Galaxies and the Universe: Galaxies and the Universe


What Are Galaxies?: What Are Galaxies? Greek galax = milk William Herschel, 1783: A disk with the Sun slightly off-center


What Are Galaxies?: What Are Galaxies? 19th Century: 'Spiral Nebulae' Nearby? Maybe Solar Systems in Formation? 1920: Galaxies are Stars 1920’s: Galaxies are like the Milky Way Biggest single increase in our mental picture of the Universe in human history


Where Are We in our Galaxy?: Where Are We in our Galaxy? The visible Milky Way suggests our galaxy is a flat disk Surrounding other galaxies is a spherical halo of Globular Star Clusters


Galaxies and Globular Clusters: Galaxies and Globular Clusters


The Milky Way’s Globular Clusters: The Milky Way’s Globular Clusters


The Milky Way As We See It: The Milky Way As We See It


Anatomy of a Galaxy: Anatomy of a Galaxy


Spiral Arms: Spiral Arms


In Microwaves, We Can See the Hub of the Galaxy: In Microwaves, We Can See the Hub of the Galaxy


Mapping the Neighborhood: Mapping the Neighborhood


Mapping the Neighborhood: Mapping the Neighborhood


Mapping the Galaxy: Not There Yet: Mapping the Galaxy: Not There Yet


Mapping the Galaxy: Not There Yet: Mapping the Galaxy: Not There Yet


The Local Group: The Local Group


Downtown: The Virgo Cluster: 50 m.l.y: Downtown: The Virgo Cluster: 50 m.l.y


The Local Super-cluster: The Local Super-cluster


The Coma Cluster350 m.l.y.: The Coma Cluster 350 m.l.y.


Large-Scale Structure of the Universe to 500 m.l.y.: Large-Scale Structure of the Universe to 500 m.l.y.


Travel to the Stars?: Travel to the Stars? Kinetic Energy = 1/2 Mv2 What does it take to get a 1000-ton spaceship to 10% of the speed of light? (43 years to Alpha Centauri) M=106 kg, v = 3 x 107 m/sec KE = 1/2 x 106 x 9 x 1014 = 4.5 x 1020 joules Equals U.S. Energy Production for 4.5 years Once you get there, you have to stop.


Relativity: Relativity Speed of Light is Independent of Source Michelson and Morley, 1887 - Speed of Light Independent of Observer 'One of the Most Unexpected Results in the History of Science' - Isaac Asimov Conclusion: Speed of Light is the Same for All Observers Implication: Space and Time Must Change to Keep Speed of Light Constant


Why the Speed of Light is a Speed Limit: Why the Speed of Light is a Speed Limit Energy of a Moving Object in Relativity: E = mc2 -------------------------------------------------------------------------------  1 - v2/c2 One consequence: as v approaches c, Energy goes to infinity Also, as we approach c, Energy goes up very fast


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Fuel Economy of a Starship: Fuel Economy of a Starship


Another Consequence of Relativity- Gravitational Lenses: Another Consequence of Relativity- Gravitational Lenses


“The Big Bang”: 'The Big Bang' Edwin Hubble, Recession of Galaxies, 1929 Red-shift increases with distance Cosmic Microwave Background, 1965 Estimated Age of Universe: 12-15 b.y. 'Big Bang' originally a derisive term, coined by Fred Hoyle


As Far Out as We Can See - Ten Days With the Hubble Telescope: As Far Out as We Can See - Ten Days With the Hubble Telescope


A New Name for the “Big Bang?”(Sky and Telescope, 1995): A New Name for the 'Big Bang?' (Sky and Telescope, 1995) The Big Boot God’s Log-On Fred Withair Day ('Nobody ever named anything else after me, so why not?') What Happens If I Push This Button? You’re Never Going To Get It All Back In There Again


90% of the Universe is “Missing”: 90% of the Universe is 'Missing' Outer Stars in Galaxies revolve faster than expected What holds clusters of galaxies together? Conclusion: There must be a lot of invisible mass in the Universe Not really 'missing', just non-luminous


Astronomers Are Not As Upset As One Might Expect: Astronomers Are Not As Upset As One Might Expect MACHO’s (Massive Compact Halo Objects): faint stars, brown dwarfs, planets Cool non-luminous gas Massive Neutrinos? WIMP’s (Weakly Interacting Massive Particles) Magnetic monopoles Exotic objects: strings, mini-black holes