Presentation on theme: "Chapter 18: Cosmology For a humorous approach to quarks, check out the Jefferson Lab’s game. In Looking for the Top Quark, each player receives six quarks."— Presentation transcript:
1Chapter 18: CosmologyFor a humorous approach to quarks, check out the Jefferson Lab’s game. In Looking for the Top Quark, each player receives six quarks that they hide on a grid. The players use coordinates to find their opponent's hidden quarks. The first player to find all six of their opponent's quarks wins! education.jlab.org/topquarkgame/Information on the Planck mission will be found at
2WHAT DO YOU THINK? What does the Universe include? Did the Universe have a beginning?Is the Universe expanding, fixed in size, or contracting?Will the Universe last forever?
3You will discover…Cosmology, which seeks to explain how the Universe began, how it evolves, and its fate.The best theory we have for the evolution of the Universe – the Big Bang.How astronomers explain the overall structure of the Universe.Our understanding of the fate of the Universe.
4In the Beginning – the Big Bang The Universe began 13.7 billion years ago with an event called the “Big Bang.”All of space-time, matter, and energy were created at the Big Bang.The left-over energy from the Big Bang can be detected today as the Cosmic Microwave Background Radiation.The temperature of this radiation is only a few degrees above absolute zero.
6In Search of The Earliest Photons FIGURE 18-3 In Search of Primordial Photons (a) TheWilkinson Microwave Anisotropy Probe (WMAP) satellite, launchedin 2001, improved upon the measurements of the spectrum andangular distribution of the cosmic microwave background takenby the COBE satellite. (b) The balloon-carried telescopeBOOMERANG orbited above Antarctica for 10 days collecting dataused to resolve the cosmic microwave background with 10 timeshigher resolution than that of COBE. All these experiments foundlocal temperature variations across the sky, but no overalldeviation from a perfect blackbody spectrum. (a: NASA/WMAPScience Team b: The BOOMERANG Group, University of California, SantaBarbara)Wilkinson Microwave Anisotropy Probe (WMAP) satellite, launched in 2001
7WMAP’s Baby Picture of the Universe – Cosmic Microwave Background Radiation
8The Universe is Expanding The Redshift of Superclusters shows us that the Universe is expanding. This Redshift is called the “Cosmological Redshift,” because it is caused by the expansion of space.The farther away a galaxy is from us, the faster it moves away from us.
9The Expansion of the Universe – Cosmological Redshift FIGURE 18-1 Cosmological Redshift Just as the waves drawnon this rubber band are stretched along with the rubber band,so too are the wavelengths of photons stretched as the universeexpands.Space itself is expanding.
10Expanding Cake Analogy The Expanding Chocolate Chip CakeAnalogy The expanding universe can becompared to a chocolate chip cake bakingand expanding in the Space Shuttle’s microwave oven. Justas all the chocolate chips move apart asthe cake rises, all the superclusters ofgalaxies recede from each other as theuniverse expands.Just as all the chocolate chips move apart as the cake rises, all the superclusters of galaxies move away from each other as the space of the Universe expands.
11The Observable Universe FIGURE The Observable UniverseThis diagram shows why we only see partof the entire universe. As time passes, thisvolume grows, meaning that light frommore distant galaxies reaches us. Thegalaxies we see at the farthest reaches ofour telescopes’ resolving power are as theywere within a few hundred million yearsafter the Big Bang (see inset). Thesegalaxies, formed at the same time as theMilky Way, appear young because the lightfrom their beginnings is just now reachingus. The radius of the cosmic light horizon isequal to the distance that light has traveledsince the Big Bang. Because the Big Bangoccurred about 13.8 billion years ago,the cosmic light horizon today is about13.8 billion light-years away in all directions.Inset: This image of the Hubble Deep Fieldshows some of the most distant galaxieswe have seen. (inset: Robert Williams and theHubble Deep Field Team, STScI and NASA)The cosmic light horizon today is about 13.7 billion light-years away in all directions.
