ultimate fate of the universe
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The ultimate fate of the universe is a topic in
physical cosmology Physical cosmology is a branch of cosmology concerned with the study of cosmological models. A cosmological model, or simply cosmology, provides a description of the largest-scale structures and dynamics of the universe and allows study of f ...
, whose theoretical restrictions allow possible scenarios for the
evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
and ultimate fate of the
universe The universe is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy. The Big Bang theory is the prevailing cosmological description of the development of the universe. Acc ...
to be described and evaluated. Based on available observational evidence, deciding the fate and evolution of the universe has become a valid cosmological question, being beyond the mostly untestable constraints of mythological or theological beliefs. Several possible futures have been predicted by different scientific hypotheses, including that the universe might have existed for a finite and infinite duration, or towards explaining the manner and circumstances of its beginning. Observations made by
Edwin Hubble Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an Americans, American astronomer. He played a crucial role in establishing the fields of extragalactic astronomy and observational cosmology. Hubble proved that many objects ...
during the 1930s–1950s found that galaxies appeared to be moving away from each other, leading to the currently accepted
Big Bang The Big Bang event is a physical theory that describes how the universe expanded from an initial state of high density and temperature. Various cosmological models of the Big Bang explain the evolution of the observable universe from the ...
theory. This suggests that the universe began very dense about 13.787 billion years ago, and it has expanded and (on average) become less
dense Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematically ...
ever since. Confirmation of the Big Bang mostly depends on knowing the rate of expansion, average density of matter, and the physical properties of the mass–energy in the universe. There is a strong consensus among
cosmologists Physical cosmology is a branch of cosmology concerned with the study of cosmological models. A cosmological model, or simply cosmology, provides a description of the largest-scale structures and dynamics of the universe and allows study of f ...
that the shape of the universe is considered "flat" (
parallel lines In geometry, parallel lines are coplanar straight lines that do not intersect at any point. Parallel planes are planes in the same three-dimensional space that never meet. ''Parallel curves'' are curves that do not touch each other or int ...
stay parallel) and will continue to expand forever. Factors that need to be considered in determining the universe's origin and ultimate fate include the average motions of galaxies, the shape and structure of the universe, and the amount of
dark matter Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Dark matter is called "dark" because it does not appear to interact with the electromagnetic field, which means it does not ab ...
and
dark energy In physical cosmology and astronomy, dark energy is an unknown form of energy that affects the universe on the largest scales. The first observational evidence for its existence came from measurements of supernovas, which showed that the univer ...
that the universe contains.


Emerging scientific basis


Theory

The theoretical scientific exploration of the ultimate fate of the universe became possible with
Albert Einstein Albert Einstein ( ; ; 14 March 1879 – 18 April 1955) was a German-born theoretical physicist, widely acknowledged to be one of the greatest and most influential physicists of all time. Einstein is best known for developing the theory ...
's 1915 theory of
general relativity General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics ...
. General relativity can be employed to describe the universe on the largest possible scale. There are several possible solutions to the equations of general relativity, and each solution implies a possible ultimate fate of the universe.
Alexander Friedmann Alexander Alexandrovich Friedmann (also spelled Friedman or Fridman ; russian: Алекса́ндр Алекса́ндрович Фри́дман) (June 16 .S. 4 1888 – September 16, 1925) was a Russian and Soviet physicist and mathematician ...
proposed several
solution Solution may refer to: * Solution (chemistry), a mixture where one substance is dissolved in another * Solution (equation), in mathematics ** Numerical solution, in numerical analysis, approximate solutions within specified error bounds * Soluti ...
s in 1922, as did
Georges Lemaître Georges Henri Joseph Édouard Lemaître ( ; ; 17 July 1894 – 20 June 1966) was a Belgian Catholic priest, theoretical physicist, mathematician, astronomer, and professor of physics at the Catholic University of Louvain. He was the first to th ...
in 1927. ''translated by A. S. Eddington'': In some of these solutions, the universe has been expanding from an initial singularity which was, essentially, the Big Bang.


