God and Cosmology

1
God and Cosmology

• William Golightly

2
The Fundamental Forces of Nature
3
The Laws of Nature General Relativity and
Quantum Mechanics

• General relativity explains gravity as a warping
  of space and time
• Quantum mechanics says there is an inherent
  unpredictability, or fuzziness, to nature on
  microscopic distance scales
• Quantum mechanics applies to both particles and
  fields

4
How Forces Arise in Quantum Mechanics
5
The Fundamental Particles of Nature
6
The Expanding Universe

• Edwin Hubble studied the spectra of galaxies and
  found from their redshifts that nearly all
  galaxies are receding from us
• The speed of recession is roughly proportional to
  distance

7
The Hubble Law
8
The Balloon Analogy
9
The Cosmic Microwave Background Radiation
10
The Cosmic Microwave Background Spectrum
11
The Creation of Matter

• In the first moments after the Big Bang, the
  universe was extremely hot
• Intense heat created particle-antiparticle pairs,
  which then annihilated and became photons
• A slight asymmetry in matter and antimatter
  allowed about one in a billion matter particles
  to survive
• As the universe cooled, protons and neutrons were
  able to form from quarks

12
Big Bang Nucleosynthesis
13
The Geometry of the Universe

• Geometry of the universe depends on its average
  density
• Closed geometry (positive curvature) has average
  density greater than critical density eventually
  collapses
• Open geometry (negative curvature) has average
  density less than the critical density expands
  forever
• Flat geometry (zero curvature) has average
  density equal to critical density expands forever

14
Dark Energy and the Accelerating Expansion of the
Universe

• Observations of distant supernovae show that the
  universe was expanding more slowly a few billion
  years ago, so expansion rate is now accelerating
• The vacuum energy (dark energy) of an unknown
  field is believed responsible
• Vacuum energy has a large negative pressure,
  creating repulsive gravity, accelerating the
  expansion
• The puzzle is not that vacuum energy exists, but
  that it is not far greater (perhaps 10120 times
  greater) than it is crucial to existence of life

15
Formation of Structure in the Universe

• Had to be some roughness in early universe for
  structure to develop and eventually lead to stars
  and galaxies
• Non-interacting dark matter was able to clump
  together from the start essential for life
• Visible matter (nuclei and electrons) formed a
  plasma and underwent acoustic oscillations until
  atoms formed 380,000 years after the Big Bang
• Degree of roughness was just right for life to
  exist

16
Cosmic Microwave Background Shows Early Roughness
17
Spectrum of microwave background is a powerful
tool

• Temperature fluctuation spectrum shows harmonics
  pattern (angles are smaller toward the right)
• Details of the pattern show the universe is flat,
  with 4 visible matter, 23 dark matter, and 73
  dark energy, in agreement with other observations
• Polarization spectrum agrees well with
  theoretical predictions

18
Summary of Evidence for Big Bang

• Redshifts of galaxies indicates expanding
  universe age of 13.7 billion years consistent
  with measurements of ages of oldest stars
• Observed abundances of elements agrees well with
  predictions of Big Bang model
• Cosmic microwave background has the temperature
  and frequency spectrum predicted by Big Bang, as
  well as the temperature fluctuation and
  polarization spectrum
• Computer simulations of development of universe
  based on Big Bang model yield accurate
  predictions

19
The Universe is Just Right for Life

• Quantum mechanics Pauli exclusion principle and
  characteristics of electrons allow atoms and
  molecules to exist
• Slight early asymmetry of matter and antimatter
  allowed permanent matter to exist
• Both visible and dark matter needed for stars to
  form and life to exist
• Dark energy field is weak enough for stars and
  galaxies to have formed contrary to expectation

20
The Universe is Just Right for Life

• Neutron-proton mass difference
• The neutron is just slightly more massive than
  the proton
• If neutron mass were slightly greater relative to
  proton mass, atomic nuclei could not form
• More equal proton and neutron masses would have
  caused nearly all hydrogen to fuse into helium
  stellar lifetimes greatly shortened
• Neutron mass slightly smaller than proton mass
  would lead to an all-neutron universe

21
The Universe is Just Right for Life

• Strength of the Weak Nuclear Force
• If much weaker, proton/neutron ratio would be
  nearly 1 during nucleosynthesis nearly all
  hydrogen fuses to helium
• If much stronger or weaker, ability of neutrinos
  to push heavy elements away from supernovae could
  be compromised

22
The Universe is Just Right for Life

• Production of Carbon in Stars
• Excited state of carbon is at just the right
  energy for 3 helium nuclei to be able to fuse
  into carbon
• Excited state of oxygen allows both carbon and
  oxygen to exist

23
The Universe is Just Right for Life

• Weakening of strong force by 50 or more would
  prevent heavy elements essential to life from
  forming
• Gravity is 1037 times weaker than electromagnetic
  force if only 1033 times weaker, stellar
  lifetimes greatly shortened
• Universe has three spatial dimensions and one
  time dimension ideal for complex but orderly
  universe

