How The Life Begin

Before observations of dark energy, cosmologists considered two scenarios for the future of the universe. If the mass  density  of the universe were greater than the  critical density , then the universe would reach a maximum size and then begin to collapse. It would become denser and hotter again, ending with a state similar to that in which it started—a Big Crunch. Alternatively, if the density in the universe were equal to or below the critical density, the expansion would slow down but never stop. Star formation would cease with the consumption of interstellar gas in each galaxy; stars would burn out, leaving  white dwarfs ,  neutron stars , and  black holes . Very gradually, collisions between these would result in mass accumulating into larger and larger black holes. The average temperature of the universe would asymptotically approach  absolute zero —a  Big Freeze .Moreover, if the proton were  unstable , then baryonic mat...

Cause Main article:  Problem of why there is anything at all Gottfried Wilhelm Leibniz  wrote: "Why is there something rather than nothing? The sufficient reason [...] is found in a substance which [...] is a necessary being bearing the reason for its existence within itself." [120]  Philosopher of physics Dean Rickles [121]  has argued that numbers and mathematics (or their underlying laws) may necessarily exist. [122] [123]  Physics may conclude that  time  did not exist before 'Big Bang', but 'started' with the Big Bang and hence there might be no 'beginning', 'before' or potentially 'cause' and instead always existed. [124] [125]  Some also argue that nothing cannot exist or that non-existence might never have been an option. [126] [127] [128] [129]   Quantum fluctuations , or other laws of physics that may have existed at the start of the Big Bang could then create the conditions for matter to occur.

Magnetic Monopole ————————————— The  magnetic monopole  objection was raised in the late 1970s.  Grand unified theories  predicted  topological defects  in space that would manifest as  magnetic monopoles . These objects would be produced efficiently in the hot early universe, resulting in a density much higher than is consistent with observations, given that no monopoles have been found. This problem is also resolved by  cosmic inflation , which removes all point defects from the observable universe, in the same way that it drives the geometry to flatness. [116] Flatness problem The overall  geometry of the universe  is determined by whether the  Omega cosmological parameter  is less than, equal to or greater than 1. Shown from top to bottom are a  closed universe  with positive curvature, a  hyperbolic universe  with negative curvature and a  flat universe  with zero curvature. The  flat...

The  horizon problem  results from the premise that information cannot travel  faster than light . In a universe of finite age this sets a limit—the   particle horizon —on the separation of any two regions of space that are in  causal  contact.The observed isotropy of the  CMB  is problematic in this regard: if the universe had been dominated by radiation or matter at all times up to the epoch of last scattering, the particle horizon at that time would correspond to about 2 degrees on the sky. There would then be no mechanism to cause wider regions to have the same temperature. :191–202 A resolution to this apparent inconsistency is offered by  inflationary theory  in which a homogeneous and isotropic scalar energy field dominates the universe at some very early period (before baryogenesis ). During inflation, the universe undergoes exponential expansion, and the particle horizon expands much more rapidly than previou...

Dark matter Main article:  Dark matter Chart  shows the proportion of different components of the universe  – about 95% is  dark matter  and  dark energy . During the 1970s and the 1980s, various observations showed that there is not sufficient visible matter in the universe to account for the apparent strength of gravitational forces within and between galaxies. This led to the idea that up to 90% of the matter in the universe is dark matter that does not emit light or interact with normal  baryonic  matter. In addition, the assumption that the universe is mostly normal matter led to predictions that were strongly inconsistent with observations. In particular, the universe today is far more lumpy and contains far less deuterium than can be accounted for without dark matter. While dark matter has always been controversial, it is inferred by various observations: the anisotropies in the CMB,  galaxy cluster  velocity dispersions...

