The Setting
Objective
Earth special place for the development of modern life needs first to be explored in the broader context of planetary formation and Earth’s early evolution, so we start this unit with a brief examination of the origin of our solar system. Our current knowledge of astronomy has led to an age estimate of our Universe of ~14 billion years. The evidence is obtained from movements of large objects, such as galaxies, and from evidence of the microwave background radiation. The red shift of moving objects and today’s temperature of the Universe, among other lines of evidence, led to the theory of the Big Bang. Within this broad framework, the first question for us is the ages of our planet, which we obtain from radiometric measurements.