From galaxies to DNA and the brain, from cars to computers and antibiotics, humanity in the last 100 years has gained knowledge of and control over nature with profound consequences for both benefit and harm.
The twentieth century will be remembered for consciousness-raising and scientific/technological breakthroughs. This century made racism a shameful practice; recognized gender oppression as a social evil; proclaimed human rights as transcending race, caste, and religion; pleaded for international economic justice; began to celebrate diversity and to care for the disabled; and condemned exploitation of the young. It released millions from colonial shackles and established world organizations in which free nations join to solve problems of food and health, promote trade and education, and resolve political differences through discussion.
The twentieth century also made more scientific discoveries, introduced more technologies, and launched more assaults on the environment than all previous time spans combined. As one example, consider electricity: Through minibatteries and mammoth generators, from wind and waves, from sun and coal, energy is extracted to make electrons flow as the currents that light up the dark, heat the oven, and serve a hundred other needful or luxurious purposes. Humanity and electricity are forever bound together. And so it is with dozens of other profound contributions to science and technology.
Let us take a bird's-eye view of some of the milestones in science and technology achieved during the last century.
Space and time
We intuitively experience space and time as the core of the physical universe. Events happen in time and occur on the stage we call space. It seems that for every experienced instant there must be a corresponding instant in every nook of the universe and that the length of a rod must be the same no matter where it is measured. But Albert Einstein (1905) uncovered that space and time, movements and events are not as independent and absolute as they seem. The stationary book on a table in a train is moving with respect to the tracks; the tracks (on Earth) are moving with respect to the Sun; the Sun with respect to the center of the galaxy; and so on. Rest and motion are always relative.
We know too, thanks to Einstein again, that contrary to ordinary impression, there is no absolute ticking time that uniformly palpitates across the expanse of the universe, nor lengths and breadths independent of the place from which they are measured. Space intervals (lengths) and time intervals have meaning only with respect to reference systems. Space and time are as inextricably intertwined as heart and mind, separate to all appearances but functionally nonexistent without each other. These and other such subtleties are of little relevance in the context of daily experience, but they have profound significance in our understanding of the world. They also have far-reaching consequences, The most important of which is the equivalence between matter and energy, known through the most famous formula of the twentieth century:E = mc2. This equivalence has found gory expression in nuclear bombs, but it has also been harnessed in reactors that feed the energy hunger of millions of people. As well, it operates in the core of stars, where matter is continuously transformed into energy that radiates into the surrounding void.
Galaxies and the big bang
In the seventeenth century, the telescope revealed lunar mountains, Jovian satellites, and Saturn's rings. With time, it revealed double stars, asteroids, new planets, and more. Finally, in the twentieth century, George Hale's 254-cm telescope (1917)--200,000 times more powerful than the eye--revealed galaxies. During the 1920s vast stellar agglomerations were spotted beyond our stupendous Milky Way. In size and content, with multiple billions of stars, galaxies are inconceivably large miniuniverses. Elliptical, spiral, and irregular in shape, they are strewn throughout the vastness of space.
These monstrous swarms of stars are hurtling every which way at enormous speeds; the farther away the galaxies the faster they are moving. Edwin Hubble described our universe as expanding (1929): a revolutionary view, for the expanse above had been pictured as a static, permanent panorama. In 1927, Georges Lema"tre had proposed the model of a cosmic egg hatching the world, its splinters moving along in various directions.
Aeons ago, theorists surmised, the galaxies must have been much closer together; if we try, we can envision a moment when the totality was compressed into a minuscule region of immense density. By the late 1940s, this idea had been elaborated by George Gamow as the big bang theory. For the first time, scientists began to speak about the genesis of the universe.
But there is more to science than fanciful models. In 1965, Arno Penzias and Robert Wilson discovered cosmic interference in their satellite-tracking radio dish--a uniform, universal radiation emanating from every direction in the heavens, which could only be interpreted as feeble remnants of the big bang that started it all. In the 1990s, NASA's Cosmic Background Explorer studied the radiation with greater thoroughness, further confirming the twentieth century's cosmic worldview: Our expanding universe of countless galaxies is the fruit of a founding cataclysmic happening some 15 billion years ago.
