PAUL DIRAC, ANTIMATTER, AND YOU

A Riddle

What have these in common?

1. 1926: A graduate student, Cambridge University

2. Billions of years ago: Quasars exploding

3. 1908: A Siberian forest devastated

4. 10 million years ago: A galaxy exploding 5. 1932: A cloud-chamber track, Pasadena, Calif.

Answer: All may, and 1 and 5 do involve antimatter.

(ANTI matter?)'

Yes—like ordinary matter with electrical properties of particles reversed. Each atom of matter is one or more nucleons surrounded by one or more electrons; charges add up to zero. A hydrogen atom has a proton with positive charge as nucleus, surrounded by an electron with negative charge, A proton is 1836.11 times as massive as an electron, but their charges are equal and opposite: +1-1 0. Uranium-235 (or ₉₂U²³⁵, meaning "an isotope of element 92, uranium, nuclear weight 235") has 235 nucleons: 143 neutrons of zero charge and 92 protons of positive charge (143 + 92 - 235; hence its name); these 235 are surrounded by 92 electrons (negative), so total charge is zero: 0 + 92-92 = 0. (Nuclear weight is never zero, being the mass of all the nucleons.)

Portrait of Paul Dirac by Stephen Fabian.

Make electrons positive, protons negative: charges still balance; nuclear weight is unchanged—but it is not an atom of matter; it is an antiatom of antimatter. "Touch Me Not!"

In an antimatter world, antimatter behaves like matter. Bread dough rises, weapons kill, kisses still taste sweet. You would be antimatter and not notice it.

WARNING! Since your body is matter (else you could not be reading this), don't kiss an antimatter girl. You both would explode with violence unbelievable.

But you'll never meet one, nor will your grandchildren. (I'm not sure about their grandchildren.) E = mc²

Antimatter is no science-fiction nightmare; it's as real as Texas. That Cambridge graduate student was Paul A. M. Dirac inventing new mathematics to merge Albert Einstein's special theory of relativity with Max Planck's quantum theory. Both theories worked—but conflicted. Dirac sought to merge them without conflict.

He succeeded.

His equations were published in 1928, and from them, in 1930, he made an incredible prediction: each sort of particle had antiparticles of opposite charge: "antimatter."

Scientists have their human foibles; a scientist can grow as fond of his world concept as a cat of its "own" chair. By 1930 the cozy 19th-century "world" of physics had been repeatedly outraged. This ridiculous new assault insulted all common sense.

But in 1932 at the California Institute of Technology, Carl D. Anderson photographed proof of the electron's antiparticle (named "positron" for its positive charge but otherwise twin to the electron). Radical theory has seldom been confirmed so quickly or rewarded so promptly: Dirac received the Nobel prize in 1933, Anderson in 1936—each barely 31 years of age when awarded it.

A photograph taken in 1932 by Carl D. Anderson through the glass wall of a wilson cloud chamber at the California Institute of Technology, provided the first proof of the existence of an antiparticle. Using a lead plate (viewed edge on as the vertical band in photo) to slow down the rapidly moving particle and thereby increase the curvature (caused by an applied magnetic field of known strength and polarity) of its track, Anderson first determined from the leftward movement that the particle was positively charged like a proton. Calculations based on the degree of the track's arc and magnetic field strength, however, revealed the particle's mass to be that of an electron. The particle tracked was therefore a positively charged electron — an antiparticle, or "positron" as Anderson called.

Since 1932 so many sorts of antiparticles have been detected that no doubt remains: antimatter matches matter in every sort of particle. Matching is not always as simple as electron (e-) and positron (e+). Photons are their own antiparticles. Neutrons and neutrinos (zero charges) are matched by antineutrons and anti-neutrinos, also of zero charge—this sounds like meaningless redundancy because English is not appropriate language; abstract mathematics is the language required for precise statements in physical theory. (Try writing the score of a symphony solely in words with no musical symbols whatever.)

