•
Rainer K. Sachs (1932–2024) discovered gravitationally induced redshifts in the cosmic background radiation •
Carl Sagan (1934–1996) American astrophysicist, cosmologist and author •
Andrei Sakharov (1921–1989) invented the theory of twins, CPT-symmetric universes •
Allan Sandage (1936–2010) set the
cosmological distance scale and accurately estimated the speed of
expansion of the universe •
Brian P. Schmidt (1967–) used supernova data to measure the acceleration in the expansion of the universe •
David N. Schramm (1945–1997) was an expert on big bang theory and an early proponent of dark matter •
Dennis W. Sciama (1926–1999) studied many aspects of cosmology and supervised many other leading cosmologists •
Irving Segal (1918–1998) created chronometric cosmology with alternative explanation of redshift in spectra of distant sources •
Seleucus of Seleucia (c.190–c.150 BC) used tidal observations to support a heliocentric model •
Roman Ulrich Sexl (1939–1986) developed an ether-based theory of
absolute simultaneity that is mathematically equivalent to special relativity •
Al-Sijzi (c. 945–1020) invented an
astrolabe based on the Earth's rotation •
Joseph Silk (1942–) explained the homogeneity of the early universe using
photon diffusion damping •
Willem de Sitter (1872–1934) developed a theory of dark matter with Einstein, found an expanding matterless solution to general relativity •
Vesto Slipher (1875–1969) performed the first measurements of
radial velocities for galaxies, providing the empirical basis for the expansion of the universe •
Lee Smolin (1955–) studied quantum gravity, popularized a theory of
cosmological natural selection •
George F. Smoot (1945–2025) used
Cosmic Background Explorer satellite to measure the temperature and anisotropy of the early universe •
David N. Spergel (1961–) used Wilkinson Microwave Anisotropy Probe satellite to measure the temperature and anisotropy of the early universe •
Paul Steinhardt (1952–) pioneered
inflationary cosmology, introduced first example of
eternal inflation, introduced quintessential dark energy, introduced the concept of strongly self-interacting dark matter, studied
brane cosmology and cyclic models of the universe •
Abd al-Rahman al-Sufi (903–986) wrote the
Book of Fixed Stars, which lists over forty constellations and the stars within them •
Nicholas B. Suntzeff (1952–) used supernova observations to discover acceleration in the expansion of the universe, calibrated the supernova distance scale •
Rashid Sunyaev (1943–) developed a theory of density fluctuations in the early universe, described how to use cosmic background distortion to observe large-scale density fluctuations •
Alex Szalay (1949–) was working on structure formation in a neutrino-dominated universe, biased galaxy formation in a cold dark matter dominated universe and computing the power spectrum in hot, cold and warm dark matter dominated universes == T ==