query: what was the role of dark energy in the early universe

pos: Dark energy negative pressure field, similar in concept to dark energy, could drive cosmic inflation in the very early universe. Inflation postulates that some repulsive force, qualitatively similar to dark energy, resulted in an enormous and exponential expansion of the universe slightly after the Big Bang. Such expansion is an essential feature of most current models of the Big Bang. However, inflation must have occurred at a much higher energy density than the dark energy we observe today and is thought to have completely ended when the universe was just a fraction of a second old. It is unclear what relation, if

pos: Dark energy negative pressure field, similar in concept to dark energy, could drive cosmic inflation in the very early universe. Inflation postulates that some repulsive force, qualitatively similar to dark energy, resulted in an enormous and exponential expansion of the universe slightly after the Big Bang. Such expansion is an essential feature of most current models of the Big Bang. However, inflation must have occurred at a much higher energy density than the dark energy we observe today and is thought to have completely ended when the universe was just a fraction of a second old. It is unclear what relation, if

neg: Ultimate fate of the universe 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 parametrize. 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. Choosing among these rival scenarios is done by 'weighing' the universe, for example, measuring the relative contributions

neg: Physics a central role in all modern cosmological theories. In the early 20th century, Hubble's discovery that the universe is expanding, as shown by the Hubble diagram, prompted rival explanations known as the steady state universe and the Big Bang. The Big Bang was confirmed by the success of Big Bang nucleosynthesis and the discovery of the cosmic microwave background in 1964. The Big Bang model rests on two theoretical pillars: Albert Einstein's general relativity and the cosmological principle. Cosmologists have recently established the ΛCDM model of the evolution of the universe, which includes cosmic inflation, dark energy, and dark matter.

neg: History of subatomic physics it was tentatively confirmed that the newly discovered particle was a Higgs Boson. Although they have never been seen, Higgslike fields play an important role in theories of the universe and in string theory. Under certain conditions, according to the strange accounting of Einsteinian physics, they can become suffused with energy that exerts an antigravitational force. Such fields have been proposed as the source of an enormous burst of expansion, known as inflation, early in the universe and, possibly, as the secret of the dark energy that now seems to be speeding up the expansion of the universe. Modern theoretical

neg: Sergei Odintsov of view to dark energy: dark energy is caused by a modification of gravitational theory. Based on this idea and developing it Odintsov and Shin'ichi Nojiri proposed the first fundamental unified picture for the evolution of the universe based on modified gravity. According to this the evolution of the universe changes the gravitational theory, so that modified gravity changes the evolution of the universe making it to be accelerating at the very early and very late epoch. Later, they also demonstrated that such unified inflationary-dark energy universe may be achieved in modified Gauss-Bonnet gravity and non-local gravity. This picture became

neg: Universe widely accepted model of our universe. It suggests that about [2015] of the mass and energy in the universe is a scalar field known as dark energy which is responsible for the current expansion of space, and about 25.8% [2015] is dark matter. Ordinary ("baryonic") matter is therefore only 4.9% [2015] of the physical universe. Stars, planets, and visible gas clouds only form about 6% of ordinary matter, or about 0.3% of the entire universe. There are many competing hypotheses about the ultimate fate of the universe and about what, if anything, preceded the Big Bang, while other physicists and

neg: National Optical Astronomy Observatory wavelengths. The Blanco 4m played the central role in discovery of Dark Energy, a poorly understood component to the universe which is currently causing the universe to accelerate in its expansion. The Blanco began hosting a new 3-degree field of view camera called the Dark Energy Camera, also known as DECam, in 2012. This camera is being built at Fermilab in Chicago, USA, and will be operated by CTIO. This instrument was built to execute the Dark Energy Survey, an undertaking to image a large part of the sky to faint light levels, detecting galaxy large scale structure as a

neg: Scale factor (cosmology) dominated by dark energy, but examination of the roles of matter and radiation are most important for understanding the early universe. Using the dimensionless scale factor to characterize the expansion of the universe, the effective energy densities of radiation and matter scale differently. This leads to a radiation-dominated era in the very early universe but a transition to a matter-dominated era at a later time and, since about 4 billion years ago, a subsequent dark-energy-dominated era. Some insight into the expansion can be obtained from a Newtonian expansion model which leads to a simplified version of the Friedman equation. It

neg: Dark energy first proposed by Einstein as a mechanism to obtain a solution of the gravitational field equation that would lead to a static universe, effectively using dark energy to balance gravity. Einstein gave the cosmological constant the symbol Λ (capital lambda). Einstein stated that the cosmological constant required that `empty space takes the role of gravitating negative masses which are distributed all over the interstellar space'.. The mechanism was an example of fine-tuning, and it was later realized that Einstein's static universe would not be stable: local inhomogeneities would ultimately lead to either the runaway expansion or contraction of the universe.