But a hint lies in noting that there are reaction series in which protons and electrons yield neutrons—one example: the soi-disant "Solar Phoenix" (solar power theory, Hans Bethe); if we ignore details, the Solar Phoenix can be summarized as changing four hydrogen atoms (four of ₁H¹) into one helium atom (₂H⁴). We start with four protons and four electrons; we end up six stages later with two neutrons, two protons, and two electrons—and that is neither precise nor adequate and is not an equation and ignores other isotopes involved, creation of positrons, release of energy through mutual annihilations of positrons and free electrons, and several other features, plus the fact that this transformation can occur by a variety of routes.

(But such are the booby traps of English or any verbal language where abstract mathematics is the only correct language.)

A wide variety of other transformations permits an-tiprotons and positrons to yield antineutrons. The twin types of varieties of transformations mentioned above are simply samples; there are many other types being both predicted mathematically and detected in the laboratories almost daily—and many or most transformation series involve antiparticles of antimatter.

Nevertheless, antimatter is scarce in our corner of the universe—lucky for us because, when matter encounters antimatter, both explode in total annihilation. E = mc² is known to everyone since its awful truth was demonstrated at Hiroshima, Japan. It states that energy is equivalent to mass, mass to energy, in this relation: energy equals mass times the square of the velocity of light in empty space.

That velocity is almost inconceivable. In blasting for the moon our astronauts reached nearly 7 miles/ second; light travels almost 27,000 times that speed— 186,282.4 (±0.1) miles or 299,792.5 (±0.15) kilometers each second. Round off that last figure as 300,000; then use the compatible units of science (grams, centimeters, ergs) and write in centimeters 3 x 10¹⁰, then square it: 9 x 10²⁰, or 900,000,000,000,000,000,000. (!!!)

This fantastic figure shouts that a tiny mass can become a monstrous blast of energy—grim proof: Hiroshima.

But maximum possible efficiency of U²³⁵ fission is about 1/10 of 1%; the Hiroshima bomb's actual efficiency was much lower, and H-bomb fusion has still lower maximum (H-bombs can be more powerful through having no limit on size; all fission bombs have sharp limits). But fission or fusion, almost all the reacting mass splits or combines into other elements; only a trifle becomes energy.

In matter-antimatter reaction, however, all of both become energy. An engineer might say "200% efficient" as antimatter undergoing annihilation converts into raw energy an equal mass of matter.

Mathematical Physicists

An experimental physicist uses expensive giant accelerators to shoot particles at 99.9%+ of the speed of light, or sometimes gadgets built on his own time with scrounged materials. Large or small, cheap or costly, he works with things.

The world's great theoretical physicists have included (left to right, top to bottom) Nicolaus Copernicus (1473-1543); Johannes Kepler (1571-1630); Sir Isaac Newton (1643-1727); James Clerk Maxwell (1831-1879); Max Planck (1858-1947); Albert Einstein (1879-1955); and Paul A.M. Dirac(1902- ).

Left to right, top to bottom, courtesy of Yerkes Observatory and the University of Chicago Press; Archiv fur Kunst and Geschichte; National Portrait Gallery, London; National Portrait Gallery, London; EB Inc.; German Information Center.

A mathematical physicist uses pencil, paper, and brain. Not my brain or yours—unless you are of the rare few with "mathematical intuition."

That's a tag for an unexplainable. It is a gift, not a skill, and cannot be learned or taught. Even advanced mathematics ("advanced" to laymen) such as higher calculus, Fourier analysis, n-dimensional and non-Euclidean geometries are skills requiring only patience and normal intelligence . . . after they have been invented by persons having mathematical intuition.

The oft-heard plaint "I can't cope with math!" may mean subnormal intelligence (unlikely), laziness (more likely), or poor teaching (extremely likely). But that plaint usually refers to common arithmetic—a trivial skill in the eyes of a mathematician. (Creating it was not trivial. Zero, positional notation, decimal-or-base point all took genius; imagine doing a Form 1040 in Roman numerals.)

