Cosmology is the study of the history of the universe, its birth, its past and its
future. This timeline was developed by astronomers and cosmologists after many
hundreds of years of the analysis of our night sky and years of asking: "how could we
play the major trends that we see backwards and forwards through time."
Because of spectral analysis and the insights of Edwin Hubble we know that the large
bodies in our universe are all moving away from each other. Because we can tell that
all of the mass and energy in the universe is now spreading apart- we can assume that at
one time in the distant past, all of the matter and energy were at one time very close
together. Actually all of the matter and the energy in the universe were, 14 billion
years ago, squeezed into a point of zero volume and infinite density.
This timeline follows the path of this energy (and the matter that it creates) as it spread
out, cooled and assumed different forms. As the energy in the universe dissipated
some of it began to take on the form of matter. The process of expansion and cooling
has created both the physical universe in which we live and the material components of
our own bodies and minds.
0 Seconds After the Big Bang:
Everything that we can see in space, and all of the distant energy and matter that we
cannot see (but can infer the existence of) make up our universe. From the way that
our galaxy is moving in relationship to other galaxies and from other clues that we can
observe with high powered telescopes, we can tell that around 14 billion years ago, our
universe exploded outwards from an infintesimally small point, at an incredibly fast
Roger Penrose applied general relativity to show that a giant star may collapse to a
singularity and become a black hole. Stephen Hawking used some of the same
mathematical procedures and a few generally accepted premises to go on to show that
a similar singularity must have been what gave rise to the big bang.
As Einstein’s general relativity tells us energy, matter, space and time are inextricably
related, it is almost impossible to physically describe one without the others. For this
reason and for many others we believe that neither energy, space or time existed prior
to the big bang. Because the big bang generated the dimensions of space and time, it
was the first event to happen in the history of our universe.
10 ^-43 Seconds: Plank Time and the GUT era
At this time, a very small fraction of a second after the big bang, the universe was still
very small. The universe may have had a radius of 10^-35 centimeters. Prior to this
time- Plank Time- each of the four forces in the universe were unified. After this point
in time the gravitational force became distinct from the other three forces which, even
today, are still undifferentiated. The other three forces are the electromagnetic force,
the weak nuclear force and the strong nuclear force. These three forces are unified as
the Grand Unified Theory (GUT) force. Because we do not know how the laws of the
universe worked before gravity became differentiated, it is impossible for us to know
how the energy released by the big bang behaved before Plank Time.
The universe has been expanding rapidly since the big bang. The energy that was
released from it is observable in many forms including gravitational energy, and
electromagnetic energy. The temperature has fallen to 1028K and the universe is
about the size of our solar system.
10^-32 Seconds: The Electro-Weak Era
The strong nuclear force along with the electroweak force, which is a combination of
the weak nuclear force and the electromagnetic force, become distinct. The electro-
weak era is marked by the smoothing of inflation.
The electro-weak force breaks up into its aforementioned component forces and so by
now the energy released by the big bang is present primarily as electromagnetic
Because of the findings of Einstein we know that matter and energy are equivalent. A
very small amount of matter is equal to huge amount of energy. The tremendous
amounts of energy released by the big bang begin to reorganize and form some of the
subatomic particles (forms of matter) that make up atoms. Basically, highly energetic
photons (rays of light) turn into particles of matter. For every particle that is created
though, an antiparticle is also created. When these two opposing forms of matter meet,
they annihilate and turn back into energy in the form of photons. The matter that makes
up the majority of our solar system is made of particles whose corresponding
antiparticles have already been annihilated. (For every 109 particle/antiparticle pairs
one extra particle is created. For this reason, after every pair undergoes annihilation,
there are some normal particles left over, leaving 109 photons for every particle in the
Because particles occur slightly more often than antiparticles, most of our material
universe is made of particles.
Not even one second of the universe has passed and it is already much bigger than our
solar system. Because the universe has cooled to 1012K the energy density is no
longer high enough to create protons, the building blocks of matter.
