astronomy 305/frontiers in astronomy

11/18/03 Prof. Lynn Cominsky 1

Class web site: Class web site: http://glast.sonoma.edu/~lynnc/courses/ahttp://glast.sonoma.edu/~lynnc/courses/a305305

Office: Darwin 329AOffice: Darwin 329A

(707) 664-2655(707) 664-2655

Best way to reach me: Best way to reach me: [email protected]@charmian.sonoma.edu

Astronomy 305/Frontiers in Astronomy 305/Frontiers in AstronomyAstronomy


Group 12Group 12


Golden Age of CosmologyGolden Age of Cosmology Standard Big Bang CosmologyStandard Big Bang Cosmology Big Bang NucleosynthesisBig Bang Nucleosynthesis Cosmic Microwave BackgroundCosmic Microwave Background Did the Universe have a bout of Did the Universe have a bout of

Inflation?Inflation? Horizon ProblemHorizon Problem Flatness ProblemFlatness Problem MultiversesMultiverses Geometry and Curvature of SpaceGeometry and Curvature of Space


Big Bang?Big Bang?


Big Bang TimelineBig Bang Timeline

We are here

Big Bang

Big Bang Nucleosynthesis


Standard Big Bang CosmologyStandard Big Bang Cosmology Sometime in the distant past there was Sometime in the distant past there was

nothing – space and time did not existnothing – space and time did not exist Vacuum fluctuations created a singularity Vacuum fluctuations created a singularity

that was very hot and densethat was very hot and dense The Universe expanded from this The Universe expanded from this

singularitysingularity As it expanded, it cooledAs it expanded, it cooled

Photons became quarksPhotons became quarks Quarks became neutrons and protonsQuarks became neutrons and protons Neutrons and protons made atomsNeutrons and protons made atoms Atoms clumped together to make stars and Atoms clumped together to make stars and

galaxiesgalaxies


Standard Big Bang CosmologyStandard Big Bang Cosmology

Top three reasons to believe big bang Top three reasons to believe big bang cosmologycosmology

1.1. Big Bang Nucleosynthesis Big Bang Nucleosynthesis

2.2. Cosmic Microwave Background Cosmic Microwave Background

3.3. Hubble Expansion Hubble Expansion

Big Bang by Physics Chanteuse Lynda Williams


Big Bang NucleosynthesisBig Bang Nucleosynthesis

Light elements (namely deuterium, Light elements (namely deuterium, helium, and lithium) were produced in helium, and lithium) were produced in the first few minutes of the Big Bangthe first few minutes of the Big Bang

The predicted abundance of light elements heavier than hydrogen, as a function of the density of baryons in the universe (where 1 is critical)

Note the steep dependence of deuterium on critical density.

Goal is to find a critical density that explains all the abundances that are measured


Big Bang NucleosynthesisBig Bang Nucleosynthesis Heavier elements than Heavier elements than 44He are produced in the He are produced in the

stars and through supernovaestars and through supernovae However, enough helium and deuterium cannot However, enough helium and deuterium cannot

be produced in stars to match what is observed – be produced in stars to match what is observed – in fact, stars destroy deuterium in their cores, in fact, stars destroy deuterium in their cores, which are too hot for deuterium to survive.which are too hot for deuterium to survive.

So all the deuterium we see must have been So all the deuterium we see must have been made around three minutes after the big bang, made around three minutes after the big bang, when T~10when T~1099 K K

BBN predicts that 25% of the matter in the BBN predicts that 25% of the matter in the Universe should be helium, and about 0.001% Universe should be helium, and about 0.001% should be deterium, which is what we see.should be deterium, which is what we see.

BBN also predicts the correct amounts of BBN also predicts the correct amounts of 33He and He and 77LiLi



We are here

Cosmic Microwave

Background


Cosmic Microwave BackgroundCosmic Microwave Background Discovered in 1965 by Arno Discovered in 1965 by Arno

Penzias and Robert Wilson who Penzias and Robert Wilson who were working at Bell Labswere working at Bell Labs

Clinched the hot big bang theory Clinched the hot big bang theory

Excess noise in horned antennae was not due to pigeon dung!


