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final exam!!!Cosmological Redshiftthe Beginning&End of TimeThinking Back in TimeAt the BeginningGlow of the UniverseCosmic Microwave Background (CMB)Composition of Light ElementsSlide 9Formation of StructureFate of the UniverseEnough Matter?Slide 13Is the Expansion Slowing Down?Slide 15Is Life Out There?The Search for LifeSETISETI Still GoingDrake EquationMessages from EarthSlide 22final exam!!!Today we will discuss Cosmology and the Big BangWednesday we will finish the Big Bang, have a short discussion of Life in the Universe, and review for the final examRemember:Cosmological RedshiftWe now know 3 kinds of redshiftDoppler shiftdue to motionGravitational shiftdue to distortion of space-time by massCosmological shiftdue to stretching of spacenot due to relative motionas space stretches, the wavelength stretches and becomes longerthe Beginning End of TimeToday’s Lecture: purpose & goalsAST 1002Planets, Stars and Galaxies1) The “Beginning”2) The Age of the Universe3) The “End of Time”4) Life in the Universe5) Review for FinalThinking Back in TimeWe can calculate the age of the Universe using Hubble’s LawIf Ho = 70 km/(s.Mpc), what is the age of the Universe, THubble?v = H0 x dd = v/H0But distance = rate x time(the time here is how long the expansion has been going on  The Age of the Universe)tHubble = 1/H0tHubble = 1/H0( Mpc )=1 sec.Mpc70 km106 pc( pc )3.26 l.y.( l.y. )1013 km=3.26x1019 sec70=4.657x1017 sec(3600sec)1 hr(24 hr)1 day(365.25day)1 yr=1.475x1010 yr= 14.7 Billion Years!!At the BeginningOriginally all the energy (and matter) of the Universe was condensed into an incredibly small regionMUCH smaller than the size of a protonEnergy, matter, space and time were all very different than today   what we call matter was then almost entirely energy (gamma-ray photons)need a new “theory of everything” to understandnot yet possible11-dimensional space??? (models are very weird)During early expansion, space-time and gravity became separate from energy and massparticles and antiparticles were being created from energy and annihilating into energy all the timeGlow of the UniverseThe early Universe was very hot and denseglowed with blackbody radiationbut so dense the light kept getting absorbed (opaque)Eventually the Universe cooled enough to form hydrogen atomsblackbody radiation could now travel freelyThat time called “recombination of the Universe”Light from that time should be all around us and be detectable.3K background radiationThis light should be cosmologically redshiftedMostly into microwave regionCMB was first seen in 1960sPensias & Wilson (Bell Labs)– won Nobel prize in physics for thistwenty years after predictionCOBE satellite mapped the CMBmeasured the spectrumwonderful match between theory and data  Temperature = 2.73Kcooled glow from recombination era.Incredibly uniform across sky. Cosmic Microwave Background (CMB)Composition of Light ElementsHeliumBig Bang model predicts the percentage of light elementsHydrogen (1H), deuterium (heavy hydrogen, 2H), helium (4He), lithium (7Li), beryllium (9Be), boron (10B and 11B),…elements formed before recombination out of cooling extremely hot plasma (created out of light!)percentages depend upon density and temperature of early Universe, and how fast it cooled.Observed percentages agree with Big Bang model predictionsAlmost all that was created as hydrogen (1H) and helium (4He), with only trace amounts of anything else.  must have cooled from something very hot.Notice no stable mass 5 or 8 isotopesE N R I C H M E N TBig Bang model predicts the percentage of light elements, & observed percentages agree with Big Bang model predictionsAlmost all that was created in the Big Bang was hydrogen (1H) and helium (4He), only trace amounts of anything else.Helium (4He), was enriched in Main Sequence starsCarbon (12C), and the elements up to Iron (56Fe), created in massive Blue Giants and dying Red giant and Supergiant starsThe heaviest elements, like Gold (197Au) and Uranium (235U), were created only in supernovaeFormation of Structure(early in the Universe)Normal matter was spread fairly evenlydue to interactions and radiationDark matter was not distributed smoothlyWMAP and Boomerang (follow-ups of COBE) show the seeds of that nonuniformity)clumps remainedExpansion spread things outbut gravity held large clumps of dark matter togetherDark matter attracted normal mattersource of galaxies and structureFate of the UniverseThe Universe is expandingBut gravity should be pulling it back inSo what should the Universe’s fate be:Continue expanding foreverHave expansion keep getting slower forever and stop at infinite timeExpansion stops and eventually Universe collapses upon itselfThese possibilities are calledopen universe – ends in cold dark blacknessflat universeclosed universe– ends in blinding white light “Big Crunch”Enough Matter?The amount of matter in the Universe helps determine its fateif there is enough mass, gravity winsgiven H0 = 70 km/(s Mpc), critical mass density is 8x10-27 kg/m3define MASS as the actual density of mass in the Universe divided by the critical densityMASS < 1 is an open universeMASS = 1 is a flat universeMASS > 1 is a closed universeEnough Matter?Visible matter (stars in galaxies, & hot gas)only 2% of critical density; MASS = 0.02Dark matter in galaxies (measured by galaxy rotation curves)about 10 times as much; MASS = 0.2Dark matter between galaxies (measured by watching galaxies fall inward in galactic clusters and from gravitational lensing)raises total to 30% of critical densityMASS = 0.3We do not observe enough matter to cause the Universe to be closedBut it’s not the end of the story…Is the Expansion Slowing Down?Answer: Strangely enough…the rate of expansion is speeding up!Use Type 1a supernovaea standard candleuse brightness to determine distanceuse redshift to determine speedcompare themdata lies below prediction (galaxies are speeding up!!)Life?Is Life Out There?Actually, so far, we have no direct evidence of life beyond Earth!!What possibilities are there?Requires


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FSU AST 1002 - Lecture Notes

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