Scientific discoveries require scientific ideas. Scientific ideas primarily act on society through technology, but they also change our sense of who we are and of what the world is. Modern science is a uniquely Western cultural phenomenon, and the combination of abstract scientific knowledge with practical know-how in the 19th century made possible "techno-science," which has remained a relentless driver of social change ever since.
Writing is a core commitment of science because scientific knowledge is an abstraction-not embodied in concrete things or processes. Cultures without writing may be quite sophisticated in other ways, and cultures can be highly literate without developing an idea of science.
The idea of knowledge had to be invented. Plato and Aristotle defined knowledge as something universal, not linked to probabilities or context. For them, knowledge was timeless, universal, necessary, and certain, and their paradigm was deductive logical reasoning, as in geometry.
Plato believed that true reality was form, which exists separately from matter. Aristotle broke decisively with Plato by declaring there is only one reality, which is nature, and that all natural phenomena are to be explained within the framework of nature. Parmenides posited that reality was manifested in changeless things, while Heraclitus said reality was change or process-and the tension between these two approaches continues to this day.
Pythagoras proposed a mathematical order underlying nature, and mathematics could be used to describe natural phenomena. Although Aristotle generally dismissed the value of mathematics for the study of nature, Archimedes and others followed the example of Pythagoras.
In the 1st century B.C.E., the Roman architect Vitruvius wrote about the fruitful combination of abstract knowledge with practical know-how. Today we would call a person who combines both an engineer. Vitruvius did not originate this idea, but Roman society from his time forward experienced the first heyday of machines whose invention depended on mathematical knowledge.
In the 12th century, social pressure to make life better and to explore knowledge spawned universities across Europe. From the 12th through the 16th centuries, universities revived and extended Classical and Islamic learning in mathematics, philosophy, medicine, and science.
Parallel with the rise of universities was an explosion of technical skills supporting the development of water mills, sawmills, blast furnaces, and the like. The most famous gear-related invention of the age was the weight-driven mechanical clock. Improved sailing and navigation technologies supported increased trade. Banks and corporations were established.
The notion of progress did not begin with technology but with Petrarch and a concern about language. Humanist scholars developed scholarly techniques for reconstructing Classical texts then sought to surpass Classical learning. The Humanist idea of progress paved the way for the idea of social reform based on scientific reason.
Printing of texts and movable type were old technologies when Gutenberg introduced the latter to Europe. Unlike China and the Middle East, the West embraced metallic movable type and became "print drunk." The response triggered the creation of a vast sociotechnic system to supply, produce, and distribute texts. Institutions were created to protect and reward producers and increase literacy, promoting further increases in text production and distribution.
The technique of perspective used by Renaissance painters made visual the notion that "reality" is structured by mathematics. The rebirth of techno-science depended largely on their work, with further contributions by Renaissance mapmaking, instrument tuning (musical theory), and books illustrating the design of machines.
Pythagoreans claimed that astronomical bodies were spheres, their orbits circles, and their motion constant because they were perfect. Copernicus replaced Ptolemy's Earth-centered model with a Sun-centered model, but it remained for his followers to make the planetary orbits elliptical, rather than circular, and posit an infinite universe.
Bringing together all of the ideas discussed to this point was the 17th century's idea of modern science. A new emphasis on scientific method was a critical factor in pulling everything together, though founding figures of this period such as René Descartes and Francis Bacon championed radically different methods.
During the 16th and 17th centuries, mathematics in the West took a remarkable turn. It moved from geometry, which the ancient Greeks had favored, to embrace algebra-which was as momentous as the transition from Ptolemaic astronomy to Copernican astronomy. Calculus provided an unprecedented tool for knowledge about change, and the mathematics of probability opened the way for knowledge about uncertainty.
Experience suggests that nature is orderly and lawful; if so, then something has to be conserved. From this notion slowly developed the ideas of conservation of momentum, matter, and energy; Einstein's idea that matter and energy are jointly conserved; and the use of mathematical invariances to understand deep symmetries in nature.
Galileo saw what he described as moons around Jupiter in the 17th century, but his description could not be verified independently for many years. If a scientific instrument gives a result that cannot be verified independently, then the result is really an extension of the mind rather than of the senses. This is no less true today: particle accelerators, for example, provide mountains of mathematical data that require interpretation.
An idea becomes a scientific idea when it functions in the context of a scientific explanation. The idea of time is an excellent example. If, as Plato claimed, both real knowledge and ultimate reality are timeless, then time is insignificant. However, by the 18th century, the idea of time was increasingly regarded as the dimension containing hope for an improvement in the human condition. This, in turn, prefigured 19th-century scientific ideas of time as both irreversible and significant.
The theory of the atom began as an extension of Parmenides's view of reality as ultimately changeless. John Dalton in the early 19th century used a theory of changeless atoms in his examination of chemical reactions, and atomism gained prominence thereafter even as the atom was discovered to be mainly empty space and composed of parts, each with distinct properties.
