The Big Bang

1
The Big Bang

• Cyclic model vs Inflationary Model

2
Sources

• Endless Universe by Paul Steinhardt and Neil
  Turok
• 2007, by Doubleday

3

• There is a theory which states that if ever
  anyone discovers exactly what the Universe is for
  and why it is here, it will instantly disappear
  and be replaced by something even more bizarre
  and inexplicable. There is another theory which
  states that this has already happened.
• Douglas Adams, The Restaurant at the End of the
  Universe

4
WMAP (W-map)

• Satellite mission to investigate the thin, dark
  layer of space at the outermost edge of the
  visible galaxy
• Wilkinson Microwave Anisotropy Probe - 2001
• Probes to gather light emitted from the dark
  layer nearly 14 billion years ago at a time when
  atoms were first forming
• 2003 data analysis on-going
• John Bahcall Every astronomer will remember
  where he or she was when hey first heard the WMAP
  results. For cosmology, the announcement today
  represents a rite of passage from speculation to
  precision science.

5
Present Ideas

• The universe emerged from a very hot, dense state
  14 billions years ago and has been expanding and
  cooling every since.
• Dark Matter and Dark Energy
• String Theory
• Membrane (M Theory)
• Repeating cycles of evolution

6
Standard Big Bang

• Inflationary model of the universe
• Hot, big bang model (early 20th century)
• Inflation mechanisms (1980s)
• Dark energy hypothesis (1990s)
• Space and time emerged somehow????
• Just after the bang, a small region of universe
  expands a googol (10100 ) times in 10-30 of a
  second

7
Standard Big Bang cont.

• Energy causing inflation transformed into a
  dense gas of hot radiation
• This gas cooled and the expansion slowed,
  allowing atoms and molecules to clump into
  galaxies and stars.
• After 9 billion years had passed, a mysterious
  force called dark energy takes over and starts to
  accelerate the expansion again.
• In this standard picture, the expansion will
  accelerate forever, turning all space into a vast
  and nearly perfect vacuum.

8
Big Bang segments

• String Era from Bang to 10-43 seconds
• small size, all nine space dimensions were same
  size,
• everything was very hot (about 1032 K) with only
  one kind of particle or string and one kind of
  force (called supergravity)

9
GUTS Era

• From 10-43 to 10-35 seconds
• Phase change with quarks and electrons evolving
• Universe could be thought of as a quark plasma

10
Inflationary Era

• From 10-35 to 10-32 seconds
• Universe inflates like a balloon with a drop in
  temperature (over a billion K)
• This temperature change caused the strong and
  weak forces to separate sending temperature back
  up to 1027 K

11
Quark Era

• From 10-32 to 10-6 seconds
• Growth to around the size of our solar system and
  another temperature drop to around 1013 K
• Matter and antimatter neutralize each other
  releasing light and other particles (protons and
  neutrons do not join to form atomic nuclei
  because of high temperatures)
• Electromagnetic and weak forces divide into
  separate forces

12
Plasma Era

• From 10-6 to 180 seconds
• Small atomic nuclei (H, He, Li) form
• Neutrinos appear after 1 second
• Expansion causes cooling down to 109 K
• Universe consisted of a plasma of electrically
  charged particles, nuclei, and free electrons
  (similar to plasma in fusion reaction)

13
Expansion Era

• From about 3 minutes to 7 E 5 years
• more cooling and expansion
• Empty space begins to exist
• Light and neutrinos could travel without
  encountering other particles

14
Present Era

• From 105 to 109 years
• Todays universe takes shape
• Gravitational collapse causes fusion reactions
  that release heat and light and neutrinos

15
Agreements

• Inflationary model in agreement with WMAP
• Agreement also with
• Clustering of galaxies
• Distribution of infrared radiation and X-rays
• Expansion rate of universe and its age
• Abundances of elements (to within 10 or better)

16
Problems with Inflationary Model

• Inflationary model seems contrived
• Parts of theory seem to have been added to make
  it sensible
• Ordinary matter
• Dark matter
• Dark energy
• Inflationary energy needed to drive expansion
  that then must decay away
• Model doesnt always match up well with
  fundamental physics in unified theory

