The Big Bang Necessary? –Expansion of the Universe –Origin of CMBR 400 photons/cc Black body...
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Transcript of The Big Bang Necessary? –Expansion of the Universe –Origin of CMBR 400 photons/cc Black body...
The Big Bang
Necessary?– Expansion of the Universe– Origin of CMBR
• 400 photons/cc• Black body temperature profile
– Helium content• Universal nucleosynthesis (like a star)
Basics– Universe was hotter, denser in the past
A few assumptions– Universe is a closed system
• Physically• Heating/cooling – adiabatic
– Treat like an adiabatic fluid (easy!)Energy of the Universe
E=kT
Second law of Thermodynamics
E=p V
Change in energy depends on change in volume
Pressure defined
p = 1/3 e
e=energy density – all radiation early on
Energy of light
ef=hf
So energy density = ef/volume
So the energy of the Universe goes down as the size goes up
Since E=kT, the temperature goes down as it expands
Energy = all energy
Photons, mass (via E=mc2), velocity, gravity, etc…
lengthVe
VeEV
hc
V
hfe
/1
Time=10-43 sec
Time=Planck time
Based on quantum physics principles
Temperature = 1032 K
Density = 1093 gm/cc
Scale = very small
Interactions between energy/matter
Quantum physics (QED), gravity – separate
Can use them to describe characteristics of the Universe
How?
Some boring math…
Planck lengths, time, masses…
Okay what does that mean?
Have to define some more stuff….
cmctl
gmtc
hm
htmc
htE
sc
hGt
pp
pp
p
33
52
2
435
107.1
105.22
2
2
102
Compton time – time for a mass to violate conservation of energy law
This activity is known as “quantum fluctuations”
Formation of particles (matter/anti-matter) out of energy, quick destruction
Happens over a quantum length (Compton length)
cc
c
ctlmc
ht
22
Schwarzschild Radius – “size” of a black hole
Schwarzschild Time – time for a photon to travel across a black hole
This defines the realm of “gravity”
c
lt
c
Gml
ss
s
2
2
2 types of ways to describe the Universe– Planck length, time = QED– Compton length, time = QED– Schwarzschild length, time = gravity
The way these are related defines who is in charge – gravity or QED
Funny feature: a Planck mass into the formula for Compton, Schwarzschild lengths = Planck length
Also, all times are equal.
Meaning?
Planck mass = black hole that exists for Planck time!
If mass>Planck mass
Enter the realm of gravity (relativity),
QED not important
If mass<Planck mass
QED important, gravity loses.
This time, this mass, this realm is when there are two separate forces – gravity, GUT
GUT = grand unified theory (QED laws)
So what is REALLY happening?
Mini-black holes can come into/out of existence
Gravity brings them into being
Hawking radiation destroys them
Particles (non-black holes) come into/out of existence (Compton stuff)
Have energy, some particles, strange things going on – still not easy to define (or understand).
Time=10-35 sec
During GUT – quarks, leptons identicalNow the GUT breaks down into
Strong nuclear force (quarks force)Electoweak force (lepton/photon force)
Breaks “symmetry” of the Universe“Freezing out” of forces – loss of freedom
Release of energy (vacuum energy)Inflation startsQuarks form (along with anti-quarks)
Time=10-32 sec
End of Inflation
After inflation, size of Universe increased by factor of 1050
Really?
Expains uniformity of Universe
Flatness of Universe
Time=10-12 sec
Another symmetry breaking
Electroweak force breaks down into
electromagnetic force
weak nuclear force
Leptons/anti-leptons form
Universe full of energy (photons), quarks, leptons
Time=10-10 sec
Quarks win over anti-quarks
Another symmetry breaking!
Protons/neutrons can form
Interactions between all sorts of things
Not what happens today
Neutrinos forced into interactions
nep
npe
e
e
Time=10-5 sec
End of neutrino interactions
Universe too cool (10 billion K)
Neutrinos still out there!
Where are they?
Time=1-3 Minutes
Nucleosynthesis
Universe Temperature = Stellar interior
Protons, Neutrons combine to make– H2, H3 (Deuterium, Tritium)– He3, He4
– Li6, Li7, Be7
End composition: 75% p+ (H), 25% He4
(~0.01% - the rest)
Gravity starts to become noticeable
Time = 1 year
Energy and Matter starting to diverge
Cooling down at their own rates
Energy (photons) – cooled by the expansion
Matter – temperature determined by photons, fewer interactions
Time=380,000 years
Era of Decoupling
Energy + Matter intertwined before now
After this, they go their separate ways
Energy of photons too low to interact effectively
Universe becomes “transparent” to radiation
Matter (gravity) controls Universe
Time <1 billion years
Galaxy Formation/Cluster formation?
Proto-galaxy formation?
Something is starting to happen….
This would be the epoch of the largest observable redshifts
Might have missed a previous step (or two)