What is it?
1. It is a theory that the universe as
we know it began 10 – 15 billion years ago.
2. Initial state was a hot, dense uniform
soup of particles that filled space uniformly, and was expanding
One of the most persistently asked questions
has been 'How was the universe created?' In the past many individuals
believed that the universe had no beginning or end and was truly
infinite. By introducing the Big Bang theory however no longer could
the universe be considered infinite. As a consequence the universe
was forced to take on the properties of a finite phenomenon, possessing
a history and a beginning...
Scientists estimate that about fifteen million
years ago a tremendous explosion started the expansion of the universe,
an explosion known as the 'Big Bang.' At the point of this event
all of the matter and energy of space was contained at one spot.
hat existed prior to this event is something not yet known and at
this point in time is down to pure speculation. This occurrence
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. What we must realise at this point is that
the Big Bang was rather an explosion within itself, rather than
say an explosion of a bomb, where fragments are thrown outwards.
The galaxies were not all clumped together, the Big Bang simply
lay the foundations for the universe.
So where can the origins of the Big Bang
theory be traced to? Many papers credit this to one Edwin Hubble,
who made the observation that the universe was a body that was continuously
expanding. He discovered that a galaxies velocity is proportional
to its distance. Galaxies that are twice as far from us move twice
as fast. Another finding was 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.
Since the Big Bang the universe has been continuously
expanding and thus there have been more and more distance between
clusters and galaxies. This phenomenon of galaxies moving further
away from each other is known as the red shift. As light from distant
galaxies approach earth there is an increase in space between earth
and the galaxy., which leaves to wavelengths being stretched.
In addition to the understanding of the velocities
of galaxies emanating from a single point there is further
evidence for the Big Bang. In 1964 two astronomers, Penzias and
Wislon, in an attempt to detect microwaves from space, inadvertently
discovered a noise of extraterrestrial origin. The noise however did
not seem to emanate from one source, but instead came from all directions!
It became apparent to them that what they were hearing was in fact
radiation from the fairest reaches of the universe, which had been
left over from the big bang. The discovery of this radioactive aftermath
of the initial explosion gives much credence to the Big Bang theory.
A more recent discovery by Nasa's COBE satellite
was able to detect cosmic microwaves emanating from the outer reaches
of the universe. These microwaves were remarkably uniform, illustrating
the homogeneity of the early stages of the universe. However the
satellite further discovered that the universe began to cool and
was still expanding, and as a result small fluctuations began to
exist due to temperature differences. These fluctuations 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 we will discuss later.
What happened next?
Thus far we have grappled wit the theory
of the Big Bang...and so the next logical step is to ask what happened
next. Immediately after the Big Bang the universe would have been
tremendously hot as a result of both particles of matter and anti
matter rushing apart in all directions. As it began to cool, at
around 10"-43 seconds after creation , there existed almost
an equal yet asymmetrical amount of matter and anti matter. As these
two materials are created together they collide and destroy one
another creating pure energy. However perhaps more fortunately for
our own existence there was an asymmetry in favour of matter. As
the direct result of the excess of about one part per billion, the
universe was able to mature in a way favourable for matter to persist.
As the universe first began to expand, this discrepancy grew larger.
The particles which began to dominate were those of matter. They
were created and that decayed without the accompaniment of an equal
creation or decay of an anti particle.
As the universe expanded further, and so
cooled, common particles began to form. such particles are known
as baryons, and contain photons, neutrinos, electrons and quarks,
which would become the building blocks of matter and life as we
know it. During the baryon genesis period there were no recognizable
heavy particles such as protons and neutrons because of the still
After the universe had cooled to about 3000
billion degrees Kelvin a radical transition began which has been
likened to the phase transition of water to ice. Composite particles
such as protons and neutrons became the common state of matter after
this transition. Still complex matter could not form at these temperatures.
After one to three minutes since the creation
of the universe protons and neutrons began to react with each other
to form deuterium, an isotope of hydrogen. Deuterium, or heavy hydrogen,
soon collected another neutron to form tritium. Rapidly following
this reaction was the addition of another proton which formed a
helium nucleus. scientists believe that there was one helium nucleus
for every ten protons within the first three minutes of the universe.
