Timeline of the Big Bang
Table of contents
1 Overview
2 Planck Epoch
3 Grand Unification Epoch
4 Electroweak Epoch
5 Hadron Epoch
6 Lepton Epoch
7 Epoch of Nucelosynthesis
Overview
According to the Big Bang theory, the following sequence of events is believed to have occurred.
The starting point for this timeline, 13.7 � 0.2 billion years ago, is the time at which in general
relativity there exists a gravitational singularity. At this time, general relativity is unable to make
statements about what the Universe is like because the theory gives infinite values for the
temperature and density of the universe.
It is believed that general relativity is insufficient to make predictions about the very beginning
of the universe and that a theory of quantum gravity will be needed to do so. Nevertheless the
time at which general relativity predicts a singularity makes a convenient starting point to begin
the timeline, despite the fact that this singularity may or may not actually have existed.
One concept which is important to understand this table is the concept of decoupling or
freezeout. Imagine a block of ice and an aluminum Coca-Cola can. If you increase the
temperature to an extremely high value, then both objects will vaporize and one will have a
mixture of water and aluminum vapor which can be considered a single entity. Now if one
decreases the temperature, then below a certain value the aluminium will condense and freeze
and stop interacting with the water vapor. The exact temperature at which this occurs can be
estimated.
A similar process occurs during the course of the Big Bang as entities freeze out and decouple
from the rest of the soup that makes up the universe. The temperature at which freezeout occurs
can be estimated and the temperature corresponds to the time after the Big Bang.
One final note is that this timeline will refer to the diameter of the universe. This is not the total
size of the universe, which may be infinite. Rather one starts with the current size of the
observable universe which is about thirteen billion light years because thirteen billion years is the
estimated length of time since the beginning of the universe and anything outside that sphere
cannot be observed. One then calculates how large that sphere is at a particular time.
Stephen Hawking has theorized that the events of the Big Bang (the expansion of a singularity
into the current space time continuum) can be seen as a reversal of the events that occur in a
black hole, where space-time condenses into a singularity.
Science tells us nothing about what happened from the time of the Big Bang until 10-43 seconds,
a concept known as Planck time. After this, the time is grouped into epochs.
Planck Epoch
The Planck Epoch covers the time from 10-43 to 10-35 seconds after the Big Bang. The
temperature during this epoch is estimated to decrease from 1032 K to 1027 K.
10-43 seconds
A length of 10-43 seconds is known as Planck time. At this point, the force of gravity
separated from the other three forces, collectively known as the electronuclear force. This
is important because it is currently unknown how gravity combines with the other forces.
The diameter of the currently observable universe is theorized as 10-33 cm.
10-36 seconds
Separation of the strong force from the electronuclear force, leaving three forces: gravity,
strong, and electroweak forces. The particles which are involved in the strong force are
considerably more massive than the particles which are involved with the other forces
and so are believed to "condense" out earlier.
Grand Unification Epoch
The Grand Unification Epoch covers the time from 10-35 to 10-12 seconds after the Big Bang.
The temperature during this epoch is estimated to decrease from 1027 K to 1015 K.
10-35 seconds
For the period of time between 10-35 seconds and 10-33 seconds, it is believed that the size
of the universe expands by a factor of approximately 1020 to 1030 cm. Postulating the
existence of inflation solves a number of problems which are described in cosmic
inflation.
This period is also very important for the existence of matter in the universe.
Individually, the strong and the electroweak forces behave exactly the same way toward
matter and antimatter. Which means that there is no opportunity after this time for more
matter to be created than antimatter. The strong and the electroweak forces are mixed and
act as a single force. Grand unification theories suggest that when this is the case, it may
be possible to have particle reactions which create more matter than antimatter.
-33
10 seconds
The temperature of the Universe is approximately 1025 Kelvin. The Quark-Antiquark
Freezeout begins and lasts until 10-5 seconds. At these temperatures, quarks are able to
condense out but the temperatures are still too hot for protons and neutrons to exist.
Birth of quarks, which appear in particle-antiparticle pairs. Quarks and anti-quarks
annihilate each other to create photons, but quarks are created at a ratio of approximately
109 (1 billion) anti-quarks to 109+1 (1,000,000,001) quarks, resulting in one quark per
billion matter-antimatter interactions. Free quarks multiply rapidly.
Electroweak Epoch
The Electroweak Epoch covers the time from 10-12 to 10-6 seconds after the Big Bang. The
temperature during this epoch is estimated to decrease from 1015 K to 1013 K.
10-12 seconds
The diameter of the currently observable universe increases to approximately 1013 meters.
The weak force, which involves massive particles, condenses and separates from the
electromagnetic force, which involves a massless particle, leaving us with the four
separate forces we know today.
Hadron Epoch
The Hadron Epoch covers the time from 10-6 seconds to 1 second after the Big Bang. The
temperature during this epoch is estimated to decrease from 1013 K to 1010 K.
10-6 seconds
Electrons and positrons annihilate each other during the hadron epoch.
10-5 seconds
The temperature of the Universe is approximately 1013 K. Quarks combine to form
protons and neutrons. The lowering temperature allows quark/anti-quark pairs to combine
into mesons. After this period quarks and anti-quarks can no longer exist as free particles.
10-4 seconds
The temperature of the Universe is approximately 1010 (10 million) Kelvin. The existence
of antimatter is cancelled out, as lepton/anti-lepton pairs are annihilated by existing
photons. Neutrinos break free and exist on their own.
Lepton Epoch
The Lepton Epoch covers the time from 1 second to 3 minutes after the Big Bang. The
temperature during this epoch is estimated to decrease from 1010 K to 109 K.
1 second after the Big Bang
Formation of hydrogen nucleus, the first atomic nuclei. Nuclear fusion begins to occur as
the universe is now cool enough for atomic nuclei to form and still hot enough for them
to collide to form heavier elements.
Epoch of Nucelosynthesis
The Epoch of Nucleosynthesis covers the time from 3 minutes to 300,000 years after the Big
Bang. The temperature during this epoch is estimated to decrease from 109 K to 3000 K.
3 minutes after the Big Bang
Three minutes after the Big Bang, the universe is too cool for nuclear activity to occur,
and these reactions stop. At this point the universe consists of about 75% hydrogen, 25%
helium and trace amounts of deuterium, lithium, beryllium, and boron. Elements heavier
than this do not have time to form before nuclear reactions stop. By looking at conditions
between 1 second and 3 minutes after the Big Bang, one can predict the elemental
abundance of the Universe. These predictions are broadly in agreement with
observations.
300,000 years after the Big Bang
The temperature of the Universe is approximately 10,000 Kelvin. At this temperature
hydrogen nuclei capture electrons to form stable atoms. This is particularly significant
because free electrons are effective at scattering light, which is why fire is not
transparent, while hydrogen atoms will allow light to pass through.
This implies that this is the time at which space becomes transparent to light, since
photons no longer interact strongly with atoms. This means that what we normally think
of as matter and what we normally think of as energy become separate.
The light from the moment at which the universe became transparent has been redshifted
to radio waves and makes up the cosmic microwave background.
For later events, see Timeline of the Universe.