Where is the CMBR?Where is the CMBR? Map of redshift vs. time after Big Map of redshift vs. time after Big

BangBang

CMBR

Z=1000

Universe has expanded and cooled

down by 1+z (about 1000)

since the photons last scattered off the CMBR


CMBRCMBR Photons in CMBR come from surface of Photons in CMBR come from surface of

last scattering – where they stop last scattering – where they stop interacting with matter and travel freely interacting with matter and travel freely through spacethrough space

CMBR photons emanate from a cosmic CMBR photons emanate from a cosmic photosphere – like the surface of the Sun photosphere – like the surface of the Sun – except that we inside it looking out– except that we inside it looking out

The cosmic photosphere has a The cosmic photosphere has a temperature which characterizes the temperature which characterizes the radiation that is emitted radiation that is emitted

It has cooled since it was formed by more It has cooled since it was formed by more than 1000 to 2.73 degrees Kthan 1000 to 2.73 degrees K



We are here

Inflation


What is inflation?What is inflation? Inflation refers to a class of cosmological Inflation refers to a class of cosmological

models in which the Universe exponentially models in which the Universe exponentially increased in size by about 10increased in size by about 1043 43 between between about 10about 10-35-35 and 10 and 10-32-32 s after the Big Bang s after the Big Bang (It has since expanded by another 10(It has since expanded by another 102626))

Inflation is a modification of standard Big Inflation is a modification of standard Big Bang cosmologyBang cosmology

It was originated by Alan Guth in 1979 and It was originated by Alan Guth in 1979 and since modified by Andreas Albrecht, Paul since modified by Andreas Albrecht, Paul Steinhardt and Andre Linde (among others)Steinhardt and Andre Linde (among others)


Why believe in inflation?Why believe in inflation? Inflation is a prediction of grand unified Inflation is a prediction of grand unified

theories in particle physics that was theories in particle physics that was applied to cosmology – it was not just applied to cosmology – it was not just invented to solve problems in invented to solve problems in cosmologycosmology

It provides the solution to two long It provides the solution to two long standing problems with standard Big standing problems with standard Big Bang theoryBang theory Horizon problemHorizon problem Flatness problemFlatness problem Alan Guth


Horizon ProblemHorizon Problem The Universe looks the same The Universe looks the same

everywhere in the sky that we look, yet everywhere in the sky that we look, yet there has not been enough time since there has not been enough time since the Big Bang for light to travel between the Big Bang for light to travel between two points on opposite horizonstwo points on opposite horizons

This remains true even if we extrapolate This remains true even if we extrapolate the traditional big bang expansion back the traditional big bang expansion back to the very beginningto the very beginning

So, how did the opposite horizons turn So, how did the opposite horizons turn out the same (e.g., the CMBR out the same (e.g., the CMBR temperature)?temperature)?


Horizon problemHorizon problem The Universe at t = 300,000 y after the The Universe at t = 300,000 y after the

Big Bang (when the CMBR was formed)Big Bang (when the CMBR was formed)

A and B are sources of photons that are now arriving on Earth

Horizon distance is 1/100 of the distance between A and B

Horizon distance is 3 x 300,000 y because the Universe is expanding – tells you how far light could travel


Horizon ProblemHorizon Problem

Inflation Inflation allows the allows the early early Universe to Universe to be small be small enough so enough so that light that light can easily can easily cross it at cross it at early times early times


No inflationNo inflation At t=10At t=10-35-35 s, the Universe expands s, the Universe expands

from about 1 cm to what we see from about 1 cm to what we see todaytoday

1 cm is much larger than the 1 cm is much larger than the horizon, which at that time was 3 x horizon, which at that time was 3 x 1010-25-25 cm cm


With inflationWith inflation

Space Space expands expands from 3 x 10from 3 x 10--

2525 cm to cm to much much bigger than bigger than the the Universe we Universe we see todaysee today


CMBR vs. InflationCMBR vs. Inflation Inflation also predicts a distinct spectrum Inflation also predicts a distinct spectrum

of fluctuations for the CMBR which arise of fluctuations for the CMBR which arise from the original quantum fluctuations in from the original quantum fluctuations in the pre-inflation bubblethe pre-inflation bubble

Everything we see in the Universe

started out as a quantum fluctuation!


Flatness ProblemFlatness Problem Why does the Universe today appear to Why does the Universe today appear to

have have between 0.1 and 1 – the critical between 0.1 and 1 – the critical dividing line between an open and dividing line between an open and closed Universe?closed Universe?

