The 100 Most Influential Scientists of All Time (31 page)

Pondering how such a heavy, charged particle as the alpha could be turned by electrostatic attraction or repulsion through such a large angle, Rutherford conceived in 1911 that the atom could not be a uniform solid but rather consisted mostly of empty space, with its mass concentrated in a tiny nucleus. This insight, combined with his supporting experimental evidence, was Rutherford's greatest
scientific contribution, but it received little attention beyond Manchester.

In 1913, however, the Danish physicist Niels Bohr showed its importance. Bohr had visited Rutherford's laboratory the year before, and he returned as a faculty member for the period 1914–16. Radioactivity, he explained, lies in the nucleus, while chemical properties are due to orbital electrons. His theory wove the new concept of quanta (or specific discrete energy values) into the electrodynamics of orbits, and he explained spectral lines as the release or absorption of energy by electrons as they jump from orbit to orbit. Henry Moseley, another of Rutherford's many pupils, similarly explained the sequence of the X-ray spectrum of elements as due to the charge on the nucleus. Thus, a coherent new picture of atomic physics, as well as the field of nuclear physics, was developed.

Rutherford later examined the collision of alpha particles with gases. With hydrogen, as expected, nuclei (individual protons) were propelled to the detector. But, surprisingly, protons also appeared when alphas crashed into nitrogen. In 1919 Rutherford explained his third great discovery: he had artificially provoked a nuclear reaction in a stable element.

Such nuclear reactions occupied Rutherford for the remainder of his career, which was spent back at the University of Cambridge, where he succeeded Thomson in 1919 as director of the Cavendish Laboratory.

The Cavendish was home to exciting work. The neutron's existence had been predicted in a speech by Rutherford in 1920. After a long search, Rutherford's colleague, physicist James Chadwick, discovered this neutral
particle in 1932, indicating that the nucleus was composed of neutrons and protons. With a gift of some of the newly discovered heavy water from the United States, in 1934 Rutherford, Australian physicist Mark Oliphant, and German physical chemist Paul Harteck bombarded deuterium with deuterons, producing tritium in the first fusion reaction.

(b. July 26, 1875, Kesswil, Switz.—d. June 6, 1961, Küsnacht)

S
wiss psychologist and psychiatrist Carl Jung founded analytic psychology, in some aspects a response to Sigmund Freud's psychoanalysis. Jung proposed and developed the concepts of the extraverted and the introverted personality, archetypes, and the collective unconscious. His work has been influential in psychiatry and in the study of religion, literature, and related fields.

Jung's early researches led him to understand Freud's investigations; his findings confirmed many of Freud's ideas, and, for a period of five years (between 1907 and 1912), he was Freud's close collaborator. He held important positions in the psychoanalytic movement and was widely thought of as the most likely successor to the founder of psychoanalysis. However, Jung differed with Freud largely over the latter's insistence on the sexual bases of neurosis. A serious disagreement came in 1912, with the publication of Jung's
Wandlungen und Symbole der Libido
(
Psychology of the Unconscious
, 1916), which ran counter to many of Freud's ideas.

Jung's first achievement was to differentiate two classes of people according to attitude types: extraverted
(outward-looking) and introverted (inward-looking). Later he differentiated four functions of the mind—thinking, feeling, sensation, and intuition—one or more of which predominate in any given person. Results of this study were embodied in
Psychologische Typen
(1921;
Psychological Types
, 1923).

Jung later developed the theory that powerful fantasies and natural free expression came from an area of the mind that he called the collective unconscious, which he held was shared by everyone. This much-contested conception was combined with a theory of archetypes that Jung held as fundamental to the study of the psychology of religion. In Jung's terms, archetypes are instinctive patterns, have a universal character, and are expressed in behaviour and images.

Jung devoted the rest of his life to developing his ideas, especially those on the relation between psychology and religion. In his view, obscure and often neglected texts of writers in the past shed unexpected light not only on Jung's own dreams and fantasies but also on those of his patients; he thought it necessary for the successful practice of their art that psychotherapists become familiar with writings of the old masters.

Besides the development of new psychotherapeutic methods that derived from his own experience and the theories developed from them, Jung gave fresh importance to the so-called Hermetic tradition. He conceived that the Christian religion was part of a historic process necessary for the development of consciousness, and he also thought that the heretical movements, starting with Gnosticism and ending in alchemy, were manifestations of unconscious archetypal elements not adequately expressed in the mainstream forms of Christianity. He was
particularly impressed with his finding that alchemical-like symbols could be found frequently in modern dreams and fantasies, and he thought that alchemists had constructed a kind of textbook of the collective unconscious. He expounded on this in 4 out of the 18 volumes that make up his
Collected Works
.

His historical studies aided him in pioneering the psychotherapy of the middle-aged and elderly, especially those who felt their lives had lost meaning. He helped them to appreciate the place of their lives in the sequence of history. Most of these patients had lost their religious belief; Jung found that if they could discover their own myth as expressed in dream and imagination they would become more complete personalities. He called this process individuation.

(b. March 14, 1879, Ulm, Württemberg, Ger.—d. April 18, 1955, Princeton, N.J., U.S.)

G
erman-born physicist Albert Einstein developed the special and general theories of relativity. He won the Nobel Prize for Physics in 1921 for his explanation of the photoelectric effect. Einstein is generally considered the most influential physicist of the 20th century.