Of billions living and dead perhaps a few thousand have been gifted with mathematical intuition; a few hundred have lived in circumstances permitting use of it; a smaller fraction have been mathematical physicists. Of these a few dozen have left permanent marks on physics.

But without these few we would not have science. Mathematical physics is basic to all sciences. No exceptions. None.

Mathematical physicists sometimes hint that experimentalists are frustrated pipefitters; experimentalists mutter that theoreticians are so lost in fog they need guardians. But they are indispensable to each other. Piling up facts is not science—science is facts-and-theories. Facts alone have limited use and lack meaning; a valid theory organizes them into far greater usefulness. To be valid a theory must be confirmed by all relevant facts. A "natural law" is theory repeatedly confirmed and drops back to "approximation" when one fact contradicts it. Then search resumes for better theory to embrace old facts plus this stubborn new one.

No "natural law" of 500 years ago is "law" today; all our present laws are probably approximations, useful but not perfect. Some scientists, notably Paul Dirac, suspect that perfection is unattainable.

A powerful theory not only embraces old facts and new but also discloses unsuspected facts. These are landmarks of science: Nicolaus Copernicus' heliocentric theory, Johannes Kepler's refining it into conic-sections ballistics, Isaac Newton's laws of motion and theory of universal gravitation, James C. Maxwell's equations linking electricity with magnetism, Planck's quantum theory, Einstein's relativity, Dirac's synthesis of quantum theory and special relativity—a few more, not many.

Mathematical physicists strive to create a mathematical structure interrelating all space-time events, past and future, from infinitesimally small to inconceivably huge and remote in space and time, a "unified field theory" embracing 10 or 20 billion years and light-years, more likely 80 billion or so—or possibly eternity in an infinity of multiple universes.

Some order!

They try. Newton made great strides. So did Einstein. Nearly 50 years ago Dirac brought it closer, has steadily added to it, is working on it today.

Paul Dirac may be and probably is the greatest living theoretical scientist. Dirac, Newton, and Einstein are equals. Paul A. M. Dirac

The experimentalists' slur about theoretical physicists holds a grain of truth. Newton apparently never noticed the lovely sex in all his years. Einstein ignored such trivialities as socks. One mathematical physicist who swayed World War II could not be trusted with a screwdriver.

Dirac is not that sort of man.

Other than genius, his only unusual trait is strong dislike for idle talk. (His Cambridge students coined a unit the dirac—one word per light-year.) But he lectures and writes with admirable clarity. Taciturn, he is not unsocial; in 1937 he married a most charming Hungarian lady. They have two daughters and a son.

He can be trusted with tools; he sometimes builds instruments and performs his own experiments. He graduated in engineering before he became a mathematical physicist; this influenced his life. Engineers find working solutions from incomplete data; approximations are close enough if they do the job—too fussy wastes man-hours. But when a job needs it, a true engineer gives his utmost to achieve as near perfection as possible.

Dirac brought this attitude to theoretical physics; his successes justify his approach.

He was born in Bristol, England, Aug. 8, 1902, and named Paul Adrien Maurice Dirac. His precocity in mathematics showed early; his father supplied books and encouraged him to study on his own. Solitary walks and study were the boy's notion of fun—and are of the man today. Dirac works (and plays) hardest by doing and saying nothing . . . while his mind roams the universe.

When barely 16 years old, he entered the University of Bristol. At 18 he graduated, bachelor of science in electrical engineering. In 1923 a grant enabled him to return to school at the foremost institution for mathematics, Cambridge University. In three years of study for a doctorate Dirac published 12 papers in mathematical physics, 5 in The Proceedings of the Royal Society. A cub with only an engineering degree from a minor university has trouble getting published in any journal of science; to appear at the age of 22 in the most highly respected of them all is amazing.

Dirac received his doctorate in May 1926, his dissertation being "Quantum Mechanics"—the stickiest subject in physical science. He tackled it his first year at Cambridge and has continued to unravel its paradoxes throughout his career; out of 123 publications over the last 50 years the word quantum can be found 45 times in his titles.

