Overview: Physical Sciences 1950-present

The Legacy of 1900-1949

In the first half of the twentieth century, modern physics emerged out of a watershed of theory and discovery concerning the realm of the atomic nucleus and subatomic energies and speeds. From the profound insights of Albert Einstein's (1879-1955) relativity to the compartmental order of Max Planck's (1858-1947) quantum theory and its antecedent quantum mechanics, humanity was upon the threshold of an atomic age. Likewise, chemists also delved into the study of atomic structure following ground-breaking investigations of chemical reactions and equilibrium laws, new elemental gases, radioactive elements, their isotopes and chemistry, and atomic weights. Shared areas of study included surface chemistry, molecular structure, chemical bonding, and the synthesis of new radioactive elements.

In contrast to study of the physically infinitesimal, study of the vast universe advanced through the use of large aperture telescopes, beginning at Mount Wilson in California. These celestial studies confirmed early relativistic physics and provided new evidence, put forth by Edwin Hubble (1889-1953), suggesting that the universe is expanding. Or was it static or contracting? Complementing these questions, early astrophysics, such as Ejnar Hertzsprung (1873-1967), analyzed the physical and chemical makeup of the stars and their life cycles. New cosmological theories also emerged, such as genesis via the Big Bang, in late 1940s. Between the two world wars, researchers in the earth sciences were defining atmospheric motion mathematically as a subset of fluid and hydrodynamics, represented by the work of Vilhelm Bjerknes (1862-1951), mapping the ocean floors, and peeling away the structure of the earth to its very core.

The Further Rise of Applied Physical Science

It is perhaps not surprising that after World War II, with its negative application of science and technology for destructive purposes, that subsequent scientific endeavors focused on Mother Earth, threatened rather than embraced by the realities of the atomic age. The postwar peace quickly evolved into a Cold War world of polarized superpowers, of bigger government accommodating bigger science and military interests. However, in 1957-58 an extraordinary, six-year cooperative international effort to study the total physical earth system came to fruition with the International Geophysical Year (IGY). The design of the ICBM missile served just as well for IGY rockets lifting the first satellites into near space orbit. A mammoth IGY database supported many scientific advances, including the development of plate tectonic theory, new understanding of charged particles in the upper atmosphere (called Van Allen Belts), and a new perspective of the unity of the solar system.

By 1950 several high-speed computers were already half a decade old and pushing the envelope of evolving mass data needs. Princeton's MANIAC pointed to the potential of modeling physical phenomena through vast scientific data banks. It demonstrated its power in 1952 with the first numerical weather forecasts. By about 1961, using computer models of atmospheric flow, MIT theoretical meteorologist Edward Lorenz (1917- ) formulated chaotic system theory to show that extended forecasting of atmospheric dynamics had its limits. He thus introduced the applications of determinate chaos theory to the sciences. Computer modeling surged from the 1970s through the 1990s, with a progression of applications to study most physical and chemical phenomena of nature. Sophisticated submersible technology and robotics made possible visits to the deepest of ocean floors in 1960, and enabled the collection of oceanographic and geological data encompassing complex ocean currents, volcanic activity, and deep sea vents, as well as the biology around such vents. The planetary sciences of the solar system graduated from complex sensory satellites to space probes equipped with computer-controlled cameras and sensors, making flyby and orbiting data missions to nearly all of our planetary neighbors. As part of this effort, chemists designed special chemical analysis instruments and automatic experimental devices for probe landings.

During the second half of the twentieth century, astronomers looked to the stars with clearer eyes and a perspective further into cosmic origins with the Hale 200-inch (5-meter) reflector on Mount Palomar (1948), the largest in the world for decades to come. The simplistic idea of glimpsing a horizon of the universe with the Hale, as anticipated by some, led to more complex cosmic spatial quandaries as the 1960s approached, including new curving and multidimensional models of the universe. Other radiative wavelengths beyond the visual became cosmos-searching tools. The radio telescope's steady refinements, including the use of several together, or aperture synthesis, proved that the Milky Way is a spiral galaxy and detected the first pulsars (neutron stars) in 1968. In addition to cosmic ray and infrared detectors, the use of other wavelength detectors followed in the 1950s, including gamma rays (Explorer 11, 1961), x rays (rocket detection, 1962), cosmic background microwave remnants of the Big Bang (1965, 1966), cosmic ray detection of quasars (energetic distant galactic nuclei, 1963) and cosmic sources of infrared radiation (IRAS, 1983).