Observation

In 1929,
Edwin Hubble Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an Americans, American astronomer. He played a crucial role in establishing the fields of extragalactic astronomy and observational cosmology. Hubble proved that many objects ...
published his conclusion, based on his observations of
Cepheid variable A Cepheid variable () is a type of star that pulsates radially, varying in both diameter and temperature and producing changes in brightness with a well-defined stable period and amplitude. A strong direct relationship between a Cepheid varia ...
stars in distant galaxies, that the universe was expanding. From then on, the ''beginning'' of the universe and its possible ''end'' have been the subjects of serious scientific investigation.


Big Bang and Steady State theories

In 1927,
Georges Lemaître Georges Henri Joseph Édouard Lemaître ( ; ; 17 July 1894 – 20 June 1966) was a Belgian Catholic priest, theoretical physicist, mathematician, astronomer, and professor of physics at the Catholic University of Louvain. He was the first to th ...
set out a theory that has since come to be called the Big Bang theory of the origin of the universe. In 1948,
Fred Hoyle Sir Fred Hoyle FRS (24 June 1915 – 20 August 2001) was an English astronomer who formulated the theory of stellar nucleosynthesis and was one of the authors of the influential B2FH paper. He also held controversial stances on other sci ...
set out his opposing
Steady State theory In cosmology, the steady-state model, or steady state theory is an alternative to the Big Bang theory of evolution of the universe. In the steady-state model, the density of matter in the expanding universe remains unchanged due to a continuous ...
in which the universe continually expanded but remained statistically unchanged as new matter is constantly created. These two theories were active contenders until the 1965 discovery, by
Arno Penzias Arno Allan Penzias (; born April 26, 1933) is an American physicist, radio astronomer and Nobel laureate in physics. Along with Robert Woodrow Wilson, he discovered the cosmic microwave background radiation, which helped establish the Big Bang ...
and Robert Wilson, of the
cosmic microwave background In Big Bang cosmology the cosmic microwave background (CMB, CMBR) is electromagnetic radiation that is a remnant from an early stage of the universe, also known as "relic radiation". The CMB is faint cosmic background radiation filling all spac ...
radiation, a fact that is a straightforward prediction of the Big Bang theory, and one that the original Steady State theory could not account for. As a result, the Big Bang theory quickly became the most widely held view of the origin of the universe.


Cosmological constant

Einstein and his contemporaries believed in a
static universe In cosmology, a static universe (also referred to as stationary, infinite, static infinite or static eternal) is a cosmological model in which the universe is both spatially and temporally infinite, and space is neither expanding nor contract ...
. When Einstein found that his
general relativity General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics ...
equations could easily be solved in such a way as to allow the universe to be expanding at the present and contracting in the far future, he added to those equations what he called a
cosmological constant In cosmology, the cosmological constant (usually denoted by the Greek capital letter lambda: ), alternatively called Einstein's cosmological constant, is the constant coefficient of a term that Albert Einstein temporarily added to his field eq ...
 ⁠— ⁠essentially a constant energy density, unaffected by any expansion or contraction ⁠— ⁠whose role was to offset the effect of gravity on the universe as a whole in such a way that the universe would remain static. However, after Hubble announced his conclusion that the universe was expanding, Einstein would write that his cosmological constant was "the greatest blunder of my life."


Density parameter

An important parameter in fate of the universe theory is the
density parameter The Friedmann equations are a set of equations in physical cosmology that govern the expansion of space in homogeneous and isotropic models of the universe within the context of general relativity. They were first derived by Alexander Friedma ...
, omega (\Omega), defined as the average matter density of the universe divided by a critical value of that density. This selects one of three possible
geometries This is a list of geometry topics. Types, methodologies, and terminologies of geometry. * Absolute geometry * Affine geometry * Algebraic geometry * Analytic geometry * Archimedes' use of infinitesimals * Birational geometry * Complex geomet ...
depending on whether \Omega is equal to, less than, or greater than 1. These are called, respectively, the flat, open and closed universes. These three adjectives refer to the overall geometry of the universe, and not to the local curving of
spacetime In physics, spacetime is a mathematical model that combines the three dimensions of space and one dimension of time into a single four-dimensional manifold. Spacetime diagrams can be used to visualize relativistic effects, such as why differen ...
caused by smaller clumps of mass (for example,
galaxies A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. ...
and
star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...
s). If the primary content of the universe is inert matter, as in the dust models popular for much of the 20th century, there is a particular fate corresponding to each geometry. Hence cosmologists aimed to determine the fate of the universe by measuring \Omega, or equivalently the rate at which the expansion was decelerating.