DNA and the basis of life
In the first decade of the twentieth century, the word gene began to denote the entity that transmits inherited characteristics. Before 1930 it was recognized that at the root of genetic inheritance are two types of nucleic acids (DNA and RNA), each incorporating a different type of sugar. In 1944 Oswald Avery established that DNA carries genetic information. But how could a molecule carry information for transferring life identities? In 1953 James Watson and Francis Crick discovered the double-helical DNA structure. Their discovery opened the way for understanding the genetic code embodied in the complementary and bonded facing pairs of molecular units forming each "rung" of the three-dimensional DNA. Replication involves separation of the DNA strands, each of which becomes a template for a complementary strand.
This climactic revealing of the genetic code, which reads like a detective story involving many researchers, was a landmark among efforts to unscramble life's secrets. Understanding heredity's mechanism has opened up undreamed-of possibilities for manipulating organisms. Finding cures for inherited diseases and engineering organisms are now within human reach. The technique of incorporating genes from an organism into bacterial cells (recombinant DNA: 1970s) enables us to make artificial insulin and enhance agricultural yields for a growing world population. These conquests are not without possible harm for our species. Of particular interest is the Human Genome Project, which has become a race among governments and private companies. Its goal is to sort out the order of some three billion nucleotides in human DNA. When this is achieved in the first years of the twenty-first century, our understanding of (and power over) human beings will be enhanced in incalculable and unimaginable ways.
We are accustomed to matter in both small and large dimensions, to sand and dust, to boulders and mountains, to the Moon and more massive celestial bodies. One could fathom conceptually, even in ancient times, the core of matter and talk of uncuttable microunits that no eye can see and no instrument probe. But armed with mathematics, instruments, and the sturdy framework of empirical science, twentieth-century scientists penetrated the innermost depths of matter and came upon a whole new world of atoms, electrons, and such: the microcosm, wherein wondrous phenomena occur, creating the kind of world we experience.
Ultimately, the physical universe has only gross matter as tangible particles and insubstantial energy as intangible waves. The century began with the revelation that the two are distinct only in their manifestations, for they can be interconverted (1905). Then it was discovered that they change garbs in the microcosm: Matter there can behave as waves (1920s), and energy is granular (1901). The laws of quantum physics govern this netherworld of matter waves and quanta. Here the rigid rules of predictable patterns formulated in everyday physics don't operate. Rather, wavering uncertainties come into play, resulting in processes that seem magical on our scale; electrons seep through sturdy barriers and particles leak through strongly confining nuclear walls, making transistors and radioactivity possible. We have also discovered strange new forces and subtle fluctuations in empty nothingness.
The microcosm is populated by particles such as quarks and leptons, possessing indescribable qualities like spin, parity, and baryon number. These entities emerge and decay and sometimes transform into one another. They conform to marvelous mathematical symmetries. Most remarkably, our understanding of the mysteries of the microcosm points the way to a deeper and more coherent knowledge of how the whole phenomenal universe came to be.
Of all the splendors in the universe nothing is more marvelous than the human brain. This three-pound complex of tissues, fluids, and blood vessels, made up of billions of cells, is at the root of all our actions and sensations, pains and pleasures, thoughts and ideas. The twentieth century has trophies here, too.
The brain has been reflected upon and examined since ancient times. The first decade of the twentieth century recognized Santiago Ram-n y Cajal's view of the nervous system as a chain of barely touching neurons sending unidirectional signals. The century identified the specific roles of different parts of the brain and the functions of the right and left lobes. It discovered measurable electrical activities in the brain and related them to specific states of the mind. It has gone deep into the molecular structures and chemical processes sustaining the brain, connecting macroscopic capacities like learning and memory with particular molecules. It has revealed that new brain cells are generated even in adult brains and has found connections between the brain and immune system. The list can go on and on. All this knowledge holds promise for finding cures for neurodegenerative diseases like Parkinson's and Alzheimer's.
Some think neuroscience can never explain love and compassion, truth and beauty. But, with instruments and concepts, science is exploring the ultimate frontier: the most fascinating and perhaps dangerous territory. It is seeking to unscramble the mystery of consciousness. How does this intensely personal experience arise in each of us, unique and untransferable? What is self-awareness? How is it linked to the core of the neuron? We will wait and perhaps learn from the neuroscientists of the twenty-first century.
