The formation and differentiation of Earth

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Source:  Bernard Wood, Physics Today pg. 40
Excerpt: The solar system began to form 4568 million years ago, from a disk of dust and gas around the young Sun. Within a few million years, Jupiter and Saturn had formed and the terrestrial planets had reached significant fractions of their present size. The processes by which the planets formed are of particular interest at a time when the search for Earth-like planets around other stars occupies considerable attention. Earth-like exoplanets somewhat larger than our own are already detectable, ... The mechanisms of initial growth toward large bodies are poorly understood … some combination of mechanical sticking and eventually gravitational perturbation must have formed many 10-km-sized objects in the first 10^4–10^5 years. ...Although some planetesimals would have been destroyed in collisions, others would have continued to accrete….

 www.physicstoday.org/resource/1/phtoad/v64/i12/p40_s1

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