This collection of essays presented to Carl Friedrich von Weizsäcker on the occasion of his 90th birthday addresses a wide readership interested in astronomy, physics, and the history and philosophy of science. The articles treat subjects such as the social responsibility of scientists, thermonuclear processes in stars and stellar neutrinos, turbulence and the emergence of planetary systems. Furthermore, considerable attention is paid to the unity of nature, the nature of time, and to information about, and interpretation of, the structure of quantum theory, all important philosophical problems of our times. The last section describes von Weizsäcker's ur-hypothesis and how it will theoretically permit the construction of particles and interactions from quantized bits of information.