Download Objectives: 1.

Objectives:
1. relate the cosmological principle to isotropy and
homgeneity of the universe.
2. understand how Hubble’s law is used to map the
universe, and look back in time.
3. Know each of the major predictions of the Big
Bang theory, and corresponding confirmations by
observation.
4. relate how and what observations tell us about
the properties of the young universe.
vocabulary
Cosmology
Universe
Galaxy
Hubble law and constant
George Gamow
Penzias and Wilson
Cosmic background radiation
COBE satelite
WMAP
Big bang nucleosynthesis
Helium-4
• Cosmology: the study of the universe itself,
including the history, origins, and fate.
• Galaxy: A gravitationally bound system that
consists of stars and star clusters, gas, dust,
and dark matter.
• Immanuel Kant (1724-1804): proposed that
little smudges of light were “island universes”
separate from our own milky way.
• There are more galaxies than there are stars in
our own galaxy.
• There are billions of stars in the milky way
galaxy.
• The universe contains billions and billions of
galaxies.
Edwin Hubble
• Edwin Hubble: the first
astronomer to measure the
distance to another galaxy.
• These immense distances are
measure in Mega-light years
(Mly) = million light years.
The Cosmological Principle
• The cosmological principle: the center of our
conception understanding of the universe,
and a testable theory that makes predictions
that have confirmed by observation.
• Isotropic: the same in all directions.
• Homogenous: the stars and galaxies in our
part of the universe are the same as they are
in remote corners of the universe.
We Live in an Expanding Universe
Hubble Law
• Edwin Hubble: noticed a red shift in the light
of all galaxies relative to the milky way galaxy.
• Hubble Law: The amount of red shift (or
Velocity of a galaxy) is proportional to the
distance of the galaxy from the milky way.
• The further away a galaxy is the greater the
red shift, and the faster is it moving away from
us.
Interpretation of Hubble Law
• Conclusion: all galaxies are moving away from
the milky way.
• Interpretation: the universe is expanding.
• Hubble Constant: 22 km/s/Mly
All Observers see the same Hubble
expansion
• Since the universe is homogenous and
isotropic (cosmological principle), an observer
at any point in the universe would also see
galaxies moving away from them.
• Big Bang Theory (explains why):
In the image on the left, the universe is isotropic.
the right, the universe is homogeneous.
Galaxies are not flying through space
The space around them is expanding, “pushing”
them away from each other.
On the small scale gravity holds the closed
system of a galaxy together, so we don’t
expand.
Prediction #1:
the age of the universe
• By using hubble’s constant we can run the
cosmological clock backwards.
• Hubbles law implies that everything in the
universe was at the same place 13.7 bya
(billion years ago).
George Gamow (1904-1968)
• Gamow related the temperature to the early
conditions of the universe.
• Predicted that left over energy from the big
bang should be detectable as microwave
radiation. (1948).
Bell Labs: Penzias and Wilson
• Telstar (1962): The first telecommunication
satellite was launched, but phone reception
had a strange hissing interference.
• Microwave radiation left over from the big
bang was causing the interference.
• The first direct evidence that the universe was
created by the big bang.
Cosmic Background Explorer
(COBE Satellite)
• Launched by NASA in the mid 1980’s, the COBE
satelite took the first picture of the early
universe.
• Showed the matter and energy was not uniform
during the creation of the early universe, but the
early universe had clumps of matter beside vast
empty spaces.
• COBE answered none of the essential questions
about the age, composition, expansion of the
universe.
WMAP
The story of the early Universe is a
story about Temperature
• The early Universe is so inconceivably hot that
all matter and the forces of nature are
combined into one super force.
• As the universe cools and expands matter and
the forces of nature are manifested in the
universe.
Forces and the Particles of
Matter
The Strong Nuclear Force Appears
• Causes Inflation: rapid expansion and cooling
of the Universe.
• The first pieces of matter materialize in the
universe, the photon and the electron.
• The strong nuclear force is responsible for
holding quarks together to form protons and
neutrons.
The Electromagnetic Force Appears
• As the Universe further expands and cools,
the electromagnetic force separates out.
• For the first time there is light in the universe.
• When the electromagnetic force separates, we
have the formation of the first sub-atomic
particles called Hadrons.
• Two common examples of Hadrons are the
Proton and the Neutron.
• We have the first Atoms in the Universe!
Hydrogen and Helium
• The only two atoms that are
created as a direct result of the
big bang are the two simplest. H
and He
• Gravity begins to work on this
matter forming large gaseous
clouds of Hydrogen and Helium.
• The gaseous clouds will form the
first stars in the universe.
• Big bang predicts a ration of 75%
Hydrogen, and 25% helium. Hey
that’s what we see in the
universe still today.
Stellar Nuclear Fusion
• Nuclear fusion: fuses atomic nuclei
together forming larger elements.
Example, fusing two Helium atoms
forms one Beryllium atom.
• Nuclear fusion produces larges
amounts of energy in the form of
heat, light, and radiation.
• Nuclear Fusion can form elements as
large as Iron (Fe) element number 26
Super Nova
• After a star has fused all of its Hydrogen and
Helium, forming mostly Iron, It dies in an
enormous of explosion.
• The energy of a Super Nova can further fuse
atomic nuclei into the heavier elements,
forming elements up to Uranium.