July 27, 2004

Part I: Expanding Universe Part II: What’s the matter in the

Universe?

July 27, 2004

July 27, 2004

Big Bang?

• Did the Big Bang really happen?

• Is the Universe really expanding?

• Did the BB include inflation?

• How can we find out?

July 27, 2004

Debate preparation

• Big bang vs. steady state Universe

July 27, 2004

Debate and Debrief

• Debrief slides follow

July 27, 2004

Standard Big Bang Cosmology

• Sometime in the distant past there was nothing – space and time did not exist

• Vacuum fluctuations created a singularity that was very hot and dense

• The Universe expanded from this singularity• As it expanded, it cooled

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

galaxies

July 27, 2004

Standard Big Bang Cosmology

• Top three reasons to believe standard big bang cosmology

1. Hubble Expansion

2. Big Bang Nucleosynthesis

3. Cosmic Microwave Background

Big Bang by Physics Chanteuse Lynda Williams

July 27, 2004

Cepheid variables and Nebulae

• In 1923, Hubble used new Mt. Wilson 100 inch telescope to observe Cepheid variables in the nearby “nebula” Andromeda. He recognized that the fuzzy patches called nebulae were actually distant galaxies, outside of our own Milky Way

L =K P1.3

This relation was calibrated by Hertzsprung and Shapley

July 27, 2004

Hubble LawThe Hubble constant

Ho = 558 km s -1 Mpc -1

is the slope of these graphs

Compared to modern measurements, Hubble’s

results were off by a factor of ten!

July 27, 2004

Recall Doppler Shift

Redshift z is a non-relativistic approximation that relates the Doppler shift to the velocity of the object

Redshift is determined by comparing laboratory wavelength to observed wavelength

=

vc

=z =

July 27, 2004

Hubble Law• v = Ho d = cz where

– v = velocity from spectral line measurements– d = distance to object– Ho = Hubble constant in km s-1 Mpc -1 – z is the redshift

Space between the galaxies expands while galaxies stay the same size

July 27, 2004

Expanding Universe

• Expanding Universe of Dots– Why it always looks as though you are at

the center of the expanding universe

• Expanding Universe of Students– The farther things are, the faster they are

moving away

July 27, 2004

Doppler shifting spectral lines

• When a star or galaxy is moving, its spectral lines are Doppler shifted by = obs – lab

• The redshift Z = /lab

• The velocity of the star or galaxy is found from the redshift using v = ZAVG c

H and K lines

July 27, 2004

Hubble constant

• Contemporary Lab Experiences in Astronomy Project CLEA

• You will plot the velocities (km/sec) vs. the distances (Mpc) that you obtain from a sample of galaxies

• The slope of this line is known as the Hubble constant – it is given in km/sec/Mpc

Ho = v/D

July 27, 2004

Contemporary Lab Experiences in Astronomy Project CLEA

• Read through “The Hubble Redshift Distance Relation” student manual

• This manual will walk you through the steps to running the lab.

• Break up into 6 groups of four

July 27, 2004

The age of the Universe

• What is the relationship to the Hubble constant and the age of the Universe?

• Recall Ho = v/D• What are the units?

– D must be in km – V must be in km/sec

• What does this give us?• How do we convert this number into years?

July 27, 2004

Big Bang Timeline

We are hereBig Bang Nucleosynthesis

July 27, 2004

Big Bang Nucleosynthesis• Light elements (namely deuterium, helium, and

lithium) were produced in the first few minutes after the Big BangThe predicted abundance of light elements heavier than hydrogen, as a function of the density of matter in the universe (where 1 is critical)

Note the steep dependence of deuterium on critical density.

Goal is to find a density that explains all the abundances that are measured (blue line)

July 27, 2004

Big Bang Nucleosynthesis

• Heavier elements than 4He are produced in the stars and through supernovae

• However, enough helium and deuterium cannot be produced in stars to match what is observed – in fact, stars destroy deuterium in their cores, which are too hot for deuterium to survive.