Dirac remained at Cambridge—taught, thought, published. In 1932, the year before his Nobel prize, he received an honor rarer than that prize, one formerly held by Newton: Lucasian professor of mathematics. Dirac kept it 37 years, until he resigned from Cambridge. He accepted other posts during his Cantabrigian years: member of the Institute for Advanced Study at Princeton, N.J., professor of the Dublin Institute for Advanced Studies, visiting professorships here and there.

Intuitive mathematicians often burn out young. Not Dirac!—he is a Michelangelo who started very young, never stopped, is still going strong. Antimatter is not necessarily his contribution most esteemed by colleagues, but his other major ones are so abstruse as to defy putting them into common words:

A mathematical attribute of particles dubbed "spin"; coinvention of the Fermi-Dirac statistics; an abstract mathematical replacement for the "pellucid aether" of classical mechanics. For centuries, ether was used and its "physical reality" generally accepted either as "axiomatic" or "proved" through various negative proofs. Both "axiom" and "negative proof" are treacherous; the 1887 Michelson-Morley experiment showed no physical reality behind the concept of ether, and many variations of that experiment over many years gave the same null results.

So Einstein omitted ether from his treatments of relativity—while less brilliant men ignored the observed facts and clung to classical ether for at least 40 years.

Dirac's ether (circa 1950) is solely abstract mathematics, more useful thereby than classical ether as it avoids the paradoxes of the earlier concepts. Dirac has consistently warned against treating mathematical equations as if they were pictures of something that could be visualized in the way one may visualize the Taj Mahal or a loaf of bread; his equations are rules concerning space-time events—not pictures.

(This may be the key to his extraordinary successes.)

One more example must represent a long list: Dirac's work on Georges Lemaitre's "primeval egg"— later popularized as the "big bang."

Honors also are too many to list in full: fellow of the Royal Society, its Royal Medal, its Copley Medal, honorary degrees (always refused), foreign associate of the American Academy of Sciences, Oppenheimer Memorial Prize, and (most valued by Dirac) Great Britain's Order of Merit.

Dirac "retired" by accepting a research professorship at Florida State University, where he is now working on gravitation theory. In 1937 he had theorized that Newton's "constant of gravitation" was in fact a decreasing variable . . . but the amount of decrease he predicted was so small that it could not be verified in 1937.

Today the decrease can be measured. In July 1974 Thomas C. Van Flandern of the U.S. Naval Observatory reported measurements showing a decrease in gravitation of about a ten-billionth each year (1 per 10¹⁰ per annum). This amount seems trivial, but it is very large in astronomical and geological time. If these findings are confirmed and if they continue to support Dirac's mathematical theory, he will have upset physical science even more than he did in 1928 and 1930.

Here is an incomplete list of the sciences that would undergo radical revision: physics from micro- through astro-, astronomy, geology, paleontology, meteorology, chemistry, cosmology, cosmogony, geogony, ballistics. It is too early to speculate about effects on the life sciences, but we exist inside this physical world and gravitation is the most pervasive feature of our world.

Courtesy Kitt Peak National Observatory

The Nicholas U. Mayall 158-inch reflecting mirror telescope at Arizona's Kitt Peak National Observatory has the widest field of view of any single-mirror telescope, effectively reaching out to the edges of the universe.

Theory of biological evolution would certainly be affected. It is possible that understanding gravitation could result in changes in engineering technology too sweeping easily to be imagined.

Antimatter and You

Of cosmologies there is no end; astrophysicists enjoy "playing God." It's safe fun, too, as the questions are so sweeping, the data so confusing, that any cosmology is hard to prove or disprove. But since 1932 antimatter has been a necessary datum. Many cosmologists feel that the universe (universes?) has as much antimatter as matter—but they disagree over how to balance the two.

