Final Exam Study Guide

Transcription

1 Final Exam Study Guide

2 Final is Comprehensive! Covers content of the entire course Please be sure to look at the Study Guides for the first three in-class exams All of that material will be on the final exam Study the questions on previous exams carefully! This guide covers only the additional material that will be on the final exam from the last two weeks of class

3 The Milky Way: The Milky Way is our Galaxy Diffuse band of light crossing the sky Galileo: Milky Way consists of many faint stars The Nature of the Milky Way Philosophical Speculations: Wright & Kant Star Counts: Herschels & Kapteyn Globular Cluster Distribution: Shapley

4 The Milky Way and Other Galaxies: Disk & Spheroid Structure of the Galaxy Pop I Stars: Young, metal-rich, disk stars Ordered, nearly circular orbits in the disk Pop II Stars: Old, metal-poor, spheroid stars Disordered, elliptical orbits in all directions Gives clues to the formation of the Galaxy.

5 Other Galaxies: Three basic types of Galaxies: Spirals Disk and spheroid component Rotation of disk allows measurement of galaxy mass Ellipticals Irregulars Differ in terms of Relative Gas content Star Formation History Internal Motions Galaxies tend to group into Clusters Groups, clusters, and superclusters Galaxies can collide and merge Some galaxies have active nuclei Powered by large Black holes in the center

6 Special Relativity: Postulates of Special Relativity: The laws of physics are the same for all uniformly moving observers. The speed of light is the same for all observers. Consequences: Different observers measure different times, lengths, and masses. Only spacetime is observer independent.

7 General Relativity: General Relativity: Modern Theory of Gravitation Matter tells spacetime how to curve. Curved spacetime tells matter how to move. Tests of General Relativity: Perihelion Precession of Mercury Bending of Starlight near the Sun The Binary Pulsar (Gravitational Waves)

8 Expansion of the Universe: Hubble s Law: Galaxies are receding from us. Recession velocity gets larger with distance. Hubble Constant: Rate of expansion of the Universe. Cosmological Redshift: Redshift distances Redshift maps of the Universe.

9 Cosmology: Cosmological Principle: The Universe is Homogeneous and Isotropic on Large Scales. No special places or directions. General Relativity predicts an expanding universe. Cosmological Constant

10 Big Bang: Big Bang Model of the Universe Starts in a hot, dense state Universe expands and cools Expansion and Redshift Critical Density Geometry of the Universe Hubble Time = Maximum age of the Universe

11 Evidence for the Big Bang: Fundamental Tests of the Big Bang Primordial Nucleosynthesis Primordial Deuterium & Helium Primordial light elements (Li, B, Be) Cosmic Background Radiation Relic blackbody radiation from Big Bang Temperature: T = K

12 First 3 Minutes in the History of the Universe: Physics of the Early Universe Informed by experimental & theoretical physics The Cosmic Timeline: Observations go back to t~3 minutes Reasonably firm physics back to t~10-6 sec Speculative back before t~10-12 sec Present theories stop at t~10-43 sec

13 Critical Density All galaxies attract each other via gravity. Gravitational attraction slows the expansion. How it behaves depends on the density: High Density: Expansion slows, stops, & reverses. Low Density: Keeps expanding forever. Dividing Line = Critical Density

14 Density Parameter: W W average density of Universe critical density W>1: High Density Closed Universe W=1: Critical Density Open Universe W<1: Low Density Open Universe

15 End of Universe: The Fate of the Universe depends on the density of matter. Closed Universe: Enough matter to stop the expansion Collapses in a Big Crunch Open Universe: Expands forever Ends in a cold, disordered state Dark Energy seems to make this outcome more likely