Science in the Middle Ages
Muslim Preservation of Learning
With the eclipse of the Greek and Roman cultures, many of their works passed into the hands of the Muslims, who by the 7th and 8th cent. A.D. had extended their influence through much of the world surrounding the Mediterranean. All of the Greek works were translated into Arabic, and commentaries were added. Important developments from the East were also transmitted, and the Hindu numeral system was introduced, as well as the manufacture of paper and gunpowder, learned from the Chinese. Scholars gathered at cities like Damascus, Baghdad, and Cairo, at one end of the Mediterranean, and at Cordova and Toledo, in Spain, at the other end. Many astronomical observations were made at different locations, but there was little effort to improve or modify the Greek model of Ptolemy. In medicine important contributions were made by Al-Razi (Rhazes, 865-925) and Ibn-Sina (Avicenna, 980-1037), and in alchemy and pharmacology by Jabir (Geber, 9th cent.), whose work was expanded in the 10th cent. by a mystical sect aligned with the Sufi tradition. At Cairo, Al-Hazen (965-1038) studied optics, particularly the properties of lenses, and Maimonides (1135-1204), the Jewish philosopher, came there from Spain to practice medicine as physician to Saladin, the Sultan. The Arabs thus preserved the scientific works of the Greeks and added to them, and also introduced other contributions from Asia. This body of learning first began to be discovered by Europeans in the 11th cent.
The Craft Tradition and Early Empiricism in Europe
Certain technical innovations during the Dark Ages, e.g., development of the heavy plow, the windmill, and the magnetic compass, as well as improvements in ship design, had increased agricultural productivity and navigation and contributed to the rise of cities, with their craft guilds and universities. These changes were more pronounced in N Europe than in the south. The introduction of papermaking (12th cent.) and printing (1436-50) made possible the recording of craft traditions that had been handed down orally in previous centuries. This served to reduce the gap between the artisan classes and the scholar classes and contributed to the development of certain individuals who combined elements of both traditions-the artist-engineers such as Leonardo da Vinci, whose studies of flight and other technological problems were far beyond their time, and the artist-mathematicians, such as Albrecht Dürer, who examined the laws of perspective and wrote a textbook on geometry. Many artists came to study anatomy in detail.
Beginning in the 12th cent. the Arabic versions of Greek works were translated into Latin, an edition of Ptolemy's Almagest being translated at Toledo, and one of Aristotle's biological works in Sicily. Leonardo da Pisa (Fibonacci) presented some of the new Hindu-Arabic mathematics in the early 13th cent., and the medical and alchemical works were also translated. Also in the 13th cent., a trend toward empiricism was promoted by Roger Bacon and others, but this was short-lived. The dominant philosophy of science and other fields was the Christianized version of Aristotelian philosophy created by Albertus Magnus and Thomas Aquinas in the 13th cent. This view tended to treat scientific theories as extensions of philosophy and, for example, postulated the existence of angelic agents to account for the movements of the heavenly bodies. Even so, the craft traditions continued to develop in an independent manner, particularly medieval alchemy, and certain schools grew up that were not dominated by the main scholastic philosophy. The rebirth, or Renaissance, of learning spread throughout the West from the 14th to the 16th cent. and was further enhanced by the great voyages of discovery that began in the 15th cent.
The Age of Classical Science
The history of science during the 18th and 19th cent. is largely the history of the individual branches as they developed into the traditional forms by which they are still recognized today.
The Evolution of Mathematics and Physics
In mathematics the calculus invented by Newton and G. W. Leibniz was developed by the Bernoullis, Leonhard Euler, and J. L. Lagrange into a powerful tool that was to be used not only in mathematics but also in physics and astronomy. Newtonian physics spread to the Continent slowly, its acceptance being hindered by adherents of the older Cartesian philosophy and by disputes over priority in the invention of the calculus. However, by the late 18th cent. it was firmly established. Other branches of physics came into their own during this period. The study of electricity expanded to include electric currents and magnetism, and it was finally synthesized in the theory of electromagnetic radiation of J. C. Maxwell in the second half of the 19th cent. These discoveries provided the foundation for the technological advances in communications and in other fields using electrical energy. The wave theory of light was revived at the beginning of the 19th cent. by Thomas Young and developed by others; Maxwell's theory showed that light was one form of electromagnetic energy. In the 18th cent. scientists thought that heat was a kind of fluid called caloric. However, by the early 19th cent. it became apparent that heat is a form of motion-the motion of the particles of which substances are composed. The classical theory of heat and thermodynamics was developed by J. P. Joule, Lord Kelvin, R. J. E. Clausius, and others, who showed the relation between heat and other forms of energy and formulated the law of conservation of energy. Maxwell, Ludwig Boltzmann and others developed statistical mechanics, which treats matter as a large aggregate of many particles and applies statistical methods to the prediction of its behavior.