Density today will differ greatly from Density today will differ greatly from density of early Universe, due to density of early Universe, due to expansion – if expansion – if starts out <1, it will get starts out <1, it will get much lower and vice versa much lower and vice versa only only values of values of very near 1 can persistvery near 1 can persist

A value for A value for =1=1also implies the also implies the existence of dark matter as well as the existence of dark matter as well as the cosmological constantcosmological constant


Flatness ProblemFlatness Problem Density of Density of

early early Universe Universe must be must be correct to 1 correct to 1 part in 10part in 106060 in order to in order to achieve the achieve the balance balance that we seethat we see


Flatness ProblemFlatness Problem Inflation flattens out spacetime the Inflation flattens out spacetime the

same way that blowing up a balloon same way that blowing up a balloon flattens the surfaceflattens the surface

Since the Universe is far bigger than we Since the Universe is far bigger than we can see, the part of it that we can see can see, the part of it that we can see looks flatlooks flat


Big Bang RevisitedBig Bang Revisited Extrapolating back in time, we conclude Extrapolating back in time, we conclude

that the Universe must have begun as a that the Universe must have begun as a singularity – a place where the laws of singularity – a place where the laws of physics and even space and time break physics and even space and time break downdown

However, our theories of space and time However, our theories of space and time break down before the singularity, at a time break down before the singularity, at a time of 10of 10-43-43 s, a length of 10 s, a length of 10-33-33 cm, and a cm, and a density of 10density of 109494 cm cm3 3

This is known as the Planck scale This is known as the Planck scale Uncertainty Principle E t = h


Planck scale activityPlanck scale activity

The goal of this activity is to The goal of this activity is to calculate the Planck mass, length, calculate the Planck mass, length, time and energy.time and energy.

RememberRemember

Uncertainty Principle x p = h/2

Uncertainty Principle E t = h/2


Vacuum fluctuationsVacuum fluctuations Virtual particle pairs Virtual particle pairs

continually emerge continually emerge and disappear into and disappear into the quantum vacuumthe quantum vacuum

If you observe the If you observe the particles, you give particles, you give them enough energy them enough energy to become realto become real

The particles can The particles can also get energy from also get energy from any nearby force any nearby force fieldfield


Quantum UniverseQuantum Universe Edward Tryon (1970) suggested that the Edward Tryon (1970) suggested that the

Universe has a total E=0 because in a flat Universe has a total E=0 because in a flat Universe, the negative energy of gravity is Universe, the negative energy of gravity is exactly balanced by the positive energy of exactly balanced by the positive energy of mattermatter

With E=0, there is no time limit on the With E=0, there is no time limit on the Universe’s existence from the Uncertainty Universe’s existence from the Uncertainty PrinciplePrinciple

The quantum fluctuation Universe will collapse The quantum fluctuation Universe will collapse again due to the gravity of the singularity, again due to the gravity of the singularity, unless it is given a sudden surge of energyunless it is given a sudden surge of energy

Spontaneous symmetry breaking of the Spontaneous symmetry breaking of the previously unified forces provides this energypreviously unified forces provides this energy


Unified ForcesUnified Forces The 4 forces are all unified (and The 4 forces are all unified (and

therefore symmetric) at the Planck therefore symmetric) at the Planck scale energyscale energy

Planck scale

inflation


Symmetry BreakingSymmetry Breaking

Here is an example: it is unclear Here is an example: it is unclear which glass goes with which place which glass goes with which place setting until the first one is chosensetting until the first one is chosen


Broken SymmetryBroken Symmetry At high T, the Universe is in a At high T, the Universe is in a

symmetrical state, with a unique point symmetrical state, with a unique point of minimum energyof minimum energy

As the Universe cools, there are many As the Universe cools, there are many possible final states – but only one is possible final states – but only one is chosen when the symmetry breakschosen when the symmetry breaks


False VacuumFalse Vacuum The unified (symmetric) state of the The unified (symmetric) state of the

very early Universe is a state of very early Universe is a state of negative energy called the false negative energy called the false vacuumvacuum

A phase transition turns the false A phase transition turns the false vacuum into the true vacuum and vacuum into the true vacuum and provides the surge of energy that provides the surge of energy that drives inflation – similar to the energy drives inflation – similar to the energy released when water freezes into icereleased when water freezes into ice

During inflation, spacetime itself During inflation, spacetime itself expands faster than the speed of lightexpands faster than the speed of light


False VacuumFalse Vacuum The Universe is now stuck in a state of The Universe is now stuck in a state of

false vacuum which decays very slowlyfalse vacuum which decays very slowly When it reaches the true vacuum state, When it reaches the true vacuum state,

inflation will stop and particles will forminflation will stop and particles will form

The shallow slope near the false vacuum

allows the Universe to keep the energy density almost

constant as it expands


Pocket UniversesPocket Universes As the false vacuum decays, As the false vacuum decays,

particles are created in “pocket particles are created in “pocket universes”universes”In each time

slice, the original pocket universe expands by a

factor of 3 while new ones are created out of

the false vacuum in a fractal

pattern


Formation of child Formation of child UniverseUniverse

As false As false vacuum vacuum expands, expands, space space distorts to distorts to form a form a wormholewormhole

True vacuum

False vacuum

wormhole

This entire region is 10-

25 cm


Child UniverseChild Universe The child universe disconnects The child universe disconnects

from the original spacefrom the original space

True vacuum

False vacuum

Child Universe

Observers in the parent

universe see a black hole form!