Repulsive force

Starting in 1998, observations of
supernova A supernova is a powerful and luminous explosion of a star. It has the plural form supernovae or supernovas, and is abbreviated SN or SNe. This transient astronomical event occurs during the last evolutionary stages of a massive star or when ...
s in distant
galaxies A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. ...
have been interpreted as consistent with a universe whose expansion is accelerating. Subsequent cosmological theorizing has been designed so as to allow for this possible acceleration, nearly always by invoking
dark energy In physical cosmology and astronomy, dark energy is an unknown form of energy that affects the universe on the largest scales. The first observational evidence for its existence came from measurements of supernovas, which showed that the univer ...
, which in its simplest form is just a positive cosmological constant. In general, dark energy is a catch-all term for any hypothesized field with negative pressure, usually with a density that changes as the universe expands.


Role of the shape of the universe

The current scientific consensus of most cosmologists is that the ultimate fate of the universe depends on its overall shape, how much
dark energy In physical cosmology and astronomy, dark energy is an unknown form of energy that affects the universe on the largest scales. The first observational evidence for its existence came from measurements of supernovas, which showed that the univer ...
it contains and on the
equation of state In physics, chemistry, and thermodynamics, an equation of state is a thermodynamic equation relating state variables, which describe the state of matter under a given set of physical conditions, such as pressure, volume, temperature, or internal ...
which determines how the dark energy density responds to the expansion of the universe. Recent observations conclude, from 7.5 billion years after the Big Bang, that the expansion rate of the universe has probably been increasing, commensurate with the Open Universe theory. However, other recent measurements by Wilkinson Microwave Anisotropy Probe suggest that the universe is either flat or very close to flat.


Closed universe

If \Omega > 1, the geometry of space is closed like the surface of a sphere. The sum of the angles of a triangle exceeds 180 degrees and there are no parallel lines; all lines eventually meet. The geometry of the universe is, at least on a very large scale,
elliptic In mathematics, an ellipse is a plane curve surrounding two focal points, such that for all points on the curve, the sum of the two distances to the focal points is a constant. It generalizes a circle, which is the special type of ellipse in ...
. In a closed universe, gravity eventually stops the expansion of the universe, after which it starts to contract until all matter in the universe collapses to a point, a final singularity termed the " Big Crunch", the opposite of the
Big Bang The Big Bang event is a physical theory that describes how the universe expanded from an initial state of high density and temperature. Various cosmological models of the Big Bang explain the evolution of the observable universe from the ...
. Some new modern theories assume the universe may have a significant amount of dark energy, whose repulsive force may be sufficient to cause the expansion of the universe to continue forever—even if \Omega > 1.