Innovations in Chemistry
Chemistry became increasingly quantitative and experimental during the 18th cent. Joseph Priestley and other English scientists made a number of discoveries which served as the basis for A. L. Lavoisier's explanation of the role of oxygen in combustion and respiration. John Dalton proposed the modern version of the atomic theory in the early 19th cent. and Dmitri Mendeleev, in his periodic table, showed how the chemical elements described by the atomic theory could be arranged in a systematic way. In the mid-19th cent. R. W. Bunsen and G. R. Kirchhoff developed spectroscopy as a tool for chemical analysis. Also in the 19th cent., the synthesis of urea by Friedrich Wöhler (1828) established that organic substances are composed of the same kinds of atoms as inorganic substances, thus opening a new era in the study of organic chemistry.
Advances in Astronomy
Astronomy progressed on the theoretical level through the contributions to celestial mechanics of P. S. Laplace and others, and on the observational level through the work of many scientists. They included William Herschel, who built telescopes and discovered Uranus (1781), the first planet found in modern times, and his son John Herschel, who extended his father's observations to the Southern Hemisphere skies and pioneered in astrophotography, which in modern astronomy is the chief method of observation. Another tool that found important application in astronomy was the spectroscope. Increasingly astronomers made use of the instruments, techniques, and theories of other fields, particularly physics.
Birth of Modern Geology
Modern geology may be said to date from the work of James Hutton, who postulated (1785) that the geologic processes and forces that had shaped the earth were still in operation and could be observed directly. Georges Cuvier, the French naturalist, founded the field of comparative anatomy and applied its principles to geology in the study of the fossil remains of animals of the distant past, thus also founding the field of paleontology.
New Ideas in Biology
In biology Carolus Linnaeus instituted a system of classification of animals and plants, and improvements in this system helped scientists to arrange different forms of life according to complexity, suggesting to some that organisms may evolve from simple to complex forms. In the 19th cent. K. E. von Baer founded the field of embryology, the study of the earliest stages of different forms of life, and Matthias Schleiden and Theodor Schwann identified the cell as the basic unit of living matter. In medicine the treatment of disease was furthered by the introduction of smallpox vaccination by Edward Jenner and the recognition of the role of germs and viruses in causing diseases. A number of ways of reducing the growth of such organisms were introduced, including pasteurization of foods and antiseptic surgery. Anesthetics were introduced in the 19th cent. by several scientists, and, through chemistry, new medications were developed that aimed at treatment of specific ailments.
Science and the Industrial Revolution
Some of the greatest changes were in the area of technology, in the development of new sources of energy and their application in transportation, communications, and industry. Among the important aspects of the Industrial Revolution were the invention of the steam engine by James Watt and its use in factories, mines, ships, and railroad engines; the development of the internal-combustion engine and the companion growth of petroleum technology to provide fuel for it; the invention of many different kinds of agricultural machinery and the resulting enormous increase in productivity; the improvement of many metallurgical processes, particularly those involving iron and steel; and the invention of the electric generator, electric motor, and numerous electric devices that are now commonplace.
Revolutions in Modern Science
The enormous growth of science during the classical period engendered an optimistic attitude on the part of many that all the major scientific discoveries had been made and that all that remained was the working out of minor details. Faith in the absolute truth of science was in some ways comparable to the faith of earlier centuries in such ancient authorities as Aristotle and Ptolemy. This optimism was shattered in the late 19th and early 20th cent. by a number of revolutionary discoveries. These in turn attracted increasing numbers of individuals into science, so that whereas a particular problem might have been studied by a single investigator a century ago, or by a small group of scientists a few decades ago, today such a problem is attacked by a virtual army of highly trained, technically proficient scholars. The growth of science in the 20th cent. has been unprecedented.
