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Looking back at Earth from orbit of Saturn(Voyager)

Looking back at Earth from orbit of Saturn(Voyager). A blue water planet with 30% reflectivity (clouds, ice, snow). About as many stars in the observable universe as the number of grains of dry sand on all the beaches of world. Carl Sagan.

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Looking back at Earth from orbit of Saturn(Voyager)

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  1. Looking back at Earth from orbit of Saturn(Voyager)

  2. A blue water planet with 30% reflectivity (clouds, ice, snow)

  3. About as many stars in the observable universe as the number of grains of dry sand on all the beaches of world. Carl Sagan ~100 billion galaxies, each with ~100 billion stars, so N ~1022 Compare: number of H2O molecules in 1 ml of water, or about N = 3 x1022

  4. Early periodic table Russian Chemist Dmitri Mendeleev

  5. The Periodic Table of Chemical Elements

  6. A different way to view the periodic table

  7. What keeps the sun shining?? Net reaction: 4 protons (H) fuse to make a helium (He) nucleus, releasing energy: ~0.7% mass converted to energy by ∆E = mc2

  8. The Crab Nebula: remnant from supernova explosion, observed in 1054 A.D. Left behind: a pulsar, spinning neutron star. SN explosions, the only way to make the elements beyond iron (Fe).

  9. Relative atomic abundances in the galaxy, normalized to Hydrogen (H =1.00). Universe is still ~98% (H, He), as forged in the first minutes of the Big Bang. Notice the Fe ‘hill’ of higher abundance (most stable nucleus) Why might a carbon-based life, with H2O solvent be expected elsewhere?

  10. The mass of atoms is in the nucleus, the size of an atom is the size of the electron ‘cloud’ (Heisenberg Uncertainty Principle)

  11. The structure of atoms with ~all mass in the nucleus (protons and neutrons), surrounded by a cloud of electrons

  12. Rutherford’s experiment showed that the mass of atoms was concentrated in a very small nucleus.

  13. Bohr with Heisenberg (discussing the ‘critical mass’ for fission?)

  14. Niels Bohr • (early model of H atom) • Albert Einstein • (photo-electric effect)

  15. Naming atoms Proton number defines the element Isotopes have different numbers of neutrons for the same number of protons (same element)

  16. Electromagnetic radiation travels at the speed of light (c) Photons have no mass Energy is proportional to frequency of the radiation

  17. (Wavelength) times (frequency) = speed of propagation = c

  18. The electromagnetic spectrum by wavelength

  19. Electromagnetic energy is directly proportional to the frequency, and inversely proportional to wavelength

  20. Photon Emission System drops from a higher energy level to a lower one by spontaneously emitting a photon. Emission

  21. “Continuous” spectrum “Quantized” spectrum DE DE Any DE is possible Only certain DE are ‘allowed’ transitions

  22. White light can be spread into a rainbow of different wavelengths (colors) by a prism or grating (Newton)

  23. Emission spectrum of atomic H Light Bulb: Continuous spectrum Hydrogen Lamp: Discrete lines only Quantized, not continuous

  24. The spectrum of molecular hydrogen H2: a very complex pattern of emission lines unique to this species (‘fingerprint’) Spectral lines correspond to electron jumps between discrete (’quantized’) energy levels of atoms, ions, and molecules

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