Open universe

If \Omega < 1, the geometry of space is
open Open or OPEN may refer to: Music * Open (band), Australian pop/rock band * The Open (band), English indie rock band * ''Open'' (Blues Image album), 1969 * ''Open'' (Gotthard album), 1999 * ''Open'' (Cowboy Junkies album), 2001 * ''Open'' (YF ...
, i.e., negatively curved like the surface of a saddle. The angles of a triangle sum to less than 180 degrees, and lines that do not meet are never equidistant; they have a point of least distance and otherwise grow apart. The geometry of such a universe is
hyperbolic Hyperbolic is an adjective describing something that resembles or pertains to a hyperbola (a curve), to hyperbole (an overstatement or exaggeration), or to hyperbolic geometry. The following phenomena are described as ''hyperbolic'' because they ...
. Even without dark energy, a negatively curved universe expands forever, with gravity negligibly slowing the rate of expansion. With dark energy, the expansion not only continues but accelerates. The ultimate fate of an open universe is either universal
heat death Heat death may refer to: *Heat death of the universe, a proposed cosmological event ** Heat death paradox, a philosophical examination of the cosmological event *Hyperthermia, injury up to and including death, from excessive heat *Thermal shock ...
, a "
Big Freeze The heat death of the universe (also known as the Big Chill or Big Freeze) is a hypothesis on the ultimate fate of the universe, which suggests the universe will evolve to a state of no thermodynamic free energy, and will therefore be unabl ...
" (not to be confused with
heat death Heat death may refer to: *Heat death of the universe, a proposed cosmological event ** Heat death paradox, a philosophical examination of the cosmological event *Hyperthermia, injury up to and including death, from excessive heat *Thermal shock ...
, despite seemingly similar name interpretation ⁠; see ''§Theories about the end of the universe'' below), or a "
Big Rip In physical cosmology, the Big Rip is a hypothetical cosmological model concerning the ultimate fate of the universe, in which the matter of the universe, from stars and galaxies to atoms and subatomic particles, and even spacetime itself, is ...
" — in particular
dark energy In physical cosmology and astronomy, dark energy is an unknown form of energy that affects the universe on the largest scales. The first observational evidence for its existence came from measurements of supernovas, which showed that the univer ...
, quintessence, and the
Big Rip In physical cosmology, the Big Rip is a hypothetical cosmological model concerning the ultimate fate of the universe, in which the matter of the universe, from stars and galaxies to atoms and subatomic particles, and even spacetime itself, is ...
scenario — where the acceleration caused by dark energy eventually becomes so strong that it completely overwhelms the effects of the
gravitational In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stron ...
,
electromagnetic In physics, electromagnetism is an interaction that occurs between particles with electric charge. It is the second-strongest of the four fundamental interactions, after the strong force, and it is the dominant force in the interactions of a ...
and strong binding forces. Conversely, a ''negative''
cosmological constant In cosmology, the cosmological constant (usually denoted by the Greek capital letter lambda: ), alternatively called Einstein's cosmological constant, is the constant coefficient of a term that Albert Einstein temporarily added to his field eq ...
, which would correspond to a negative energy density and positive pressure, would cause even an open universe to re-collapse to a big crunch.


Flat universe

If the average density of the universe exactly equals the critical density so that \Omega = 1, then the geometry of the universe is flat: as in
Euclidean geometry Euclidean geometry is a mathematical system attributed to ancient Greek mathematics, Greek mathematician Euclid, which he described in his textbook on geometry: the ''Euclid's Elements, Elements''. Euclid's approach consists in assuming a small ...
, the sum of the angles of a triangle is 180 degrees and parallel lines continuously maintain the same distance. Measurements from the Wilkinson Microwave Anisotropy Probe have confirmed the universe is flat within a 0.4% margin of error. In the absence of dark energy, a flat universe expands forever but at a continually decelerating rate, with expansion asymptotically approaching zero. With dark energy, the expansion rate of the universe initially slows down, due to the effects of gravity, but eventually increases, and the ultimate fate of the universe becomes the same as that of an open universe.


Theories about the end of the universe

The fate of the universe may be determined by its density. The preponderance of evidence to date, based on measurements of the rate of expansion and the mass density, favors a universe that will continue to expand indefinitely, resulting in the "Big Freeze" scenario below. However, observations are not conclusive, and alternative models are still possible.