• So all the deuterium we see must have been made around three minutes after the big bang, when T~109 K

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

• BBN also predicts the correct amounts of 3He and 7Li

July 27, 2004

Big Bang Timeline

We are hereCosmic

Microwave Background

July 27, 2004

Cosmic Microwave Background

• Discovered in 1965 by Arno Penzias and Robert Wilson who were working at Bell Labs

• Clinched the hot big bang theory

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

July 27, 2004

• Photons in CMB come from the time in the Universe where they stop interacting with matter and travel freely through space

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

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

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

CMB

July 27, 2004

COBE data• “Wrinkles on the face of God”

July 27, 2004

COBE data• Fluctuations in CMB are at the level of one part in 100,000

Blue spots mean greater density

Red spots mean lesser density

(in the early Universe)

July 27, 2004

• Insert WMAP BE Video

July 27, 2004

WMAP vs. COBE

• The WMAP image brings the COBE picture into sharp focus.

movie

July 27, 2004

Universe’s Baby Pictures

Red is warmer

Blue is cooler Credit:

NASA/WMAP

July 27, 2004

Compare MAPs at other wavelengths

• Visible to microwave galaxy images

• Compare the dynamic range

movie

July 27, 2004

WMAP measures geometry

July 27, 2004

Another way to measure geometry

See how parallel laser light beams fired by the space slug are affected by the geometry of space

July 27, 2004

Big Bang Timeline

We are hereInflation

July 27, 2004

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

models in which the Universe exponentially increased in size by about 1043 between about 10-35 and 10-32 s after the Big Bang (It has since expanded by another 1026)

• Inflation is a modification of standard Big Bang cosmology

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

July 27, 2004

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

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

• It provides the solution to two long standing problems with standard Big Bang theory

– Horizon problem

– Flatness problem

Alan Guth

July 27, 2004

WMAP supports inflation

• Inflation - a VERY rapid expansion in the first 10-35 s of the Universe – predicts:– That the density of the universe is close to the

critical density, and thus the geometry of the universe is flat.

– That the fluctuations in the primordial density in the early universe had the same amplitude on all physical scales.

– That there should be, on average, equal numbers of hot and cold spots in the fluctuations of the cosmic microwave background temperature.

• WMAP sees a geometrically flat Universe

July 27, 2004

Horizon Problem• The Universe looks the same everywhere in

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

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

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

July 27, 2004

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

about 1 cm to what we see today

• 1 cm is much larger than the horizon, which at that time was 3 x 10-25 cm

July 27, 2004

With inflation

• Space expands from 3 x 10-25 cm to much bigger than the Universe we see today

July 27, 2004

Flatness Problem• Why does the Universe seem to be flat?• Inflation flattens out spacetime the same way

that blowing up a balloon flattens the surface• Since the Universe is far bigger than we can

see, the part of it that we can see looks flat

July 27, 2004

Lunch

• What’s the matter in the universe?

• Why are there so many more particles than anti-particles?

• How do we know?

July 27, 2004

Big Bang Timeline

We are here

This lecture

July 27, 2004

Probing structure of matter

• Given: a large wooden board, a mystery shape and marbles

• Try to identify the shape that is hiding under the wooden board. You can only roll marbles against the hidden object and observe the deflected paths that the marbles take. Take at least five minutes to "observe" a shape. Then do a second shape.

• Place a piece of paper under the board for sketching the paths of the marbles. Then analyze this information to determine the object's actual shape.

July 27, 2004

Analysis

• Black vertical line shows path of incoming marble

• Red line shows path of outgoing marble

• Green dotted line bisects the angle made by the incoming and outgoing lines

• Reflecting surface is perpendicular to bisecting line

July 27, 2004

Questions

• Draw a small picture of each shape you studied in your binder.

• Can you tell the size of the object as well as its shape?

• How could you find out whether the shape has features that are small compared to the size of your marbles?

• Without looking, how can you be sure of your conclusions?

July 27, 2004

Atomic Structure

• Rutherford shot alpha-particles (Helium nuclei) at a thin gold foil. He found that most went right through. However, some were deflected, and a percentage of those bounced right back at him! He said that “it was like firing a cannonball at tissue paper, and having it ricochet off!”

• Can you see how he concluded that the nucleus was a hard small sphere, and that most of the atom was empty space? (As opposed to a plum pudding?)

July 27, 2004

Atomic Particles

• Atoms are made of protons, neutrons and electrons

• 99.999999999999% of the atom is empty space• Electrons have locations

described by probability functions

• Nuclei have protons and neutrons

nucleus

mp = 1836 me

July 27, 2004

Leptons

• An electron is the most common example of a lepton – particles which appear pointlike

• Neutrinos are also leptons• There are 3 generations of leptons, each has

a massive particle and an associated neutrino• Each lepton also has an anti-lepton (for

example the electron and positron)• Heavier leptons decay into lighter leptons

plus neutrinos (but lepton number must be conserved in these decays)

July 27, 2004

Types of Leptons

Lepton Charge

Mass (GeV/c2)

Electron neutrino

0 0

Electron -1 0.000511

Muon neutrino

0 0

Muon -1 0.106

Tau neutrino

0 0

Tau -1 175

July 27, 2004

Quarks

• Experiments have shown that protons and neutrons are made of smaller particles

• We call them “quarks”, a phrase coined by Murray Gellman after James Joyce’s “three quarks for Muster Mark”

