David Raymond Layzer (born December 31, 1925 in Ohio  , † August 16, 2019 in Belmont , Massachusetts  ) was an American astrophysicist and cosmologist .Layzer studied at Harvard University with a bachelor's degree in 1947 and a doctorate in 1950 in theoretical astrophysics. 1951/52 he was lecturer at the University of California, Berkeley , 1952/53 at Princeton University and from 1953 again at Harvard, where he became lecturer in 1955 and 1960 professor of astronomy. From 1980 he was Donald H. Menzel professor of astrophysics. According to Layzer, the time arrow is associated with the development from special initial conditions in the universe and the subsequent increase in entropy as part of the expansion of the universe, whereby the expansion took place faster than the process rates required for the establishment of a thermodynamic equilibrium of maximum entropy, so that the entropy of the universe is behind maximum possible entropy remained constantly. This created space for the development of order in the universe (understood as negative entropy or information that, according to Layzer, was hardly available in the initial state) and thus solves a fundamental paradox, since order is actually based on the second law in closed systems such as the universe should decrease. With regard to the cause of free will, Layzer took the view that this is independent of the quantum mechanical uncertainty in the microscopic range. According to Layzer, irrespective of quantum mechanics, there are sources of unpredictability in the macroscopic area that have to do with the boundary and initial conditions of processes. The same applies, according to Layzer, to the predictability of evolutionary development. In this sense, Layzer's biology cannot be reduced to physics either. In addition to theoretical astrophysics and cosmology, he also dealt with atomic physics and ionospheric physics, population genetics and evolution, the measurement problem and the problem of free will in the context of quantum mechanics. He was married in 1959 and had six children. Layzer was a member of the American Academy of Arts and Sciences from 1963 . Writings (selection) Cosmic Evolution and Thermodynamic Irreversibility, Pure and Applied Chemistry, Volume 22, 1970, pp. 457-468.