The Big Bang Necessary? –Expansion of the Universe –Origin of CMBR 400 photons/cc Black body temperature profile –Helium content Universal nucleosynthesis.

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

Zero-th Step

Time <0

Anything before the BB?

How could we tell?

Where could we look?

Time=0

What’s it like?

Don’t know…

Gravity + QED = Quantum Gravity = ?

Haven’t figured it out yet

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)

Time = Now

You’re looking at this.

End of story (for now)