The solar neutrino problem could be explained in three ways. Either Davis’s experiment was wrong, or the standard model of the sun was wrong, or the standard theory of the neutrino was wrong. For many years, most of the experts believed that the experiment was wrong, that Davis missed two thirds of the argon atoms because they slipped through his counters. Davis did some careful tests that convinced the experts that his counters were not to blame, and then they mostly believed that the model of the sun was wrong. The model of the sun was checked by accurate measurements of seismic waves traveling through the sun, and turned out to be correct. So the experts finally had to admit that their theory of the neutrino was wrong.
We now know that there are three kinds of neutrinos. Only one kind is produced in the sun, and only that kind was detected in Davis’s tank, but many switch smoothly from one kind to another while they are traveling from the sun to the earth. Two thirds of them are the wrong kind to be detected when they arrive at the tank, neatly explaining Davis’s result. This discovery was the first evidence for processes not included in the scheme that Wilczek calls the Core. Davis was awarded a belated Nobel Prize for it in 2002. During the years while Davis was working alone with his tank, larger teams of physicists and engineers were making discoveries at a rapid pace with accelerators. The accelerator era was in full swing. Particle physics as we know it today is largely the fruit of accelerators.
So much for the history. Now I turn from the past to the future. Wilczek’s expectation, that the advent of the LHC will bring a golden age of particle physics, is widely shared among physicists and widely propagated in the press and television. The public is led to believe that the LHC is the only road to glory. This belief is dangerous because it promises too much. If it should happen that the LHC fails, the public may decide that particle physics is no longer worth supporting. The public needs to hear some bad news and some good news. The bad news is that the LHC may fail. The good news is that if the LHC fails, there are other ways to explore the world of particles and arrive at a golden age. The failure of the LHC would be a serious setback, but it would not be the end of particle physics.
There are two reasons to be skeptical about the importance of the LHC: one technical and one historical. The technical weakness of the LHC arises from the nature of the collisions that it studies. These are collisions of protons with protons, and they have the unfortunate habit of being messy. Two protons colliding at the energy of the LHC behave rather like two sandbags, splitting open and strewing sand in all directions. A typical proton–proton collision in the LHC will produce a large spray of secondary particles, and the collisions are occurring at a rate of millions per second. The machine must automatically discard the vast majority of the collisions, so that the small minority that might be scientifically important can be precisely recorded and analyzed. The criteria for discarding events must be written into the software program that controls the handling of information. The software program tells the detectors which collisions to ignore. There is a serious danger that the LHC can discover only things that the programmers of the software expected. The most important discoveries may be things that nobody expected. The most important discoveries may be missed.
Another way to go ahead with particle physics is to follow the lead of Davis and build large passive detectors observing natural radiation. In the last twenty years, the two most ambitious passive detectors were built in Canada and Japan. Both of these detectors made important discoveries, confirming and completing the work of Davis. In a well-designed passive detector deep underground, events of any kind are rare, every event is recorded in detail, and if anything unexpected happens you will see it.
There are also historical reasons not to expect too much from the LHC. I have made a survey of the history of important discoveries in particle physics over the last sixty years. To avoid making personal judgments about importance, I define an important discovery to be one that resulted in a Nobel Prize for the discoverers. This is an objective criterion, and it usually agrees with my subjective judgment. In my opinion, the Nobel Committee has made remarkably few mistakes in its awards. There have been sixteen important experimental discoveries between 1945 and 2008.
Each experimental discovery lies on one of three frontiers between known and unknown territory. It is on the energy frontier if it reaches a new range of energy of particles. It is on the rarity frontier if it reaches a new range of rarity of events. It is on the accuracy frontier if it reaches a new range of accuracy of measurements. I assigned each of the sixteen important discoveries to one of the three frontiers. In most cases, the assignments are unambiguous. For example, two of the three discoveries that I mentioned earlier, Powell’s discovery of double-stopping mesons and Davis’s discovery of missing solar neutrinos, lie on the rarity frontier, while only one, Segrè and Chamberlain’s discovery of the antiproton, lies on the energy frontier.
The results of my survey are then as follows: four discoveries on the energy frontier, four on the rarity frontier, eight on the accuracy frontier. Only a quarter of the discoveries were made on the energy frontier, while half of them were made on the accuracy frontier. For making important discoveries, high accuracy was more useful than high energy. The historical record contradicts the prevailing view that the LHC is the indispensable tool for new discoveries because it has the highest energy.
The majority of young particle physicists today believe in big accelerators as the essential tools of their trade. Like Napoleon, they believe that God is on the side of the big battalions. They consider passive detectors of natural radiation to be quaint relics of ancient times. When I say that passive detectors may still beat accelerators at the game of discovery, they think this is the wishful thinking of an old man in love with the past. I freely admit that I am guilty of wishful thinking. I have a sentimental attachment to passive detectors, and a dislike of machines that cost billions of dollars to build and inevitably become embroiled in politics. But I see evidence, in the recent triumphs of passive detectors and the diminishing fertility of accelerators, that nature may share my prejudices. I leave it to nature to decide whether passive detectors or the LHC will prevail in the race to discover her secrets.