MultiversesMultiverses

Universe was originally defined to include Universe was originally defined to include everythingeverything

However, with inflation, the possibility exists However, with inflation, the possibility exists that our “bubble universe” is only one of that our “bubble universe” is only one of many such regions that could have formedmany such regions that could have formed

The other universes could have very The other universes could have very different physical conditions as a result of different physical conditions as a result of different ways that the unified symmetry different ways that the unified symmetry was brokenwas broken

New universes may be forming with each New universes may be forming with each gamma-ray burst that makes a black hole!gamma-ray burst that makes a black hole!


A Humbling ThoughtA Humbling Thought

Not only do we not occupy a preferred Not only do we not occupy a preferred place in our Universe, we don’t occupy place in our Universe, we don’t occupy any preferred universe in the any preferred universe in the Multiverse!Multiverse!


Cosmological curvature Cosmological curvature

parametersparameters

= density of the universe / critical density= density of the universe / critical density

hyperbolic geometry

flat or Euclidean

spherical geometry


Flatland by Edwin A. Flatland by Edwin A. AbbottAbbott

The characters in Flatland:The characters in Flatland:Rank in Flatland is a function of increasing symmetry:

A woman, soldier, workman,merchant, professional man, gentleman, nobleman, high priest


FlatlandFlatland

What do they see What do they see when a 3D being when a 3D being (Lord Sphere) (Lord Sphere) comes to visit?comes to visit?

3D cross-sections of Lord Sphere float through the 2D

world of Flatland


Troubles in FlatlandTroubles in Flatland

It’s hard to eat in It’s hard to eat in a 2D world!a 2D world!

It is also It is also impossible to tie impossible to tie your shoes! your shoes! Why?Why?

A digestive tract cuts a 2D being in half!



A Square and his A Square and his wife alone in their wife alone in their 2D house, when 2D house, when Lord Sphere Lord Sphere drops in from the drops in from the third dimensionthird dimension

There is no privacy in 2D from a 3D being!



A 3D being would A 3D being would be able to be able to change the change the symmetry of a symmetry of a 2D resident or 2D resident or help him escape help him escape from jail!from jail!

The 3D being can lift the 2D resident up out

of Flatland!



How do How do Flatlanders know Flatlanders know the shape of the shape of their Universe?their Universe?

A flat plane (with A flat plane (with edges) is an edges) is an open 2D open 2D UniverseUniverse

Is there a closed Is there a closed 2D Universe?2D Universe?

A Moebius strip is a 2D closed universe

movie


Exploring GeometriesExploring Geometries

Take the newspaperTake the newspaper Cut a long skinny stripCut a long skinny strip Twist one end of the strip once and tape Twist one end of the strip once and tape

togethertogether Congratulations – you have just made a Congratulations – you have just made a

Moebius strip!Moebius strip! How many sides does this have? Try How many sides does this have? Try

drawing on it to see.drawing on it to see. What happens to it when you cut it all What happens to it when you cut it all

around the strip direction?around the strip direction?



What would What would happen if happen if Flatlanders walked Flatlanders walked all the way around all the way around a closed 2D world?a closed 2D world?

They would be They would be mirror-reversed!mirror-reversed!

Flat torus – Flat torus – another example another example of a closed 2D of a closed 2D worldworld


Infinite Universe?Infinite Universe?

Is the Universe infinite or just Is the Universe infinite or just really, really, really big?really, really, really big?

Some scientists (like Janna Levin) Some scientists (like Janna Levin) prefer to think of the Universe as prefer to think of the Universe as finite but unbounded. An example finite but unbounded. An example of such a space is a 3D torus.of such a space is a 3D torus.