Big Freeze or Heat Death

The
Big Freeze The heat death of the universe (also known as the Big Chill or Big Freeze) is a hypothesis on the ultimate fate of the universe, which suggests the universe will evolve to a state of no thermodynamic free energy, and will therefore be unabl ...
(or Big Chill) is a scenario under which continued expansion results in a universe that
asymptotically In analytic geometry, an asymptote () of a curve is a line such that the distance between the curve and the line approaches zero as one or both of the ''x'' or ''y'' coordinates tends to infinity. In projective geometry and related contexts, ...
approaches
absolute zero Absolute zero is the lowest limit of the thermodynamic temperature scale, a state at which the enthalpy and entropy of a cooled ideal gas reach their minimum value, taken as zero kelvin. The fundamental particles of nature have minimum vibration ...
temperature. This scenario, in combination with the Big Rip scenario, is gaining ground as the most important hypothesis. It could, in the absence of dark energy, occur only under a flat or hyperbolic geometry. With a positive cosmological constant, it could also occur in a closed universe. In this scenario,
star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...
s are expected to form normally for 1012 to 1014 (1–100 trillion) years, but eventually the supply of gas needed for
star formation Star formation is the process by which dense regions within molecular clouds in The "medium" is present further soon.-->interstellar space
will be exhausted. As existing stars run out of fuel and cease to shine, the universe will slowly and inexorably grow darker. Eventually
black hole A black hole is a region of spacetime where gravitation, gravity is so strong that nothing, including light or other Electromagnetic radiation, electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts t ...
s will dominate the universe, which themselves will disappear over time as they emit
Hawking radiation Hawking radiation is theoretical black body radiation that is theorized to be released outside a black hole's event horizon because of relativistic quantum effects. It is named after the physicist Stephen Hawking, who developed a theoretical a ...
. Over infinite time, there would be a spontaneous
entropy Entropy is a scientific concept, as well as a measurable physical property, that is most commonly associated with a state of disorder, randomness, or uncertainty. The term and the concept are used in diverse fields, from classical thermodynam ...
decrease by the Poincaré recurrence theorem,
thermal fluctuations In statistical mechanics, thermal fluctuations are random deviations of a system from its average state, that occur in a system at equilibrium.In statistical mechanics they are often simply referred to as fluctuations. All thermal fluctuations b ...
, and the
fluctuation theorem The fluctuation theorem (FT), which originated from statistical mechanics, deals with the relative probability that the entropy of a system which is currently away from thermodynamic equilibrium (i.e., maximum entropy) will increase or decrease ov ...
. A related scenario is
heat death Heat death may refer to: *Heat death of the universe, a proposed cosmological event ** Heat death paradox, a philosophical examination of the cosmological event *Hyperthermia, injury up to and including death, from excessive heat *Thermal shock ...
, which states that the universe goes to a state of maximum
entropy Entropy is a scientific concept, as well as a measurable physical property, that is most commonly associated with a state of disorder, randomness, or uncertainty. The term and the concept are used in diverse fields, from classical thermodynam ...
in which everything is evenly distributed and there are no
gradient In vector calculus, the gradient of a scalar-valued differentiable function of several variables is the vector field (or vector-valued function) \nabla f whose value at a point p is the "direction and rate of fastest increase". If the gradi ...
s—which are needed to sustain
information processing Information processing is the change (processing) of information in any manner detectable by an observer. As such, it is a process that ''describes'' everything that happens (changes) in the universe, from the falling of a rock (a change in posit ...
, one form of which is
life Life is a quality that distinguishes matter that has biological processes, such as signaling and self-sustaining processes, from that which does not, and is defined by the capacity for growth, reaction to stimuli, metabolism, energ ...
. The heat death scenario is compatible with any of the three spatial models, but requires that the universe reaches an eventual temperature minimum.


Big Rip

The current
Hubble constant Hubble's law, also known as the Hubble–Lemaître law, is the observation in physical cosmology that galaxies are moving away from Earth at speeds proportional to their distance. In other words, the farther they are, the faster they are moving ...
defines a rate of acceleration of the universe not large enough to destroy local structures like galaxies, which are held together by gravity, but large enough to increase the space between them. A steady increase in the Hubble constant to infinity would result in all material objects in the universe, starting with galaxies and eventually (in a finite time) all forms, no matter how small, disintegrating into unbound
elementary particles In particle physics, an elementary particle or fundamental particle is a subatomic particle that is not composed of other particles. Particles currently thought to be elementary include electrons, the fundamental fermions (quarks, leptons, anti ...
, radiation and beyond. As the energy density, scale factor and expansion rate become infinite the universe ends as what is effectively a singularity. In the special case of phantom dark energy, which has supposed negative kinetic energy that would result in a higher rate of acceleration than other cosmological constants predict, a more sudden big rip could occur.