neg: Dark energy different facets of the same unknown substance, or postulate that cold dark matter decays into dark energy. Another class of theories that unifies dark matter and dark energy are suggested to be covariant theories of modified gravities. These theories alter the dynamics of the space-time such that the modified dynamic stems what have been assigned to the presence of dark energy and dark matter. The density of dark energy might have varied in time over the history of the universe. Modern observational data allow for estimates of the present density. Using baryon acoustic oscillations, it is possible to investigate the

neg: Dark Energy Spectroscopic Instrument in the Sonoran Desert 55 miles distant from Tucson, Arizona. The expansion history and large-scale structure of the Universe is a key prediction of cosmological models, and DESI observations will permit scientists to probe diverse aspects of cosmology, from dark energy to alternatives to General Relativity to neutrino masses to the early Universe. The data from DESI will be used to create three-dimensional maps of the distribution of matter covering an unprecedented volume of the Universe with unparalleled detail. This will provide insight into the nature of dark energy and establish whether cosmic acceleration is due to a cosmic-scale modification

neg: Zero-point energy Universe appears to be the same in all directions (isotropic), why the cosmic microwave background radiation is distributed evenly, why the Universe is flat, and why no magnetic monopoles have been observed. The mechanism for inflation is unclear, it is similar in effect to dark energy but is a far more energetic and short lived process. As with dark energy the best explanation is some form of vacuum energy arising from quantum fluctuations. It may be that inflation caused baryogenesis, the hypothetical physical processes that produced an asymmetry (imbalance) between baryons and antibaryons produced in the very early universe, but

neg: Universe million years and 1 billion years, and also for seeding the universe with elements heavier than helium, through stellar nucleosynthesis. The Universe also contains a mysterious energy - possibly a scalar field - called dark energy, the density of which does not change over time. After about 9.8 billion years, the Universe had expanded sufficiently so that the density of matter was less than the density of dark energy, marking the beginning of the present dark-energy-dominated era. In this era, the expansion of the Universe is accelerating due to dark energy. Of the four fundamental interactions, gravitation is the dominant

neg: Cosmological constant density to stop the universe from expanding forever. This ratio is usually denoted Ω, and is estimated to be , according to results published by the Planck Collaboration in 2018. In a flat universe, Ω is the fraction of the energy of the universe due to the cosmological constant, i.e., what we would intuitively call the fraction of the universe that is made up of dark energy. Note that this value changes over time: the critical density changes with cosmological time, but the energy density due to the cosmological constant remains unchanged throughout the history of the universe: the amount

neg: Rachel Bean community, specifically teams and missions surrounding dark energy in the universe. LSST, the Dark Energy Spectroscopic Instrument (DESI), and the Euclid mission are just a few teams that she is a part of that are all focused on the behavior of dark energy and how it affects our universe and its expansion. She has been the recipient of various awards including the Presidential Early Career Award for Scientists and Engineers (PECASE), a for excellence in research and teaching, and a co-recipient of a NASA Group Achievement Award and the Gruber Prize. Rachel Bean Rachel Bean is an American astronomer, currently

neg: Dark energy dark energy and 27.4% of a combination of dark matter and baryonic matter. The existence of dark energy, in whatever form, is needed to reconcile the measured geometry of space with the total amount of matter in the universe. Measurements of cosmic microwave background (CMB) anisotropies indicate that the universe is close to flat. For the shape of the universe to be flat, the mass-energy density of the universe must be equal to the critical density. The total amount of matter in the universe (including baryons and dark matter), as measured from the CMB spectrum, accounts for only about 30%

neg: Chronology of the universe by the cosmologist community. By far the most accepted understanding is that this is due to an unknown form of energy which has been given the name "dark energy". "Dark" in this context means that it is not directly observed, but can currently only be studied by examining the effect it has on the universe. Research is ongoing to understand this dark energy. Dark energy is now believed to be the single largest component of the universe, as it constitutes about 68.3% of the entire mass-energy of the physical universe. Dark energy is believed to act like a cosmological constant

neg: Dark energy Dark energy In physical cosmology and astronomy, dark energy is an unknown form of energy which is hypothesized to permeate all of space, tending to accelerate the expansion of the universe. Dark energy is the most accepted hypothesis to explain the observations since the 1990s indicating that the universe is expanding at an accelerating rate. Assuming that the standard model of cosmology is correct, the best current measurements indicate that dark energy contributes 68% of the total energy in the present-day observable universe. The mass–energy of dark matter and ordinary (baryonic) matter contribute 27% and 5%, respectively, and other components

neg: Hydrogen Intensity and Real-time Analysis eXperiment known about it beyond the fact that it must currently comprise approximately 70% of the energy density of the universe. Dark matter also plays a significant role in the growth of structures within the universe. It is believed to be a form of matter that interacts with the gravitational force, but not the electromagnetic force, and it is known to make up approximately 25% of the energy density of the universe, but the exact nature of it is not understood. The remaining 5% of the energy density of the universe is the baryonic matter which we can see; the stars,

neg: Dark energy all professional astrophysicists are confident that dark energy exists, and that none of the competing theories successfully explain observations to the same level of precision as standard dark energy. Cosmologists estimate that the acceleration began roughly 5 billion years ago. Before that, it is thought that the expansion was decelerating, due to the attractive influence of matter. The density of dark matter in an expanding universe decreases more quickly than dark energy, and eventually the dark energy dominates. Specifically, when the volume of the universe doubles, the density of dark matter is halved, but the density of dark energy is

neg: Dark energy scenario, the Local Group would ultimately suffer heat death, just as was hypothesized for the flat, matter-dominated universe before measurements of cosmic acceleration. There are other, more speculative ideas about the future of the universe. The phantom energy model of dark energy results in "divergent" expansion, which would imply that the effective force of dark energy continues growing until it dominates all other forces in the universe. Under this scenario, dark energy would ultimately tear apart all gravitationally bound structures, including galaxies and solar systems, and eventually overcome the electrical and nuclear forces to tear apart atoms themselves, ending the