Fortunately, passive detectors are much cheaper than the LHC. The best of the existing passive detectors were built by Canada and Japan, countries that could not afford to build giant accelerators. The race for important discoveries does not always go to the highest energy and the most expensive machine. More often than not, the race goes to the smartest brain. After all, that is why Wilczek won a Nobel Prize.
Note added in 2014: To be fair to Wilczek, I include his response to the review.
I know you’d be disappointed if I agreed with everything you said, so I’ll append my response to someone who asked about it: Although I enjoyed Dyson’s review, a few points of his seemed off to me. For instance, I don’t think it’s reasonable to compare particle physics today to biology before Darwin. In fundamental physics we have very sophisticated, specific, successful mathematical theories, of a kind that biologists can barely dream of even today. As to “active versus passive,” I don’t think it’s an either/or proposition. Different questions call for different methods of investigation. Without going into technicalities, here’s a short list of central open questions that are more suitable for non-accelerator versus accelerator physics. Non-accelerator: proton decay, intrinsic electric dipole moments, dark matter annihilation signatures, axion or other ultra-light particle searches. Accelerator: Higgs sector, supersymmetry, production of dark matter candidate particles, surprises in high energy interactions.
With all best wishes,
Frank W.
*The Lightness of Being: Mass, Ether, and the Unification of Forces (Basic Books, 2008).
9
WHEN SCIENCE AND POETRY WERE FRIENDS
THE AGE OF WONDER means the period of sixty years between 1770 and 1830, commonly called the Romantic Age. It is most clearly defined as an age of poetr
y. As every English schoolchild of my generation learned, the Romantic Age had three major poets, Blake and Wordsworth and Coleridge, at the beginning, and three more major poets, Shelley and Keats and Byron, at the end. In literary style it is sharply different from the Classical Age before it (Dryden and Pope) and the Victorian Age after it (Tennyson and Browning). Looking at nature, Blake saw a vision of wildness:
Tyger, tyger, burning bright,
In the forests of the night;
What immortal hand or eye,
Could frame thy fearful symmetry?
Byron saw a vision of darkness:
The bright sun was extinguish’d, and the stars
Did wander darkling in the eternal space,
Rayless, and pathless, and the icy earth
Swung blind and blackening in the moonless air.…
During the same period there were great Romantic poets in other countries, Goethe and Schiller in Germany and Pushkin in Russia, but in his book The Age of Wonder, Richard Holmes writes only about the local scene in England.*
Holmes is well known as a biographer. He has published biographies of Coleridge and Shelley and other literary heroes. But this book is primarily concerned with scientists rather than with poets. The central figures in the story are the botanist Joseph Banks; the chemists Humphry Davy and Michael Faraday; the astronomers William Herschel and his sister, Caroline, and son, John; the medical doctors Erasmus Darwin and William Lawrence; and the explorers James Cook and Mungo Park. The scientists of that age were as romantic as the poets. The scientific discoveries were as unexpected and intoxicating as the poems. Many of the poets were intensely interested in science, and many of the scientists in poetry.
The scientists and the poets belonged to a single culture and were in many cases personal friends. Erasmus Darwin, the grandfather of Charles Darwin and progenitor of many of Charles’s ideas, published his speculations about evolution in a book-length poem, The Botanic Garden, in 1791. Davy wrote poetry all his life and published much of it. He was a close friend of Coleridge, Shelley a close friend of Lawrence. The boundless prodigality of nature inspired scientists and poets with the same feelings of wonder. The Age of Wonder is popular history at its best, racy, readable, and well documented. The subtitle, “How the Romantic Generation Discovered the Beauty and Terror of Science,” accurately describes what happened.
Holmes presents the drama in ten scenes, each dominated by one or two of the leading characters. The first scene belongs to Joseph Banks, who sailed with Captain James Cook on the ship Endeavour. This was Cook’s first voyage around the world. One of the purposes of the expedition was to observe the transit of Venus across the disk of the sun on June 3, 1769, from the island of Tahiti in the South Pacific. The tracking of the transit from the Southern Hemisphere, in combination with similar observations made from Europe, would give astronomers more accurate knowledge of the distance of the earth from the sun. Banks was officially the chief botanist of the expedition, but he quickly became more interested in the human inhabitants of the island than in the plants. The ship stayed for three months at Tahiti, and he spent most of the time, including the nights, ashore. During the nights he was not observing plants.
