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The Last Epoch

The Last Epoch. Sections 39.4-39.5. Reminders & Update. There are no more Mallard-based quizzes . The final examination will be on December 13, Thursday, from 7 :50 AM - 9:50 AM.

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The Last Epoch

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  1. The Last Epoch Sections 39.4-39.5

  2. Reminders & Update • There are no more Mallard-based quizzes. • The final examination will be on December 13, Thursday, from 7:50 AM - 9:50 AM. • deals with Chs. 29, 37–39 (23 points) and review (12 points) plus extra credit based on questions from earlier chapters (6 points)– max. score 117% • 5 questions are mathematical; perhaps two other questions have mathematical components that do not require actual numberical problem solving. • Course evaluation begins momentarily...

  3. Galaxy Formation Uncertain • Did galaxy or star formation come first? • Unclear, and problem is confounded by the presence of dark matter the nature of which is completely unknown. • Its presence is deduced from rotation curves.

  4. Birth of a Star • Gravity, with a bit of help from various collisions, forms stars. • At the center of a cloud, T increases to 10 million Kelvin and the P-P cycle starts. • Gravity balanced by radiation pressure for a long period of time depending on mass.

  5. Death of a Star • 6P–>3He–>C–>N–>O–> • Near the end of their life spans, stars become red giants. • Three possible end states determined by the mass of the star: • White dwarf (low mass) • Neutron star (medium) • Black hole (high mass)

  6. White Dwarfs • Produced in planetary nebula phase where atmosphere begins a run away process. • An earth-sized core is revealed at 100,000K +

  7. Neutron Stars • Produced during a supernova explosion resulting in a pulsar. • Protons and electrons are crushed to produce neutrons.

  8. Black Holes • Produced in supernova explosions but neutron degeneracy cannot stop collapse. • Gravity is so strong that even light cannot escape. • Accretion disk (such as Cygnus X-1) often found in binary star systems.

  9. Black Hole Detection • X-ray sources • Gravitational effects on binary star companion • Gravitational lensing • Gravitational ripples • Accretion disk jets

  10. Review: Ch 12 • Evidence for + and – charges. • Coulomb’s law: • F = kq1q2/r2 • Parallel to Newton’s law of gravitation • Electric fields: • replace “action at a distance” • Forces propagated at the speed of light • Field lines and the “test particle” • F = Eq (E is measured in N/C)

  11. Review: Ch 13 • Faraday – first produced electricity from magnetism and introduced magnetic field • Örsted – discovers that flowing electrical charges produce a magnetic field. • Earth’s magnetic field: • Earth’s south magnetic pole in northern hemisphere • Produced by a poorly understood dynamo effect • Electricity is produced by spinning a coil of wire in the presence of a magnetic field. • Current flow is related to the time-rate change of flux.

  12. Review: Ch14 • Maxwell “updates” and modifies work of Coulomb, Örsted, Faraday, and Ampère to produce what are now known as Maxwell’s laws. • Maxwell’s laws govern all electromagnetism. • Maxwell predicts EM waves with v = c • Electromagnetic spectrum includes radio and microwaves, infrared, visible light, UV, X rays, etc. • EM waves are produced via the oscillation of electric charges.

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