The Universe

• Characteristics– Expanding (Hubble’s Law)– Finite age – Cool now, hotter long ago– Composition

• 70% H, 28% He, 2% the rest – Why?

– Most matter is dark (unseen)– Most content is dark energy > gravity

• Accelerates the Universe’s expansion

Universe Content

• Matter – Composed of elementary particles– QED – quantum electrodynamic theory– Quarks, leptons, lions, tigers, and bears, oh my!– These particles interact via force carriers

• 3 out of 4 forces covered – gravity not

• How did this stuff form?• How does it behave under extreme conditions?

Quarks u – up

+2/3

c – charm

Mass > s

t – top

Heaviest

– photon E-M

d – down

-1/3

s – strange

Mass > d,u

b – bottom

Mass>c

g – gluon Strong Nuclear

Leptons

e – electron neutrino

– mu neutrino

– tau neutrino

Z – z boson Weak Nuclear

e – electron

-1

– muon

Mass>e

– tau

Mass>W – w boson

Proton = uudNeutron = udd

Universe’s Energy

Total Energy = Energy of motion + Energy of gravity

Combined with other laws to get the Friedmann Equation -

H = Hubble’s “constant” H, , R are

= density of the Universe time dependent

k = curvature measure

R = scale of the Universe

22

3

8

R

kGH

k > 0

• Positive curvature, hyperbolic shape• Kinetic Energy rules• Open Universe• Eventually….

– 1012 – 1014 years - Star formation ends– 1020 years – Galaxy mergers end– 1030 years – Galaxy death (massive black hole)

• 1030 – 1035 years – proton decay• 10100 years – black hole evaporation

– Eventually “heat death”

k < 0

• Negative curvature, spherical shape• Gravity rules• Closed Universe• Eventually…

– Galaxy redshifts become blueshifts– Universe’s temperature increases– Cluster collisions– Black hole growth, matter evaporation– Total collapse

k = 0

• No curvature, Flat

• Perfect balance between gravity, energy

• Marginally Open

• Eventually– Like the k>0 case, but slower

Which is it?

Define critical densityG

H

G

H ocritical

8

3

8

3 22

Other options?

Einstein’s Idea– Static Universe– No motion requires anti-

gravity effect – Change the formulae

The Field Equations = Cosmological Constant

An “anti-gravity” term

That can’t really exist, can it?

33

4

33

8

2

2

2222

RGR

dt

Rd

Rk

GR

dt

dRv

1997

West Coast – Supernova Cosmology Project

East Coast – High-z Supernova Team

Type I SN – best for great distances– Testing expansion rate of the Universe– How much is gravity slowing the expansion?– How fast was the expansion in the past?– Current expansion rate? (Hubble constant)

Low redshifts

Where is the SN?

Higher redshifts

Best result is caseWhere 0!

Also find k=0

> 0 Universe

> 0 Accelerating Universek =0 implies a Flat UniverseDensity of the Universe = Critical Density?• What is the “density”

– Matter• Dark and regular

– Energy (remember E=mc2)• Energy of light, radiation• Energy of motion - gravity• Energy of motion – anti-gravity!

• Continual acceleration?– No, varies with z (distance)– Initial deceleration for z>1– Acceleration took over later, z<1

Confusing terms

• k=curvature (0 = Flat, <0 Closed, >0 Open)• Define Flat, <1 Open, >1 Closed)• =cosmological constant

– Also written as

• M = matter density (regular and dark)– Also written as M

General rule - = + M

Universal Light - CMBR

• Cosmic Microwave Background Radiation – Everywhere– Black body temperature = 2.725 K– First detected in 1963 by Penzias, Wilson

WMAP Results

Launched 2001

First results – 2003– Flat (k=0, =1)– Age = 13.7 billion years– Hubble Constant = 72 km/s/Mpc– Most of the Universe = Dark Energy

– M =.27

– =.73

Same results - Supernova projectsCMBR projectsGalaxy Cluster projects

Options for the Universe?

Big Rip

should increase with expansion

Lead to a tearing apart of all matter?

When?~22 Billion years from now

• Galaxy cluster dissolve (1 Gyr before end)• Galaxies dissolve (60 Myr before end)• Solar systems dissolve (3 months before end)• Planets dissolve (1/2 hour before end)• Atoms dissolve (10-19 seconds before end)