08 - Earth image by Apollo 17 Dec.7 1972 Hubble telescope...

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Unformatted text preview: Earth image by Apollo 17 Dec.7, 1972 Hubble telescope image of a nebula with remnant central star Cosmology scientific study of the large scale properties origin, evolution, and future of the Universe like all science- uses hypotheses and data to science "Big Bang" is theory or origin of Universe Bang" that is best supported by current level of understanding / data make testable predictions of the Universe as a whole Prevailing theory: Big Bang apparent "beginning" of universe beginning" All of the mass and energy in the universe The Modern Universe was packed into a single microscopic point Exploded 14 billion years ago, and has been expanding ever since astronomers calculate based on real data Big Bang 1 How to build a solar system in a few easy steps... A nebula (large, diffuse gas cloud of gas and dust) contracts under gravity- it heats, flattens, and spins Star born in center and planets form in disk Nuclear fusion begins at 10 million C H atoms fuse to form He Smaller atomic nuclei join forming larger nuclei Hubble telescope image- April 1, 1995; M16, Eagle Nebula; birth of a star; molecular hydrogen gas Birth of a solar system (con't) H and He remain gaseous, but other materials can condense into solid "seeds" for building planets Warm temperatures allow only metal/rock "seeds" to condense in the inner solar system Cold temperatures allow "seeds" to contain abundant ice in outer solar system. "Leftovers" become asteroids (metal/rock) and comets (mostly ice) Death of a star- birth of elements length of star life depends on initial mass As H is consumed, starts to consume heavier atoms (C and O) and form heavier atoms (up to Fe) swells, energy output rises = Red Giant H is depleted, collapses on itself, cataclysmic expansion (blows to bits) = Supernova all atoms heavier than Fe formed and sprayed into space supernova 2 Hubble telescope in orbit launched in 1990 after 20 years of work by over 1000 scientists images and data collected by this instrument have revolutionized cosmology we have observed these processes in action! 9/6/07 Milky Way galaxy Stellar origin of Earth, ocean, and biological components Our solar nebula struck by a shock wave from supernova (Earth has all of the heavy elements!) ~5 billion years ago Earth, oceans, organisms are all made of stardust 75% H, 23% He, 2% other (heavy elements, gas, dust, ice) artist rendition of Milky Way forming 3 This image of the sun was This image of the sun was taken on 3/27/07 by the taken on 3/27/07 by the SECCHI Extreme UltraViolet SECCHI Extreme UltraViolet Imager (EUVI) mounted on the Imager (EUVI) mounted on the STEREO-B spacecraft; JPL STEREO-B spacecraft; JPL SOHO Extreme UV imaging telescope Planet Earth formation accretion small particles clump into larger masses density stratification heavier stuff sinks- lighter matter forms crust sinksLighter matter and silicates Iron Early Earth formation 4.6 billion years ago along with rest of solar system solar output ~70% of today very hot (molten, steamy, boiling rain) frequent bombardment (asteroids / comets) moon knocked off by large impact 4 Early atmosphere first atmosphere stripped away from intense young sun radiation gas burped out from molten interior to form new atmosphere rich in CO2, N, H20, NH4 (ammonia), CH4 (methane) gradual alteration to present composition (mostly N and O; "the oxygen revolution"!) revolution" see evidence of this in the changing composition of rocks over time (early atm not oxidizing) 100 Concentration of Atmospheric Gases (%) Methane, ammonia 75 Atmosphere unknown Nitrogen 50 Water Carbon dioxide Oxygen 25 0 4.5 3 4 Time (billions of years ago) 2 1 Early ocean water source: icy comets volcanic out-gassing out- too hot for liquid water at first gradual salt accumulation Earliest life likely in ocean 3.5 billion years old microscopic filament from Australia bacteria-like bacteria Earth not around for long without it all water on Earth has some form of life 5 Geologic ages: How do we know? radioactive decay Within a given time period a fixed proportion of atoms of unstable elements spontaneously disintegrates to form atoms of a new element. This radioactivity is a property the atom. For example: Polonium (with mass of 214) converts to Lead (with mass of 210) many geologic materials contain radioactive elements Periodic table of the Elements elements with unstable radiogenic isotopes with half-lives over 0.5 m.y. 238U 235U 232Th 40K 87Rb 147Sm 14C Examples of isotope systems used to date geologic materials Parent Daughter 206Pb 207Pb 208Pb 40Ar & 40Ca 87Sr 143Nd 14N 1/2 4.47 b.y 707 m.y 14 b.y 1.28 b.y 48 b.y 106 b.y. 5,730 y Useful Range >10 million years >10,000 years >10 million years 100 - 70,000 years Type of Material Igneous & sometimes metamorphic rocks and minerals Organic Material 6 Dating Meteorites (clues to age of Earth) Oldest rocks on Earth = ~ 4 billion years old Age of Earth and solar system = ~ 4.6 billion years old Oldest rocks with evidence of life ~ 3.5-3.8 billion years old Type Chondrites (CM, CV, H, L, LL, E) Carbonaceous chondrites Chondrites (undisturbed H, LL, E) Chondrites (H, L, LL, E) H Chondrites (undisturbed) H Chondrites L Chondrites (relatively undisturbed) L Chondrites LL Chondrites (undisturbed) LL Chondrites E Chondrites (undisturbed) E Chondrites Eucrites (polymict) Eucrites Eucrites Diogenites Iron (plus iron from St. Severin) Number Dated 13 4 38 50 17 15 6 5 13 10 8 8 23 11 13 5 8 Method Sm-Nd Rb-Sr Rb-Sr Rb-Sr Rb-Sr Rb-Sr Rb-Sr Rb-Sr Rb-Sr Rb-Sr Rb-Sr Rb-Sr Rb-Sr Rb-Sr Lu-Hf Rb-Sr Re-Os Age (billions of years) 4.21 +/- 0.76 4.37 +/- 0.34 4.50 +/- 0.02 4.43 +/- 0.04 4.52 +/- 0.04 4.59 +/- 0.06 4.44 +/- 0.12 4.38 +/- 0.12 4.49 +/- 0.02 4.46 +/- 0.06 4.51 +/- 0.04 4.44 +/- 0.13 4.53 +/- 0.19 4.44 +/- 0.30 4.57 +/- 0.19 4.45 +/- 0.18 4.57 +/- 0.21 It's below us! - Installation of accelerator in 1968 Prime Lab, Purdue University Accelerator Mass Spectrometer (measures radioactive isotopes) http://www.physics.purdue.edu/primelab/ Quiz #1 1. What is the scientifically accepted age of the Earth? 2. True or false: Lines of LONGITUDE are always an equal distance apart. 3. Is the following a "scientific hypothesis" hypothesis" (explain why or why not) The rain in Spain falls mainly on the plain. 7 ...
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