neg: Matter the early universe and the Big Bang theory require that this matter have energy and mass, but is not composed ordinary baryons (protons and neutrons). The commonly accepted view is that most of the dark matter is non-baryonic in nature. As such, it is composed of particles as yet unobserved in the laboratory. Perhaps they are supersymmetric particles, which are not Standard Model particles, but relics formed at very high energies in the early phase of the universe and still floating about. In cosmology, "dark energy" is the name given to source of the repelling influence that is accelerating the

neg: Cosmic microwave background the deep sky when the cosmos was about years old. The imprint reflects ripples that arose as early, in the existence of the universe, as the first nonillionth of a second. Apparently, these ripples gave rise to the present vast cosmic web of galaxy clusters and dark matter. Based on the 2013 data, the universe contains 4.9% ordinary matter, 26.8% dark matter and 68.3% dark energy. On 5 February 2015, new data was released by the Planck mission, according to which the age of the universe is billion years old and the Hubble constant was measured to be . Additional

neg: Canadian Hydrogen Intensity Mapping Experiment Earth turns. CHIME is a partnership between the University of British Columbia, McGill University, the University of Toronto and the Canadian National Research Council's Dominion Radio Astrophysical Observatory. A first light ceremony was held on 7 September 2017 to inaugurate the commissioning phase. One of the biggest puzzles in contemporary cosmology is why the expansion of the Universe is accelerating.<ref name="albrecht/etal"></ref> About seventy percent of the Universe today consists of so-called dark energy that counteracts gravity's attractive force and causes this acceleration. Very little is known about what dark energy is. CHIME will make precise measurements of the acceleration of

neg: Astronomy In the course of this expansion, the Universe underwent several evolutionary stages. In the very early moments, it is theorized that the Universe experienced a very rapid cosmic inflation, which homogenized the starting conditions. Thereafter, nucleosynthesis produced the elemental abundance of the early Universe. (See also nucleocosmochronology.) When the first neutral atoms formed from a sea of primordial ions, space became transparent to radiation, releasing the energy viewed today as the microwave background radiation. The expanding Universe then underwent a Dark Age due to the lack of stellar energy sources. A hierarchical structure of matter began to form from minute

neg: Outer space indicate that the spatial geometry of the observable universe is "flat", meaning that photons on parallel paths at one point remain parallel as they travel through space to the limit of the observable universe, except for local gravity. The flat Universe, combined with the measured mass density of the Universe and the accelerating expansion of the Universe, indicates that space has a non-zero vacuum energy, which is called dark energy. Estimates put the average energy density of the present day Universe at the equivalent of 5.9 protons per cubic meter, including dark energy, dark matter, and baryonic matter (ordinary matter

neg: Cosmology observational astronomy and particle physics; more specifically, a standard parameterization of the Big Bang with dark matter and dark energy, known as the Lambda-CDM model. Theoretical astrophysicist David N. Spergel has described cosmology as a "historical science" because "when we look out in space, we look back in time" due to the finite nature of the speed of light. Physics and astrophysics have played a central role in shaping the understanding of the universe through scientific observation and experiment. Physical cosmology was shaped through both mathematics and observation in an analysis of the whole universe. The universe is generally understood

neg: Big Bang estimated to be less than 0.0062. Independent lines of evidence from Type Ia supernovae and the CMB imply that the universe today is dominated by a mysterious form of energy known as dark energy, which apparently permeates all of space. The observations suggest 73% of the total energy density of today's universe is in this form. When the universe was very young, it was likely infused with dark energy, but with less space and everything closer together, gravity predominated, and it was slowly braking the expansion. But eventually, after numerous billion years of expansion, the growing abundance of dark energy

neg: Physical cosmology nucleosynthesis and the cosmic microwave background, it must not cluster in haloes like baryons and dark matter. There is strong observational evidence for dark energy, as the total energy density of the universe is known through constraints on the flatness of the universe, but the amount of clustering matter is tightly measured, and is much less than this. The case for dark energy was strengthened in 1999, when measurements demonstrated that the expansion of the universe has begun to gradually accelerate. Apart from its density and its clustering properties, nothing is known about dark energy. "Quantum field theory" predicts a

neg: Gravitationally-interacting massive particles energy. This would roughly confirm Einstein's hope in 1919 that all particles in the universe would follow the traceless version of his equation. If we identify all matter as the sum of dark energy plus dark matter in the form of GIMPs, his expectation would turn out to have been "almost" right. Matter would play a similar role as the point charges in the homogenous Maxwell equation formula_1 in which delta functions are ignored. The sum of dark matter plus dark energy makes up 76% of all matter, which is sufficient to allow computer simulations to produce a good impression

neg: Accelerating expansion of the universe density of dark energy (see equation of state) and, eventually, dark energy dominates. Specifically, when the scale of the universe doubles, the density of matter is reduced by a factor of 8, but the density of dark energy is nearly unchanged (it is exactly constant if the dark energy is a cosmological constant). In models where dark energy is a cosmological constant, the universe will expand exponentially with time in the far future, coming closer and closer to a de Sitter spacetime. This will eventually lead to all evidence for the Big Bang disappearing, as the cosmic microwave background is

