The film "Why does the sun shine?" - the fifth, final film of the "Operation" Helium "cycle covers the period of the emergence in 1928 of the hypothesis of the fusion of hydrogen nuclei of helium as a source of stellar energy to modern research on controlled thermonuclear fusion in Russia (Institute of Atomic Energy named after IV Kurchatov) and in Great Britain (United European Thermonuclear Reactor) Part 1 The sun The sun goes down the horizon The sun sets behind a cloud Germany, Göttingen Streets, a fountain on the square with a sculpture "Girl with a goose", a university building Austrian scientist -physicist F. Houtermans recalls the scientific activity at the University of Göttingen on the study of thermonuclear reactions inside the sun in the late 1940s (sync. in German) Newsreel footage: prominences in the sun, the explosion of a hydrogen bomb (1952-1953 yy), a torchlight procession of the Nazis, the Nazis burn books at the stake, burning buildings, German equipment, including a rocket launcher, on the street of the occupied Kharkov city (1941), transport and city residents on the streets of military Berlin. 2nd part. Starry sky. Photos of theoretical physicists A.D. Sakharov, L.A. Artsimovich, M.A. Leontovich. Books by A.D.Sakharov and I.E. Tamm. Model of the experimental installation "Tokamak". Installation "Tokamak" in the physical laboratory of the Institute of Atomic Energy. I.V. Kurchatov. Physicist, Academician of the USSR Academy of Sciences B.B. Kadomtsev in a group of scientists. Great Britain. A view of the buildings of the physics laboratories in Culham near Oxford. European thermonuclear installation "Jet", on which during the experiment it was possible to achieve the power of a thermonuclear reaction of about two million watts. International congress of physicists from 12 countries of Europe, Russia, USA and Japan. Scientists in the meeting room. Among those present - theoretical physicist, academician E.P. Velikhov. Signing by representatives of the countries participating in the Congress of an agreement on the joint construction of the International Thermonuclear Experimental Reactor. Academician E.P. Velikhov signs an agreement. Newsreel footage: Moscow Kremlin, the building of the USSR Council of Ministers, theoretical physicist, academician of the USSR Academy of Sciences A.D. Sakharov at the blackboard with calculations, theoretical physicist, academician of the USSR Academy of Sciences I.E. Tamm in his office at work, employees of the Institute of Atomic Energy named after ... IV Kurchatov in the laboratory at work, an interview with a theoretical physicist, academician L.A. Artsimovich on the problem of thermonuclear fusion (sync.).