Post on 18-Jan-2016
transcript
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)