neg: Ultimate fate of the universe so as to allow for this possible acceleration, nearly always by invoking dark energy, which in its simplest form is just a positive cosmological constant. In general, dark energy is a catch-all term for any hypothesised field with negative pressure, usually with a density that changes as the universe expands. The current scientific consensus of most cosmologists is that the ultimate fate of the universe depends on its overall shape, how much dark energy it contains, and on the equation of state which determines how the dark energy density responds to the expansion of the universe. Recent observations conclude, from

neg: Big Bang matter, 4.6% regular matter and less than 1% neutrinos. According to theory, the energy density in matter decreases with the expansion of the universe, but the dark energy density remains constant (or nearly so) as the universe expands. Therefore, matter made up a larger fraction of the total energy of the universe in the past than it does today, but its fractional contribution will fall in the far future as dark energy becomes even more dominant. The dark energy component of the universe has been explained by theorists using a variety of competing theories including Einstein's cosmological constant but also

neg: Wilkinson Microwave Anisotropy Probe cosmic microwave background. The map suggests the universe is slightly older than previously thought. According to the map, subtle fluctuations in temperature were imprinted on the deep sky when the cosmos was about 370,000 years old. The imprint reflects ripples that arose as early, in the existence of the universe, as the first nonillionth (10) of a second. Apparently, these ripples gave rise to the present vast cosmic web of galaxy clusters and dark matter. Based on the 2013 data, the universe contains 4.9% ordinary matter, 26.8% dark matter and 68.3% dark energy. On 5 February 2015, new data was

neg: Big Bang 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

neg: Wilkinson Microwave Anisotropy Probe – 72.8% (within 1.6%) as non 'particle' background, and dark matter – 22.7% (within 1.4%) of non baryonic (sub atomic) 'particle' energy. This leaves matter, or baryonic particles (atoms) at only 4.56% (within 0.16%). On December 20, 2012, the nine-year WMAP data and related images were released. billion-year-old temperature fluctuations and a temperature range of ± 200 microkelvins are shown in the image. In addition, the study found that 95% of the early universe is composed of dark matter and dark energy, the curvature of space is less than 0.4 percent of "flat" and the universe emerged from the cosmic

neg: Varun Sahni to physical sciences in 2000. Sahni is reported to have studied the universe, more specifically its large-scale structure, the early inflationary phase and cosmological constant. His achievements include the establishment of a cosmic no-hair theorem related to inflation, analysis of the universe structure using self-developed statistical methods, discovery of novel models of dark energy and dark matter, design of unified models of Inflation and dark energy and the elucidation of Big Bang theory using Braneworld physics. His studies have been documented by way of a number of articles and the online article repository of the Indian Academy of Sciences has

neg: Dark matter is usually ascribed to dark energy. Since observations indicate the universe is almost flat, it is expected that the total energy density of everything in the universe to sum to 1 (Ω ~ 1). The measured dark energy density is Ω = ~0.690; the observed ordinary (baryonic) matter energy density is Ω = ~0.0482 and the energy density of radiation is negligible. This leaves a missing Ω = ~0.258 that nonetheless behaves like matter (see technical definition section above)—dark matter. Baryon acoustic oscillations (BAO) are fluctuations in the density of the visible baryonic matter (normal matter) of the universe on

neg: De Sitter universe inflation in the early universe can be performed in de Sitter space rather than a more realistic inflationary universe. By using the de Sitter universe instead, where the expansion is truly exponential, there are many simplifications. De Sitter universe A de Sitter universe is a cosmological solution to the Einstein field equations of general relativity, named after Willem de Sitter. It models the universe as spatially flat and neglects ordinary matter, so the dynamics of the universe are dominated by the cosmological constant, thought to correspond to dark energy in our universe or the inflaton field in the early universe.

neg: The 4 Percent Universe The 4 Percent Universe The 4 Percent Universe: Dark Matter, Dark Energy, and the Race to Discover the Rest of Reality is a nonfiction book by writer and professor Richard Panek and published by Houghton Mifflin Harcourt on January 10, 2011. The book's namesake comes from the scientific confusion over how ordinary matter makes up only four percent of the mass-energy in the universe, with the rest consisting of mysterious dark matter and dark energy that are both invisible and almost impossible to detect. It is due to dark matter that galaxies are able to keep their shape, with the

neg: Joint Dark Energy Mission the universe, scientists need to see greater redshifts from supernovas than what is seen from Earth. The SNAP can detect redshifts of 1.7 from distant supernovas up to 10 billion light years away. At this distance, the acceleration of the universe will be easily seen. To measure the presence of dark energy, a process called weak lensing will be used. The SNAP will use an optical setup called the three-mirror anastigmat. This consists of a main mirror with a diameter of 2 meters to take in light. It reflects this light to a second mirror. Then this light is transferred

neg: Quintessence (physics) would cause a big rip in the universe due to the growing energy density of dark energy which would cause the expansion of the universe to increase at a faster-than-exponential rate. Holographic Dark Energy models compared to Cosmological Constant models, imply a high degeneracy. It has been suggested that dark energy might originate from quantum fluctuations of spacetime, and are limited by the event horizon of the universe. Studies with quintessence dark energy found that it dominates gravitational collapse in a spacetime simulation, based on the holographic thermalization. These results show that the smaller the state parameter of quintessence is,

neg: George Chapline Jr. vacuum. The Chapline–Laughlin theory predicts that space-times with a large vacuum energy are unstable to the formation of dark energy stars; in the context of the early universe, this provides a natural explanation for both dark matter and the metric fluctuations which led to the formation of galaxies. A remarkable astrophysical prediction of the Chapline–Laughlin theory is that dark energy stars should be prolific sources of positrons because nucleons decay when they encounter the surface of a dark energy star, which may explain the strong positron annihilation radiation observed coming from the central region of our galaxy. Chapline's interest in

