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ASAL USUL ALAM SEMESTA: TEORI BIG BANG
1. Permulaan Alam Semesta
2. Pengembangan Alam Semesta (The expanding universe)
Learning outcomes :
Modeling how the Big Bang has created an expanding universe
Identify that the distance between objects in the universe continues to expand along
with the universe, itself.
Introduction:
In the 1920s astronomer Edwin Hubble used the red shift of the spectra of stars to
determine that the universe was expanding. By carefully observing the light from
galaxies at different distances from Earth, he determined that the farther something
was from Earth, the faster it seemed to be moving away. This relationship has become
known as Hubbleís Law, and it ís just one piece of a bigger puzzle known as the Big
Bang theory.
Big Bang Theory
About the origin of the Universe exist various
theories, at the moment most scientists
accept the Big Bang theory as the start of the
Universe.
This theory states that the Universe in its
current shape is only a phase of a process
that started with a gigantic explosion about
15 billion years ago.
In the beginning the Universe was all in one
point, all its matter and energy where
squished into an infinitely small volume,
mathematically expressed a singularity.
From this singularity the Universe exploded
and by this native explosion not only matter
and energy was created, however also space
and time.
Figure 1: Big Bang Theory
Bang
The theory says that it is not of any use to speak of the period before the Big Bang,
there is no 'before' because time (and space) did not exist.
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Science assumes to have a good idea of the developemnts after the Big Bang.
Immediately after the explosion the small space was filled with energy (as radiation)
and had an extreme high temperature, one milion billion billion billion (10 with 32
zeros) degrees Kelvin, this stage is called the primordial fireball.
In a fraction of a second elementary matter came into existence: protons, neutrons
and electrons, followed by a very fast expansion (inflation). Since the beginning the
Universe cools down and expands more and more. This time is called the radiation
era, as electromagnetic radiation was the most important thing in the Universe.
After several hundred thousand years the temperature drop was large enough for
atoms to develop from elementary particles, in particular hydrogen and helium, this
is called the matter era.
After 300,000 years the Universe had cooled down enough to become transparent for
radiation, at that time the first Galaxies arose.
In 1964, the Big Bang Theory received its most powerful
observational support. While using a horn radio antenna in Holmdel,
N.J. to isolate, identify and measure sources of noise in the
atmosphere, Bell Labs scientists Arno Penzias (right) and Robert
Wilson discover faint cosmic radiation from the farthest reaches of
known space.
Image credit: Lucent Technologies Inc.
Resource: http://www.bnsc.gov.uk/4728.aspx
The evidence of the Big Bang.
The first observation that indicates the Big Bang is the fact that the Universe is
expanding. Edwin Hubble noticed this in 1929.
If the Universe is expanding, than a simple conclusion may be that it must have been
smaller in the past. By imagening the expansion in a reversed direction astronomers
can determine how long ago the Universe was at size zero and the Big Bang must
have taken place: about 15 billion years ago.
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The second observation is the presence of Cosmic Background Microwave
Radiation.
The cooling down and expansion of the Universe still continues. In case the Universe
really started by the Big Bang about 15 billion years ago, then at present the
Universe should to be cooled down to a temperature of about 3 Kelvin (this 3
degrees above the absolute zeropoint).
Astronomers do indeed observe this in the entire Universe by means of
radiotelescopes and distortion of radio signals that correspond with a temperature of
3 Kelvin.
The third evidence is the presence of large quantities of Helium in the Universe
(about 25% of all matter).
The lifetime of the Universe is simply too short to explain these large quantities of
Helium, except when the Universe has had a period of extreme heat and density.
Under these conditions the Helium is formed from Hydrogen by nuclear reactions.
Calculations indicate that during such a phase -an extremely hot Big Bang- about
25% of all the Universal matter would be turned into Helium. And that is what is
observed.
The Expanding Universe
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The time line of the big bang
The Universe today
The End of the Universe
For the time being nobody is able to predict what will finally happen to the Universe. Based
upon the theory that the Universe is still expanding from the Big Bang, two possibilities are
the most likely.
Depending on the actual expansion rate and if it will change in the future (due to dark
energy increasing, staying the same, or decreasing as time goes on), the universe may end
in a few different scenarios. The most likely is that the universe will continue to expand at
the same rate until all the stars and galaxies go dark. If the universe accelerates at a
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greater rate in the future due to the increase of dark energy, the rate will be so great the
even the space between stars within galaxies will expand and the universe will rip itself
apart. In the other version, if dark energy decreases in the future, the force of gravity will
overcome and pull the universe back to its starting point and collapse in on itself.
Resources :
Internet Link :
- The Big Bang Theory
http://www.geocities.com/beyondearth2001/bigbang.htm
- Universe Beginning
http://www.youtube.com/watch?v=3Cpp_UD3soM
- Big Bang
http://en.wikipedia.org/wiki/Big_Bang
http://library.thinkquest.org/18188/english/universe/cosmos/bigba
ng.htm
- The Expanding Universe
http://btc.montana.edu/ceres/html/Universe/uni1.html#activity5
References :
Alpher, R. A.; R. Herman (August 1988). Reflections on early work on 'big bang' cosmology .
Physics Today, 24–34
Barrow, John D. (1994). The Origin of the Universe: To the Edge of Space and Time .
Phoenix, 150.
Davies, Paul (1992). The Mind of God. Simon & Schuster UK. ISBN 0-671-71069-9.
Hubble, Edwin (1929). "A relation between distance and radial velocity among extra-galactic
nebulae". PNAS 15: 168–173. doi:0.1073/pnas.15.3.168 (inactive 2008-07-21).
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Mather, John C.; John Boslough (1996). The very first light: the true inside story of the
scientific journey back to the dawn of the universe , 300. ISBN 0-465-01575-1.
e-Books :
Kolb, Edward; Michael Turner (1988). The Early Universe. Addison-Wesley. ISBN 0-
201-11604-9.
Peacock, John (1999). Cosmological Physics. Cambridge University Press. ISBN
0521422701.
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