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 BangWednesday we will finish the Big Bang, have a short discussion of Life in the Universe, and review for the final examRemember:Cosmological RedshiftWe now know 3 kinds of redshiftDoppler shiftdue to motionGravitational shiftdue to distortion of space-time by massCosmological shiftdue to stretching of spacenot due to relative motionas 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 TimeWe can calculate the age of the Universe using Hubble’s LawIf Ho = 70 km/(s.Mpc), what is the age of the Universe, THubble?v = H0 x dd = 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 BeginningOriginally all the energy (and matter) of the Universe was condensed into an incredibly small regionMUCH smaller than the size of a protonEnergy, 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 understandnot yet possible11-dimensional space??? (models are very weird)During early expansion, space-time and gravity became separate from energy and massparticles and antiparticles were being created from energy and annihilating into energy all the timeGlow of the UniverseThe early Universe was very hot and denseglowed with blackbody radiationbut so dense the light kept getting absorbed (opaque)Eventually the Universe cooled enough to form hydrogen atomsblackbody radiation could now travel freelyThat time called “recombination of the Universe”Light from that time should be all around us and be detectable.3K background radiationThis light should be cosmologically redshiftedMostly into microwave regionCMB was first seen in 1960sPensias & Wilson (Bell Labs)– won Nobel prize in physics for thistwenty years after predictionCOBE satellite mapped the CMBmeasured the spectrumwonderful match between theory and data Temperature = 2.73Kcooled glow from recombination era.Incredibly uniform across sky. Cosmic Microwave Background (CMB)Composition of Light ElementsHeliumBig Bang model predicts the percentage of light elementsHydrogen (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 predictionsAlmost 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 TBig Bang model predicts the percentage of light elements, & observed percentages agree with Big Bang model predictionsAlmost 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 starsCarbon (12C), and the elements up to Iron (56Fe), created in massive Blue Giants and dying Red giant and Supergiant starsThe heaviest elements, like Gold (197Au) and Uranium (235U), were created only in supernovaeFormation of Structure(early in the Universe)Normal matter was spread fairly evenlydue to interactions and radiationDark matter was not distributed smoothlyWMAP and Boomerang (follow-ups of COBE) show the seeds of that nonuniformity)clumps remainedExpansion spread things outbut gravity held large clumps of dark matter togetherDark matter attracted normal mattersource of galaxies and structureFate of the UniverseThe Universe is expandingBut gravity should be pulling it back inSo what should the Universe’s fate be:Continue expanding foreverHave expansion keep getting slower forever and stop at infinite timeExpansion stops and eventually Universe collapses upon itselfThese possibilities are calledopen universe – ends in cold dark blacknessflat universeclosed universe– ends in blinding white light “Big Crunch”Enough Matter?The amount of matter in the Universe helps determine its fateif there is enough mass, gravity winsgiven H0 = 70 km/(s Mpc), critical mass density is 8x10-27 kg/m3define MASS as the actual density of mass in the Universe divided by the critical densityMASS < 1 is an open universeMASS = 1 is a flat universeMASS > 1 is a closed universeEnough Matter?Visible matter (stars in galaxies, & hot gas)only 2% of critical density; MASS = 0.02Dark matter in galaxies (measured by galaxy rotation curves)about 10 times as much; MASS = 0.2Dark matter between galaxies (measured by watching galaxies fall inward in galactic clusters and from gravitational lensing)raises total to 30% of critical densityMASS = 0.3We do not observe enough matter to cause the Universe to be closedBut 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 supernovaea standard candleuse brightness to determine distanceuse redshift to determine speedcompare themdata 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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