Big Crunch

The Big Crunch hypothesis is a symmetric view of the ultimate fate of the universe. Just as the Big Bang started as a cosmological expansion, this theory assumes that the average density of the universe will be enough to stop its expansion and the universe will begin contracting. The result is unknown; a simple estimation would have all the matter and space-time in the universe collapse into a dimensionless singularity back into how the universe started with the Big Bang, but at these scales unknown quantum effects need to be considered (see
Quantum gravity Quantum gravity (QG) is a field of theoretical physics that seeks to describe gravity according to the principles of quantum mechanics; it deals with environments in which neither gravitational nor quantum effects can be ignored, such as in the vi ...
). Recent evidence suggests that this scenario is unlikely but has not been ruled out, as measurements have been available only over a short period of time, relatively speaking, and could reverse in the future. This scenario allows the Big Bang to occur immediately after the Big Crunch of a preceding universe. If this happens repeatedly, it creates a
cyclic model A cyclic model (or oscillating model) is any of several cosmological models in which the universe follows infinite, or indefinite, self-sustaining cycles. For example, the oscillating universe theory briefly considered by Albert Einstein in 1930 t ...
, which is also known as an oscillatory universe. The universe could then consist of an infinite sequence of finite universes, with each finite universe ending with a Big Crunch that is also the Big Bang of the next universe. A problem with the cyclic universe is that it does not reconcile with the
second law of thermodynamics The second law of thermodynamics is a physical law based on universal experience concerning heat and Energy transformation, energy interconversions. One simple statement of the law is that heat always moves from hotter objects to colder objects ( ...
, as entropy would build up from oscillation to oscillation and cause the eventual
heat death Heat death may refer to: *Heat death of the universe, a proposed cosmological event ** Heat death paradox, a philosophical examination of the cosmological event *Hyperthermia, injury up to and including death, from excessive heat *Thermal shock ...
of the universe . Current evidence also indicates the universe is not closed. This has caused cosmologists to abandon the oscillating universe model. A somewhat similar idea is embraced by the
cyclic model A cyclic model (or oscillating model) is any of several cosmological models in which the universe follows infinite, or indefinite, self-sustaining cycles. For example, the oscillating universe theory briefly considered by Albert Einstein in 1930 t ...
, but this idea evades
heat death Heat death may refer to: *Heat death of the universe, a proposed cosmological event ** Heat death paradox, a philosophical examination of the cosmological event *Hyperthermia, injury up to and including death, from excessive heat *Thermal shock ...
because of an expansion of the
brane In string theory and related theories such as supergravity theories, a brane is a physical object that generalizes the notion of a point particle to higher dimensions. Branes are dynamical objects which can propagate through spacetime accordin ...
s that dilutes entropy accumulated in the previous cycle.


Big Bounce

The Big Bounce is a theorized scientific model related to the beginning of the known universe. It derives from the oscillatory universe or cyclic repetition interpretation of the Big Bang where the first cosmological event was the result of the collapse of a previous universe. According to one version of the Big Bang theory of cosmology, in the beginning the universe was infinitely dense. Such a description seems to be at odds with other more widely accepted theories, especially quantum mechanics and its
uncertainty principle In quantum mechanics, the uncertainty principle (also known as Heisenberg's uncertainty principle) is any of a variety of mathematical inequalities asserting a fundamental limit to the accuracy with which the values for certain pairs of physic ...
. Therefore, quantum mechanics has given rise to an alternative version of the Big Bang theory, specifically that the universe tunneled into existence and had a finite density consistent with quantum mechanics, before evolving in a manner governed by classical physics. Also, if the universe is closed, this theory would predict that once this universe collapses it will spawn another universe in an event similar to the Big Bang after a universal singularity is reached or a repulsive quantum force causes re-expansion. In simple terms, this theory states that the universe will continuously repeat the cycle of a Big Bang, followed up with a Big Crunch.


Cosmic uncertainty

Each possibility described so far is based on a very simple form for the dark energy equation of state. However, as the name is meant to imply, very little is currently known about the physics of
dark energy In physical cosmology and astronomy, dark energy is an unknown form of energy that affects the universe on the largest scales. The first observational evidence for its existence came from measurements of supernovas, which showed that the univer ...
. If the theory of
inflation In economics, inflation is an increase in the general price level of goods and services in an economy. When the general price level rises, each unit of currency buys fewer goods and services; consequently, inflation corresponds to a reductio ...
is true, the universe went through an episode dominated by a different form of dark energy in the first moments of the Big Bang, but inflation ended, indicating an equation of state far more complex than those assumed so far for present-day dark energy. It is possible that the dark energy equation of state could change again, resulting in an event that would have consequences which are extremely difficult to predict or parameterize. As the nature of dark energy and dark matter remain enigmatic, even hypothetical, the possibilities surrounding their coming role in the universe are currently unknown. None of these theoretic endings for the universe are certain. In other words, considering the universe is only around 14 billion years old, extrapolating the trends observed in the cosmic history so far to a considerably longer timescale can be criticized as being insufficiently substantiated.


