Dennis William Siahou Sciama, FRS (/ʃiˈæmə/; 18 November 1926 – 18 December 1999)[7][8] was an English physicist who, through his own work and that of his students, played a major role in developing British physics after the Second World War.

[9][10] He was the PhD supervisor to many famous physicists and astrophysicists, including John D. Barrow, David Deutsch, George F. R. Ellis, Stephen Hawking, Adrian Melott and Martin Rees, among others; he is considered one of the fathers of modern cosmology.

[16] Sciama earned his PhD in 1953 at the University of Cambridge supervised by Paul Dirac,[2] with a dissertation on Mach's principle and inertia.

When evidence against the steady state theory, e.g., the cosmic microwave radiation, mounted in the 1960s, Sciama abandoned it and worked on the Big Bang cosmology; he was perhaps the only prominent Steady-State supporter to switch sides (Hoyle continued to work on modifications of steady-state for the rest of his life, while Bondi and Gold moved away from cosmology during the 1960s).

Among other aspects, he pursued a theory of dark matter that consists of a heavy neutrino, certainly disfavored in his realization, but still possible in a more complicated scenario.

The 1960s group he led in Cambridge (which included Ellis, Hawking,[20] Rees, and Carter), has proved of lasting influence.