neg: Sachs–Wolfe effect is also caused by gravitational redshift, but it occurs between the surface of last scattering and the Earth, so it is not part of the primordial CMB. It occurs when the Universe is dominated in its energy density by something other than matter. If the Universe is dominated by matter, then large-scale gravitational potential energy wells and hills do not evolve significantly. If the Universe is dominated by radiation, or by dark energy, though, those potentials do evolve, subtly changing the energy of photons passing through them. There are two contributions to the ISW effect. The "early-time" ISW occurs immediately

neg: Observable universe In this context, mass refers to ordinary matter and includes the interstellar medium (ISM) and the intergalactic medium (IGM). However, it excludes dark matter and dark energy. This quoted value for the mass of ordinary matter in the universe can be estimated based on critical density. The calculations are for the observable universe only as the volume of the whole is unknown and may be infinite. Critical density is the energy density for which the universe is flat. If there is no dark energy, it is also the density for which the expansion of the universe is poised between continued

neg: Michael Bolte of the University of Chicago he published in 1995 an early prediction of what became known as "Dark Energy" as a dominate component of the Universe. With Kathryn Johnston (Columbia) and Lars Hernquist (Harvard) published one of the early papers on identifying "fossil" structures in the Galactic halo left by tidally shredded dwarf galaxies: "Fossil Signatures of Ancient Accretion Events in the Halo" With Don Vandenberg (University of Victoria) and Peter Stetson (Herzberg Institute for Astrophysics) he published a new technique for measuring age differences between globular clusters that was insensitive to the cluster distances, reddening and overall metallicity. This

neg: Accelerating expansion of the universe and in analyses of the clustering of galaxies. The accelerated expansion of the universe is thought to have begun since the universe entered its dark-energy-dominated era roughly 5 billion years ago. Within the framework of general relativity, an accelerated expansion can be accounted for by a positive value of the cosmological constant , equivalent to the presence of a positive vacuum energy, dubbed "dark energy". While there are alternative possible explanations, the description assuming dark energy (positive ) is used in the current standard model of cosmology, which also includes cold dark matter (CDM) and is known as the Lambda-CDM

neg: De Sitter universe De Sitter universe A de Sitter universe is a cosmological solution to the Einstein field equations of general relativity, named after Willem de Sitter. It models the universe as spatially flat and neglects ordinary matter, so the dynamics of the universe are dominated by the cosmological constant, thought to correspond to dark energy in our universe or the inflaton field in the early universe. According to the models of inflation and current observations of the accelerating universe, the concordance models of physical cosmology are converging on a consistent model where our universe was best described as a de Sitter universe

neg: The Beginning and End of the Universe how we came to know what we know, such as how elements are forged inside stars and how gravity provides the key to the fate of the universe, and what we don't know, such as the nature of dark matter and dark energy. Jack Seale, writing for "The Guardian", commends the Al-Khalili for, "his usual mix of spectacular locations, clear explanations, a few gags and the stories of scientists who made crucial breakthroughs." Gary Rose, writing for "RadioTimes" however points out that while Al-Khalili is "as watchable as ever", this series, unlike his earlier series "Atom", covers well-trodden ground and

neg: Weakly interacting massive particles the early Universe, the dark matter particle and its antiparticle would have been both forming from and annihilating into lighter particles. As the Universe expanded and cooled, the average thermal energy of these lighter particles decreased and eventually became insufficient to form a dark matter particle-antiparticle pair. The annihilation of the dark matter particle-antiparticle pairs, however, would have continued, and the number density of dark matter particles would have begun to decrease exponentially. Eventually, however, the number density would become so low that the dark matter particle and antiparticle interaction would cease, and the number of dark matter particles would

neg: Big Rip eventually in many billions of years' time the scale factor would become infinitely large, pulling even subatomic particles and the fabric of spacetime apart, ending our universe. The possibility of sudden singularities and crunch or rip singularities occur only for hypothetical matter with implausible physical properties. The hypothesis relies crucially on the type of dark energy in the universe. The type that could cause this hypothesis is a constantly increasing form of dark 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

neg: Dark energy universe in a "Big Rip". It is also possible the universe may never have an end and continue in its present state forever (see The second thermodynamics law as a law of disorder). On the other hand, dark energy might dissipate with time or even become attractive. Such uncertainties leave open the possibility that gravity might yet rule the day and lead to a universe that contracts in on itself in a "Big Crunch", or that there may even be a dark energy cycle, which implies a cyclic model of the universe in which every iteration (Big Bang then eventually

neg: Shape of the universe the critical energy density, that is, the mass energy needed for a universe to be flat. Put another way, One can experimentally calculate this to determine the curvature two ways. One is to count up all the mass-energy in the universe and take its average density then divide that average by the critical energy density. Data from Wilkinson Microwave Anisotropy Probe (WMAP) as well as the Planck spacecraft give values for the three constituents of all the mass-energy in the universe – normal mass (baryonic matter and dark matter), relativistic particles (photons and neutrinos), and dark energy or the cosmological

