Chapter 18: Chapter 18: Cosmology
WHAT DO YOU THINK?
What does the universe encompass? Is the universe expanding, fixed in size,
or contracting?Will the universe last forever?
You will discover…You 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 trace the emergence of matter and the formation of galaxies
how astronomers explain the overall structure of the universe
our understanding of the fate of the universe
Cosmological RedshiftCosmological Redshift
Expanding Cake AnalogyExpanding Cake Analogy
Just as all the chocolate chips move apart as the cake rises, all the superclusters of galaxies recede from each other as the universe expands.
Bell Labs Horn AntennaBell Labs Horn Antenna
Arno Penzias (right) and Robert Wilson
In Search of Primordial PhotonsIn Search of Primordial Photons
Wilkinson Microwave Anisotropy Probe (WMAP) satellite, launched in 2001
In Search of Primordial PhotonsIn Search of Primordial Photons
The balloon-carried telescope BOOMERANG
Spectrum of the Cosmic Spectrum of the Cosmic Microwave BackgroundMicrowave Background
The Microwave SkyThe Microwave Sky
The Doppler shift across the sky is caused by the Earth’s motion through the microwave background.
Our Motion Through the Our Motion Through the Microwave BackgroundMicrowave Background
Because of the Doppler effect, we detect shorter wavelengths in the microwave background and a higher temperature of radiation in that part of the sky toward which we are moving.
Unification of the Four ForcesUnification of the Four Forces
Early History of the UniverseEarly History of the Universe
The Cause of InflationThe Cause of Inflation
Observable Universe BeforeObservable Universe Beforeand After Inflationand After Inflation
Pair Production and AnnihilationPair Production and Annihilation
Evolution of DensityEvolution of Density
Era of RecombinationEra of Recombination
Observable UniverseObservable Universe
The cosmic light horizon today is about 13.8 billion light-years away in all directions. Inset: This HST Deep Field Telescope image shows some of the most distant galaxies we have seen.
Structure of the Early UniverseStructure of the Early Universe
This Wilkinson Microwave Anisotropy Probe (WMAP) image shows temperature variations in the cosmic microwave background. Inset: Tiny temperature fluctuations, observed by BOOMERANG, are related to the large-scale structure of the universe today, indicating where superclusters and voids grew.
Galaxies Forming by Combining Galaxies Forming by Combining Smaller UnitsSmaller Units
This painting indicates how astronomers visualize the burst of star formation that occurred within a few hundred million years after the Big Bang.
Galaxies Forming by Combining Galaxies Forming by Combining Smaller UnitsSmaller Units
Hubble and Keck telescope images of two groups of stars that are believed to be protogalaxies, from which bigger galaxies grew
Galaxies Forming by Combining Galaxies Forming by Combining Smaller UnitsSmaller Units
This Chandra X-ray telescope image shows gravitationally bound gas around the distant galaxy 3C 294. The X-ray emission from this gas is the signature of an extremely massive cluster of galaxies.
Stellar Birth RatesStellar Birth Rates
Star formation continued actively for billions of years when the universe was very young.
Stellar Birth RatesStellar Birth Rates
Most of the stars in an elliptical galaxy are created in a brief burst of star formation when the galaxy is very young. In spiral galaxies, stars form at a more leisurely pace that extends over billions of years.
Creation of Spiral andCreation of Spiral andElliptical GalaxiesElliptical Galaxies
A galaxy begins as a huge cloud of primordial gas that collapses gravitationally.
A Cosmic TimelineA Cosmic Timeline
Possible Geometries of the Possible Geometries of the UniverseUniverse
The curvature is eitherThe curvature is either
(a)(a) PositivePositive
(b)(b) ZeroZero
(c)(c) negativenegative
Cosmic Microwave Background Cosmic Microwave Background and the Curvature of Spaceand the Curvature of Space
Dimmer Distant SupernovaDimmer Distant Supernova
•These HST images show the galaxy in which the supernova SN 1997ff occurred. •This supernova was dimmer than expected. •The distance to it is greater than it would be if the universe had been continually slowing down. •An outward force is acting over vast distances in the universe.
Dimmer Distant SupernovaDimmer Distant Supernova
WHAT DID YOU THINK?
What is the universe? It is all the matter, energy, and spacetime that
will ever be detectable from the Earth or that will ever affect us.
Did the universe have a beginning? Yes, it occurred about 13.8 billion years ago in
an event called the Big Bang. Will the universe last forever? Current observations support the belief that the
universe will last forever.
Key TermsKey TermsBig Bangclosed universeconfinementcosmic light horizoncosmic microwave backgroundcosmological constantcosmological redshiftcosmologydark agesdark energydecouplingera of recombinationexpanding universegrand unified theory (GUT)homogeneityhorizon problem
inflationinflationary epochisotropyisotropy problemmatter-dominated universeopen universepair productionPlanck eraPlanck timeprimordial fireballquarkquintessenceradiation-dominated universestrong nuclear forcesuperstringuniverseweak nuclear force