10^-3 to 100 seconds: The Era of Nucleosynthesis
The protons in the universe interact to create helium nuclei, one of the lightest and
simplest elements on the elemental chart. By the end of this era the vast majority of
nuclear reactions have taken place and the universe contains hydrogen, helium and
traces of deuterium, lithium, boron and beryllium. The other elements will be made
later inside the burning cores of stars.
100 seconds to 300,000 Years
At this point the universe is actually opaque, meaning that radiation can not pass
through it. It is opaque because the electrons that occupy much of the available space
absorb the photons of light. When we look back into the farthest reaches of space to
the light that is finally reaching us from this era, we see completely opaque space.
300,000 Years: Recombination
At this point in time the universe changes from being opaque to being translucent. The
universe is now matter dominated.
Most of the universe that we can see from earth is transparent. Yet when we look into
the farthest reaches we can see evidence of the opacity of the early universe. This is
apparent to us as the “cosmic microwave background.” It turns out that this cosmic
microwave background is actually the explosion of the big bang- and we are enveloped
in it. Luckily for us this remaining heat from the big bang is only about three degrees
Kelvin or negative 270 degrees Celsius.
Scientists predicted that the detection of the microwave background would be evidence
for the theory of the big bang. Several years later when radio astronomers (Arno
Penzias and Robert Wilson) found this background radiation, seemingly on accident,
we were able to be much more secure about our theory of the creation of the universe,
our big bang theory.
One Billion Years: The Stelliferous Era
Stars begin to form from clouds of gas. Through the atom crunching nuclear reactions
that they derive their fuel from, stars began to create all of the 92 natural elements in
our universe. In other words, the explosion of the big bang began to form the energy
into matter- really into just a few of the elements, mainly helium and hydrogen. Stars
were responsible for transforming these huge pools of helium and hydrogen into the
other elements that are found in space, on our earth and in our bodies. In fact the sun
and stars in our universe are still performing these transformations today. The carbon
and oxygen in your body was actually made in a star. Soon after, galaxies (large groups
of stars) of many shapes and sizes began to form all over the universe.
9 Billion years
Our sun and our solar system form.
14 Billion Years: Now
We live about 14 billion years after the big bang.
15 Billion Years
One billion years from now the sun will be bright enough to heat the earth to very high
temperatures. The average temperature on earth will be near the boiling point of water.
19 Billion Years
The Sun becomes a red giant and engulfs many of the planets in our solar system
including the earth.
20 Billion Years
The sun shrinks and becomes a white dwarf
10^13 Years: The Degenerate Era
This is a much older universe which has been cooling steadily. By now the average
kinetic movement in the molecules of matter is reaching 0 Kelvin. There are no
longer any stars shining in the universe. The stelliferous era has come to an end.
Universal Expansion has carried all galaxies out of sight of our own. The universe is
getting progressively colder, very quickly.
All matter in the universe is now in black holes, neutron stars, white dwarfs, brown
dwarfs and planets.
10^33- 10^37: The End Of Matter
The protons and other particles of matter decay into energy. Matter is a type of
potential energy and the universe is too “cold” to sustain it.
10^60 – 10^100 The Black Hole Era
Most of the large formations of energy in our universe are in the form of black holes.
Before 10^100 years after the big bang most black holes will have completely
The universe is a dilute and ever-expanding mix of photons, neutrinos, electrons, and
their antiparticles. Eventually all particles will annihilate with their antiparticles.
The shape of the universe is determined by the interaction of two forces. One is the
pull of gravity that pulls all of the massive bodies together. The second force is the
momentum of expansion that was applied to all of the massive bodies in the original
explosion- the big bang. For a long time scientists thought that the gravity of the
massive bodies in the universe would have been strong enough to eventually pull all of
the matter back together, in what it called the big crunch. But now we know that the
matter is moving too fast to ever be pulled back together.
Because our universe is inflating above the critical speed, it is actually still
accelerating from the blast of the big bang. We know that the force of gravity between
the massive objects in our universe is not great enough to pull the universe back
together. Our universe will continue expanding after the average temperature of all of
the objects within it reaches absolute zero and all atomic and molecular movement
stops. It will actually continue to expand forever.
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