Big Bang

began in an extremely dense and hot condition and has expanded. The theory suggests that redshift proves the universe is expanding.]]
The **Big Bang** is a physical theory about how the universe started expanding, and then made the stars and galaxies we see today. The Big Bang is the name that scientists use for the most common theory of the universe, from the very early stages to the present day.
The most commonly considered alternatives are called the Steady State theory and Plasma cosmology, according to both of which the universe has no beginning or end.

According to the theory the Big Bang began as a very hot, small, and dense superforce (the mix of the four fundamental forces), with no stars, atoms, form, or structure (called a "singularity"). Then about 13.8 billion years ago,

## Evidence 
Scientists base the Big Bang theory on many different observations. The most important is the redshift of very far away galaxies. Cosmological redshift is the Doppler effect occurring in light. When an object moves away from Earth, its color rays look more similar to the color red than they actually are, because the movement stretches the wavelength of light given off by the object. Scientists use the word "red hot" to describe this stretched light wave because red is the longest wavelength on the visible spectrum. The more redshift there is, the faster the object is moving away. By measuring the redshift, scientists proved that the universe is expanding, and they can work out how fast the object is moving away from the Earth. With very exact observation and measurements, scientists believe that the universe was a singularity approximately 13.8 billion years ago. Because most things become colder as they expand, scientists assume that the universe was very small and very hot when it started. This does not take into account other possible (non-cosmological)  causes of redshift.

Other observations that support the Big Bang theory are the amounts of chemical elements in the universe. Amounts of very light elements, such as hydrogen, helium, and lithium seem to agree with the theory of the Big Bang. The same is true, however, for Static State theory and plasma cosmology. Scientists also detected what they call the cosmic microwave background radiation. These electromagnetic waves are everywhere in the universe. This radiation is now very weak and cold, but is thought to have been very strong and very hot a long time ago. noted in his award presentation that he does not support the Big Bang Theory due to the lack of concrete supporting evidence, and stated, "It's very unfortunate that one thinks of the beginning whereas in fact, we have no good theory of such a thing as the beginning."

## Graphical timeline of the universe 
Many things happened in the first picosecond of the universe's time:

ImageSize  = width:720 height:1000
PlotArea   = left:40 right:256 bottom:75 top:75

Colors =
  id:period1  value:rgb(1,1,0.7) # light yellow
  id:period2  value:rgb(0.7,0.7,1) # light blue
  id:events   value:rgb(1,0.7,1) # light purple
  id:era1     Value:yellowgreen
  id:era2     value:lightorange
  id:time1    Value:coral
  id:time2    Value:lavender

DateFormat  = yyyy
Period      = from:-430 till:155
TimeAxis    = format:yyyy orientation:vertical # order:reverse does not work
ScaleMajor  = unit:year increment:10 start:-430 # second
ScaleMinor  = unit:year increment:2 start:-430

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  bar:Era
  bar:Dummy3
  bar:Periods
  bar:Dummy4
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  pos:(240,75)
  text:Planck epoch
  pos:(250,50)
  text:Big Bang
  pos:(20,50)
  text:"0: Linear time"
  pos:(10,980)
  text:"Logarithmic time:"
  text:"10 · log10 second"
  pos:(154,946)
  text:"NEXT"
  pos:(117,931)
  text:The Stelliferous Era
  pos:(245,950)
  text:"Reionization"

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  at:123  frompos:358 tillpos:369   width:0.5  # Matter domination
  points:(369,878)(402,800)  width:0.5
  points:(402,800)(413,800)  width:0.5

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  textcolor:black  fontsize:M

  width:53
  bar:Clock  color:events  align:right  shift:(28,3)  mark:(line,teal)
  at:-120 text:"One picosecond"
  at:-90  text:"One nanosecond"
  at:-60  text:"One microsecond"
  at:-30  text:"One millisecond"
  at:0    text:"One second"
  at:36   text:"One hour"
  at:75   text:"One year"
  at:105  text:"One thousand years"  shift:(43,3)
  at:135  text:"One million years"

  width:53
  bar:Era  mark:(line,white)  align:center  shift:(0,0)
  from:-430  till:135  color:era1  text:"The Primordial Era"

  width:53
  bar:Dummy3

  width:158
  bar:Periods  align:center  shift:(0,0)  mark:(line,white)
  from:-430 till:-360 color:period1  text:Grand unification epoch
  from:-360 till:-120 color:period2  text:Electroweak epoch
  from:-120 till:-60  color:period1  text:Quark epoch
  from:-60  till:0 shift:(-40,0) align:left  color:period2  text:Hadron epoch
  from: 0   till:23   color:period1  text:Lepton epoch
  from: 23   till:131  color:period2  text:Photon epoch
  from:131  till:155  color:period1  text:"Dark Ages"

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  at:-430 shift:(30,-12) text:"Planck time, the smallest theoretically observable ~unit of time and the time before which science is ~unable to describe the universe. At this point, the ~force of gravity separated from the electronuclear ~force."
  at:-360           text:"Separation of the strong force from the ~electronuclear force."
  from:-360 till:-320 align:left shift:(-55,0) color:time1  text:"Inflationary epoch. The Universe expands exponentially"
  at:-320  shift:(30,4) text:"Reheating after inflation populates universe ~with quarks and anti-quarks."
  at:-120           text:"The **weak** force separates from the ~electromagnetic force resulting in the four ~separate forces we know today."
  at:-60            text:"Quarks become confined within hadrons."
  at:-30            mark:(line,white) text:"Formation of hydrogen nuclei."
  at:0              text:"Neutrinos cease to interact with other particles."
  at:23 shift:(30,-11)   text:"Lepton/anti-lepton pairs annihilate."
  from:23  till:31  align:center shift:(0,-4) color:time2  text:"Big Bang nucleosynthesis"
  at:31 shift:(30,2)  text:"3 to 20 minutes: Formation of helium nuclei"
  from:129 till:131  shift:(-114,-2) color:time1 mark:(line,white) text:"Recombination"
#  at:123  shift:(30,-32) text:"70,000 years: Matter domination"
  at:123  mark:(line,white)  shift:(30,-83)  text:"70,000 years: Matter domination"
  at:131  text:"379,000 years: Hydrogen and helium nuclei ~capture electrons to form stable atoms. Photons ~are no longer able to interact strongly with atoms. ~Cosmic microwave background radiation streams ~freely."
  at:155  text:"100 million years: First star begins to shine."

## Related pages 
* Universe
* Galaxy

## References 
## More reading 
*