Science in Action
The transportation revolution
Some of our distant ancestors were nomads who wandered the continents. Yet, during the five millennia of settled civilizations, few people ever traveled much. Locomotion took time and effort. Steamships and locomotives helped somewhat during the nineteenth century. During the twentieth century, two major technological revolutions forever altered human mobility. The first began in Detroit, where Ransom Eli Olds' factory brought out 433 automobiles in 1901. In less than a decade, 240 companies were in this business. By the close of the century, countless cars and trucks were in use all over the world. While they make road travel fast, cozy, and universal, they also pollute and in accidents kill or maim tens of thousands of people each year. Associated with the automobile are many thousands of miles of paved roads and highways crisscrossing the world, replacing the muddy pathways, dirt roads, and cobblestone streets that sufficed in an earlier era.
The second revolution began when the Wright brothers' Flyer I soared in 1903. The heavier-than-air, engine-powered plane was to inspire the aviation industry. None before this century could have imagined that someday people would be carried across land and sea in comfort, traveling far above the clouds aboard jets in supersonic flight. A further development was rocketry and missions both to distant planets and beyond our solar system. These efforts reached a climax of global and historical import in 1969 when U.S. astronauts landed on the Moon. Their achievement was an unsurpassed, spectacular success in the history of the human family.
From the moment speech began, human culture evolved. Indeed, society cannot continue without communication. Landmarks in communication have transformed civilization significantly.
Telegraphy, a child of the nineteenth century, was the first instance of telecommunication. From then on, telecommunication relied on advances in physics, especially electromagnetism. In 1876, Alexander Graham Bell transmitted his voice across eight miles over a wire: a first in human history. So began the saga of the telephone, which became essential equipment for the twentieth-century home, office, and factory.
In December 1901, Guglielmo Marconi sent radio signals across the Atlantic; a sound in England was heard right away in Newfoundland. News soon traveled fast and far by radio, and entertainment came into living rooms. By the mid-1920s, inventors had managed to send images from place to place, initiating what would become TV, an invention with extraordinary potentials for informing, improving, and hurting society. Videotapes record events and sounds that can be experienced by generations yet unborn. Imagine how exciting it would be if we had videos of Socrates, Buddha, Caesar, and Christ!
Computers (1940s), artificial satellites (1950s), lasers and fiber optics (1960s) have all played a part in the telecommunication revolution. In the early 1980s, cellular phones were introduced in Chicago. Now they have spread the world over. Finally, an as yet unrealized dream of twentieth- century astronomers is to receive communication from intelligent life on a distant planet. What grander telecommunication could there be?
Efforts to prevent and cure diseases are as ancient as civilization. Microorganisms, visible only under microscopes, were first seen in the 1600s. But the connection between diseases and minuscule creatures was not recognized until the latter half of the nineteenth century.
Conceptually, this discovery led to a simple solution for prevention and cure of diseases that could be traced to bacteria: kill the bacteria or inhibit their growth. During the nineteenth century, drugs such as quinine were already used against certain diseases. Many were discovered during the twentieth century, and a stupendous international infrastructure for manufacture and distribution of antibiotic pharmaceuticals was developed.
In 1915 Frederick Twort identified bacteria-eating viruses, or bacteriophages. Alexander Fleming discovered lysozyme in 1922: a bacteria-killing substance that our bodies produce. He also found that certain molds (penicillin) make lysozyme very effectively. This line of research proved very productive, generating a series of antibiotics such as streptomycin and erythromycin. In the 1930s, Gerhard Domagk and others discovered drugs like Prontosil and chemically synthesized molecules--called wonder drugs--which also destroy harmful bacteria. Rene Dubos (1930s) initiated techniques using microorganisms to produce antibacterial chemicals. In our century, medicine has learned to combat infectious diseases like pneumonia, tuberculosis, and typhoid, saving millions of lives.
Both overuse and underuse of antibiotics have spurred development of resistant bacterial strains. With tuberculosis killing more than two million people in 1998, staphylococcus infecting and killing patients in hospitals, and fatal pneumonia a possible outcome of severe colds, new chapters will, no doubt, be added to the story of antibiotics in the twenty-first century.
Life is sustained by energy from the Sun, but what is the source of the Sun's endless energy? The twentieth century has found the process and replicated it.
Matter-to-energy conversions associated with atomic nuclei occur in varied forms and environments, yet conform to the formula E = mc2, which gives the precise energy value of a given amount of matter. Thus, Sun and stars transform matter in their cores into radiant energy; nature on Earth has been releasing nuclear energy from radioactive substances since time immemorial. Scientists produced radioactivity in the 1930s and first harnessed nuclear energy from uranium by fission, in which heavy nuclei are split asunder. This rarely, if ever, happens spontaneously in nature.
