Chapter 3 - Origin of Earth, its Past and Future

Abstract

Publisher Summary This chapter discusses the origin of Earth, its past, and its future. According to the modern cosmogonic concepts, the Earth group's planets, including Earth and the Moon, formed due to accretion of solid particles in the gas–dust protoplanetary cloud. Usually, the initial density of the interstellar clouds is not high enough for gravity compression and development of the independent star- and planet-forming processes. Supernova explosions, however, are accompanied by shock waves in the interstellar medium. If such waves hit a gas–dust cloud, pressure and matter density drastically increase on the wave-front. The result may be clots capable of the subsequent compression due to the self-gravity. That is why supernova explosions not only deliver the new matter into the cosmic space but also serve as the mechanism, which eventually leads to the formation of new generations of stars and their surrounding planetary systems. Apparently, such a situation arose about 4.56 BY ago in the vicinity of the protosolar gas–dust cloud. After having received an impulse of the initial compression and evolution and having been added a new matter, the cloud subsequently began to compress irreversibly, now affected by its own gravity field. With the compression, pressure and temperature in the cloud's center rapidly increased. Gradually, a giant gas clot, the Proto-Sun, formed in that zone. However, prior to the “kindling” of the nuclear reactions and the Proto-Sun entering the main sequence of the stellar evolution, its temperature was relatively low, not above 1000–1500 °C, and the radiation was mostly in the infrared (IR) and red spectral bands.