12HST – Galaxies >13 Billion LY Away This HST Ultra Deep Field Telescope image shows some of the most distant galaxies we have seen.FIGURE Distant Galaxies (a) The young cluster ofgalaxies MS , shown on the left, contains many orbitingpairs of galaxies, as well as remnants of recent galaxy collisions.Several of these systems are shown at the right. This cluster islocated 8 billion light-years away from Earth. (b) This image ofmore than 300 spiral, elliptical, and irregular galaxies containsseveral that are an estimated 12 billion light-years from Earth.Two of the most distant galaxies are shown in the images on theright, colored in red at the centers of the pictures. (a, b: P. VanDokkum, Uner of Granengen, ESA and NASA)
13Early Universe Temperature Variations FIGURE Structure of theEarly Universe This microwavemap of the entire sky, producedfrom data taken by the WilkinsonMicrowave Anisotropy Probe(WMAP), shows temperaturevariations in the cosmic microwavebackground. Red regions are aboutK warmer than theaverage temperature of 2.73 K; blueregions are about K coolerthan the average. Inset: These tinytemperature fluctuations, observedby BOOMERANG, are related to thelarge-scale structure of theuniverse today, indicating wheresuperclusters and voids grew. Theradiation detected to make this mapis from a time 379,000 years afterthe Big Bang. (NASA/WMAP ScienceTeam; inset: NSF/NASA)Tiny temperature fluctuations in the Cosmic Microwave Background Radiation are related to the large-scale structure of the Universe today, indicating where Superclusters and voids grew.
14The First Stars – much larger than the Sun – with much shorter lives FIGURE Galaxies Forming by Combining Smaller Units(a) This painting indicates how astronomers visualize the burst ofstar formation that occurred within a few hundred million yearsafter the Big Bang. The arcs and irregular circles representinterstellar gas that is illuminated by supernovae. (b) Using theHubble and Keck telescopes, astronomers discovered two groups ofstars (arrows) 13.4 Bly away that are believed to be protogalaxies,from which bigger galaxies grew. These protogalaxies werediscovered because they were enlarged by the gravitational lensingof an intervening cluster of galaxies. (c) The Chandra X-raytelescope imaged gravitationally bound gas around the distantgalaxy 3C 294. The X-ray emission from this gas is the signature ofan extremely massive cluster of galaxies, in this case at a distanceof about 11.2 Bly from us. (a: Adolf Schaller, STScI/NASA/K. Lanzetta,SUNY; b: Richard Ellis (Caltech) and Jean-Paul Kneib (Observatorie Midi-Pyrenees, France), NASA, ESA; c: NASA)The burst of star formation that occurred within a few hundred million years after the Big Bang.
15Proto-Galaxy Formation FIGURE Galaxies Forming by Combining Smaller Units(a) This painting indicates how astronomers visualize the burst ofstar formation that occurred within a few hundred million yearsafter the Big Bang. The arcs and irregular circles representinterstellar gas that is illuminated by supernovae. (b) Using theHubble and Keck telescopes, astronomers discovered two groups ofstars (arrows) 13.4 Bly away that are believed to be protogalaxies,from which bigger galaxies grew. These protogalaxies werediscovered because they were enlarged by the gravitational lensingof an intervening cluster of galaxies. (c) The Chandra X-raytelescope imaged gravitationally bound gas around the distantgalaxy 3C 294. The X-ray emission from this gas is the signature ofan extremely massive cluster of galaxies, in this case at a distanceof about 11.2 Bly from us. (a: Adolf Schaller, STScI/NASA/K. Lanzetta,SUNY; b: Richard Ellis (Caltech) and Jean-Paul Kneib (Observatorie Midi-Pyrenees, France), NASA, ESA; c: NASA)Hubble and Keck telescope images of two groups of stars that are believed to be proto-galaxies, from which bigger galaxies grew
16Creation of Spiral and Elliptical Galaxies If the rate of star formation was low, then a spiral galaxy formed.If the rate of star formation was high, then an elliptical galaxy formed.FIGURE The Creation of Spiral andElliptical Galaxies A galaxy begins as a hugecloud of primordial gas that collapsesgravitationally. (a) If the rate of star birth is low,then much of the gas collapses to form a disk,and a spiral galaxy is created. (b) If the rate ofstar birth is high, then the gas is converted intostars before a disk can form, resulting in anelliptical galaxy.A galaxy begins as a huge cloud of primordial gas that collapses gravitationally.
