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According to the Big Bang theory, a sequence of events described below is believed to have taken place starting 13.7 ± 0.2 billion years ago, a time at which in general relativity there is a gravitational singularity.
General relativity cannot describe the Universe at this time, 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 such predictions require a theory of quantum gravity. Nevertheless, the time at which general relativity predicts a singularity makes a convenient starting point to begin the timeline, whether there was such a singularity or not.
Important for understanding this table is the concept of decoupling or freezeout. Imagine a block of ice and an aluminium Coca-Cola can. If you increase the temperature to an extremely high value, then both objects will vaporize, producing a mixture of water and aluminium vapor which can be considered a single entity. If the temperature decreases, then below a certain value the aluminium will condense and freeze and stop interacting with the water vapor. The temperature at which this occurs can be estimated.
Similarly, during the Big Bang, entities froze out and decoupled from the rest of the soup that made up the universe. The freezeout temperature can be estimated, and the temperature corresponds to the time after the Big Bang.
This timeline refers to the diameter of "the universe". This is not the total size of the universe, which may be infinite, but the historical radius of the spherical universe we can now in principle observe, about 13.7 billion light years. We cannot observe anything outside that sphere, as information from it would have taken longer to reach us than the life of the universe. As the universe expanded, what is now in that sphere occupied regions of different diameters at different historical times, and it is to those diameters that we refer.
Stephen HawkingReuters/Stephen Hird Stephen William Hawking, CH CBE FRS (born January 8 1942) is one of the world's leading theoretical physicists. Hawking is Lucasian professor of mathematics at the University of Cambridge (a post once held by Isaac Newton). Biography 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 holeThis article is about the astronomical body. For other uses, see Black hole (disambiguation). roche limit. Infalling matter forms an accretion disk, with some of the matter being ejected in highly energetic polar jets. A black hole is a concentration of m, where space-time condenses into a singularity.Science tells us nothing about what happened from the time of the Big Bang until 10-43 secondThis article is about the unit of time. See second (disambiguation) for other uses The second (symbol s is a unit for time, and one of seven SI base units. It is defined as the duration of 9,192,631,770 periods of the radiation corresponding to the transis, a concept known as Planck timeThe Planck time is the natural unit of time, denoted by t. It is considered the smallest possible measurement of time. 391 × 10-44 seconds where: is Dirac's constant G is the gravitational constant c is the speed of light in a vacuum The Planck time is th. After this, the time is grouped into epochThe word epoch can mean either an interval of time, or a particular point in time used as a reference point. In common usage, the term is often used to apply to a period of time when significant related events took place. see also period, era) In geology,s. At first, these are very short periods; of the seven epochs described below, the first five together last for three minutes.