Lecture 24: The Beginning

"Let there be light."
Genesis

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Date: April 27, 1995
Reading Assignment: pp. 613-635

Description : the early evolution of the universe after the big bang

Objectives

to be able to describe how conditions in the early universe were different than they are now

be able to describe the stages in the Matter Era from the present back to the Cosmic Background Radiation

be able to describe how the universe evolved in the Radiation Era and how particles formed in this Era

be able to describe the conditions and time that primordial nucleosynthesis took place and how this produced Helium

be able to describe the flatness problem and the horizon problems, and how they are solved by the Inflation Model

be able to describe why we think there is a Grand Unified Theory and what this theory will predict

be able to describe the observations which are used to test the models of the early universe

Lecture Outline

Slide # 1: The Early Universe

The Beginning

Slide # 2: Emergency Back Up Computer

if using OSF1 and lynx, type

http://galileo.gmu.edu

if using Netscape

open Location

http://galileo.gmu.edu

Slide # 3: Today's Lecture (GRAPHICS)

the matter era

the radiation era

primordial nucleosynthesis

GUTS

Inflation

Slide # 4: The Steady State Universe

infinitely old

infinitely large

constant density

expanding (Hubble's law)

CONTINUOUS CREATION OF MATTER

Slide # 5: The Steady State Universe (GRAPHICS)

expansion creates hydrogen atoms

Slide # 6: Continuous Creation (GRAPHICS)

one hydrogen atom appears every year in a one-cubic mile volume

Slide # 7: The Big Bang

finite age

infinite size (?)

expanding

universe formed at one time

Slide # 8: The Big Bang

finite age

infinite size (?)

expanding

universe formed at one time

Slide # 9: Finite Age

rapid expansion implies a young universe

things closer together in the recent past

slow expansion implies an older universe

things closer together in the more distant past

Slide # 10: The Background Radiation

the universe was hotter

hydrogen was ionized and opaque

the gas temperature was about 10,000K

it occurred at a high redshift

it would appear to be a 3K black body

Slide # 11: Penzias and Wilson

accidently discovered the cosmic background radiation in 1964

worked for Bell Labs

awarded Nobel Prize in 1978

Slide # 12: Will the Expansion:

continue forever

stop

reverse

Slide # 13: The Universe (GRAPHICS)

three possibilities

Slide # 14: Fate of the Universe

rate of expansion

kinetic energy

density of the universe

total gravitational energy

the Cosmological Constant

Slide # 15: Questions

what is the universe expanding into?

how can the universe be infinite?

how can the universe be finite?

Slide # 16: Expanding Universe

every part of the universe is expanding

what is it expanding into?

Slide # 17: Expanding Universe (GRAPHICS)

ant on a balloon

Slide # 18: Expanding Universe

answer: a higher dimension

in the ant's case, 3 dimensional space

in our case, time

Slide # 19: Infinite Universe

how can we have an infinite universe?

we only observe things a finite distance away

Slide # 20: Infinite Universe (GRAPHICS)

universe 12 billion years old

Slide # 21: Infinite Universe (GRAPHICS)

universe 1 billion year old

Slide # 22: Infinite Universe

what we can see is continuously expanding

this will continue, if we have an open universe

Slide # 23: Finite Universe

if the universe is closed, it is finite in size

what is beyond the edge of a finite universe?

Slide # 24: Finite Universe (GRAPHICS)

ant on an expanding balloon

can't keep up with the expansion

Slide # 25: The Early Universe

density was higher

temperature was higher

Slide # 26: Higher Temperatures

stars form at < 10 K

galaxies shaped blobs form at 100 K

hydrogen ionized at 10,000 K

nuclear reactions at 10,000,000 K

particles being formed at > 109 K

Slide # 27: Higher Temperatures

mass and energy are related

E = mc2

matter is more common than radiation now

radiation was more common in the early universe when the density was higher

Slide # 28: Density of the Universe (GRAPHICS)

changing density of the universe

Slide # 29: Matter Era

matter dominates the evolution of the universe

atoms, galaxies and stars are formed

Slide # 30: Matter Era

atomic epoch

recombination

electrons and protons combine to form Hydrogen

3K background radiation!

galactic epoch

galaxy sized blobs form out of gas

stellar epoch

stars formed inside galaxies

where we are now

Slide # 31: Radiation Era

radiation dominates evolution of the universe

much higher temperatures

much stranger physics

Slide # 32: Radiation Era

Nuclear Epoch

Helium and Deuterium form

Lepton Epoch

electrons and neutrinos created from energy

Hadron Epoch

protons and neutrons created

GUTS

strong, weak and electromagnetic laws unified

Planck

unknown physics

Slide # 33: Nuclear Epoch

temperature and density high enough for hydrogen fusion

heavy elements were NOT formed in the big bang

formed in supernova explosions

computer models can exactly match the abundance of helium and deuterium in the

Slide # 34: Lepton Epoch

electrons and neutrinos formed from energy

the process is called Pair Production

Slide # 35: Pair Production (GRAPHICS)

two photons collide

Slide # 36: Pair Production (GRAPHICS)

electron and positron produced

Slide # 37: Very Early Universe

hadrons stopped forming 10-4 seconds after the big bang

they started forming 10-35 seconds after the big bang

we understand most of the story up to this point

Slide # 38: GUTS

Grand Unified Theories

links strong nuclear, weak nuclear, and electromagnetic forces

no clearly superior theory

many competing theories

Slide # 39: TOES

Theories of Everything

before 10-43 seconds, we know gravity as as important to particles an nuclear

we have no clue how this worked

Slide # 40: Problems with the Big Bang

why is the universe so close to being "flat"?

the flatnes problem

why is the universe so isotropic?

the horizon problem

Slide # 41: Flatness

any small deviation from flatness is greatly amplified with time

we know that the current universe has ad density of about 30% of critical

at nucleosynthesis, the universe was within 1 part in 1015 of critical

why is the universe so close to critical density?

Slide # 42: Horizon

things in opposite directions cannot be connected by cause and effect

light cannot reach across the horizon size of our universe

why is the universe exactly alike in all directions?

Slide # 43: Tests of Cosmology

3K background radiation

uniform? isotropic? thermal?

nucleosynthesis

right amounts of He? H? D? Li?

galaxy formation

can we observe this occuring?

Slide # 44: Magnetic Monopoles

almost all GUTS predict magnetic monopoles would be VERY common in our univers

we observe NONE

where did they go?

Slide # 45: Inflation

perhaps the universe had a period of VERY rapid expansion

space expanded faster than the speed of light

this would solve horizon, flatness, and monopole problems

Slide # 46: Inflation

theory of inflation suggested in 1980's

likely modification to big bang

occurred in Hadronic Era

Slide # 47: Constellation Corner (GRAPHICS)

Constellation De Jour

Slide # 48: Constellations

Booties and Arcturus

Leo and Regulus

Hercules

Sagittarius

Scorpius and Antaries

Slide # 49: Constellation Hints

arc to Arcturus - bottom of the Kite

backwards question mark Lion

Sagittarius the teapot

Slide # 50: Spring Sky (GRAPHICS)

Mar 15 - midnight - all sky

Slide # 51: Summer Sky (GRAPHICS)

Jun 15 - midnight - all sky