neg: Dark Energy Spectroscopic Instrument of General Relativity. DESI will be transformative in the understanding of dark energy and the expansion rate of the Universe at early times, one of the greatest mysteries in the understanding of the physical laws. DESI will measure the expansion history of the Universe using the baryon acoustic oscillations (BAO) imprinted in the clustering of galaxies, quasars, and the intergalactic medium.<ref name="seo/eisenstein"></ref> The BAO technique is a robust way to extract cosmological distance information from the clustering of matter and galaxies. It relies only on very large-scale structure and it does so in a manner that enables scientists to separate

neg: Planck (spacecraft) that arose as early in the existence of the Universe as the first nonillionth (10) of a second. It is currently theorised that these ripples gave rise to the present vast cosmic web of galactic clusters and dark matter. According to the team, the Universe is x10 years old, and contains ordinary matter, dark matter and dark energy. The Hubble constant was also measured to be . Results from an analysis of "Planck" full mission were made public on 1 December 2014 at a conference in Ferrara, Italy. A full set of papers detailing the mission results were released in

neg: Jo Dunkley her models to understand the universe from cosmological observations. Alongside estimating how much the universe weighs, Dunkley can identify the proportions of Dark Energy and Dark Matter. She used gravitational lensing within the CMB as evidence for Dark Energy within the universe, selected by Physics Today as a highlight of 2011. Dunkley rejoined Princeton in 2016. Her new research, using the Simons Observatory, looks for “new physics, complexities and extra particles that could have existed when the universe was very young,”. In 2017, she was awarded the Breakthrough Prize for Physics with 22 members of the NASA WMAP Science Team.

neg: Dark energy high significance in 2008 by Ho "et al." and Giannantonio "et al." A new approach to test evidence of dark energy through observational Hubble constant data (OHD) has gained significant attention in recent years. The Hubble constant, "H"("z"), is measured as a function of cosmological redshift. OHD directly tracks the expansion history of the universe by taking passively evolving early-type galaxies as “cosmic chronometers”. From this point, this approach provides standard clocks in the universe. The core of this idea is the measurement of the differential age evolution as a function of redshift of these cosmic chronometers. Thus, it provides

neg: Dark Energy Survey composition of our Universe and its corresponding expansion history: where formula_2 is the luminosity distance, z is the redshift, c is the speed of light, formula_6 is the local expansion rate, formula_7 is the matter content of the universe, formula_8 is the dark energy content of the universe, formula_9 due to curvature, and formula_10 is the dark energy equation of state parameter. For different models of Universe, we can thus infer the luminosity distance relationship with redshift respectively. Comparing the redshift with the distance for a large number of supernovae, we can derive the history of the cosmic expansion rate

neg: VLT Survey Telescope of dark energy. The survey aims to detect small-amplitude oscillations known as ´baryon wiggles’ that can be detected in the power-spectrum of galaxies and are the imprint of sound waves in the early Universe on the distribution of matter. The dark energy equation of state can be determined by measuring the features of these oscillations. Extrapolating from previous surveys, it is very likely that the VST will make some unexpected discoveries with major consequences for the current understanding of the Universe. The first released VST image (below on the right) shows the spectacular star-forming region Messier 17, also known as

neg: Accelerating expansion of the universe (). Current observations allow the possibility of a cosmological model containing a dark energy component with equation of state . This phantom energy density would become infinite in finite time, causing such a huge gravitational repulsion that the universe would lose all structure and end in a Big Rip. For example, for and =70 km·s·Mpc, the time remaining before the universe ends in this Big Rip is 22 billion years. There are many alternative explanations for the accelerating universe. Some examples are quintessence, a proposed form of dark energy with a non-constant state equation, whose density decreases with time. Dark

neg: Future of an expanding universe given the non-zero probability of producing a new Big Bang in roughly 10 years. Over an infinite time there could be a spontaneous entropy decrease, by a Poincaré recurrence or through thermal fluctuations (see also fluctuation theorem). The possibilities above are based on a simple form of dark energy. But the physics of dark energy are still a very active area of research, and the actual form of dark energy could be much more complex. For example, during inflation dark energy affected the universe very differently than it does today, so it's possible that dark energy could trigger another inflationary

neg: Universe of the contents of the Universe. The present overall density of this type of matter is very low, roughly 4.5 × 10 grams per cubic centimetre, corresponding to a density of the order of only one proton for every four cubic meters of volume. The nature of both dark energy and dark matter is unknown. Dark matter, a mysterious form of matter that has not yet been identified, accounts for 26.8% of the cosmic contents. Dark energy, which is the energy of empty space and is causing the expansion of the Universe to accelerate, accounts for the remaining 68.3% of

neg: Future of an expanding universe a different form of dark energy in the first moments of the Big Bang; but inflation ended, indicating an equation of state much more complicated 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 parametrize or predict. In the 1970s, the future of an expanding universe was studied by the astrophysicist Jamal Islam and the physicist Freeman Dyson. Then, in their 1999 book The Five Ages of the Universe, the astrophysicists Fred Adams and

neg: Joint Dark Energy Mission cost is around $1.6 billion. The Dark Energy Space Telescope (Destiny), was a planned project by NASA and DOE, designed to perform precision measurements of the universe to provide an understanding of dark energy. The space observatory will derive the expansion of the universe by measuring up to 3,000 distant supernovae each year of its three-year mission lifetime, and will additionally study the structure of matter in the universe by measuring millions of galaxies in a weak gravitational lensing survey. The Destiny spacecraft features an optical telescope with a 1.65m primary mirror. The telescope images infrared light onto an array