After further cooling these excess protons would be able to capture
an electron to create common hydrogen. Consequently, the universe
today is observed to contain one helium atom for every ten or eleven
atoms of hydrogen.
The existence of the universe
Thus far we have began to answer two key
questions...what was the big bang and what happened directly after
it. The third question would need to address the age of the universe
today...Science has been able to expand upon this question by applying
the common physical equation of distance over velocity equaling
time, which again uses Hubble's observations - by which an approximation
can be made.
The two primary measurements needed are the
distance of a galaxy moving away from us and the galaxies red shift.
An unsuccessful first attempt was made to find these distances through
trigonometry. Scientists were able to calculate the diameter of
the earths orbit around the sun, which was augmented through the
calculation of the suns motion through our own galaxy. However this
calculation could not be used alone to determine the enormous distance
between our galaxy and those which would enable us to estimate the
age of the universe because of the significant errors involved.
The next step was an understanding of the
pulsation of stars. It had been observed that stars of the same
luminosity blinked at the same rate, much how a lighthouse would
work when rotating say every 30 seconds. with such knowledge scientists
assumed that stars in our galaxy that blinked at the same rate as
stars in distant galaxies must have the same intensity. Using trig
they were able to calculate the distance to the star in our galaxy.
Therefore the distance of the distant star could be calculated by
studying the difference in their intensity much like determining
the distance of two cars in the night. Assuming the two cars lights
had the same intensity it would be possible to infer that the car
whose headlights appear dimmer was further away from the observer
than the other car whose headlights would seem brighter. However
this theory could not be used as a standalone measurement, afterall
after a certain distance it would become impossible to distinguish
individual stars from the galaxies in which they exist. Because
of the large red shifts in these galaxies a further method had to
be devised to find distance using entire galaxy clusters rather
than stars alone.
By studying the sizes of galaxy clusters
that are near to us, scientists can gain an idea of what the sizes
of other clusters might be. As a consequence a prediction can be
made about their distance from the milky way much in the same way
that the distance of stars was learned. Through a calculation involving
the supposed distance of the far off cluster and its red shift,
a final estimation can be made as to how long the galaxy has been
moving away from us. In turn this number can be used inversely to
turn back the clock when the two galaxies were in the same place
at the same time, or the moment of the Big Bang. The equation which
shows the age of the universe is as follows.....
of a particular galaxy) / (That galaxies velocity) = Time
When figures are applied to this equation
(which we will not go into) the answer comes out to be around fifteen
billion years. This calculation is almost exactly the same for every
galaxy that can be studied, and therefore when using this evidence
that is what we estimate the age of the universe to be.
In summarising what we have thus far we seem
to have made an attempt to explain the answers surrounding the universe.
Our understanding of the Big Bang, the first atoms and the age of
the universe is obviously incomplete. As time wears on more discoveries
are made, leading to more questions which will need answering.
Since its conception the theory of the Big
Bang has been constantly challenged. These challenges have led those
who believe in the theory to search for more concrete evidence which
would prove them correct. For example in June 1995 astronomers were
able to confirm one of the requirements for the foundation of the
universe through the Big Bang.....the detection of primordial helium,
such as deuterium, in the far reaches of the universe. These findings
are consistent with an important aspect of the Big Bang theory that
a mixture of hydrogen and helium was created at the beginning of
In addition the Hubble telescope has provided
certain clues as to what elements were present following creation.
Astronomers using Hubble have found the element boron in extremely
ancient stars. They postulate that its presence could be either
a remnant of energetic events at the birth of galaxies or it could
indicate that boron is even older, dating back to the Big Bang itself.
Again if the latter is true then scientists will have to review
their theory of the Big Bang, as at present such a heavy and complex
atom could not have existed. These are just a few examples that
support the theory of the Big Bang...so what do its critics state
when arguing against it.......
What is describes
1. How the early universe expanded and
2. How the light elements formed
3. How the matter congealed to form stars,
galaxies, and clusters of galaxies
What it doesn't describe
1. What caused the expansion
2. Where did the matter come from