Measurements of the  redshift – magnitude  relation for  type Ia supernovae  indicate that the expansion of the universe has been  accelerating  since the universe was about half its present age. To explain this acceleration, general relativity requires that much of the energy in the universe consists of a component with large  negative pressure , dubbed "dark energy". Dark energy, though speculative, solves numerous problems. Measurements of the  cosmic microwave background  indicate that the universe is very nearly spatially flat, and therefore according to general relativity the universe must have almost exactly the  critical density  of mass/energy. But the mass density of the universe can be measured from its gravitational clustering, and is found to have only about 30% of the critical density.Since theory suggests that dark energy does not cluster in the usual way it is the best explanation for the "missing" energy den...

As with any theory, a number of mysteries and problems have arisen as a result of the development of the Big Bang theory. Some of these mysteries and problems have been resolved while others are still outstanding. Proposed solutions to some of the problems in the Big Bang model have revealed new mysteries of their own. For example, the  horizon problem , the  magnetic monopole problem , and the  flatness problem  are most commonly resolved with  inflationary theory , but the details of the inflationary universe are still left unresolved and many, including some founders of the theory, say it has been disproven. What follows are a list of the mysterious aspects of the Big Bang theory still under intense investigation by cosmologists and astrophysicists. Baryon asymmetry ( Main article:  Baryon asymmetry ) —————————————————–– It is not ye...

Detailed observations of the  morphology  and  distribution  of galaxies and  quasars  are in agreement with the current state of the Big Bang theory. A combination of observations and theory suggest that the first quasars and galaxies formed about a billion years after the Big Bang, and since then, larger structures have been forming, such as  galaxy clusters  and  superclusters . Populations of stars have been aging and evolving, so that distant galaxies (which are observed as they were in the early universe) appear very different from nearby galaxies (observed in a more recent state). Moreover, galaxies that formed relatively recently, appear markedly different from galaxies formed at similar distances but shortly after the Big Bang. These observations are strong arguments against the steady-state model. Observations of  star formation , galaxy and quasar distributions and larger structures, agree well with Big Bang simulations of t...

     Abundance of primordial elements.  -------------------------------------------      the Big Bang model it is possible to calculate the concentration of  helium-4 ,  helium-3 , deuterium, and  lithium-7  in the universe as ratios to the amount of ordinary hydrogen.The relative abundances depend on a single parameter, the ratio of  photons  to baryons. This value can be calculated independently from the detailed structure of  CMB  fluctuations. The ratios predicted (by mass, not by number) are about 0.25 for  4 He / H , about 10 −3  for  2 H / H , about 10 −4  for  3 He / H  and about 10 −9  for  7 Li / H . The measured abundances all agree at least roughly with those predicted from a single value of the baryon-to-photon ratio. The agreement is excellent for deuterium, close but formally discrepant for  4 He , and off by a factor of two for ...

In 1964  Arno Penzias  and  Robert Wilson  serendipitously discovered the cosmic background radiation, an omnidirectional signal in the  microwave  band. Their discovery provided substantial confirmation of the big-bang predictions by Alpher , Herman and Gamow around 1950. Through the 1970s the radiation was found to be approximately consistent with a black body spectrum in all directions; this spectrum has been redshifted by the expansion of the universe, and today corresponds to approximately 2.725 K. This tipped the balance of evidence in favor of the Big Bang model, and Penzias and Wilson were awarded a  Nobel Prize  in 1978. The cosmic microwave background spectrum measured by the FIRAS instrument on the COBE satellite is the most-precisely measured black body spectrum in nature. The  data points  and  error bars  on this graph are obscured by the theoretical curve. The surface of last scatteri...

Observations of distant galaxies and  quasars  show that these objects are redshifted—the   light  emitted from them has been shifted to longer wavelengths. This can be seen by taking a  frequency spectrum  of an object and matching the  spectroscopic  pattern of  emission lines  or  absorption lines  corresponding to  atoms  of the  chemical elements  interacting with the light. These redshifts are  uniformly  isotropic, distributed evenly among the observed objects in all directions. If the redshift is interpreted as a Doppler shift, the recessional  velocity  of the object can be calculated. For some galaxies, it is possible to estimate distances via the  cosmic distance ladder . When the recessional velocities are plotted against these distances, a linear relationship known as Hubble's law is observed:{\displaystyle v=H_{0}D}  where {\displaystyle v}  is the rec...

