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The Big Bang etc getting Time off to a good start 1 Origins
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Part II why is the night sky dark? atomic spectra measuring recessional velocity measuring distance: parallax cepheid variables, and supernovae Origins 2
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Why Is The Night Sky Dark? Heinrich Wilhelm Matthias Olbers (1758- 1840) Origins 3
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Night Sky Paradox Origins 4
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Georges Lemaitre (1894-1966) Belgian astronomer proposed a version of the Big Bang (1927) Ante-dated Hubble by two years Explosive expansion permits permits a finite universe Origins 5
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Edwin Hubble (1889-1953) Observations showed that distant galaxies were red-shifted. Presumed to be receding. Requires measurements of recession speed and distance. Origins 6
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Measuring Recession Speed Figure 02-02
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Absorption Lines in Solar Spectrum Figure 02-03
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Figure 02-04 How to Build a Habitable Planet Copyright © Princeton University Press 2012
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Figure 02-05 How to Build a Habitable Planet Copyright © Princeton University Press 2012
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Measuring Distance
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Figure 02-07 How to Build a Habitable Planet Copyright © Princeton University Press 2012
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Parsec Astronomical distances outside the solar system are usually expressed in parsecs. A parsec is the distance to a star with a parallax of one arcsecond. One parsec is 3.26 light years. Origins 13
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Figure 02-06 How to Build a Habitable Planet Copyright © Princeton University Press 2012 Parallax Measurement of Distance
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Hipparcos Origins 15
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Parallax Limits Origins 16
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Extending Beyond Parallax Standard Candle Methods (I) Cepheid Variables Large variables with periods of days to months Due to ionized He layer around the star Origins 17
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Figure 02-08 How to Build a Habitable Planet Copyright © Princeton University Press 2012
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Extending Beyond Parallax Standard Candle Methods (II) Type Ia supernovae Characteristic brightness curve One or two per century per galaxy Origins 19
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Type Ia Supernova Origins 20
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SN 1987a Origins 21
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Origins 22
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How to Build a Habitable Planet Copyright © Princeton University Press 2012 Methods Based on Galaxy Sizes
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Distance Toolkit Origins 24
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Figure 02-10 How to Build a Habitable Planet Copyright © Princeton University Press 2012
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Origin Time Origins 26
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Additional Big Bang Evidence Origins 27
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Accelerating Expansion Origins 28
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Expansion Timeline Origins 29
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Figure 02-15 How to Build a Habitable Planet Copyright © Princeton University Press 2012 Dark matter: 23%
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Earliest Stars Had No Rocky Planets No heavy elements in the Universe at that time Origins 31
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