[en] An introduction to solar oscillations, their properties and diagnostic potential, and a review of our present knowledge is presented. The solar irradiance data from the ACRIM (Active Cavity Radiometer for Irradiance Monitoring) solar constant experiment on board the Solar Maximum Mission satellite (SMM) are used to search for solar gravity modes, which yield a direct information on the structure of the solar core. The power spectra of the time series of 270 days in 1980 and of 240 days in 1984 are analysed using a statistical method for the determination of the basic g-mode period separation P₀ and the rotational frequency ν_r. The results of the analysis in the frequency range from 15 to 35 μHz yield a P_o of 29.7 minutes. This indicates a nearly isothermal core - a possible explanation of the low (high energy) neutrino count in the Davis experiment. Moreover, it is close to the expected value for a WIMP model such as proposed by Faulkner. The rotational period in the center of the sun inferred from the splitting of the g-modes amounts to 10.7 days which is about 2.5 times the photospheric rate