دانلود کتاب مسائل مدرن در اخترفیزیک هسته‌ای و نوترینو، ویرایش دوم

Shortly after the discovery of the law of conservation of energy by Mayer (1942) and Helmholtz (1847) it was J. R. Mayer who raised the question for the origin of the radiative energy emitted by the Sun. J.R. Mayer’s law of conservation of energy (_irst law of thermodynamics) took into account the energy due to heat. If dQ is the amount of heat energy which is absorbed by the system under question from its surroundings, then this law of conservation of energy is, dQ=dU+dW; where dU is the change in internal energy of the system when going from one equilibrium state to another, and dW is the amount of work done by the system on its surroundings. In 1848 J. R. Mayer stated that the source of the solar radiation energy should be the kinetic energy of infalling meteorites. At last a re_inement of J. R. Mayer’s idea we meet in the hypothesis of Helmholtz (1847) and Lord Kelvin (1861) who were able to show that the gravitational contraction of the Sun itself could be the signi_icant source of radiated energy. However, already on the basis of Lane’s (1870) considerations of a stellar con_iguration in convective equilibrium taking into account internal gravitation and Ritter’s (1878) results on the uniform expansion and contraction of gaseous con_igurations it has been shown that gravitational contraction cannot keep the Sun shining (HELMHOLTZ-KELVIN contraction time scale).