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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 fu ...
, the Big Rip is a hypothetical
cosmological model 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 fu ...
concerning the ultimate fate of the universe, in which the
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 pa ...
of the
universe The universe is all of space and time and their contents. It comprises all of existence, any fundamental interaction, physical process and physical constant, and therefore all forms of matter and energy, and the structures they form, from s ...
, from stars and galaxies to atoms and subatomic particles, and even
spacetime In physics, spacetime, also called the space-time continuum, is a mathematical model that fuses the three dimensions of space and the one dimension of time into a single four-dimensional continuum. Spacetime diagrams are useful in visualiz ...
itself, is progressively torn apart by the
expansion of the universe The expansion of the universe is the increase in proper length, distance between Gravitational binding energy, gravitationally unbound parts of the observable universe with time. It is an intrinsic and extrinsic properties (philosophy), intrins ...
at a certain time in the future, until distances between particles will infinitely increase. According to the standard model of cosmology, the scale factor of the universe is accelerating, and, in the future era of cosmological constant dominance, will increase exponentially. But this expansion is similar for every moment of time (hence the exponential law—the expansion of a local volume is the same number of times over the same time interval), and is characterized by an unchanging, small
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 a galaxy is from the Earth, the faste ...
, effectively ignored by any bound material structures. By contrast, in the Big Rip scenario the Hubble constant increases to infinity in a finite time. According to recent studies, the universe is set for a constant expansion and heat death, because the
equation of state In physics and chemistry, 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 energy. Most mo ...
parameter ''w'' = −1. The possibility of sudden rip singularity occurs only for hypothetical matter ( phantom energy) with implausible physical properties.


Overview

The truth of the hypothesis relies on the type of
dark energy In physical cosmology and astronomy, dark energy is a proposed form of energy that affects the universe on the largest scales. Its primary effect is to drive the accelerating expansion of the universe. It also slows the rate of structure format ...
present in our
universe The universe is all of space and time and their contents. It comprises all of existence, any fundamental interaction, physical process and physical constant, and therefore all forms of matter and energy, and the structures they form, from s ...
. The type that could prove this hypothesis is a constantly increasing form of dark energy known as phantom energy. If the dark energy in the universe increases without limit, it could overcome all forces that hold the universe together. The key value is the
equation of state In physics and chemistry, 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 energy. Most mo ...
parameter ''w'', the
ratio In mathematics, a ratio () shows how many times one number contains another. For example, if there are eight oranges and six lemons in a bowl of fruit, then the ratio of oranges to lemons is eight to six (that is, 8:6, which is equivalent to the ...
between the dark energy pressure and its
energy density In physics, energy density is the quotient between the amount of energy stored in a given system or contained in a given region of space and the volume of the system or region considered. Often only the ''useful'' or extractable energy is measure ...
. If −1 < ''w'' < 0, the expansion of the universe tends to accelerate, but the dark energy tends to dissipate over time, and the Big Rip does not happen. Phantom energy has ''w'' < −1, which means that its density increases as the universe expands. A universe dominated by phantom energy is an accelerating universe, expanding at an ever-increasing rate. But this implies that the size of the
observable universe The observable universe is a Ball (mathematics), spherical region of the universe consisting of all matter that can be observation, observed from Earth; the electromagnetic radiation from these astronomical object, objects has had time to reach t ...
and the cosmological event horizon is continually shrinking—the distance at which objects can influence an observer becomes ever closer, and the distance over which interactions can propagate becomes ever shorter. When the size of the horizon becomes smaller than any particular structure, no interaction by any of the
fundamental forces In physics, the fundamental interactions or fundamental forces are interactions in nature that appear not to be reducible to more basic interactions. There are four fundamental interactions known to exist: * gravity * electromagnetism * weak int ...
can occur between the most remote parts of the structure, and the structure is "ripped apart". The progression of time itself will stop. The model implies that after a finite time there will be a final singularity, called the "Big Rip", in which the observable universe eventually reaches zero size and all distances diverge to infinite values. The authors of this hypothesis, led by Robert R. Caldwell of
Dartmouth College Dartmouth College ( ) is a Private university, private Ivy League research university in Hanover, New Hampshire, United States. Established in 1769 by Eleazar Wheelock, Dartmouth is one of the nine colonial colleges chartered before the America ...
, calculate the time from the present to the Big Rip to be t_\mathrm - t_ \approx \frac where ''w'' is defined above, ''H''0 is Hubble's constant and ''Ω''m is the present value of the density of all the matter in the universe. Observations of galaxy cluster speeds by the Chandra X-ray Observatory seem to suggest the value of ''w'' is between approximately −0.907 and −1.075, meaning the Big Rip cannot be ruled out. Based on the above equation, if the observation determines that ''w'' is less than −1 but greater than or equal to −1.075, the Big Rip would occur in approximately 152 billion years at the earliest. More recent data from Planck mission indicates the value of ''w'' to be −1.028 (±0.031), pushing the earliest possible time of Big Rip to approximately 200 billion years into the future.


Hypothetical example

In their paper, the authors consider a hypothetical example with ''w'' = −1.5, ''H''0 = 70 km/s/Mpc, and ''Ω''m = 0.3, in which case the Big Rip would happen approximately 22 billion years from the present. In this scenario, galaxies would first be separated from each other about 200 million years before the Big Rip. About 60 million years before the Big Rip, galaxies would begin to disintegrate as gravity becomes too weak to hold them together.
Planetary system A planetary system is a set of gravity, gravitationally bound non-stellar Astronomical object, bodies in or out of orbit around a star or star system. Generally speaking, systems with one or more planets constitute a planetary system, although ...
s like the
Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...
would become gravitationally unbound about three months before the Big Rip, and planets would fly off into the rapidly expanding universe. In the last minutes, stars and planets would be torn apart, and the now-dispersed
atom Atoms are the basic particles of the chemical elements. An atom consists of a atomic nucleus, nucleus of protons and generally neutrons, surrounded by an electromagnetically bound swarm of electrons. The chemical elements are distinguished fr ...
s would be destroyed about 10−19 seconds before the end (the atoms will first be
ionized Ionization or ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule i ...
as
electron The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...
s fly off, followed by the dissociation of the
atomic nuclei The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom, discovered in 1911 by Ernest Rutherford at the University of Manchester based on the 1909 Geiger–Marsden gold foil experiment. Aft ...
). At the time the Big Rip occurs, even spacetime itself would be ripped apart and the scale factor would be infinity.


Observed universe

Evidence indicates ''w'' to be very close to −1 in our universe, which makes ''w'' the dominating term in the equation. The closer ''w'' is to −1, the closer the denominator is to zero and the further the Big Rip is in the future. If ''w'' were exactly −1, the Big Rip could not happen, regardless of the values of ''H''0 or ''Ω''m. According to the latest cosmological data available, the uncertainties are still too large to discriminate among the three cases ''w'' < −1, ''w'' = −1, and ''w'' > −1. Moreover, it is nearly impossible to measure ''w'' to be exactly at −1 due to statistical fluctuations. This means that the measured value of ''w'' can be arbitrarily close to −1 but not exactly at −1, hence the earliest possible date of the Big Rip can be pushed back further with more accurate measurements but the Big Rip is very difficult to completely rule out.


See also

* * * * * * * " Last Contact" – A short story describing what Big Rip would be like from an everyday perspective


References


External links

* * * {{Portal bar, Astronomy, Stars, Outer space Dark energy 2003 introductions 2003 in science Ultimate fate of the universe Physical cosmology