; all matter is electrical in nature. Keep this in mind when we get to the modern era, when we discuss exotic particles "manufactured" in accelerators.

  Electricity was considered as exotic in the nineteenth century as quarks are today. Today electricity surrounds us, another example of how humans can alter their own environment.

  There were many heroes of electricity and magnetism in this early period, many of whom left their names on various electrical units. They include Charles Augustin de Coulomb (the unit of charge), André Ampère (current), Georg Ohm (resistance), James Watt (electrical power), and James Joule (energy). Luigi Galvani gave us the galvanometer, a device for measuring currents, and Alessandro Volta gave us the volt (a unit of potential or electromotive force). Similarly C. F. Gauss, Hans Christian Oersted, and W. E. Weber all made their mark and left their names on electrical quantities calculated to generate fear and loathing in future students of electrical engineering. Only Benjamin Franklin failed to get his name on any electrical unit, despite his significant contributions. Poor Ben! Well, he has his stove and his portrait on those hundred-dollar bills. Franklin noted that there are two kinds of electricity. He could have called one Joe and the other Moe, but he chose instead plus (+) and minus (—). Franklin termed the amount of, say, negative electricity on an object "electric charge." He also introduced the concept of conservation of charge, that when electricity is transferred from one body to another, the total charge must add to zero. But the giants among all of these scientists were two Englishmen, Michael Faraday and James Clerk Maxwell.

  ELECTRIC FROGS

  Our story begins in the late 1700s with Galvani's invention of the battery, which was later improved by Volta, another Italian. Galvani's study of frog reflexes—he hung frog muscles on the latticework outside his window and watched them twitch during thunderstorms—demonstrated "animal electricity." This stimulated Volta's work about 1790, and a good thing too. Think of Henry Ford installing a box of frogs in each of his cars with instructions to the motorist: "Frogs must be fed every fifteen miles." What Volta found was that the frog electricity had to do with two dissimilar metals separated by some kind of frog goop, for Galvani's frogs were hung on brass hooks on an iron latticework. Volta was able to produce an electrical current sans frog by experimenting with different pairs of metals separated by pieces of leather (standing in for the frogs) soaked in brine. He soon created a "pile" of zinc and copper plates, realizing that the larger the pile, the more current he could drive through an external circuit. Crucial to this work was Volta's invention of an electrometer for measuring the current. This research yielded two important results: a laboratory tool for producing currents and a realization that electricity could be produced by chemical reactions.

  Another important development was Coulomb's measurement of the strength and behavior of the electrical force between two charged balls. To make this measurement he invented the torsion balance, a device exquisitely sensitive to tiny forces. The force he was after, of course, was electricity. Using his torsion balance, Coulom
b determined that the force between electrical charges varied inversely as the square of the distance between them. He also discovered that like sign charges (+ + or − −) repelled one another, whereas unlike charges (+ −) attracted. Coulomb's law, giving the F for electric charges, will play a crucial role in our understanding of the atom.

  In a veritable frenzy of activity, there began a series of experiments on what scientists first believed to be the separate phenomena of electricity and magnetism. In a brief period of about fifty years (1820–1870) these experiments led to a grand synthesis that resulted in a unified theory that included not only electricity and magnetism but light as well.

  SECRET OF THE CHEMICAL BOND: PARTICLES AGAIN

  Much of our early knowledge of electricity emerged from discoveries in chemistry, specifically what is now called electrochemistry. Volta's battery taught scientists that an electrical current can flow around a circuit in a wire that reaches from one pole of the battery to the other. When the circuit is interrupted by attaching wires to pieces of metal immersed in a liquid, the current flows through the liquid. The current in the liquid, they found, creates a chemical process: decomposition. If the liquid is water; hydrogen gas appears near one piece of metal, oxygen near the other. The proportion of 2 parts hydrogen to 1 part oxygen indicates that water is being decomposed into its constituents. A solution of sodium chloride would result in a plating of sodium on one "terminal" and the appearance of the greenish gas chlorine at the other. The industry of electroplating would soon emerge.

  The decomposition of chemical compounds by an electrical current indicated something profound: a connection between atomic binding and electric forces. The notion gained currency that the attractions between atoms—that is, the "affinity" one chemical has for another—were electrical in nature.

  Michael Faraday began his work in electrochemistry by systematizing the nomenclature. As with Lavoisier's naming of chemicals, this helped a lot. Faraday called the metals immersed in the liquid "electrodes." The negative electrode was a "cathode," the positive an "anode." When the electricity zipped through the water, it impelled a migration of charged atoms through the liquid from cathode to anode. Normally, chemical atoms are neutral, having neither a positive nor a negative charge. But the electric current somehow charged the atoms. Faraday called these charged atoms "ions." Today we know that an ion is an atom that has become charged because it has lost or gained one or more electrons. In Faraday's time, they didn't know about electrons. They didn't know what electricity was. But did Faraday suspect the existence of electrons? In the 1830s he carried out a series of spectacular experiments that resulted in two simple summary statements known as Faraday's laws of electrolysis:

  The mass of chemical released at an electrode is proportional to the current multiplied by the length of time it runs. That is, the released mass is proportional to the amount of electricity that passes through the liquid.

  The mass liberated by a fixed quantity of electricity is proportional to the atomic weight of the substance multiplied by the number of atoms in the compound.

