About 15 billion years ago a tremendous explosion
started the expansion of the universe. This explosion is known as the Big Bang.
At the point of this event all of the matter and energy of space was contained
at one point. What exisisted prior to this event is completely unknown and is
a matter of pure speculation. This occurance was not a conventional explosion
but rather an event filling all of space with all of the particles of the embryonic
universe rushing away from each other. The Big Bang actually consisted of an
explosion of space within itself unlike an explosion of a bomb were fragments
are thrown outward. The galaxies were not all clumped together, but rather the
Big Bang lay the foundations for the universe.
The origin of the Big Bang theory can be credited to Edwin Hubble. Hubble made
the observation that the universe is continuously expanding. He discovered that
a galaxys velocity is proportional to its distance. Galaxies that are twice
as far from us move twice as fast. Another consequence is that the universe
is expanding in every direction. This observation means that it has taken every
galaxy the same amount of time to move from a common starting position to its
current position. Just as the Big Bang provided for the foundation of the universe,
Hubbles observations provided for the foundation of the Big Bang theory.
Since the Big Bang, the universe has been continuously expanding and, thus,
there has been more and more distance between clusters of galaxies. This phenomenon
of galaxies moving farther away from each other is known as the red shift. As
light from distant galaxies approach earth there is an increase of space between
earth and the galaxy, which leads to wavelengths being stretched.
In addition to the understanding of the velocity of galaxies emanating from
a single point, there is further evidence for the Big Bang. In 1964, two astronomers,
Arno Penzias and Robert Wilson, in an attempt to detect microwaves from outer
space, inadvertently discovered a noise of extraterrestrial origin. The noise
did not seem to emanate from one location but instead, it came from all directions
at once. It became obvious that what they heard was radiation from the farthest
reaches of the universe which had been left over from the Big Bang. This discovery
of the radioactive aftermath of the initial explosion lent much credence to
the Big Bang theory.
Even more recently, NASAs COBE satellite was able to detect cosmic microwaves
eminating from the outer reaches of the universe. These microwaves were remarkably
uniform which illustrated the homogenity of the early stages of the universe.
However, the satillite also discovered that as the universe began to cool and
was still expanding, small fluctuations began to exist due to temperature differences.
These flucuatuations verified prior calculations of the possible cooling and
development of the universe just fractions of a second after its creation. These
fluctuations in the universe provided a more detailed description of the first
moments after the Big Bang. They also helped to tell the story of the formation
of galaxies which will be discussed in the next chapter.
The Big Bang theory provides a viable solution to one of the most pressing questions
of all time. It is important to understand, however, that the theory itself
is constantly being revised. As more observations are made and more research
conducted, the Big Bang theory becomes more complete and our knowledge of the
origins of the universe more substantial. Of course there are evidences that
contradict this theory click the link above to see one