Chapter 22-23 - Lecture 1-PV.pdf - Physics 1002 Chapter 22...

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1Physics 1002Chapter 2223The Birth of the Universe, Dark Matter, DarkEnergy, and the Fate of the UniverseLecture 1IA-in-charge: Peter Ka Kwan PAK(Email: [email protected])Unseen Influences in the CosmosEvidence for Dark MatterEinstein’s “static” universeOlbers’ Paradox –dark night skyThe Big Bang ModelThree pillars supporting the Big Bang Model
2The Course at a Glance1.Developing Perspective(Ch. 13)2.Key Concepts for Astronomy (Ch. 4-6)3.Stars (Ch. 14-19)4.Galaxies (Ch. 20, 21)&Beyond (Ch. 22, 23):
3Fascinating and difficult subjects to be coveredin this andthe next lectures, with terms like:Dark Matter, Dark Energy, Beginning of Time,Fate of the UniverseFocus on the big picture and the main ideas• If you find the ideas strange and difficult to accept, don’t worry –you are not alone.You often read about these topics in newspapersand learningthrough this course, you will understand better than mostreaders
4The Present Cosmic Model:Present Parameters (2018):* Hubble ConstHo67 km/s/Mpc* Normal Matter (‘atoms’)5%Dark Matter27%Dark Energy68%GeometryflatAge13.8 Billion YearsWillacceleratinglyexpandforever!68%27%5%
5Focus on the BIG picture:Three questions1.How muchmassis in the Universe?2.Is the curvature of the Universe ‘flat’?3.Is theexpansion rateslowing down or speeding up?
How much normal matter is in the universe?
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7Dark matter:the name given to matter that weinferto exist through its gravitational effects but thatemits no detectable radiation (hence we cannever see it directly!)UnseenInfluencesin the Cosmos
8Evidence for Dark Matter1. Dark Matter in galaxies2. Dark Matter in clusters of galaxiesHubble Space Telescope maps dark matter (magenta-tinted clumps ) in a supercluster of galaxiesusinggravitational lensing.
9Masswithin Sun’s orbit:~1011MSunTotal mass:~1012MSunThe visible portion of a galaxylies deep in the heart of alarge halo of dark matter.Total mass of the Milky Way
10We canmeasurerotationcurves ofspiralgalaxiesusing theDoppler shiftof the 21-cmline ofatomic H.
11Spiral galaxiesall tendto have flat rotationcurves (in regionsbeyond the luminouspart) indicating largeamounts of dark matter.All galaxies appear to have far more mass than wecan see in the form of stars
12Elliptical galaxiesalso appear to have far more massthan we can see as stars (from the widths of theabsorption lines).More massive galaxies have more gravity so their stars are moving with fasterorbital speeds. More massive galaxies should have broader absorption lines.
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Term
Winter
Professor
N/A
Tags
Dark Matter, Big Bang, Redshift, CBR

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