Building a Model for the Universe

1
Building a Model for the Universe

• Einsteins General Relativity
• The creation of the Universe (Big Bang)
• Using the Hubble diagram
• Observing the furthest galaxies
• Masses in the Universe
• The history of our Universe
• Parallel Universes

2
A Theory for the Universe

• 1916 Einstein formulates General Relativity
• The Universe is described in a four-dimensional
  space-time
• The need for a universal constant to make the
  Universe stationary
• 1919 experimental support for Einsteins General
  Relativity

3
The Creation of the Universe

• Cosmology and Cosmogony
• V.Slipher (1912) and E.Hubble (1923) showed the
  most galaxies have the atomic spectra shifted
  towards red.
• Hubble and Humason established that this shift
  increases with the galaxies becoming dimmer and
  dimmer.
• 1965 A.Penzias and R.Wilson discover the
  Universal 3oK black body radiation.
• These two discoveries support the idea that our
  Universe was created through a Big Bang a
  universal explosion.
• 1950s Using nuclear physics G.Gamow, R.Alpher and
  R.Hermann explain the creation of helium during
  the Big Bang.

4
The First Fraction of a Second

• At 10-35 seconds and 1028 degrees superstrings
  world
• Soon after the hyper-weak force transformed
  baryons into leptons and anti-baryons into
  anti-leptons, with the disintegration of
  anti-baryons being much more probable. This
  created a Universe dominated by matter over
  anti-matter.
• After 10-4 seconds from beginning of the Big Bang
  at a temperature of 1012 degrees, a model with 6
  types of quarks can produce the small
  fluctuations which lead to the formation of
  galaxies.
• Between 10-4 and 10-3 seconds at a temperature of
  1011 degrees most heavy baryons disintegrated,
  while the radiation created pairs of electrons
  and positrons.
• At about 10-3 seconds from the beginning of the
  Big Bang, the fundamental forces were functioning
  like today.

5
The Inflationary Model
The Grand Unified Theories -based Inflationary
Model predicts a 50 orders of magnitude increase
for the 10-32 seconds old Universe.
1
10-10
size (cm)
10-50
10-60
10-35
10-25
10-15
time (sec)
6
After the First Second

• When the Universe had 1010 degrees the neutrinos
  decoupled from the rest of particles and the weak
  force stopped from changing protons and neutrons
  their ratio froze to a value 1/6-1/7.
• At 3x109 degrees the radiation was unable to
  create pairs of electrons/positrons and the
  density of photons became a constant (like that
  of neutrinos)
• At a temperature of 1 billion degrees the fusion
  of 25 of protons formed helium nuclei
• At 5000 degrees, the radiation was separated from
  heavy matter and the cooling continued separately
  for the heavy matter, for photons and for
  neutrinos.
• The first atoms were formed about 300,000 years
  from the beginning of the Big Bang, when the
  Universe was about 20,000 smaller than today

7
Galaxies and Stars Formation

• The first galaxies were formed when the Universe
  was about 100 million years old having a density
  about 10,000 larger than today.
• A possible scenario considers primordial black
  holes as the seeds for their formation.
• The first stars inside galaxies were probably
  formed in parallel to their activity as quasars.
• Our solar system corresponds to 2nd or 3rd
  generation of stars which use a large
  concentration of heavy elements produced in
  supernovas.

8
Possible Universe Models
constant expansion rate
space
Open
Flat
Big Bang
Closed
age of the Universe
time
Big Crunch
9
Using the Hubble Diagram
The difficulty in using Hubble diagrams to decide
the age of the Universe is related to the
inaccuracy of the cosmic yardstick. Best
estimates favor an open Universe.
closed U.
openU.
Galaxies speed
flat U. (critical density)
Galaxies distance
10
Observing the Furthest Galaxies

• 1992 Alan Sandage and his collaborators at the
  Space Telescope Institute in Baltimore used the
  Hubble telescope to discover a Cepheid variable
  star in the galaxy IC 4182 and determined its
  distance to be 16 million l-y.
• Astronomers already had information about a type
  Ia supernova which occurred in 1937 in IC 4182.
  That allowed a calibration of the supernova-based
  observations.
• Since 1998 there were 58 very remote (more than 9
  billion light-years) supernova type Ia
  observations which concluded that our Universe is
  open and has an age around 15 billion years.
  That result was in agreement with the fact that
  the age of some stars was close to 14 billion
  years.

11
Masses in the Universe

• Measuring galactic masses in the Milky Way the
  invisible matter is about 5 times heavier than
  the stars.
• Observing hydrogen lines in intergalactic clouds
• The existence of dead stars and black holes
• Neutrinos and other cosmic particles
• The latest estimates account for 35-40 of the
  total mass of the Universe
• Dark (vacuum) energy accounts for 60
  (alternative quintessence model)

12
The History and the Fate of the Universe

• According to the Big Bang theory the energy of
  the Universe was initially mainly radiation.
• The expansion in the first moments of the Big
  Bang was accelerated because through an
  inflationary mechanism.
• As the Universe cooled the radiation lost energy
  faster than the ordinary matter and when it was a
  few tens of thousands of years old the energy
  balance shifted in favor of matter.
• For about 9 billion years the Universe was
  dominated by heavy matter, expanding under the
  original push of the Big Bang and slowed down by
  the intergalactic gravitational attraction.
• As the distances between superclusters of
  galaxies increased vacuum dominates and dictates
  an enforced acceleration (universal constant is
  needed in Einsteins General Relativity)

13
Where Did the Universe Come From ?

• The traditional answers God created it (Plato)
  or It always existed (Aristotle) are not
  acceptable for scientists. Not because scientists
  are not religious but because scientists want a
  more complete answer.
• Two theories are competing
• Although the Universe is not eternal it has
  neither a beginning nor an end. Hawking says that
  although the Universe might be finite, it has no
  boundaries and it might have begun in imaginary
  time.
• The Universe started as a microscopic quantum
  fluctuation , possibly in a previously existing
  Universe.

14
Universal Quantum Fluctuation

• 1973 E.Tryon proposes that Big Bang created real
  matter through the uncertainty principle.
• 1981 H.Pagels and D.Atkatz show that a
  10-dimensional space, as described in the
  superstrings theory, could create particles
  during its transition to a 4-dimensional
  space-time
• A.Linde proposes self-reproducing Universes in
  his chaotic inflationary theory. Universes can
  have different physics laws.
• S.Hawkings baby Universes
• Veneziano- Gasperini showed how quantum
  fluctuations in the supertstrings theory leads to
  the formation of new Universes

15
Are There Parallel Universes ?

• 1998 University of Stanford group showed that a
  5th dimension might be curled with a macro-radius
  (about 1mm). They explained that gravity is weak
  at subatomic scale because it spreads in 5
  dimensions.
• S.Hawking proposed 4-dimensional parallel branes
  on 5-dimensional bubbles. These branes interact
  only gravitationally and therefore we cannot see
  a shadow brane, but we can feel it
  gravitationally. Collisions of the 5-dim bubbles
  lead to new Big Bangs.
• So far, our experiments show that Newtons
  gravity theory is valid down to fractions of a mm.

16
The Shifting Model for the Universe

• Greek philosophers Earth, Sun, planets were the
  Universe
• 17th century Sun at the center of our system and
  other stars
• Beginning of 20th century Milky Way is our
  Universe and there are other Universes
  corresponding to other galaxies
• Today we speak about our Universe containing
  1011 galaxies and we start studying the
  possibility of parallel Universes outside our 4
  dimensional space-time.