In much of modern science the idea of progressive change, or evolution, has been of fundamental importance. In addition to biological evolution, astronomers have been concerned with stellar and galactic evolution, and astrophysicists and chemists with nucleosynthesis, or the evolution of the chemical elements. The study of the evolution of the universe as a whole has involved such fields as non-Euclidean geometry and the general theory of relativity. Geologists have discovered that the continents are not static entities but are also evolving; according to the theory of plate tectonics, some continents are moving away from each other while others are moving closer together.
The Impact of Elementary Particles
Physics in particular was shaken to the core around the turn of the century. The atom had been presumed indestructible, but discoveries of X rays (1895), radioactivity (1896), and the electron (1897) could not be explained by the classical theories. The discovery of the atomic nucleus (1911) and of numerous subatomic particles in addition to the electron opened up the broad field of atomic and nuclear physics. Atoms were found to change not only by radioactive decay but also by more dramatic processes-nuclear fission and fusion-with the release of large amounts of energy; these discoveries found both military and peaceful applications.
Quantum Theory and the Theory of Relativity
The explanation of atomic structure required the abandonment of older, commonsense, classical notions of the nature of space, time, matter, and energy in favor of the new view of the quantum theory and the theory of relativity. The first of these two central theories of modern physics was developed by many scientists during the first three decades of the 20th cent.; the latter theory was chiefly the product of a single individual, Albert Einstein. These theories, particularly the quantum theory, revolutionized not only physics but also chemistry and other fields.
Advances in Chemistry
Knowledge of the structure of matter enabled chemists to synthesize a sweeping variety of substances, especially complex organic substances with important roles in life processes or with technological applications. Radioactive isotopes have been used as tracers in complicated chemical and biochemical reactions and have also found application in geological dating. Chemists and physicists have cooperated to create many new chemical elements, extending the periodic table beyond the naturally occurring elements.
Biology Becomes an Interdisciplinary Science
In biology the modern revolution began in the 19th cent. with the publication of Charles Darwin's theory of evolution (1859) and Gregor Mendel's theory of genetics, which was largely ignored until the end of the century. With the work of Hugo de Vries around the turn of the century biological evolution came to be interpreted in terms of mutations that result in a genetically distinct species; the survival of a given species was thus related to its ability to adapt to its environment through such mutations. The development of biochemistry and the recognition that most important biological processes take place at the molecular level led to the rapid growth of the field of molecular biology, with such fundamental results as the discovery of the structure of deoxyribonucleic acid (DNA), the molecule carrying the genetic code. Modern medicine has profited from this explosion of knowledge in biology and biochemistry, with new methods of treatment ranging from penicillin, insulin, and a vast array of other drugs to pacemakers for weak hearts and implantation of artificial or donated organs.
The Abstraction of Mathematics
In mathematics a movement toward the abstract, axiomatic approach began early in the 19th cent. with the discovery of two different types of non-Euclidean geometries and various abstract algebras, some of them noncommutative. While there has been a tendency to consolidate and unify under a few general concepts, such as those of group, set, and transformation, there has also been considerable research in the foundations of mathematics, with a close examination of the nature of these and other concepts and of the logical systems underlying mathematics.
Astronomy beyond the Visual Spectrum
In astronomy ever larger telescopes have assisted in the discovery that the sun is a rather ordinary star in a huge collection of stars, the Milky Way, which itself is only one of countless such collections, or galaxies, that in general are expanding away from each other. The study of remote objects, billions of light-years from the earth, has been carried out at all wavelengths of electromagnetic radiation, with some of the most notable results being made in radio astronomy, which has been used to map the Milky Way, study quasars, pulsars, and other unusual objects, and detect relatively complex organic molecules floating in space. The latter, coupled with the discovery of extrasolar planetary systems and possible microscopic fossils in meteorites of Martian origin, have raised new questions about the origin of life and the possible existence of intelligent life elsewhere in the universe.
Modern Science and Technology
The technological advances of modern science, which in the public mind are often identified with science itself, have affected virtually every aspect of life. The electronics industry, born in the early 20th cent., has advanced to the point where a complex device, such as a computer, that once might have filled an entire room can now be carried in an attaché case. The electronic computer has become one of the key tools of modern industry. Electronics has also been fundamental in developing new communications devices (radio, television, laser). In transportation there has been a similar leap of astounding range, from the automobile and the early airplane to the modern supersonic jet and the giant rocket that has taken astronauts to the moon. Perhaps the most overwhelming aspect of modern science is not its accomplishments but its magnitude in terms of money, equipment, numbers of workers, scope of activity, and impact on society as a whole. Never before in history has science played such a dominant role in so many areas.