Other possible fates to the universe

There are also some possible events, such as the Big Slurp, which would seriously harm the universe, although the universe as a whole would not be completely destroyed as a result.


Big Slurp

This theory posits that the universe currently exists in a false vacuum and that it could become a true vacuum at any moment. In order to best understand the false vacuum collapse theory, one must first understand the
Higgs field The Higgs boson, sometimes called the Higgs particle, is an elementary particle in the Standard Model of particle physics produced by the excited state, quantum excitation of the Higgs field, one of the field (physics), fields in particl ...
which permeates the universe. Much like an
electromagnetic field An electromagnetic field (also EM field or EMF) is a classical (i.e. non-quantum) field produced by (stationary or moving) electric charges. It is the field described by classical electrodynamics (a classical field theory) and is the classical c ...
, it varies in strength based upon its potential. A true vacuum exists so long as the universe exists in its lowest energy state, in which case the false vacuum theory is irrelevant. However, if the vacuum is not in its lowest energy state (a
false vacuum In quantum field theory, a false vacuum is a hypothetical vacuum that is relatively stable, but not in the most stable state possible. This condition is known as metastable. It may last for a very long time in that state, but could eventually d ...
), it could
tunnel A tunnel is an underground passageway, dug through surrounding soil, earth or rock, and enclosed except for the entrance and exit, commonly at each end. A pipeline is not a tunnel, though some recent tunnels have used immersed tube cons ...
into a lower-energy state. * * * * * * This is called ''
vacuum decay In quantum field theory, a false vacuum is a hypothetical vacuum that is relatively stable, but not in the most stable state possible. This condition is known as metastable. It may last for a very long time in that state, but could eventually ...
''. This has the potential to fundamentally alter our universe; in more audacious scenarios even the various
physical constant A physical constant, sometimes fundamental physical constant or universal constant, is a physical quantity that is generally believed to be both universal in nature and have constant value in time. It is contrasted with a mathematical constant, ...
s could have different values, severely affecting the foundations of
matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atoms, which are made up of interacting subatomic partic ...
,
energy In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of heat a ...
, and
spacetime In physics, spacetime is a mathematical model that combines the three dimensions of space and one dimension of time into a single four-dimensional manifold. Spacetime diagrams can be used to visualize relativistic effects, such as why differen ...
. It is also possible that all structures will be destroyed instantaneously, without any forewarning. However, only a portion of the universe would be destroyed by the Big Slurp while most of the universe would still be unaffected because galaxies located further than 4,200 megaparsecs (13 billion
light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...
s) away from each other are moving away from each other faster than the
speed of light The speed of light in vacuum, commonly denoted , is a universal physical constant that is important in many areas of physics. The speed of light is exactly equal to ). According to the special theory of relativity, is the upper limit ...
while the Big Slurp itself cannot expand faster than the speed of light.How are galaxies moving away faster than light?
/ref>


Observational constraints on theories

Choosing among these rival scenarios is done by 'weighing' the universe, for example, measuring the relative contributions of
matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atoms, which are made up of interacting subatomic partic ...
,
radiation In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes: * ''electromagnetic radiation'', such as radio waves, microwaves, infrared, visi ...
,
dark matter Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Dark matter is called "dark" because it does not appear to interact with the electromagnetic field, which means it does not ab ...
, and
dark energy In physical cosmology and astronomy, dark energy is an unknown form of energy that affects the universe on the largest scales. The first observational evidence for its existence came from measurements of supernovas, which showed that the univer ...
to the critical density. More concretely, competing scenarios are evaluated against data on
galaxy cluster A galaxy cluster, or a cluster of galaxies, is a structure that consists of anywhere from hundreds to thousands of galaxies that are bound together by gravity, with typical masses ranging from 1014 to 1015 solar masses. They are the second-l ...
ing and distant
supernova A supernova is a powerful and luminous explosion of a star. It has the plural form supernovae or supernovas, and is abbreviated SN or SNe. This transient astronomical event occurs during the last evolutionary stages of a massive star or when ...
s, and on the anisotropies in the
cosmic microwave background In Big Bang cosmology the cosmic microwave background (CMB, CMBR) is electromagnetic radiation that is a remnant from an early stage of the universe, also known as "relic radiation". The CMB is faint cosmic background radiation filling all spac ...
.


