Lecture 5 - Astro/Geo 160 Spring 2011 Lecture #5 7 February...

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Unformatted text preview: Astro/Geo 160 Spring 2011 Lecture #5 7 February 2011 Announcements MIDTERM #1 rescheduled for Monday, 14 February. Review of Lecture #4 Measuring Distances Parallax the apparent shift of an object on the sky relative to background objects caused by viewing the object from two different locations - be able to draw a picture showing how we can use parallax to measure distances to nearby stars What is significant about Cepheid variable stars? A) Their variation causes observed changes in the planets orbiting them. B) The period of their variation is tightly correlated the stars luminosity C) They are commonly found in the solar neighborhood D) They were used to accurately measure the distance to Venus Hubbles big discovery a correlation between the distance to galaxies and the velocity with which they appear to be receding from us the Universe is expanding Scale of the Universe 1 AU (Earth-Sun distance) ~ 150 x 10 6 km 50 pc (local neighborhood) ~ 150 x 10 13 km 8.5 kpc (distance to center of the MWG) ~ 2.6 x 10 17 km 50 kpc (distance to LMC) ~ 1.5 x 10 18 km 780 kpc (distance to M31) 2 Mpc (scale of the Local Group of galaxies) 10 Mpc distance to the Virgo Cluster of galaxies A Brief History of the Universe Obs. Hubble Law Remember Hubble Measured the distance to M31 (Andromeda) Correlation of recessional velocity and distance (V = H D, where H is a constant of proportionality) And Einstein GR predicts an expanding Universe A Brief History of the Universe II Hubbles Law expanding Universe! Take the expanding Universe and run the clock backwards Universe was once much smaller Thermodynamics take a gas, compress it, and it becomes much hotter BIG BANG!!!! Review of Lecture #4 contd A Really Brief History of Matter in the Universe Big Bang all energy, spontaneous conversion of energy into matter and anti-matter Universe cools, matter wins out over anti-matter left with protons (H) Spontaneous reactions that produce neutrons Universe cools and locks in a proton/neutron ratio sets the He abundance Universe continues to cool Recombination Universe continues to cool to T < 4000 K, protons and electrons combine to make neutral hydrogen...
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This note was uploaded on 02/14/2011 for the course ORGANIC CH 341 taught by Professor Idk during the Spring '11 term at Wisconsin.

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Lecture 5 - Astro/Geo 160 Spring 2011 Lecture #5 7 February...

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