Some think that, on the average, every other star in our Milky Way galaxy is antimatter. Others find that setup dangerously crowded—make it every second galaxy. Still others prefer universe-and-antiuniverse with antimatter in ours only on rare occasions when energetic particles collide so violently that some of the energy forms antiparticles. And some like higher numbers of universes—even an unlimited number.

One advantage of light's finite speed is that we can see several eons of the universe in action, rather than just one frame of a very long moving picture. Today's instruments reach not only far out into space but also far back into time; this permits us to test in some degree a proposed cosmology. The LST (Large Space Telescope), to be placed in orbit by the Space Shuttle in 1983, will have 20 times the resolving power of the best ground-based and atmosphere-distorted conventional telescope—therefore 20 times the reach, or more than enough to see clear back to the "beginning" by one cosmology, the "big bang."

(Q: What happened before the beginning? A: You tell me.)

When we double that reach—someday we will— what will we see? Empty space? Or the backs of our necks?

(Q: What's this to me? A: Patience one moment. . . .)

Currently in the design stage, the LST (Large Space Telescope) is to be orbited in 1983 and is expected to be 20 times more powerful than any current ground-based telescope.

The star nearest ours is a triplet system; one of the three resembles our sun and may have an Earthlike planet—an inviting target for our first attempt to cross interstellar space. Suppose that system is antimatter— BANG! Scratch one starship.

(Hooray for Zero Population Growth! To hell with space-travel boondoggles!)

Then consider this: June 30, 1908, a meteor struck Siberia, so blindingly bright in broad daylight that people 1,000 miles away saw it. Its roar was "deafening" at 500 miles. Its ground quake brought a train to emergency stop 400 miles from impact. North of Van-avara its air blast killed a herd of 1,500 reindeer.

Trouble and war and revolution—investigation waited 19 years. But still devastated were many hundreds of square miles. How giant trees lay pinpointed impact.

A meteor from inside our Galaxy can strike Earth at 50 miles/second.

But could one hit us from outside our Galaxy?

Yes! The only unlikely (but not impossible) routes are those plowing edgewise or nearly so through the Milky Way; most of the sky is an open road—step outside tonight and look. An antimeteor from an antigal-axy could sneak in through hard vacuum—losing an antiatom whenever it encountered a random atom but nevertheless could strike us massing, say, one pound.

One pound of antimatter at any speed or none would raise as much hell as 28,000 tons of matter striking at 50 miles/second.

Today no one knows how to amass even a gram of antimatter or how to handle and control it either for power or for weaponry. Experts assert that all three are impossible.

However . . .

Two relevant examples of "expert" predictions:

In 1908 the Tunguska region of Siberia was struck by a blast equivalent to 30 million tons of TNT, the impact of which was felt by residents 400 miles from the site and which left in its wake a 20-mile radius of charred forests. Numerous theories attempting to explain the occurrence have been suggested over the years, but none has gained consensus in the scientific community. Among the more recent theories to explain the blast is the proposal that an antimeteor, composed of antimatter, plunged through Earth's atmosphere and upon coming in contact with ordinary matter exploded with devastating force.

Robert A. Millikan, Nobel laureate in physics and distinguished second to none by a half-century of research into charges and properties of atomic particles, in quantum mechanics, and in several other areas, predicted that all the power that could ever be extracted from atoms would no more than blow the whistle on a peanut vendor's cart. (In fairness I must add that most of his colleagues agreed—and the same is true of the next example.)

Forest Ray Moulton, for many years top astronomer of the University of Chicago and foremost authority in ballistics, stated in print (1935) that there was "not the slightest possibility of such a journey" as the one the whole world watched 34 years later: Apollo 11 to the moon.

In 1938, when there was not a pinch of pure ura-nium-235 anywhere on Earth and no technology to amass or control it, Lise Meitner devised mathematics that pointed straight to atom bombs. Less than seven years after she did this, the first one blazed "like a thousand suns."

No possible way to amass antimatter?

Or ever to handle it?

Being smugly certain of that (but mistaken) could mean to you .. . and me and everyone . . .

The END