See also

*
Alan Guth Alan Harvey Guth (; born February 27, 1947) is an American theoretical physicist and cosmologist. Guth has researched elementary particle theory (and how particle theory is applicable to the early universe). He is Victor Weisskopf Professor of ...
*
Andrei Linde Andrei Dmitriyevich Linde (russian: Андре́й Дми́триевич Ли́нде; born March 2, 1948) is a Russian-American theoretical physicist and the Harald Trap Friis Professor of Physics at Stanford University. Linde is one of the ...
*
Anthropic principle The anthropic principle, also known as the "observation selection effect", is the hypothesis, first proposed in 1957 by Robert Dicke, that there is a restrictive lower bound on how statistically probable our observations of the universe are, beca ...
*
Arrow of time The arrow of time, also called time's arrow, is the concept positing the "one-way direction" or "asymmetry" of time. It was developed in 1927 by the British astrophysicist Arthur Eddington, and is an unsolved general physics question. This ...
*
Cosmological horizon A cosmological horizon is a measure of the distance from which one could possibly retrieve information. This observable constraint is due to various properties of general relativity, the expanding universe, and the physics of Big Bang cosmology. Co ...
*
Cyclic model A cyclic model (or oscillating model) is any of several cosmological models in which the universe follows infinite, or indefinite, self-sustaining cycles. For example, the oscillating universe theory briefly considered by Albert Einstein in 1930 t ...
*
Freeman Dyson Freeman John Dyson (15 December 1923 – 28 February 2020) was an English-American theoretical physicist and mathematician known for his works in quantum field theory, astrophysics, random matrices, mathematical formulation of quantum m ...
*
General relativity General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics ...
*
John D. Barrow John David Barrow (29 November 1952 – 26 September 2020) was an English cosmologist, theoretical physicist, and mathematician. He served as Gresham Professor of Geometry at Gresham College from 2008 to 2011. Barrow was also a writer of pop ...
*
Kardashev scale The Kardashev scale ( Russian: Шкала Кардашева, ''Shkala Kardasheva'') is a method of measuring a civilization's level of technological advancement based on the amount of energy it is able to use. The measure was proposed by S ...
*
Multiverse The multiverse is a hypothetical group of multiple universes. Together, these universes comprise everything that exists: the entirety of space, time, matter, energy, information, and the physical laws and constants that describe them. The di ...
* Shape of the universe *
Timeline of the far future While the future cannot be predicted with certainty, present understanding in various scientific fields allows for the prediction of some far-future events, if only in the broadest outline. These fields include astrophysics, which studies how ...
*
Zero-energy universe The zero-energy universe hypothesis proposes that the total amount of energy in the universe is exactly zero: its amount of positive energy in the form of matter is exactly canceled out by its negative energy in the form of gravity. Some physicist ...


References


Further reading

* * * * * * * * * *


External links

* Baez, J., 2004,
The End of the Universe
. * * Hjalmarsdotter, Linnea, 2005,
Cosmological parameters.
* *
A Brief History of the End of Everything
a
BBC Radio 4 BBC Radio 4 is a British national radio station owned and operated by the BBC that replaced the BBC Home Service in 1967. It broadcasts a wide variety of spoken-word programmes, including news, drama, comedy, science and history from the BBC' ...
series.
Cosmology at Caltech
*
Jamal Nazrul Islam Jamal Nazrul Islam (24 February 1939 – 16 March 2013) was a Bangladeshi mathematical physicist and cosmologist. He was a professor at University of Chittagong, served as a member of the advisory board at Shahjalal University of Science and Te ...
(1983):
The Ultimate Fate of the Universe
'.
Cambridge University Press Cambridge University Press is the university press of the University of Cambridge. Granted letters patent by Henry VIII of England, King Henry VIII in 1534, it is the oldest university press A university press is an academic publishing hou ...
,
Cambridge Cambridge ( ) is a university city and the county town in Cambridgeshire, England. It is located on the River Cam approximately north of London. As of the 2021 United Kingdom census, the population of Cambridge was 145,700. Cambridge bec ...
,
England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...
. . (Digital print version published in 2009). {{DEFAULTSORT:Ultimate Fate Of The universe Physical cosmology