17
Cyclic Model

• Big Bang was not the beginning of space and time
• Universe undergoes cycles of evolution
• In each cycle, a big bang creates hot matter and
  radiation, which expands and cools to form the
  galaxies and stars seen today
• Expansion of universe increases causing matter to
  become spread out (nearly perfect vacuum)
• After a trillion years a new big bang occurs and
  cycle begins again

18
Agreements here

• Cyclic model accounts for the WMAP results
• Agrees with all other current astronomical
  observations with the same accuracy as the
  inflationary model

19
Space - Time

• Central tenet of Einsteins theory is that space
  and time form an elastic substance called
  space-time that can stretch, contract, warp, and
  wiggle.
• The gravitational force is due to the warping
  effect that a massive object has on the space
  around it (like a bowling ball placed on a soft
  mattress).
• When objects travel in space their paths are
  distorted like a marble would be rolling on the
  mattress near the depression created by bowling
  ball.

20
Cosmological Constant

• To counter gravity Einstein proposed a new form
  of energy that has a repulsive gravitational
  effect, causing space to expand rather than
  contract.
• By setting these opposing influences in balance
  the universe is static.
• Within ten years Edwin Hubble was able to prove
  that the universe is not static but expanding at
  an ever increasing rate

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Problems with the Big Bang Theory

• The big bang is referred to as the initial
  singularity because Einsteins equations of
  general relativity break down when the
  temperature and energy density become infinite,
  and their description of the expansion of the
  universe ceases to be valid.
• Initial theories associated with the Big Bang do
  not indicate dark matter and dark energy.

22
Dark Energy Dark Matter

• Both of these neither emit nor absorb light.
• Their composition is unknown.
• They account for 95 percent of the energy of the
  known universe.
• Only similarity between them is that they do not
  absorb or scatter light.
• Dark matter dominated the past dark energy will
  shape the future. (Dark matter and ordinary
  matter reigned for the first 9 billion years
  (first atoms, stars, and galaxies formed) then
  about 5 billion years ago dark energy took over
  as dominant form of energy.

23
Dark Energy

• One major idea is that dark energy can
  gravitationally repel.
• Another name would be the cosmological constant
  or vacuum energy (the energy remaining in empty
  space after particles and all forms of radiation
  have been removed).
• It has the same density at every point in space
  and at every moment in time.
• As the universe expands the total vacuum energy
  of the universe expands

24
Dark Energy cont.

• The repulsive gravitational effect of vacuum
  energy causes space to expand even faster,
  creating more space and even more vacuum energy.
  The result is a runaway exponential expansion and
  a runaway production of vacuum energy.
• This expansion has been confirmed many different
  ways.
• If the inflationary model is correct all galaxies
  will be diluted away and space will approach a
  nearly perfect vacuum.

25
Dark Matter

• The most likely dark matter candidate would be
  the neutralino. This is the lightest of the
  hypothesized WIMPs (weakly interacting massive
  particles). These particles have mass and
  interact via the weak nuclear force. They are
  about 100 times more massive than a proton.
• These particles do not interact
  electromagnetically so we cant see them at any
  wavelength and they dont feel the strong nuclear
  force so they rarely interact with normal atomic
  nuclei.

26
General Patterns

• Out to 13.7 billion light years, there is no
  detectable curvature of space and matter and
  radiation are smoothly distributed.
• The laws of physics seem to be the same
  everywhere.
• The laws of quantum mechanics (governs structure
  of atoms and molecules), the laws of nuclear and
  statistical physics (laws governing the burning
  of stars), laws of light and electromagnetism and
  fluid dynamics, hold everywhere as well.

27
Gravity

• Gravity governs structure of stars, holds planets
  in orbit around stars, drives the collapse of
  stars, leading to supernova explosions where
  heavy elements are created, and produces giant
  black holes at the center of most galaxies.

28
Last Thoughts

• In the last 5 billion years the formation of new
  structures in the universe has ceased and the
  universe has begun to become simple and uniform
  again. This is due to the small amount of
  regular matter and the vast amount of dark
  matter.
• The dark energy (gravitationally repulsive) has
  begun to stretch out the universe. At the moment
  it appears that dark energy has won out over dark
  matter.