In his book, Brian Greene mentions a number of contemporary physicists—Gabriele Veneziano, Pierre Ramond, and Shing-Tung Yau among them—who have made important contributions to the advancement of string theory. The following list focuses primarily on the predecessors of string theory: scientists and mathematicians from earlier eras who laid the groundwork for what is now the cutting edge of physics.

### Niels Bohr (1885–1962)

A Danish physicist and contemporary of Einstein. Bohr developed quantum mechanics and was the first to apply the quantum theory to the problem of atomic structure. He received the Nobel Prize in 1922.

### Max Born (1882–1970)

A German physicist. In 1926, Born introduced one of the most bizarre—but still experimentally verifiable—aspects of quantum theory: the idea that an electron wave must be interpreted from the standpoint of probability. Born’s reinterpretation of Schrödinger’s wave equation led to a new theory of quantum mechanics.

### Prince Louis de Broglie (1892–1987)

A French nobleman. In 1923, de Broglie suggested that Einstein’s conception of the wave-particle duality of light also applied to matter. For discovering the wave-nature of electrons, Broglie was awarded the 1929 Nobel Prize for Physics.

### Sir Arthur Eddington (1882–1944)

An English physicist. Eddington tested Einstein’s theory of general relativity during a 1919 total solar eclipse and found that the bending of light rays that Einstein predicted actually occurred. (Eddington’s conclusions were later called into question, but at the time they turned Einstein into an international celebrity.)

### Albert Einstein (1879–1955)

A German-American physicist. Einstein formulated both the theories of special and of general relativity. His theory of gravitation marked a profound revision of Newton’s ideas.

### Leonhard Euler (1707–1783)

A Swiss mathematician and physicist. Euler is considered one of the founders of pure mathematics. His studies of strongly interacting particles influenced many physicists throughout the twentieth century.

### Richard Feynman (1918–1988)

An American theoretical physicist. Feynman reinvented quantum electrodynamics in the years following World War II. He advanced a powerful new way to think of Born’s probability theory, and many consider him the most important theoretical physicist since Einstein.

### Murray Gell-Mann (1929–2019)

An American physicist. In 1969, Gell-Mann won the Nobel Prize for his classification systems of atomic and subatomic particles, and the ways in which they interact. It was Gell-Mann who coined the term

### Sheldon Glashow (1932–)

An American theoretical physicist. Glashow, along with Steven Weinberg and Abdus Salam, was awarded the 1979 Nobel Prize for Physics for his revolutionary formulation of electroweak theory, which explains the unity of electromagnetism and the weal force.

### Samuel Goudsmit (1902–1978)

A Dutch-American physicist. Goudsmit, along with George Uhlenbeck, proposed the concept of electron spin, which posits that electrons rotate on an axis. This insight led to many revisions in theories about atomic structure and quantum mechanics.

### Stephen Hawking (1942–2018)

An English theoretical physicist. Hawking’s black hole theory combines quantum mechanics and general relativity. Hawking is the author of the bestseller

### Werner Heisenberg (1901–1976)

The first proponent of the uncertainty principle, which has remained the key feature of quantum mechanics since its introduction in 1927.

### Heinrich Hertz (1857–1894)

A German physicist. In 1887, Hertz found that when electromagnetic radiation (light) shines on certain metals, they release electrons. From his studies of James Clerk Maxwell’s electromagnetic theory, Hertz established that light and heat are both electromagnetic forces.

### Edwin Hubble (1889–1953)

An American astronomer. Hubble proved that the universe is expanding.

### Theodor Kaluza (1885–1954)

A German mathematician. In 1919, Kaluza proposed that the universe might contain more than three spatial dimensions. Kaluza’s theory was considered outlandish, and it took Einstein several years to consider Kaluza’s theory seriously, but string theorists today find it remarkably prescient.

### Oskar Klein (1894–1977)

A Swedish physicist. In 1926, Klein refined Theodor Kaluza’s notion of an extradimensional universe.

### Pierre-Simon de Laplace (1749–1827)

A French mathematician, astronomer, and physicist. Laplace is best known for applying Newton’s theory of gravitation to the solar system.

### James Clerk Maxwell (1831–1879)

A Scottish physicist. Maxwell developed the set of four equations that became the basis of electromagnetic theory, the single force unifying electricity and magnetism. Maxwell’s work had a huge influence on twentieth-century physics, and he is ranked alongside Isaac Newton and Albert Einstein for the scope of his contributions. Maxwell’s field equations prompted Max Planck to formulate the quantum hypothesis—the theory that radiant-heat energy is emitted only in finite quantities, or quanta.

### Max Planck (1858–1947)

A German theoretical physicist. Planck pioneered quantum theory.

### George Bernhard Riemann (1826–1866)

A German mathematician. Riemann’s geometrical studies were foundational to Einstein’s theory of relativity.

### Abdus Salam (1926–1996)

A Pakistani physicist. Salam was awarded the 1979 Nobel Prize, along with Sheldon Glashow and Steven Weinberg, for his work developing electroweak theory.

### Erwin Schrödinger (1887–1961)

An Austrian physicist. Schrödinger argued that waves were really “smeared” electrons. He objected to the then-universally accepted description of matter in terms of waves and particles, and instead advanced a quantum mechanical wave equation. Schrödinger shared the Nobel Prize of 1933.

### Karl Schwarzchild (1873–1916)

A German astronomer and physicist. Schwarzchild worked out Einstein’s field equations of general relativity while stationed on the Russian front during World War I.

### George Uhlenbeck (1900–1988)

A Dutch physicist. Uhlenbeck, along with Samuel Goudsmit, proposed the concept of electron spin, which posits that electrons rotate on an axis. This insight led to many revisions in theories about atomic structure and quantum mechanics.

### Steven Weinberg (1933–2021)

An American nuclear physicist. Weinberg shared the 1979 Nobel Prize with Sheldon Glashow and Abdus Salam for the formulation of electroweak theory. Weinberg showed that photons and bosons actually belong to the same particle family.

### Edward Witten (1951–)

An American physicist. Witten instigated the second superstring revolution in 1995. It was Witten who first proposed that the five versions of string theory were really just five interpretations of the same theory. He also introduced the important possibility that string theory encompasses far more than just strings.

### Thomas Young (1773–1829)

An English physicist. Young disproved Newton’s conception of light as a stream of particles. By allowing light to pass through two pinholes onto a screen, he found that the light beams spread apart and overlapped. In the area of overlap, Young saw bands of bright light alternating with bands of darkness. With this demonstration, he revived the century-old wave theory of light and established the principle of interference of light.