• Every quark has an anti-quark

Modern picture of atom

July 27, 2004

Atomic sizes• Atoms are about 10-10 m• Nuclei are about 10-14 m• Protons are about 10-15 m• The size of electrons and

quarks has not been measured, but they are at least 1000 times smaller than a proton

July 27, 2004

Types of QuarksFlavor Charge Mass

(GeV/c2)

Up 2/3 0.003

Down -1/3 0.006

Charm 2/3 1.3

Strange -1/3 0.1

Top 2/3 175

Bottom -1/3 4.3

• Quarks come in three generations

• All normal matter is made of the lightest 2 quarks

July 27, 2004

Quarks

• Physics Chanteuse

Up, down, charm, strange, top and bottomThe world is made up of quarks and leptons…

Quark Sing-A-long

July 27, 2004

Combining Quarks

• Particles made of quarks are called hadrons

• 3 quarks can combine to make a baryon (examples are protons and neutrons)

• A quark and an anti-quark can combine to make a meson (examples are muons and kaons)

proton

meson

• Fractional quark electromagnetic charges add to integers in all hadrons

July 27, 2004

Color charges

• Each quark has a color charge and each anti-quark has an anti-color charge

• Particles made of quarks are color neutral, either R+B+G or color + anti-color

Quarks are continually changing their colors – they are not one color

July 27, 2004

Gluon exchange• Quarks exchange gluons within a nucleon

movie

July 27, 2004

Atomic Forces

• Electrons are bound to nucleus by Coulomb (electromagnetic) force

• Protons in nucleus are held together by residual strong nuclear force

• Neutrons can beta-decay into protons by weak nuclear force, emitting an electron and an anti-neutrino

F = k q1 q2

r2

n = p + e +

July 27, 2004

Fundamental Forces

• Gravity and the electromagnetic forces both have infinite range but gravity is 1036 times weaker at a given distance

• The strong and weak forces are both short range forces (<10-14 m)

• The weak force is 10-8 times weaker than the strong force within a nucleus

July 27, 2004

Force Carriers

• Each force has a particle which carries the force

• Photons carry the electromagnetic force between charged particles

• Gluons carry the strong force between color charged quarks

July 27, 2004

Force Carriers

• Separating two quarks creates more quarks as energy from the color-force field increases until it is enough to form 2 new quarks

• Weak force is carried by W and Z particles; heavier quarks and leptons decay into lighter ones by changing flavor

July 27, 2004

Unifying Forces

• Weak and electromagnetic forces have been unified into the “electroweak” force – They have equal strength at 10-18 m– Weak force is so much weaker at larger distances

because the W and Z particles are massive and the photon is massless

• Attempts to unify the strong force with the electroweak force are called “Grand Unified Theories”• There is no accepted GUT

July 27, 2004

Gravity• Gravity may be carried by the graviton – it

has not yet been detected • Gravity is not relevant on the sub-atomic

scale because it is so weak• Scientists are trying to find a “Theory of

Everything” which can connect General Relativity (the current theory of gravity) to the other 3 forces

• There is no accepted Theory of Everything (TOE)• Superstrings are the basis of a class of TOEs

July 27, 2004

Force Summary

July 27, 2004

Standard Model

• 6 quarks (and 6 anti-quarks)• 6 leptons (and 6 anti-leptons)• 4 forces• Force carriers (, W+, W-, Zo, 8 gluons, graviton)

July 27, 2004

Some questions

• Do free quarks exist? Did they ever?• Why do we observe matter and almost no antimatter if

we believe there is a symmetry between the two in the universe?

• Why can't the Standard Model predict a particle's mass? • Are quarks and leptons actually fundamental, or made

up of even more fundamental particles? • Why are there exactly three generations of quarks and

leptons? • How does gravity fit into all of this?

July 27, 2004

Particle Accelerators

• The Standard Model of particle physics has been tested by many experiments performed in particle accelerators

• Accelerators come in two types – hadron and lepton• Heavier particles can be made by colliding lighter

particles that have added kinetic energy (because E=mc2)

• Detectors are used to record the shower of new particles that results from the collision of the particle/anti-particle beams

July 27, 2004

Particle Accelerators-SLAC

• 2 mile long accelerator which can make up to 50 GeV electrons and positrons

• Now being used as an asymmetric B-meson factory, making Bs and anti-Bs out of 9 GeV electrons and 3.1 GeV positrons