neg: History of physics they can become suffused with energy that exerts an antigravitational force. Such fields have been proposed as the source of an enormous burst of expansion, known as inflation, early in the universe and, possibly, as the secret of the dark energy that now seems to be speeding up the expansion of the universe. With increased accessibility to and elaboration upon advanced analytical techniques in the 19th century, physics was defined as much, if not more, by those techniques than by the search for universal principles of motion and energy, and the fundamental nature of matter. Fields such as acoustics, geophysics,

neg: Ultimate fate of the universe 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. 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, the "Big Freeze", or the "Big Rip", where the acceleration caused by dark energy eventually becomes so strong that it completely overwhelms the effects of the gravitational, electromagnetic and strong binding forces. Conversely, a "negative"

neg: De Sitter universe by observers necessarily diverge as expected from the expansion of physical spatial dimensions. As a model for the universe, de Sitter's solution was not considered viable for the observed universe until models for inflation and dark energy were developed. Before then, it was assumed that the Big Bang implied only an acceptance of the weaker cosmological principle, which holds that isotropy and homogeneity apply spatially but not temporally. Because our Universe entered the Dark Energy Dominated Era about five billion years ago, our universe is probably approaching a de Sitter universe in the infinite future. If the current acceleration of

neg: Big Bang way it is the best explanation for the "missing" energy density. Dark energy also helps to explain two geometrical measures of the overall curvature of the universe, one using the frequency of gravitational lenses, and the other using the characteristic pattern of the large-scale structure as a cosmic ruler. Negative pressure is believed to be a property of vacuum energy, but the exact nature and existence of dark energy remains one of the great mysteries of the Big Bang. Results from the WMAP team in 2008 are in accordance with a universe that consists of 73% dark energy, 23% dark

neg: Sunyaev–Zel'dovich Array observations of the cosmic microwave background (CMB) and supernova studies, of a form of energy that is accelerating the expansion of the universe. Dubbed dark energy by analogy with dark matter, it is believed to account for roughly 70% of the universe's energy content. While dark energy cannot be observed directly, its basic properties can be inferred from its effect on structure formation in the universe. Just as an ecologist can learn about the food supply by studying how animal populations evolve with time, physicists can learn about dark energy by studying the population statistics of the universe's inhabitants —

neg: Weakly interacting massive particles astrophysical and cosmological problems related to dark matter. There is consensus today among astronomers that most of the mass in the Universe is indeed dark. Simulations of a universe full of cold dark matter produce galaxy distributions that are roughly similar to what is observed. By contrast, hot dark matter would smear out the large-scale structure of galaxies and thus is not considered a viable cosmological model. WIMPs fit the model of a relic dark matter particle from the early Universe, when all particles were in a state of thermal equilibrium. For sufficiently high temperatures, such as those existing in

neg: Scale factor (cosmology) marking the end of the radiation era. For a matter-dominated universe the evolution of the scale factor in the Friedmann–Lemaître–Robertson–Walker metric is easily obtained solving the Friedmann equations: In physical cosmology, the dark-energy-dominated era is proposed as the last of the three phases of the known universe, the other two being the matter-dominated era and the radiation-dominated era. The dark-energy-dominated era began after the matter-dominated era, i.e. when the Universe was about 9.8 billion years old. In the era of the cosmic inflation the Hubble parameter is also thought of to be constant, so the expansion law of the dark-energy-dominated

neg: Dark energy of the critical density. This implies the existence of an additional form of energy to account for the remaining 70%. The Wilkinson Microwave Anisotropy Probe (WMAP) spacecraft seven-year analysis estimated a universe made up of 72.8% dark energy, 22.7% dark matter, and 4.5% ordinary matter. Work done in 2013 based on the Planck spacecraft observations of the CMB gave a more accurate estimate of 68.3% dark energy, 26.8% dark matter, and 4.9% ordinary matter. The theory of large-scale structure, which governs the formation of structures in the universe (stars, quasars, galaxies and galaxy groups and clusters), also suggests that the

neg: Universe radiation that corresponds to a thermal equilibrium blackbody spectrum of roughly 2.72548 kelvins. The hypothesis that the large-scale Universe is homogeneous and isotropic is known as the cosmological principle. A Universe that is both homogeneous and isotropic looks the same from all vantage points and has no center. An explanation for why the expansion of the Universe is accelerating remains elusive. It is often attributed to "dark energy", an unknown form of energy that is hypothesized to permeate space. On a mass–energy equivalence basis, the density of dark energy (~ 7 × 10 g/cm) is much less than the density

neg: Non-standard cosmology COBE and the WMAP, provided detailed quantitative measures which were consistent with standard cosmology. In the 1990s, a dawning of a "golden age of cosmology" was accompanied by a startling discovery that the expansion of the universe was, in fact, accelerating. Previous to this, it had been assumed that matter either in its visible or invisible dark matter form was the dominant energy density in the universe. This "classical" big bang cosmology was overthrown when it was discovered that nearly 70% of the energy in the universe was attributable to the cosmological constant, often referred to as "dark energy". This

neg: Paul Steinhardt is a viable candidate for the field that drives the cycles of expansion and contraction. Steinhardt has made significant contributions researching the "dark side" of the universe: dark energy, the cosmological constant problem and dark matter. In 1995, Steinhardt and Jeremiah Ostriker used a concordance of cosmological observations to show there must be a non-zero dark energy component today, more than 65 percent of the total energy density, sufficient to cause the expansion of the universe to accelerate. This was verified three years later by supernova observations in 1998. Working with colleagues, he subsequently introduced the concept of quintessence, a

