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Cosmology

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									Cosmology
        Cosmology is the study of the overall nature and behavior of the physical
universe. Relativity as in Einstein’s General Theory of Relativity is well accepted by
physicist and astronomers, it is the framework on which the prominent cosmologies of
the day are built.
        This is primarily because General Relativity is capable of dealing
simultaneously with the effects of gravitation and large velocities, where as Newton’s
theories, though applicable to ‘everyday’ problems of force and small velocities, break
down when applied to this segment of the universe.
        1. What is the framework of today’s cosmologies?
        2. What is one characteristic of galaxies that require the use of General
            Relativity instead of Newtonian theory?

        The cosmologist does not concern himself specifically with individual objects,
such as stars or galaxies, but with the whole universe. Some observable facts must be
taken into account by all cosmologists:
    1. Galaxies are arranges isotropically (uniformly in all directions) on the celestial
        sphere.
    2. There exists an isotropic background radiation. All parts of the Universe appear
        to be occupied by radiation whose spectrum is that of a black body at 3K (3°
        above Absolute Zero).
    3. Fainter galaxies have greater red shifts (If red shifts are believed to be caused by
        recession from our own galaxy).
    4. Within our own general neighborhood, velocity is proportional to the constant of
        proportionality (The Hubble Parameter) is 100 km l sec mpc (mega parsec)

LINK: http://hyperphysics.phy-astr.gsu.edu/hbase/astro/hubble.html


Recession
        Though, by Hubble’s Parameter the more distant galaxies recede faster from us
then the nearer galaxies, making it seem we are at the center of the universe with
everything receding from us, but we are in no special position.
        At any position in the universe observers will see all other galaxies receding at
speeds proportional to their distance, this is only a fact of uniform expansion.
    1. On average, are galaxies clumped in any specific direction or do they occur
        uniformly through out space?
    2. Within our general neighborhood is the velocity of recession of galaxies
        proportional to distance? (Yes or No)

LINK: http://en.wikipedia.org/wiki/Deceleration_parameter
The Steady State Universe
Major cosmologies have one axiom that they agree upon:
   1. Axiom the universe of galaxies is statistically the same from where ever it is
       viewed.
   2. All the galaxies look the same, their type, number, average density of matter, and
       speed of receding galaxies would not differ.

LINK: http://en.wikipedia.org/wiki/Steady_state_universe

The steady state theory adds a second fundamental axiom:
    Steady State Axiom: The universe of galaxies is the same whenever it is viewed.
This axiom allows us the opportunity to disprove the theory by showing that changes do
occur with time in the universe. However, the changes that the theory refers to would
take place only after billions of years, this is of course longer then astronomers have been
observing.

The consequences of the steady state theory are:
   1. The universe does not change with time; therefore it has existed for an eternity
      into the past and will continue for an eternity into the future.
   2. If the red shifts of galaxies are interpreted as due recession then some galaxies
      have been receding for an infinite time. By consequence 1 the universe is either
      infinite in size or by Einstein’s theory as galaxies retreat from us and therefore
      increase in speed (in accordance with the Hubble Parameter) they contract in the
      direction of the motion.
           The universe we would see therefore has a bend since galaxies traveling at the
      speed of light would deliver no electro-magnetic relation to us. Those unseen
      galaxies at the rim would be infinitely thin so that an infinite number could be
      packed there and still the universe would be infinite in size.
   3. A steady state also implies that the on going changes in the universe (recession of
      galaxies from each other and fusion of hydrogen into helium and other
      complicated atoms) must be neutralized.

To accomplish this neutralization, the astronomers Bondi, Gold and Hoyle proposed in
1948 that Hydrogen is continually created out of nothing. Because of this, the Steady
State Theory is also called the Continuous Creation Theory. This idea of course
violate the conversion of Energy Law; but that law is only an assumption, based on the
fact that no one has ever seen energy created from nothing.

For this to occur you would need 3-4 atoms per cubic kilometer of space, and for this
situation it would be to far for us to see. It is also in a position to combine with other
hydrogen and form new galaxies to keep the universe in a steady state.
The accumulation is slow, but so is the rate at which galaxies recede from each other
compared to inter-galactic distances.
Which of the following is the axiom upon which the major cosmologies agree?
                a. The universe of galaxies is the same whenever it is viewed.
                b. The universe of galaxies is the same wherever it is viewed.
                c. Both a and b.
                d. They agree on NO axioms.
How long has the universe existed according to the Steady State Theory?
How is it possible that the universe could have existed for an infinite amount of time in
the same state if galaxies are continuously receding from each other?



                                The Time Varying Theory
        The Time Varying Universe theory is less restrictive of the universe then the
Steady State Theory, for it allows it to behave in several different ways. Although it
agrees that the Hubble Parameter is constant in time. This appears to be true, for when
distant galaxies are observed (seen many years in the past due to their distance) they are
receding faster than they should be if Hubble’s Parameter is constant. The expansion of
the universe seems to be slowing down. The mutual gravitation effect of the galaxies
cannot be the complete cause of this slow-down, for the known density of matter is not
great enough.

Time Varying models of the universe come in 2 types:
      Oscillating Universe                        Dispersing Universe

        Both agree that the number density of galaxies is decreasing at the present time
for there are no neutralization reactions to counter the lowering of density by expansion.
If the universe is oscillating, even will follow the patter they are now for some time, then
later due to the gravitational attraction or perhaps the “comical” force, the expansion will
reverse and the universe will contract. All matter will condense into a super dense state
and then some how explode and begin the universe again.
        The Dispersing universe begins the same way, but it never contracts, for it is
believed here that the mutual gravitational attraction of the galaxies and even the
‘Comical’ force can never bring the universe together again.

LINK:          http://en.wikipedia.org/wiki/Oscillating_universe
                                  The Cosmic Egg
        The initial super dense state of the universe is often called the cosmic egg. In it
all the matter of the universe is crushed to neutrons. This is an unstable state so the eggs
explode and the universe is born!

        The expansion of the universe is therefore due to this initial ‘big bang’ theory and
so the astrophysicist George Gamow dubbed it the Big Bang Theory. After the bang all
the matter is thrown all over the universe creating a galaxy and forming the universe.
LINK:           http://en.wikipedia.org/wiki/George_Gamow

                               Expanding Universe
       The Time Varying theory’s universe is not the continually statistically similar
universe of the Steady State Theory no it is continually changing. Originally, the universe
was quite densely packed, but the expansion due to the original explosion, thinned it out.

       We have just seen that the universe will continue to thin out until we see only our
very nearest neighbors, but it may turn it’s self around and contract to a cosmic egg.
Then explode to create a new universe and expand again, but even if it does the universe
will continue to thin out for some time to come.

What was the “cosmic egg”, the super dense matter conglomerate, composed of?
Neutrons.

What is the cause of the expansion of the Time Varying universe? Big Bang

Is the Hubble Parameter constant through out time in the Time Varying universe?


        Most scientists believe the universe is Time Varying, instead of Steady State
Theory. One reason is that with its big bang the Time Varying Theory can produce high
enough temperature at the time of creation to convert hydrogen to helium. This is
believed necessary to from stars and galaxies.
Also the fact that distant galaxies appear to be receding faster then galaxies ‘now’ is a
point in favor of the Time Varying Theory. Finally radio counts of the very distant
galaxies show that at large distances (far in the past) galaxies are more densely spaced.
This, as we have seen is what the Time Varying Theory believes true.

								
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