The Amazing Story of Quantum Mechanics (2 page)

BOOK: The Amazing Story of Quantum Mechanics
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In this book I will explain the key concepts underlying quantum mechanics and show how these ideas account for the properties of metals, insulators, and semiconductors, the study of which forms the field of solid-state physics. I’ll describe how the magnetic properties of atomic nuclei and atoms, an intrinsically quantum mechanical phenomena, allow us to see inside the human body using magnetic resonance imaging and store vast libraries of information on computer hard drives. The wonders enabled by quantum mechanics are almost too many to name: devices such as lasers, light-emitting diodes, and key-chain memory sticks; strange phenomena including superconductivity and Bose-Einstein condensation; and even brighter brights and whiter whites!
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And we’ll see how the same quantum phenomena that changed the very nature of technology in the last fifty years will similarly influence the growing field of nanotechnology in the next fifty years.
For a field of physics that has spawned applications that have had such a wide-ranging impact on our lives, it is unfortunate that quantum mechanics has such a reputation for “weirdness” and incomprehensibility. OK, maybe it is weird, but it’s certainly not impossible to understand. While the mathematics required to perform calculations in quantum physics is fairly sophisticated, its central principles can be described and understood without resorting to differential equations or matrix algebra.
The cover of the book promised a “math-free” discussion, but I must confess that there will be a little bit of math involved in this presentation of quantum physics. (I hope you are reading this at home and not standing up in the aisle at the bookstore, trying to decide whether or not to purchase this book.) Compared to the rigorous mathematics that underlies the foundations of quantum mechanics, the simple equations employed here practically qualify as “math-free.” I will make use of algebraic equations no more complex than those relating distance traveled to speed and time. That is, if I told you that I drove at a speed of 50 miles per hour for 2 hours, you would know that I had traveled 100 miles. By arriving at that conclusion, you have intuitively used the simple equation distance = speed × time. None of the math that I will use here will be more complicated than this.
While it may not be incomprehensible, quantum mechanics does have a well-deserved reputation for being confusing. I do not mean that the mathematics employed in a quantum description of nature is obscure or complex—all math is hard if you do not know how to use it, just as every language is opaque if you cannot speak it. Rather, I mean that fundamental questions, such as what happens to a quantum system when a measurement of its properties is performed, are still being argued over by physicists, nearly eighty years after first being posed. One of the most amazing aspects of quantum mechanics is that one can use it correctly and productively—even if one is confused by it.
In this book I invoke a “working man’s” view of quantum mechanics that has the advantage of requiring only three suspensions of disbelief, not unlike the “miracle exception from the laws of nature” that science fiction stories or superhero comic books often implicitly employ. Some of my professorial colleagues should note—in the interest of clarity I will sidestep some of the finer points of the theory. This book is intended for non-experts interested in learning how quantum mechanics underlies many of the devices that characterize our modern lifestyle. Meditations on the interpretations of quantum theory and the “measurement problem” are fascinating, to be sure, but philosophical discussions alone do not invent the transistor.
Even keeping it simple, questions regarding the fundamental nature of matter are inescapable when considering quantum mechanics. I discuss fantastical situations such as when two electrons or atoms are so close to each other that they become “entangled” and it is actually impossible to tell them apart. I encourage you to put fear out of your mind and not shirk any necessary heavy lifting, and I’ll try to hold up my end by using easily understood analogies and examples.
There are many excellent books that describe the historical development of quantum mechanics, some of which are listed in the “Recommended Reading” section. As I am not a historian of science, I will not retrace the steps of the pioneering physicists that led the quantum revolution, but will rather focus on explicating the physical principles they discovered and their applications in solid-state physics.
SECTION 1
TALES TO ASTONISH
Figure 1:
Cover of the August 1928 issue of the science fiction pulp magazine
Amazing Stories
, which featured the debut of “Buck” Rogers.
CHAPTER ONE
Quantum Mechanics in Three Easy Steps
The future began twice:
in December 1900, and in August 1928. On the first date, at the German Physical Society, Max Planck presented a resolution to something that would come to be called the ultraviolet catastrophe. Planck suggested that atoms can lose energy only in discrete jumps, and this new idea would tip over the first domino in a chain that by the mid-1920s would lead to the development of a new field of physics termed “quantum mechanics.” On the later date, at the end of the summer of 1928, Buck Rogers first appeared in the science fiction pulp
Amazing Stories.
With its premier issue published in 1926,
Amazing Stories
was the first magazine devoted exclusively to science fiction stories, or what publisher Hugo Gernsback called “scientifiction.” The magazine’s motto was “Extravagant Fiction Today . . . Cold Fact Tomorrow.” Planck’s breakthrough marked the dawn of a new field of science and is the province of nerds, while the appearance of Buck Rogers began the future as reckoned by geeks. (I should note that as a physics professor who is also an avid fan of science fiction and comic books, I am simultaneously a nerd and a geek.)
2
Given the amazing pace of scientific progress at the end of the nineteenth century—the invention of the telegraph, telephone, and automobile had radically altered notions of distance and time, such that, not for the last time, technology had made the world a somewhat smaller place—it is perhaps not surprising that readers of
Amazing Stories
in 1928 would expect the eventual development of personal flying harnesses and disintegrator rays.
Buck Rogers’s first adventure was described in Philip Francis Nowlan’s novella
Armageddon 2419 A.D.,
published in that famous issue of
Amazing Stories.