A wealthy young man accustomed to aristocratic privileges in England, Banks quickly made friends with the Tahitian queen Oborea, who assigned one of her personal servants, Otheothea, to take care of him. With the help of Otheothea and other good friends, he acquired some fluency in the Tahitian language and customs. His journal contains a Tahitian vocabulary and detailed descriptions of the people he came to know. When the time came to set up the astronomical instruments and observe the transit of Venus, he took the trouble to explain to his Tahitian friends what was happening. “To them we shewd the planet upon the sun and made them understand that we came on purpose to see it.”
During the long months at sea after leaving Tahiti, Banks rewrote his journal entries into a formal narrative, “On the Manners and Customs of the South Sea Islands,” one of the founding documents of the science of anthropology. In a less formal essay written after his return to England, he wrote:
In the Island of Otaheite where Love is the Chief Occupation, the favourite, nay almost the Sole Luxury of the Inhabitants, both the bodies and souls of the women are modeld in the utmost perfection for that soft science.
The Tahiti that he describes was truly an earthly paradise, not yet ravaged by European greed and European diseases, twenty years before the visit of William Bligh and the Bounty mutineers, sixty-six years before the visit of Charles Darwin and the Beagle.
After exploring the South Seas, Cook sailed down the eastern coast of Australia and landed at Botany Bay. Banks failed to establish social contacts with the Australian aborigines and returned to his role as botanist, bringing back to England a treasure trove of exotic plants, many of them today carrying his name. After he returned to England, he found that he and Captain Cook had become public heroes. He was invited to meet King George III, who was then young and of sound mind and shared his passion for botany. He remained a lifelong friend of the king, who actively supported his creation of the national botanic garden at Kew.
Banks became the president of the Royal Society in 1778 and held that office for forty-two years, officially presiding over British science for more than half of the Age of Wonder. He presided with a light hand and did not attempt to turn the Royal Society into a professional organization like the academies of science in Paris and Berlin. He believed that science was best done by amateurs like himself. If some financial support was needed for people without private means, it could best be provided by aristocratic patrons.
One of those for whom Banks found support was William Herschel, the greatest astronomer of the age. Herschel was a native Hanoverian, and was conscripted at the age of seventeen to fight for Hanover in the Seven Years’ War against the French. After surviving a battle that the Hanoverians lost, he escaped to England to begin a new life as a professional musician. Starting as a penniless refugee, he rose rapidly in the English musical world. By his late twenties he was the director of the orchestra in the Pump Room at Bath, the health resort where people of wealth congregated to take the waters and listen to concerts. He stayed at Bath for sixteen years, running the musical life of the city by day and scanning the sky at night. As an astronomer he was a complete amateur, unpaid and self-taught.
At the beginning, when Herschel began observing the heavenly bodies, he believed that they were inhabited by intelligent aliens. The round objects that he saw on the moon were cities that the aliens had built. He continued throughout his life to publish wild speculations, many of which turned out later to be correct. He had two great advantages as an observer. First, he built his own instruments, and with his musician’s hands made exquisitely figured mirrors that gave sharper images than any other telescopes then existing. Second, he brought his younger sister, Caroline, over from Hanover to be his assistant, and she became an expert observer with many independent discoveries to her credit. His life as an amateur ended in 1781 when with Caroline’s help he discovered the planet Uranus.
As soon as Banks heard of the discovery, he invited Herschel to dinner, introduced him to the king, and arranged for him to be appointed the king’s personal astronomer with a salary of £200 a year, later supplemented by a separate salary of £50 a year for Caroline. Herschel’s musical career was over, and he spent the rest of his life as a professional astronomer. He obtained royal funding to build bigger telescopes, and embarked on a systematic survey of every star and nebulous object in the sky, pushing his search outward to include objects fainter and more distant than anyone else had seen.
Herschel understood that when he looked at remote objects he was looking not only into deep space but into deep time. He correctly identified many of the nebulous objects as external galaxies like our own Milky Way, and calculated that he was seeing them as they existed at least two million years in the past. He showed that the universe was not only immensely
large but immensely old. He published papers that moved away from the old Aristotelian view of the heavens as a static domain of perpetual peace and harmony, and toward the modern view of the universe as a dynamically evolving system. He wrote of “a gradual dissolution of the Milky Way” that would provide “a kind of chronometer that may be used to measure the time of its past and future existence.” This idea of a galactic chronometer was the beginning of the new science of cosmology.
As Holmes’s account suggests, all the leading scientists of the Romantic Age, like Banks and Herschel, started their lives as brilliant, unconventional, credulous, and adventurous amateurs. They blundered into science or literature in pursuit of ideas that were often absurd. They became sober professionals only after they had achieved success. Another example was Humphry Davy, who originally intended to be a physician and worked, as part of his medical training, as an assistant at the Pneumatic Institution in Bristol. The Pneumatic Institution was a clinic where patients were treated for ailments of all kinds by inhaling gases. Among the gases available for inhaling was nitrous oxide. Davy experimented enthusiastically with nitrous oxide, using himself and his friends, including Coleridge, as subjects. After one of these sessions, he wrote:
Dreams of Earth and Sky Page 13