With such a topology, we could see With such a topology, we could see the backs of our heads, if we could the backs of our heads, if we could see far enough in one directionsee far enough in one direction


Curved SpaceCurved Space

This is not an This is not an infinite series of infinite series of reflections, but is reflections, but is caused by light caused by light traveling all the traveling all the way around the way around the hyperdonuthyperdonut

A hyperdonut is A hyperdonut is one example of a one example of a curved space in curved space in 3D3D


3D Torus games3D Torus games

Play game herePlay game here


The 4D UniverseThe 4D Universe Many Many

cosmologists cosmologists believe that believe that our Universe is our Universe is a 4D a 4D hyperspherehypersphere

This is a 3D This is a 3D movie movie projection of a projection of a 4D 4D hypersurfacehypersurface

movie


Geometry in the 4Geometry in the 4thth dimension dimension

A 2D square is A 2D square is created by created by moving a line in moving a line in a perpendicular a perpendicular directiondirection

A 3D cube is A 3D cube is created by created by moving a square moving a square in a in a perpendicular perpendicular directiondirection



A Flatlander can only A Flatlander can only visualize a cube, if it is visualize a cube, if it is unfolded in 2Dunfolded in 2D

If you move a 3D cube in If you move a 3D cube in a fourth perpendicular a fourth perpendicular direction, you get a direction, you get a hypercubehypercube

A 3D being can only A 3D being can only visualize a hypercube by visualize a hypercube by unfolding it in 3D into a unfolding it in 3D into a tesseracttesseract



Christus Christus Hypercubus was Hypercubus was painted by painted by Salvador Dali in Salvador Dali in 1955 –it features 1955 –it features a tesseracta tesseract

A 4D hypercube A 4D hypercube is bounded by 8 is bounded by 8 3D cubes, has 16 3D cubes, has 16 corners and a corners and a volume Lvolume L44



Here is another Here is another 2D projection of 2D projection of a 4D hypercubea 4D hypercube

At each face, you At each face, you can see a cube in can see a cube in different different directions as you directions as you change your change your perspectiveperspectived2 = x2 + y2 + z2 + w2


Troubles in SpacelandTroubles in Spaceland

Thieves from the Thieves from the fourth dimension fourth dimension could steal things could steal things from locked safes from locked safes (or operate (or operate without cutting without cutting you open!)you open!)

There is no privacy in 3D from a 4D being!


Visitors from the 4Visitors from the 4thth dimension dimension

Try the Try the “digustoscope” “digustoscope” to see yourself as to see yourself as a 4D being in a a 4D being in a 3D world!3D world!

Do powerful beings such as a Cosmic

Creator (or the Devil) live in the

Fourth Dimension?


Angels and DevilsAngels and Devils

This 2D exercise from U Wash This 2D exercise from U Wash helps you to visualize the effects of helps you to visualize the effects of different geometriesdifferent geometries

But first, let’s see how 2D beings But first, let’s see how 2D beings would see a 3D object passing would see a 3D object passing through their world (e.g. Flatland through their world (e.g. Flatland by Abbott)by Abbott)

Cube Cube moviesmovies Sphere Sphere moviesmovies


ResourcesResources

Inflationary Universe by Alan Guth (Perseus)

A Short History of the Universe by Joseph Silk (Scientific American Library)

Before the Beginning by Martin Rees (Perseus)

Inflation for Beginners (John Gribbin) http://www.biols.susx.ac.uk/Home/John_Gribbin/cosmo.htm

Ned Wright’s Cosmology Tutorial http://www.astro.ucla.edu/~wright/cosmolog.htm

James Schombert Lectures http://zebu.uoregon.edu/~js/21st_century_science/lectures/lec24.html


ResourcesResources

Hyperspace by Michio Kaku (Anchor Books)

Fourth dimension web site http://www.math.union.edu/~dpvc/math/4D/welcome.html

Michio Kaku’s web site http://www.mkaku.org

Exploring the Shape of Space http://www.geometrygames.org/ESoS/index.html

Fourth Dimension by Rudy Rucker (Houghton Mifflin)


Web ResourcesWeb Resources

Cosmic Background Explorer Cosmic Background Explorer http://space.gsfc.nasa.gov/astro/cobe/cobe_home.htmlhttp://space.gsfc.nasa.gov/astro/cobe/cobe_home.html

University of Washington Curvature of Space http://www.astro.washington.edu/labs/clearinghouse/labs/Curvature/curvature.html

Surfing through Hyperspace by Clifford A. Pickover (Oxford)

VROOM visualization of 4 dimensions http://www.evl.uic.edu/EVL/VROOM/HTML/PROJECTS/02Sandin.html


Web ResourcesWeb Resources

Bell Labs Cosmology Archives

http://www.bell-labs.com/project/feature/archives/cosmology/

Davide P. Cervone’s Flatland cubes http://www.math.union.edu/~dpvc/courses/2000-01/MTH053-SP01/notes/

Big Bang Cosmology Primer http://cosmology.berkeley.edu/Education/IUP/Big_Bang_Primer.html

Martin White’s Cosmology Pages http://astron.berkeley.edu/~mwhite/darkmatter/bbn.html

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