Lecture 2 Jan 18 2008

Lecture 2 Jan 18 2008 - What happened at the very beginning...

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What happened at the very beginning of our universe? From an infinitesimally small, infinitely hot, infinitely dense “singularity,” our universe began expanding and cooling around 13.7 billion years ago at the moment of the “Big Bang.” Prior to that moment there was nothing; during and after that moment there was something: our universe. The Big Bang
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Our solar system began forming within a concentration of interstellar dust and hydrogen gas called a molecular cloud. The cloud contracted under its own gravity and our proto-Sun formed in the hot dense center. The remainder of the cloud formed a swirling disk called the solar nebula. Solar Nebula The Lunar and Planetary Institute http://www.lpi.usra.edu/
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Dust and ice particles in the nebula occasionally collided and merged. Through accretion, microscopic particles formed larger bodies that eventually became planetesimals (km’s across). In the inner, hotter part of the solar nebula, planetesimals were composed mostly of silicates and metals. In the outer, cooler portion of the nebula, water ice was the dominant component. Planetesimals
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influenced motions of other planetesimals, increasing the frequency of collisions. Eventually, regions of the nebula were dominated by large bodies called planetary embryos. The process of collision and accretion continued until only four large bodies remained — Mercury, Venus, Earth, and Mars. Terrestrial
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Lecture 2 Jan 18 2008 - What happened at the very beginning...

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