July 27, 2004

SLAC B-factory• Goal is to understand the

imbalance between matter and anti-matter in the Universe

• 1 out of every billion matter particles must have survived annihilation

• Decay rates of Bs and anti-Bs should be different

• Explanation goes beyond the standard model

July 27, 2004

FermiLab

• 5 accelerators which collide protons and

anti-protons at 2 TeV

Colliding Detector at Fermilab (CDF) D0

July 27, 2004

Picturing Particles Activity

• Analyze the events that are seen in different chambers of a detector

• Determine the particles that could have made these tracks

• Remember that positively charged particles curve opposite to negatively charged particles due to the magnet in the detector

• Muons are not stopped by any of the layers – they travel through the entire detector

• Electrons (positrons) and photons are stopped in the electromagnetic calorimeter layer

• Hadrons are stopped in the hadron calorimeter

July 27, 2004

Figures for activity

July 27, 2004

Break

• So now that we know some particle physics, what does this have to do with the Universe on large scales?

July 27, 2004

Unified Forces• The 4 forces are all unified (and therefore

symmetric) at the beginning of the Universe.

beginning of the Universe

inflation

July 27, 2004

Broken Symmetry

• At high T, the Universe is in a symmetrical state, with a unique point of minimum energy

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

Which glass goes with which

place setting?

July 27, 2004

Phase transitions• The unified (symmetric) state of the very early

Universe is a state of negative energy called the false vacuum

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

• This occurs when the strong nuclear force splits off from the electroweak force

• During inflation, spacetime itself expands faster than the speed of light and small density fluctuations are created to seed structure formation

July 27, 2004

Child Universes

• As the false vacuum turns into true vacuum, particles are created in “child universes”

• The child universe disconnects from the original space

True vacuum

False vacuum

Child Universe

Observers in the parent universe see a black hole form!

July 27, 2004

Multiverses

• Universe was originally defined to include everything

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

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

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

July 27, 2004

A Humbling Thought• Not only do we not occupy a preferred place

in our Universe, we don’t occupy any preferred universe in the Multiverse!

July 27, 2004

Reflection and Debrief

• Now what do we know?

• What are the big ideas here?

• What do our students need to know?

• Is there anything else we need to know?

• Misconceptions

(take notes)

July 27, 2004

Reflection and Debrief

• What are some of the effective ways to teaching these topics?

• Standards???

(take notes)

July 27, 2004

Web Resources The Particle Adventure http://particleadventure.org/

SLAC http://www.slac.stanford.edu

FermiLab http://www.fnal.gov/pub/tour.html

Virtual Space time travel machine http://www.lactamme.polytechnique.fr/Mosaic/descripteurs/demo_14.html

CERN http://public.web.cern.ch/Public/

Particle Physics Education Sites http://particleadventure.org/particleadventure/other/othersites.html

July 27, 2004

Web Resources• Cosmic Background Explorer

http://space.gsfc.nasa.gov/astro/cobe/cobe_home.html• George Smoot’s group pages http://aether.lbl.gov/

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

• 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

• CLEA Astronomy Laboratories http://www.gettysburg.edu/academics/physics/clea/CLEAsoft.overview.html

July 27, 2004

Web Resources

Ned Wright’s CMBR pages http://www.astro.ucla.edu/~wright/CMB-DT.html

Bell Labs Cosmology Archives http://www.bell-labs.com/project/feature/archives/cosmology/

Physics Web quintessence http://physicsweb.org/article/world/13/11/8Big 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

July 27, 2004

More Resources

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

July 27, 2004

Web Resources

Thanks also to Dr. Gordon Spear for providing his Hubble Law Lab spreadsheet!

July 27, 2004

Web Resources (expanding universe)

• Astronomy picture of the Day http://antwrp.gsfc.nasa.gov/apod/astropix.html

• Imagine the Universe http://imagine.gsfc.nasa.gov

• Ned Wright’s ABCs of Distance http://www.astro.ucla.edu/~wright/distance.htm

• Prof. Pogge’s class notes at OSU http://www-astronomy.mps.ohio-state.edu/~pogge/Ast162/Unit4/nebulae.html

• Hubble diagram http://physics.ucsd.edu/students/courses/fall2001/physics5/notes/ch17/sld005.htm

July 27, 2004

Resources

• 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

•

July 27, 2004

Remove slides

July 27, 2004

Is the Universe really expanding?

• Take a look at the handout• How do you interpret the 3 graphs?• Try to draw graphs of a Universe that

has– Static galaxies (not moving)– Turbulent galaxies (random motion)– Rotating galaxies (like the planets around

the Sun)– Uniformly contracting galaxies

July 27, 2004

Rules of the game activity

• Analyze the observed particle events to see what the combination rules are