Observational evidence The earliest and most direct observational evidence of the validity of the theory are the expansion of the universe according to  Hubble's law  (as indicated by the redshifts of galaxies), discovery and measurement of the  cosmic microwave background  and the relative abundances of light elements produced by  Big Bang nucleosynthesis . More recent evidence includes observations of  galaxy formation and evolution , and the distribution of  large-scale cosmic structures , These are sometimes called the "four pillars" of the Big Bang theory. Precise modern models of the Big Bang appeal to various exotic physical phenomena that have not been observed in terrestrial laboratory experiments or incorporated into the  Standard Model  of  particle physics . Of these features,  dark matter  is currently subjected to the most active laboratory investigations. Remaining issues include the  cuspy halo...

During the 1930s other ideas were proposed as  non-standard cosmologies  to explain Hubble's observations, including the  Milne model  the  oscillatory universe  (originally suggested by Friedmann , but advocated by Albert Einstein and  Richard Tolman  and  Fritz Zwicky 's   tired light   hypothesi After  World War II , two distinct possibilities emerged. One was Fred Hoyle's  steady state model , whereby new matter would be created as the universe seemed to expand. In this model the universe is roughly the same at any point in time. The other was Lemaître's Big Bang theory, advocated and developed by  George Gamow , who introduced  big bang nucleosynthesis  ( BBN )  and whose associates,  Ralph Alpher  and  Robert Herman , predicted the  CMB .  Ironically, it was Hoyle who coined the phrase that came to be applied to Lemaître's theory, referring to it as "this...

Etymology English astronomer  Fred Hoyle  is credited with coining the term "Big Bang" during a 1949 BBC radio broadcast, saying: "These theories were based on the hypothesis that all the matter in the universe was created in one big bang at a particular time in the remote past." It is popularly reported that Hoyle, who favored an alternative " steady state " cosmological model, intended this to be pejorative,but Hoyle explicitly denied this and said it was just a striking image meant to highlight the difference between the two models. : Development Hubble eXtreme Deep Field ( XDF ) XDF  size compared to the size of the  Moon  – several thousand  galaxies , each consisting of billions of  stars , are in this small view. XDF  (2012) view – each light speck is a galaxy – some of these are as old as 13.2 billion years– the universe is estimated to contain 200 billion galaxies. XDF  image shows fully mature gala...

Horizon A n important feature of the Big Bang spacetime is the presence of  particle horizons . Since the universe has a finite age, and light travels at a finite speed, there may be events in the past whose light has not had time to reach us. This places a limit or a past horizon on the most distant objects that can be observed. Conversely, because space is expanding, and more distant objects are receding ever more quickly, light emitted by us today may never "catch up" to very distant objects. This defines a future horizon, which limits the events in the future that we will be able to influence. The presence of either type of horizon depends on the details of the  FLRW  model that describes our universe. Our understanding of the universe back to very early times  suggests  that there is a past horizon, though in practice our view is also limited by the opacity of the universe at early times. So our view cannot extend further backward in time, ...

Features of BIG BANG event T he Big Bang theory depends on two major assumptions: the universality of  physical laws  and the  cosmological principle . The cosmological principle states that on large scales the universe is  homogeneous  and  isotropic . These ideas were initially taken as postulates, but today there are efforts to test each of them. For example, the first assumption has been tested by observations showing that largest possible deviation of the  fine structure constant  over much of the  age of the universe  is of order 10−5. Also, general relativity has passed stringent  tests  on the scale of the Solar System and binary stars. If the large-scale universe appears isotropic as viewed from Earth, the cosmological principle can be derived from the simpler  Copernican principle , which states that there is no preferred (or special) observer or vantage point. To this end, the cosmological principl...