Anthony Rogers—he would not gain the nickname “Buck” until his appearance in a syndicated newspaper comic strip one year later—was a citizen of both the twentieth and twenty-fifth centuries. Exposure to a gas leak in an abandoned mine near Scranton induced a former army air corps officer to lapse into a form of suspended animation. Upon awakening in the future, he rapidly adjusted to the new age. Nowlan’s hero, catapulted into the future, was just as resourceful as Twain’s Yankee thrust back into King Arthur’s court.
Rogers, armed with the weaponry of tomorrow and a military acumen acquired during his service in World War I, joins a team of rebels fighting against the evil “Hans” invaders from Asia who had conquered America in the early twenty-second century. In fact, many of the stories published in the science fiction pulps of the 1930s and 1940s are distinguished by optimism that in the future there would be continued scientific progress coupled with pessimism that there would be absolutely no improvement whatsoever in international (or interplanetary) relations.
This confidence in scientific advancement, history shows, was justified, as was the expectation of continued global strife. In the pause in hostilities among European nations between the Great War and the next Great War, a revolution in physics occurred that would lay the foundation for technological innovations that would seem outlandish in the pages of
Startling Stories.
The first half of the Roaring Twenties would see the development of what would eventually be known as quantum mechanics, where the tentative guesses and first steps of Planck, Niels Bohr, Albert Einstein, and others would inspire Erwin Schrödinger and Werner Heisenberg to separately and independently create a formal, rigorous theory of the properties of atoms and their interactions with light. Their scientific papers appeared in print the same year that Hugo Gernsback began publishing
Amazing Stories.
While quantum mechanics is not, to be sure, the last word in our understanding of nature, it did turn out to be the key missing ingredient that would enable physicists to develop the field of solid-state physics. When combined with the electromagnetic theory of the nineteenth century, quantum mechanics provides the blueprint for our current wireless world of information and communication. Scientists today, working on twenty-first-century nanotechnology, are still dining off the efforts of the quantum physicists of the 1920s.
It is plausible that the lull in global antagonisms in the brief time between the two world wars helped facilitate these advances in physics. The collaborations and interactions among scientists from Germany, France, Italy, Britain, Denmark, the Netherlands, and the United States heralded an unprecedented fertile period, which came to a close with the resumption of hostilities in Europe in 1938. Physics turned out to be in a race against history, and the pace quickened with the discovery of the structure of the atomic nucleus in the 1930s. The realization by German and Austrian physicists that it is possible to split certain large unstable nuclei, and thereby release vast amounts of energy—such that a little over two pounds of uranium would yield the same destructive force as does seventeen thousand tons of TNT—came a year before the German army marched into Poland. The quantum alliance of scientific cooperation would fracture with the formation of a geopolitical axis, and the center of gravity of physics would shift from Europe to America in the 1940s. The development of solid-state physics would have to await the end of World War II and would be carried out primarily in the United States and Britain. Unfortunately the pulp fiction writers were accurate prognosticators when they described militaristic struggles in the far future or on distant planets, suggesting that human nature evolves at a much slower pace than does technology.
Just as the hotbed of activity in physics would shift from Europe to America following World War II, the epicenter of science fiction would undergo a similar transition. Hugo Gernsback wrote in “The Rise of Scientification” in the spring 1928 issue of
Amazing Stories,
“It is a great source of satisfaction to us, and we point to it with pride, that 90 percent of the really good scientifiction authors are Americans, the rest being scattered over the world.” In Gernsback’s perhaps biased opinion, homegrown talent had eclipsed the seminal contributions to the genre by Jules Verne, H. G. Wells, and other European pioneers of “scientifiction.”
Verne in particular is considered by many to be the “father of science fiction.” He is lauded for his accurate descriptions of future technology (heavier-than-air transport, long-range submarine travel, lunar travel via rockets) as well as for his impossibly exotic locales (hollow centers of the Earth and mysterious islands). Verne’s success at prediction stems from his following the same principles that guide scientific research. Whether uncovering new scientific principles or creating a new genre of speculative fiction, one must head out for uncharted terrain. One will not discover a new continent, after all, if one travels only on paved highways. As Edward O. Wilson once cautioned, for us mere mortals, who are not able to make the dramatic leaps of a Newton or Einstein, care must be taken to not metaphorically sail too far from home, in case the world really is flat. The preferred tack is to make small excursions from the known world, trying always to keep the shore in sight. Verne would frequently make reasonable extrapolations on current scientific developments and imagine a mature technology that could exist, if a few details (and perhaps a miracle exception from the laws of nature) were finessed.
A Jules Verne adventure inevitably takes place in the time period that the novel is published, and a then physically improbable mode of transportation will bring our heroes to an exotic locale. This was the format of Verne’s first successful novel,
Five Weeks in a Balloon,
in which a trio of adventurers in 1863 travel to uncharted Africa, as well as his later novels
Journey to the Center of the Earth, 20,000 Leagues Under the Sea, From the Earth to the Moon, The Mysterious Island,
and
Robur the Conqueror.
Yet in the second novel he wrote, though it was the last to be published, Jules Verne considered the most extraordinary voyage of all—to
Paris in the Twentieth Century.
This novel marks a radical departure for Verne. Written in 1863, it describes the everyday life and mundane experiences of a young college graduate in Paris in 1960. In contrast to the optimistic view of technological wonders one associates with Verne, the novel despairs for a future world where commerce and mechanical engineering are the highest values of society, and cultural pursuits such as literature and music are disdained. So uncommercial did Verne’s publisher find this manuscript decrying the triumph of commerce that he convinced Verne to lock it away in a safe. There it sat, neglected and forgotten, until the 1990s, when the safe, which was believed to be empty and whose key had long been lost, was cut open with a blowtorch, and the tome was discovered.
BOOK: The Amazing Story of Quantum Mechanics
5.01Mb size Format: txt, pdf, ePub
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