What is life? An 18th-century debate pitting mechanism against vitalism was resolved, literally, when new microscopes of the early 19th century were used to proclaim in the late 1830s that cells were the building blocks of all living things. The view that cells were the "atoms" of life, in turn, provoked a search for what within the cell is the essence of life.
The germ theory of disease is another instance of the "atomistic" style of thinking and the cornerstone of modern scientific medicine. The notion of disease caused by imbalances within the body was undermined when Pasteur and Koch showed how illness comes from the outside, an idea dating back to Hippocrates and the notion of miasmas. Resistance to the germ theory was understandable; some people had germs in their bodies but not the disease.
Gregor Mendel was trying to confirm a theory about evolution when his experiments with pea plants led him to realize that inheritance was owed to discrete units. Yet gene theory rests less on Mendel's work than on experiments with fruit flies showing that x-rays could alter parts of chromosomes. If x-rays could do that, then genes must be real.
In the 19th century, with the rise of the science of thermodynamics, energy assumed a parallel reality to matter. Like matter, energy was seen to take many forms but was conserved. Unlike matter, the idea of energy quickly stimulated process theories in which patterns and relationships were real.
Faraday's introduction of fields as elements of physical reality in the 19th century was a giant step for modern science. But the difficulty of formulating a plausible physical mechanism for how fields work led to Maxwell's equations of electrodynamics-and a view of scientific theories as capturing our experience of a process, rather than a final truth about objects.
Beginning in 1837, a few chemists came to believe that understanding a molecule required knowing not only what atoms the molecule had, but also the spatial relationships among those atoms. Pasteur relied on this insight; it forms one of the cornerstones of organic chemistry. The recognition of relationships as real also appeared in other 19th-century disciplines including symbolic logic, mathematics, and social science.
Evolution has proven to be a cross-disciplinary idea, bringing contingency into scientific explanation and showing how novelty can emerge. Evolution also entails making time, which moves in one direction only, a fundamental feature of reality.
Modern science was founded on determinism, but determinism was undermined by the recognition of probability in nature and by the claim that certain processes obeyed statistical laws. The kinetic theory of gases, thermodynamics, and radioactivity all showed that statistical laws had a place in scientific theory. This had far-reaching implications: If nature is probabilistic, then so, too, are theories and laws of nature.
A qualitative divide separates important 18th-century innovations in textiles, iron, and steam power from such 19th- and 20th-century innovations as electric power, plastics, and radio: The latter were made possible by science-informed engineering. Successful innovations became increasingly dependent on scientific knowledge and formally trained engineering-as well as supportive business acumen.
Moving beyond improved versions of what already existed, such as water power, innovations increasingly appeared that could never have existed without scientific knowledge. Western societies accelerated this development by creating institutions explicitly designed to promote science-based innovation, including widespread engineering education, new ways of organizing companies, and supportive government policies.
Quantum physics is the most revolutionary of 20th-century theories, and it is the most predictively successful physical theory ever. But it is still controversial as well as inconsistent with the general theory of relativity. Quantum mechanics imputes randomness, probability, and uncertainty to elementary physical processes. It redefines causality, space, time, matter, energy, the nature of scientific law and explanation, and the relationship between mind and world.
Einstein's special theory of relativity forced a reconceptualization of Newtonian space and time, and proclaimed that matter and energy could be converted into one another. The general theory even redefined physical reality at the cosmological level. The properties of space and time are determined by the distribution of matter and energy; space and time are really names of relationships, not separate in their own right.
In the 1920s, the scale of the universe changed dramatically with the discovery of thousands of galaxies beyond our Milky Way and the expansion of the universe. By 1963, the expanding universe was explained with a "big bang," and by 1980, an explanation of the big bang led to the proposal that the universe was unimaginably more vast than anything we could detect.
Alan Turing conceived of a machine that could solve any problem whose solution could be specified by a finite decision procedure, or "algorithm". Turing recognized that increasingly powerful calculators could be reconceived as generalized problem-solving machines, even artificially intelligent machines. The computer went from being a calculator to a universal "simulator".
Information is organized data, the content in which we are all awash. But information as conceived in Claude Shannon's mathematical theory of information is independent of content, an idea at the foundation of powerful information technologies that continue to change the world. Moreover, DNA and the new view of black holes as information structures, suggest, almost like something out of science fiction, that information seems to be physically "real".
Atomistic thinking faces challenges from three closely related ideas from the 20th century: Phenomena are produced by systems; "chaotic" real-world systems are in fact orderly; and some systems are self-organizing. These systems display properties that aren't apparent in the properties of their individual constituents. That is, the wholes are more than the sums of their parts.
The molecular theory of life says that life can be fully explained in terms of molecules in action, using the concepts and the tools of physics and chemistry. The discovery that DNA molecules defined every life form on Earth sealed this shift. By the 1980s, the molecular theory of life was transforming medicine as well as the meaning of life.
Which scientific ideas will transform 21st-century life? Self-organization is fundamental to the emerging nanotechnology industry. Molecular biology and cognitive neuroscience continue their naturalization of human consciousness. Quantum chemistry makes possible molecular psychiatry and even molecular sociology. String theory controversially promises to unify the forces of nature into a comprehensive theory of everything.
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