Big Bang 13.7 Billion Years ago (1)
First second:
A lot of research seems to be trying to figure out what happened at the instant of the big bang.
[The Planck epoch - up to 10-43 after the bang; the Grand unification Theory (GUT) epoch - Between 10-43 seconds and 10-36 seconds after the Big Bang; ...]
Inflationary Epoch - 10-36 seconds and 10-32 seconds.
The universe undergoes an extremely rapid exponential expansion, known as cosmic inflation As of 2010, there were still a variety of proposed scenarios concerning the very early universe which differ radically. I don't stay awake at night worrying about this.

See: The Inflation Debate : Scientific American Mar. 2011

Lepton Epoch, from 1 second to 3 minutes:

Within the last part of the first second the universe is a hot, relativistic plasma of particles dominated by radiation; quarks, leptons (such as electrons) and neutrinos are formed.
It was opaque due to the constant interchange of energy between matter and radiation.
Source: The Physics of the Universe - Timeline of the Big Bang

3 minutes - 240,000 years (Nucleosynthesis,): The Universe then cooled to a temperature of ∼ 4,000 K through its expansion. At this stage, the matter does not have sufficient energy to remain ionised.

240,000 - 380,000 years The electrons combine with the protons to form atoms. Hydrogen, Helium and Lithium at first.
The universe becomes a transparent fog of about 75% hydrogen and 25% helium.

380,000 to 150 million years - Dark Age (or Dark Era)
The period after the formation of hydrogen and before the first stars is dominated by mysterious "dark matter"

The cosmic microwave background (CMB) radiation is created about 380,000 years after the big bang. In 2003 NASA lauhched the Wilkinson Microwave Anisotropy Probe (WMAP) to study the afterglow of the big bang, called the cosmic microwave background.
They produce a map of CMB from 380,000 years after the big bang.
In January, 2010 the WMAP team has reported the first direct detection of pre-stellar helium.
See youtube video

150 million to 1 billion years: The first quasars form from gravitational collapse. The intense radiation they emit reionizes the surrounding universe.

300 - 500 million years:
Early active galaxies, and population III stars.

500 million years: Cold Dark Matter cosmology - As the universe cooled clumps of dark matter began to condense, and within them gas began to condense. The primordial fluctuations gravitationally attracted gas and dark matter to the denser areas, and thus the seeds that would later become galaxies were formed.

On July 11, 2007, using the 10 metre Keck II telescope on Mauna Kea, Richard Ellis of the California Institute of Technology at Pasadena and his team found six star forming galaxies about 13.2 billion light years away and therefore created when the universe was only 500 million years old.

500 million years to present - Creation of other Chemical Elements:
Atoms of heavier elements could not be manufactured until there was a significant amount of helium. However fusing helium into heavier elements requires higher temperatures and pressures than fusing hydrogen into helium.
When massive stars run out of hydrogen they begin burning helium and then successively heavier elements until they have an iron core.

These stars then explode as a type II supernova. The supernova simultaneously manufactures the heaviest elements, and blasts material containing all the elements that the star has made in its lifetime back into the interstellar medium.

Fusion stops at iron, the boundary between fusion and fission. Fusing elements heavier than iron requires rather than releases energy.

Cosmology: A Short Bibilography. at NCSA U. Ill Urbana-Champaign
Our Cosmic Habitat, Martin Rees

(1) Until the mid-1990s the data on the rate cosmic expansion were so uncertain that the best estimates of the age the universe stood at between 10 and 20 billion years. New calculations have zeroed in on 13.7 B years.

In 2004 Astronomers announced that "The Universe is is at least 156 Billion light years across."
The cosmos is 13.7 Billion years old but the stretching of space with its expansion after the Big Bang means that simple distance measurements do not apply. Astronomers realise the Universe is more complex. It has been expanding ever since the Big Bang when energy, space and time itself began. To get the picture try to imagine the Universe a million years after the Big Bang. Light travels for a year, covering one light-year. But at that time, the Universe was about a thousand times smaller than it is today meaning that one light-year has now become stretched to about a thousand light-years.
See The Size of the Universe: A Hard Question

History > Universe

See Also:
Big Bang:
Big Bang Theory - Crystalinks
The Physics of the Universe - Timeline of the Big Bang
The Description, Origin, and Development of the Universe at nasa.gov
Foundations of Big Bang Cosmology at nasa.gov
Cosmic Evolution: An Interdisciplinar Approach at Tufts.
TimeLine at HistoryOfTheUniverse.com

Frequently Asked Questions in Cosmology at UCLA
The Hubble Deep Field
Hubble Ultra Deep Field in 3D
European Space Agency (ESA)
Solar System

last updated 17 July 2010