Caltech exists today because three of the preeminent scientists of the early twentieth century—Robert Andrews Millikan, Arthur Amos Noyes, and George Ellery Hale—sought to establish a research and educational center beyond the capacities and philosophies of existing academic institutions. Unconstrained by the prevailing focus on industrial applications of science, they envisioned an institute dedicated to the discovery and understanding of the fundamental principles of nature, believing that practical applications must flow from such advances.
Caltech quickly became one of the physics capitals of the world (and a leader in other fields). Caltech Physics, Mathematics & Astronomy faculty and alumni have received 14 Nobel Prizes in Physics, a Fields Medal, two Fundamental Physics Prizes, three Crafoord Prizes, and 16 National Medals of Science. In theoretical physics, professor David Politzer, past faculty members Richard Feynman, William Fowler, and Murray Gell-Mann, and alumnus Kenneth Wilson have all made Nobel Prize–winning discoveries.
- Fritz Zwicky, with the Carnegie Institution's Walter Baade, predicted neutron stars and correctly proposed that their births power supernovae. Zwicky predicted the existence of dark matter to explain anomalies in observed properties of galaxies.
- Richard Chace Tolman and J. Robert Oppenheimer developed the mathematical theory of neutron stars, and Oppenheimer deduced that massive stars could implode to form what we now call black holes.
- Richard Feynman invented Feynman diagrams and used them to formulate the laws of QED (quantum electrodynamics, the theory that explains quantum phenomena involving electromagnetic fields). He also made influential findings about superfluids and launched nanoscience and quantum information science.
- Willy Fowler explained how elements form by nuclear burning in stars. He spearheaded a combined theoretical, experimental, and observational program to investigate this process.
- Murray Gell-Mann predicted quarks, the building blocks of particles. He formulated the concepts of strangeness and the eight-fold way, which brought order to the hundreds of elementary particles that had just been discovered.
- Maarten Schmidt and visiting scholar Donald Lynden-Bell made fundamental contributions to the discovery and understanding of quasars and how they are powered. This work "expanded the scale of the observable Universe and led to our present view of a violent Universe in which massive black holes play a key role (Kavli Prize citation).''
- Peter Goldreich explained the observed structure of our solar system and predicted new structural features that were later observed.
- David Politzer discovered asymptotic freedom, the characteristic of quarks that allows them to form protons and neutrons. This established quantum field theory as the basic language of high energy physics.
- John Schwarz co-invented superstring theory, independently pursuing this work for 12 years until his and Michael Green's discovery of the Green–Schwarz Mechanism in 1984. That discovery catalyzed the "first superstring revolution," bringing string theory back into the mainstream.
- Kip Thorne launched a new era in gravitational astrophysics by advancing theoretical, experimental, and observational investigation of gravitational waves. Thorne's insights also underpinned new efforts to experimentally realize quantum phenomena at large scales. Together with Stephen Hawking, who visits Caltech annually as a Sherman Fairchild Distinguished Scholar, Thorne shaped theory about gravity, spacetime, and relativity.
- Mark Wise and Larry Abbott were among the early groups to calculate the gravitational wave spectrum from inflation and determine its influence on the fluctuations of the temperature of the microwave background radiation.
- Mark Wise, in collaboration with Nathan Isgur and others, developed the heavy quark expansion for the interactions of quarks with masses much larger than the scale of the strong interactions. In the process, he discovered new symmetries of the strong interactions that arise in the heavy quark mass limit. This enabled precise model independent predictions for the strong and weak interactions of hadrons containing a heavy bottom or charm quark.
- Marc Kamionkowski, collaborating with a Caltech experimental group, invented a method for measuring the large-scale geometry of the universe and probing its inflationary birth. His work enabled the group to confirm the existence of dark matter and dark energy using temperature maps of cosmic microwave background radiation. It also underpinned the BICEP2 experiment, which provided the first direct evidence of primordial gravitational waves, supporting the theory of cosmic inflation.
- John Preskill's discoveries in quantum error correction made quantum computation possible in principle.
- Alexei Kitaev, who explores and builds deep connections between condensed matter and quantum information, invented the concept of topological quantum computation.