17The Fate of the Universe The fate of the Universe depends on the shape of space-time.The shape of space-time is determined by how much total matter and energy there is in the Universe.Space-time could have one of three shapes:Sphere = positive curvature = closed.Our floor = no curvature = flat.Saddle = negative curvature = open.
18Possible Shapes of Space-time, and the Fate of the Universe Closed – Universe would collapse.Flat – Universe could slowly expand forever.Open – Universe would expand forever.FIGURE The Possible Geometries of the Universe Theshape of space (represented here as two-dimensional for ease ofvisualization) is determined by the matter and energy contained inthe universe. The curvature is either (a) positive, (b) zero, or(c) negative, depending on whether the average matter and energydensity throughout space is greater than, equal to, or less than acritical value. The lines on each curve are initially parallel. Theyconverge, remain parallel, or diverge depending on the curvatureof space.
19Cosmic Microwave Background indicates that Space-time is Flat – Universe could slowly expand forever FIGURE The Cosmic MicrowaveBackground and the Curvature of SpaceTemperature variations in the early universeappear as “hot spots” in the cosmicmicrowave background. The apparent sizesof these spots depend on the curvature ofspace. (a) In a closed universe with positivecurvature, light rays from opposite sides ofa hot spot bend toward each other. Hence,the hot spot appears larger than it actuallyis, as shown by the dashed lines. (b) Thelight rays do not bend in a flat universe. (c)In an open universe, light rays bend apart.The dashed lines show that a hot spotwould appear smaller than its actual size.(The BOOMERANG Group, University ofCalifornia, Santa Barbara)
20BUT – dimmer distant Supernovae mean the expansion of the Universe is speeding up. FIGURE Dimmer Distant Supernova(a) These Hubble Space Telescope images show thegalaxy in which the supernova SN 1997ff occurred. Thissupernova, more than 10 Bly away, was dimmer thanexpected, indicating that the distance to it is greaterthan the distance it would have if the universe hadbeen continually slowing down since the Big Bang. Thissupports the notion that an outward (cosmological)force is acting over vast distances in the universe. Thearrow on the first inset shows the galaxy in which thesupernova was discovered. The bright spot on thesecond inset shows the supernova by subtracting theconstant light emitted by all the other nearby objects.(b) The distances and brightnesses of many verydistant supernovae are plotted on this diagram. Thelocation of the most distant supernovae in the upperregion strongly indicates that the universe has beenaccelerating outward for the past 6 billion years.(a: Adam Riess, Space Telescope Science Institute, NASA)
21100 billion years from now the Universe will appear frozen in time as we look out into space. Only the light from the Local Group of galaxies will remain visible, if anyone is still around to see it.
22Expansion of the Universe is speeding up Very distant Type 1a Supernovae are not as bright as they should be.This means the expansion of the Universe is speeding up instead of slowing down or staying the same.There is something really weird called Dark Energy (not the same as Dark Matter) that is causing this acceleration.Dark Energy acts like anti-gravity, pushing the Universe apart.We do not know what this Dark Energy is, but it makes up 73% of the total energy/matter of the Universe.
23Composition of the Universe Suppose all the matter and energy in the Universe is $100 in your wallet or purse.$73 would be Dark Energy – the mysterious energy that’s pushing the Universe apart faster and faster.$23 would be Dark Matter – matter that doesn’t give off any kind of radiation, so we can’t see it – but it does have gravity.So out of your Universe of $100, $96 represents Dark Energy and Dark Matter that have yet to be identified.Only $4 would be visible matter – the regular stuff we can see, like stars, gas clouds, and dust – the same stuff we’re made of.Of the visible matter ($4), only one-tenth of it shines as stars. That’s 40 cents out of your total $100. The rest of the visible matter is gas clouds and dust.
25WHAT DID YOU THINK? What does the Universe include? It is all the matter, energy, and space-time that will ever be detectable from the Earth or that will ever affect us.Did the Universe have a beginning?Yes, it occurred about 13.7 billion years ago in an event called the Big Bang.Is the Universe expanding, fixed in size, or contracting?The Universe is expanding, faster and faster.Will the Universe last forever?Current observations support the belief that it will last (expand) forever.