In 1902 Einstein reached perhaps the lowest point in his life. He could not marry Meliva Maric, whom he loved, and support a family without a job. Desperate and unemployed, Einstein took lowly jobs. The turning point came later that year, when the father of his lifelong friend, Marcel Grossman, was able to recommend him for a position as a clerk in the Swiss patent office in Bern.

Einstein married Maric on Jan. 6, 1903. Their children, Hans Albert and Eduard, were born in Bern in 1904 and 1910, respectively. In hindsight, Einstein's job at the patent office was a blessing. He would quickly finish analyzing patent applications, leaving him time to daydream about the vision that had obsessed him since he was 16: What will happen if you race alongside a light beam?

Einstein had studied Maxwell's equations, which describe the nature of light, and discovered that the speed of light remained the same no matter how fast one moved. This violated Newton's laws of motion, however, because there is no absolute velocity in Isaac Newton's theory. This insight led Einstein to formulate the principle of relativity: “the speed of light is a constant in any inertial frame (constantly moving frame).”

During 1905, often called Einstein's “miracle year,” he published four papers in the
Annalen der Physik
, each of which would alter the course of modern physics:

1. “Über einen die Erzeugung und Verwandlung des Lichtes betreffenden heuristischen Gesichtspunkt” (“On a Heuristic Viewpoint Concerning the Production and Transformation of Light”), in which Einstein applied the quantum theory to light in order to explain the photoelectric effect. If light occurs in tiny packets (later called photons), then it should knock out electrons in a metal in a precise way.

2. “Über die von der molekularkinetischen Theorie der Wärme geforderte Bewegung von in ruhenden Flüssigkeiten suspendierten Teilchen” (“On the Movement of Small Particles Suspended in Stationary Liquids Required by the Molecular-Kinetic Theory of Heat”), in which Einstein offered the first
experimental proof of the existence of atoms. By analyzing the motion of tiny particles suspended in still water, called Brownian motion, he could calculate the size of the jostling atoms and Avogadro's number.

3. “Zur Elektrodynamik bewegter Körper” (“On the Electrodynamics of Moving Bodies”), in which Einstein laid out the mathematical theory of special relativity.

4. “Ist die Trägheit eines Körpers von seinem Energieinhalt abhängig?” (“Does the Inertia of a Body Depend Upon Its Energy Content?”), submitted almost as an afterthought, which showed that relativity theory led to the equation
E = mc
²
. This provided the first mechanism to explain the energy source of the Sun and other stars.

Einstein was the first to assemble the whole theory together and to realize that it was a universal law of nature, not a curious figment of motion in the ether.

At first Einstein's 1905 papers were ignored by the physics community. This began to change after he received the attention of just one physicist, perhaps the most influential physicist of his generation, Max Planck, the founder of the quantum theory. Soon, owing to Planck's laudatory comments and to experiments that gradually confirmed his theories, Einstein rose rapidly in the academic world.

One of the deep thoughts that consumed Einstein from 1905 to 1915 was a crucial flaw in his own theory: it made no mention of gravitation or acceleration. For the next 10 years, Einstein would be absorbed with formulating a theory of gravity in terms of the curvature of space-time. To Einstein, Newton's gravitational force was actually a by-product of a deeper reality: the bending of the fabric of space and time. In November 1915 Einstein finally completed the general theory of relativity, which he considered to be his masterpiece.

Einstein was convinced that general relativity was correct because of its mathematical beauty and because it accurately predicted the perihelion of Mercury's orbit around the Sun. His theory also predicted a measurable deflection of light around the Sun. As a consequence, he even offered to help fund an expedition to measure the deflection of starlight during an eclipse of the Sun.

After World War I, two expeditions were sent to test Einstein's prediction of deflected starlight near the Sun. One set sail for the island of Principe, off the coast of West Africa, and the other to Sobral in northern Brazil in order to observe the solar eclipse of May 29, 1919. On Nov. 6, 1919, the results were announced in London at a joint meeting of the Royal Society and the Royal Astronomical Society.

The headline of
The Times
of London read, “Revolution in Science—New Theory of the Universe—Newton's Ideas Overthrown—Momentous Pronouncement—Space ‘Warped.'” Almost immediately, Einstein became a world-renowned physicist, the successor to Isaac Newton.

In 1921 Einstein received the Nobel Prize for Physics, but for the photoelectric effect rather than for his relativity theories. During his acceptance speech, Einstein startled the audience by speaking about relativity instead of the photoelectric effect.

Einstein also launched the new science of cosmology. His equations predicted that the universe is
dynamic—expanding or contracting. This contradicted the prevailing view that the universe was static, so he reluctantly introduced a “cosmological term” to stabilize his model of the universe. In 1929 astronomer Edwin Hubble found that the universe was indeed expanding, thereby confirming Einstein's earlier work. In 1930, in a visit to the Mount Wilson Observatory near Los Angeles, Einstein met with Hubble and declared the cosmological constant to be his “greatest blunder.” Recent satellite data, however, have shown that the cosmological constant is probably not zero but actually dominates the matter-energy content of the entire universe. Einstein's “blunder” apparently determines the ultimate fate of the universe.