Origins
Origin of the Earth
• Big Bang – beginning of the expansion of
the universe • 10-20 billion years (Billion years -BY ) ago: the Universe is born • As the matter cool off forms atoms from the original matter • Most of it was H
Galaxies and Stars
• Formation of solar system • From gas cloud ( pre-solar nebula) 4.56
BY • Galaxy is an aggregation of stars, dust and gas • Milky way is our galaxy (f. 1.5) • Star – spheres of incandescent gases
Formation of Planets
• Solar Nebulae was a rotating disk • Spun faster as it condensed and the
center became the protosun • The other material became the planets • Planets including Earth, from planetesimals (asteroid-sized) bodies complete 5 BY (f.1.11)
Oceans
• There are basically three possible sources for
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the water of the Oceans, it could have: (1) separated out from the rocks that make up the bulk of the earth; (2) arrived as part of a of water- rich meteorites, or (3) arrived as part of of icy planetesimals
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• the best model for the source of the oceans at
the moment is a combination of water derived from comets and water that was caught up in the rocky body of the earth as it formed Most of the water was probably present originally as water trapped in clay minerals or as separate hydrogen (in hydrocarbons) and oxygen (in iron oxides), rather than as ice.
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• Liquid water and oceans have formed by
4.6 BY • Oldest known rocks on Earth 4.0 BY • Earliest signs of life in oceans 3.85 BY
Origin of Life
• 1953 Stanley L. Miller, did the first experiment
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designed to clarify the chemical reactions that occurred on the primitive earth. In the flask at the bottom, he created an "ocean" of water, which he heated, forcing water vapor to circulate through the apparatus. The flask at the top contained an "atmosphere" consisting of methane (CH4), ammonia (NH3), hydrogen (H2) and the circulating water vapor.
• Next he exposed the gases to a continuous
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electrical discharge ("lightning"), causing the gases to interact. Water-soluble products of those reactions then passed through a condenser and dissolved in the mock ocean. The experiment yielded many amino acids and enabled Miller to explain how they had formed
• Did life form in these experiments? • NO • Crucial compounds can be synthesized so
easily • Biosynthesis is still speculative, but at this point we do not have a better explanation
Multi-cellular organisms
• The oldest fossil, from Northern Australia,
are between 3.4-3.5 BY (f.1.18) • Multi-cellular organism suddenly appear about 600 MY
• Ice ages begin, hominids appear 2 MY • modern Homo sapiens appears ~100,000
Y