24
The Multiverse Hypothesis

• Basic idea Enormous number of universes with
  different parameters/laws of physics would
  inevitably include a universe just right for life
• If universes all independent, creates more
  problems than it solves
• Popular multiverse concept supposes all universes
  originated in the same process

25
Cosmological Puzzles

• Horizon problem How can widely separated regions
  be at the same temperature?
• Roughness problem What is the origin of the
  unevenness in the early universe that led to the
  development of structure?
• Flatness problem Why is the universe apparently
  geometrically flat? Crucial for the existence of
  stars, galaxies, and life

26
Inflation

• Alan Guths idea Intense burst of accelerating
  expansion occurred within the first second of
  universes existence

27
Inflation

• How inflation solves these problems
• Points close together before inflation could be
  very far apart after inflation horizon problem
  solved
• Quantum fluctuations during inflation would cause
  microscopic variations to be stretched out over
  large distances
• Universe would be flattened by enormous
  expansion, leaving universe at critical density
  flatness problem solved

28
Why Inflation Would Flatten the Universes
Geometry
29
The Hypothesized Cause of Inflation

• Vacuum energy of inflaton field proposed as cause
  of accelerating expansion
• Field would decay, ending inflation enormous
  energy in field would be transformed into matter,
  radiation, and heat

30
Eternal Inflation and Spontaneous Symmetry
Breaking

• Quantum fluctuations may prevent the inflaton
  field from decaying in some places, where
  exponential expansion continues
• If so, then once started, inflation continues
  indefinitely, continually producing new pocket
  universes
• Spontaneous symmetry breaking might allow
  different pocket universes to have different
  parameters/laws of physics

31
Superstring Theory

• Every particle consists of a tiny filament of
  vibrating energy different states of string
  correspond to different particles
• If true, would unify particles and forces
• Requires nine spatial dimensions six must be
  tiny and curled up (compactified)

32
Inflationary Superstring Multiverse

• Universes with different ways of curling up extra
  dimensions could have different laws of physics
  and parameters
• Could be 10500 different possible universes

33
Is Eternal Inflation True?

• Inflation has not yet been proven verified
  predictions of inflation are not unique
• Detailed observations of cosmic microwave
  background (B-mode polarization) may soon tell us
  whether inflation is correct
• Even if inflation is true, we dont know that our
  theories about how it works are right

34
Is Superstring Theory True?

• The theory has never made a specific prediction
  that has been verified by experiment or
  observation
• Existing versions of the theory we can study in
  any detail do not accurately describe our
  universe
• Superstring theory is not so much a theory, as a
  hope that a theory might someday exist

35
Comment by Leonard Susskind on String Theory

• Elegance requires that the number of defining
  equations be small. Five is better than ten, and
  one is better than five. On this score, one might
  facetiously say that String Theory is the
  ultimate epitome of elegance. With all the years
  that String Theory has been studied, no one has
  ever found a single defining equation! The
  number at present count is zero. We know neither
  what the fundamental equations of the theory are
  nor even if it has any. Well then, what is the
  theory, if not a collection of defining
  equations? We really dont know.

36
How Solid is the Multiverse?

• Comment on the multiverse by Martin Rees
• If one does not believe in providential design,
  but still thinks the fine-tuning needs some
  explanation, there is another perspective a
  highly speculative one, so I should reiterate my
  health warning at this stage. It is the one I
  much prefer, however, even though in our present
  state of knowledge any such preference can be no
  more than a hunch emphasis added.

37
Is the Multiverse Fine-Tuned?

• Comment by Paul Steinhardt and Neil Turok
• For all its strengths, the inflationary model
  rests on a significant number of unproven
  assumptions. The first, that the Big Bang was
  the beginning of time, immediately forces a
  second. To explain how the universe became so
  smooth and flat within the first second, the
  existence of a powerful new element, inflationary
  energy, has to be assumed. To perform its task,
  the inflationary energy must have specially tuned
  properties. Although the tuning is an
  unattractive feature, cosmologists accepted it
  because inflation seemed like the only idea that
  had a chance of resolving the cosmological
  problems of the early universe.

38
Is The Multiverse Fine-Tuned?

• Must have an inflaton field with the right
  properties
• General relativity needed so that vacuum fields
  can cause gravitational repulsion
• Superstring theory requires exactly nine spatial
  dimensions (or ten in M-theory)
• Must be possible for some dimensions to be
  compactified in a wide variety of ways
• Must be possible for the way space is
  compactified to spontaneously change
• Need quantum mechanics

39
Conclusions

• It is extremely unlikely that an arbitrary cosmic
  design would just happen to be compatible with
  life, or with the generation of an enormous
  number of universes with varying laws of physics
• We cannot seem to get away from the appearance of
  intelligent design we can only push the problem
  back to another level
• Unless we have some a priori commitment to a
  materialistic worldview, it seems clear that the
  solution that is simplest and requires the least
  faith is that the universe has a Creator