During the 1990s, new large telescopes and observatories were built that sharpened delineation of the origins of our galaxy and the universe. By 1986 the idea of an orbiting telescope (first theorized in 1947) placed above the visual barriers of the earth's atmosphere became reality with the Hubble Space Telescope (HST). Optical corrections to the HST improved its clarity and resulted in pictures that revealed a changing cosmos. There were indirect and then direct (1998) observations of not only proto-planetary areas of stellar dust but actual extra-solar planetary objects. Such glimpses, clues to our own primordial solar origins, add to persistent questions of cosmic order. Since the concept of black holes emerged in 1968, posited by John Wheeler (1911- ), the heart of its theory has been the nature of gravity and relativity. Black holes are physical objects, the most massive, yet spatially limited objects, in the universe, and their gravitational forces massive enough to hold even light prisoner. A span of analysis in the full electromagnetic spectrum has revealed stellar binary and galactic nuclear black hole varieties—our own Milky Way belonging to the latter variety—with energetic characters classed as dormant and active. Other theoretical by-products of black hole research have come from astrophysicists such as Stephen Hawking (1942- ), with his application of concepts including charged holes, Hawking radiation, and D-branes to Big Bang theory. The Big Bang theory itself is continually updated or compromised by new databases, so that a slightly expanding universe is challenged by various steady and quasi-steady state universes of which the outcome still lies in the future.

Mainstream Science

In addition to such theoretical and applied advances in earth and space science since 1950, mainstream physics and chemistry have provided the constant underpinning to these areas. Delving into the nuclear heart of the atom for peaceful advance of physical knowledge was foremost in the collective physics and chemistry minds at the end of World War II. The science of particle physics was just beginning, already equipped with the cloud chamber and early particle accelerators foretelling the energies needed to proceed. Framed by a quantum field theory of quantum electrodynamics (QED), the discovery of the pion (1948) and "strange" particles (1950) anticipated a whole revolutionary world of subatomic particles. Cyclotron, betatron, bevatron, and many others were all "atom smashers" to the general public. However, from the 1950s through the 1970s, in ever greater numbers, these provided the ammunition for the bubble chambers used to obtain countless photos of subnuclear collisions in the 1960s, identifying new particles and the various mesons and neutrinos. In 1962 Murray Gell-Man (1929- ) of Caltech, who coined "strangeness" as a characteristic of unstable elementary particles (1959), theorized the "eightfold way" subatomic particle interrelationship to predict particle collisions based on the eight quantum numbers describing elementary particles. This also led to his defining early "quark" model particles.

Predictions of an expanding roll call of missing particles ensued as accelerator energies continued to grow. The Greek alphabet was exhausted as a source of names, and the addition of leptons and further defined characteristics of quarks (up, down, strange, charm, bottom, and tau) resulted in reorganizations of a Standard Model of particles and the weak and strong forces defining them. This deeper inspection of the limits of the elemental world, including the discovery of the so-called top quark in 1994, gave pause to further maturing of Einstein's ideas about unifying the forces of nature from the elemental level to cosmological space-time theory, a so called "theory of everything" (TOE) or more formerly, grand-unified theory (GUT).

Yet the anomalies between the macro and subatomic levels of the physical world reflect the discontinuities between quantum theory and Einstein's general relativity. And for many scientists, so-called "string theory" holds promise as the concept that explains everything from quarks to black holes. Strings have emerged in various theories as unknown, elemental vibrating strands making up the matter of the universe and reacting by merging rather than, as the accepted atomic particles, colliding in space and time. Perhaps our familiar concepts of space and time will eventually become obsolete. As a new century dawns, our understanding of the physical world remains in a constant state of change.

WILLIAM MCPEAK