  What these laws mean is that electricity is not smooth and continuous but can be divided into "chunks." Given Dalton's idea of atoms, Faraday's laws tell us that atoms in the liquid (ions) migrate to the electrode, where each ion is presented with a unit quantity of electricity that converts it to a free atom of hydrogen, oxygen, silver, or whatever. The Faraday laws thus point to an unavoidable conclusion: there are particles of electricity. This conclusion, however had to wait about sixty years to be dramatically confirmed by the discovery of the electron at the end of the century.

  A SHOCK IN COPENHAGEN

  To continue the history of electricity—the stuff that appears in two or three slots in your electrical outlets, for a price—we have to go to Copenhagen, Denmark. In 1820 Hans Christian Oersted made a key discovery—some historians claim that it is the key discovery. He created an electric current in the approved manner, with wires connecting one terminal of a Voltaic contraption (battery) to the other. Electricity was still a mystery, but an electric current involved something called electric charge, moving through a wire. No surprise there, until Oersted placed a compass needle (a magnet) near the circuit. When the current flowed, the compass needle veered from pointing to the geographic North Pole (its normal job description) to taking a funny position at right angles to the wire. Oersted worried about this effect until it dawned on him that, after all, a compass is designed to detect magnetic fields. So the current in the wire must be producing a magnetic field, no? Oersted had discovered a connection between electricity and magnetism: currents produce magnetic fields. Magnets of course also produce magnetic fields, and their ability to attract pieces of iron (or to hold snapshots on refrigerator doors) was well studied. The news traveled across Europe and created a great stir.

  Running with this information, the Parisian André Marie Ampère found a mathematical relation between current and a magnetic field. The detailed strength and direction of this field depended on the current flowing and on the shape (straight, circular, or whatever) of the wire carrying the current. By a combination of mathematical reasoning and many experiments hastily carried out, Ampère generated a one-man storm of controversy out of which emerged, in the fullness of time, a prescription for calculating the magnetic field produced by an electric current through any configuration of wire—straight, bent, formed into a circular loop, or wound densely on a cylindrical form. Since current passed through two straight wires produces two magnetic fields, these fields can push on each other; effectively, the wires exert force on each other. This discovery made possible Faraday's invention of the electric motor. The fact that a circular loop of current produces a magnetic field was also profound. Could it be that what the ancients called lodestones, natural magnets, actually are composed of atomic-scale circular currents? Another clue to the electrical nature of atoms.

  Oersted, like so many other scientists, felt driven toward unification, simplification, reduction. He believed that gravity, electricity, and magnetism were all different manifestations of a single force, which is why his discovery of a direct connection between two of these forces was so exciting (shocking?). Ampère, too, looked for simplicity; he essentially tried to eliminate magnetism by considering it an aspect of electricity in motion (electrodynamics).

  DÉJÀ VU ALL OVER AGAIN

  Enter Michael Faraday (1791–1867). (Okay, he has already entered, but this is his formal intro. Fanfare, please.) If Faraday was not the greatest experimenter of his time, he is certainly a candidate for that tide. It is said that he has generated more biographies than Newton, Einstein, or Marilyn Monroe. Why? Partly it's the Cinderella aspect of his career. Born into poverty, at times hungry (he was once given a loaf of bread as his only food for a week), Faraday was practically unschooled, with a strong religious upbringing. Apprenticed to a bookbinder at the age of fourteen, he actually managed to read some of the books he bound. He thus educated himself while developing a manual dexterity that would serve him well as an experimenter. One day a client brought in a copy of the third edition of the Encyclopaedia Britannica to be rebound. It had an article on electricity. Faraday read it, was hooked, and the world changed.

  Think about this. Two items are received by the network news offices over the AP wires:

  FARADAY DISCOVERS ELECTRICITY, ROYAL SOCIETY LAUDS FEAT

  and

  NAPOLEON ESCAPES FROM ST. HELENA,

  CONTINENTAL ARMIES ON THE MARCH

  Which item makes the six o'clock news? Right! Napoleon. But over the next fifty years Faraday's discovery literally electrified England and set in motion as radical a change in the way people live on this planet as has ever flowed from the inventions of one human being. Now if only the gatekeepers of TV journalism had been forced to satisfy a real science requirement in college...

  CANDLES, MOTORS, DYNAMOS

  Here is what Michael Faraday accomplished. Starting his professional life as a chemist at the
age of twenty-one, he discovered a number of organic compounds, including benzene. He made the transition to physics by cleaning up electrochemistry. (If those University of Utah chemists who thought they had discovered cold fusion in 1989 had understood Faraday's laws of electrolysis better, perhaps they would never have embarrassed themselves as well as the rest of us.) Faraday then went on to make major discoveries in the fields of electricity and magnetism. He:

  discovered the law (named for him) of induction, whereby a changing magnetic field creates an electric field

  was the first to produce an electric current from a magnetic field

  invented the electric motor and dynamo

  demonstrated the relation between electricity and chemical bonding

  discovered the effect of magnetism on light

  and much more!

  All this without a Ph.D., M.A., B.A., or high school equivalency degree! He was also mathematically illiterate. He wrote up his discoveries not in equations but in plain descriptive language, often accompanied by pictures to explain the data.

  In 1990 the University of Chicago launched a TV series called The Christmas Lectures, and I was honored to give the first one. I called it "The Candle and the Universe," borrowing the idea from Faraday, who started the original Christmas lectures for children in 1826. In his first talk he argued that all known scientific processes were illustrated by the burning candle. This was true in 1826, but by 1990 we had learned about a lot of processes that do not take place in the candle because the temperature is too low. Nevertheless, Faraday's lectures on the candle were lucid and entertaining and would make a great Christmas present for your children if some silver-voiced actor would make some CD's. So add another facet to this remarkable man—Faraday as popularizer.