Nuclear fission, used in the first atom bomb (July 1945), produced a blast equivalent to 20,000 tons of TNT. Controlled nuclear reactions power modern reactors. Submarines using reactors cruise for years without refueling. More than 430 nuclear power plants generate energy in many countries. Energy in the Sun and stars arises from the fusion of lighter nuclei (hydrogen and helium). We have replicated this too, for the first time in 1952 when a hydrogen bomb was detonated. To our knowledge, Earth is the only place outside of any star where nuclear fusion has occurred.
Once it was thought that tapping the atomic nucleus would answer all our energy needs, but serious problems loom. Aside from the nuclear arsenals of the world, which are tinderboxes for global annihilation, devastations of incalculable magnitude could result from reactor accidents. Then there is the problem of nuclear waste disposal. Burial deep underground in very thick storage tanks is one possibility. Harnessing nuclear fusion, which has proved very difficult, is a safer way of tapping nuclear energy, since there are few wastes here. This too may be accomplished in the new century.
Computers and the Internet
As with individual lives, human history is dramatically changed by unexpected events. The computer has transformed civilization. Initially designed as a computing machine, it soon became a device that could store, organize, manipulate, and retrieve vast amounts of information in incredibly short times. But computers are not just superefficient secretaries accessing superspacious filing cabinets. They not only think and follow commands but can make decisions, draw, design, scan labels, automate industries, calculate, translate, communicate, and more. Through the science of artificial intelligence, computers reveal how human minds may work, and some scientists think they will enable us to create replicas of the mind.
Early computers were made with vacuum tubes, which served radios and televisions of another era. Today their heartbeat is in the microchip, invented in the late 1950s and made possible by the transistor (late 1940s), which is based on discoveries resulting from quantum physics.
Microchips are found practically everywhere in modern society: planes, trains, cars, telephones, the water supply, offices, hospitals, the stock market, and schools. They have also created the Internet. Initiated for defense purposes in the late 1960s, the Internet has grown into a mammoth communication system linking countries and individuals across the world. It makes information on every topic accessible to anyone with a computer.
Late in the 1990s some feared that computers might fail and cause widespread chaos. This attitude perhaps symbolized their negative impacts and potentials: invasion of privacy, intrusion into military secrets, and sabotage. Computers have also created a multibillion- dollar industry, providing jobs to millions.
Perilous passages ahead
With all this, the twentieth century has also created stupendous problems, both pressing and potential. A population explosion in the face of diminishing oil reserves and farmable land, environmental pollution through automobiles and industrial effluents, perilous nuclear wastes, depletion of the rain forests: These are challenges of great magnitude. Then there are social and human problems, ranging from ethnic hatred and religious bigotry to poverty and malnutrition. So, though there is much to look forward to in terms of new technologies, increasing economic opportunities, interplanetary adventures, and possible cures for deadly diseases, we will be living in a fool's paradise if we are indifferent to the problems that will face mankind in the decades ahead.
The possibilities are immense and unpredictable, for the good and the bad: The discovery of a new and limitless nonpolluting energy source could bring about a golden age of prosperity for all humanity. The rise to power of a mindless maniac with nuclear capabilities could unleash irrevocable devastation on our species. Education and science could free all mankind from ignorance and superstition, but resource scarcity could deepen the chasm between the haves and the have-nots. Religious and racial bigotry could fire simmering suspicions into horrendous conflagrations, or perhaps the emergence of an enlightened religious outlook would foster understanding and harmony among differing faiths. Or again, the long and checkered course of human history could be snuffed into a mere glitch in the planet's saga by the rude intrusion and blind fury of a stray asteroid lured by Earth's gravity. What awaits us in time, no one can tell. Not all the factors that shape the future are within our ken or control.
Recognizing these possibilities, let us join hands in our efforts to induce the positive and snub the negative potentials. Now, as never before in human history, we feel we are all passengers in the only spaceship we have. Fortified by the knowledge and power that come from the sciences, we may build on the finer values and wisdom of the ages and make our planet an even-more rewarding place to be.n
V.V. Raman is emeritus professor of physics at Rochester Institute of Technology in Rochester, New York.