neg: Dark energy echoing Fritz Zwicky's "dark matter" from the 1930s, was coined by Michael Turner in 1998. High-precision measurements of the expansion of the universe are required to understand how the expansion rate changes over time and space. In general relativity, the evolution of the expansion rate is estimated from the curvature of the universe and the cosmological equation of state (the relationship between temperature, pressure, and combined matter, energy, and vacuum energy density for any region of space). Measuring the equation of state for dark energy is one of the biggest efforts in observational cosmology today. Adding the cosmological constant to

neg: Universe of Energy Universe of Energy The Universe of Energy was a pavilion located in the eastern half of Future World at Epcot. The pavilion contained one attraction, Ellen's Energy Adventure, starring Ellen DeGeneres and Bill Nye, which was the second version of the show since the pavilion's 1982 opening. The attraction featured a combination of four separate large-format film presentations and a slow-moving dark ride through audio-animatronic filled sets. The Universe of Energy pavilion was previously sponsored by ExxonMobil (formerly Exxon) from opening day on October 1, 1982, through 2004. At D23 Expo 2017, it was announced that the Universe of Energy

neg: Hydrogen Intensity and Real-time Analysis eXperiment BAO are a fixed comoving size, and so they act as a standard ruler, marking the expansion of the universe over time, and therefore giving information about dark energy and dark matter. For example, if dark energy is not a cosmological constant, as the standard ΛCDM theory of cosmology predicts, then the rate of acceleration of the universe may not be constant over time. Due to the expansion of the universe, the 400-800MHz operating band of the HIRAX instrument corresponds to redshifted 21-cm emission from formula_1 (7-11Bya, or when the universe was between 2.5 and 6.5 billion years old). This

neg: Future of an expanding universe mission suggest that the universe is spatially flat and has a significant amount of dark energy. In this case, the universe should continue to expand at an accelerating rate. The acceleration of the universe's expansion has also been confirmed by observations of distant supernovae. If, as in the concordance model of physical cosmology (Lambda-cold dark matter or ΛCDM), dark energy is in the form of a cosmological constant, the expansion will eventually become exponential, with the size of the universe doubling at a constant rate. If the theory of inflation is true, the universe went through an episode dominated by

neg: Universe of ordinary matter or dark matter within galaxies. However, in the present dark-energy era, it dominates the mass–energy of the universe because it is uniform across space. Two proposed forms for dark energy are the cosmological constant, a "constant" energy density filling space homogeneously, and scalar fields such as quintessence or moduli, "dynamic" quantities whose energy density can vary in time and space. Contributions from scalar fields that are constant in space are usually also included in the cosmological constant. The cosmological constant can be formulated to be equivalent to vacuum energy. Scalar fields having only a slight amount of

neg: Hubble's law with time, then If "w" is constant, then implying: Therefore, for dark energy with a constant equation of state "w", formula_62. If this is substituted into the Friedman equation in a similar way as before, but this time set formula_63, which assumes a spatially flat universe, then (see Shape of the universe) If the dark energy derives from a cosmological constant such as that introduced by Einstein, it can be shown that formula_65. The equation then reduces to the last equation in the matter-dominated universe section, with formula_66 set to zero. In that case the initial dark energy density formula_67

neg: Astroparticle physics of the visible matter needed to account for their dynamics. Since the early nineties some candidates have been found to partially explain some of the missing dark matter, but they are nowhere near sufficient to offer a full explanation. The finding of an accelerating universe suggests that a large part of the missing dark matter is stored as dark energy in a dynamical vacuum. Another question for astroparticle physicists is why is there so much more matter than antimatter in the universe today. Baryogenesis is the term for the hypothetical processes that produced the unequal numbers of baryons and anitbaryons

neg: Degree Angular Scale Interferometer dark matter and dark energy. This has since become the ΛCDM Standard Model of Cosmology. From the more recent polarization results scientists could have "high confidence" of the presence of E-modes in the CMB, which added to the evidence supporting the ΛCDM Standard Model of Cosmology; the data is also helpful to understanding the mass distribution of the early universe. The temperature anisotropies revealed the existence of formations of matter in the early universe, and the polarization revealed how these formations were moving. The developments in interferometric technique achieved by this project were also thought to be helpful for future

neg: Particle physics in cosmology of the early universe. The success of the Standard Model at explaining these observations provides a confirmation of its validity outside of laboratory conditions. In addition, phenomena extrapolated from cosmological observations, such as dark matter and CP-violation, suggest a need for physics that goes beyond the Standard Model. Particle physics in cosmology Particle physics, which deals with the interactions of elementary particles at high energies, is an important component of cosmological models of the early universe, when the universe was dominated by radiation and its average energy density was very high. Because of this, pair production, scattering processes and decay

neg: International Year of Light years, searching for more information about the universe in this early cosmic signal. Initially NASA's COBE and WMAP satellites, and in recent years ESA's Planck satellite, have provided precise maps of the CMB that enable astrophysicists to delve into the history of the Universe, constraining its geometry and the properties of its constituents. Together with other observations, these data led to the "standard model" for cosmology: a spatially flat Universe dominated not only by dark matter, but also by the mysterious dark energy, responsible for accelerating the present expansion of the cosmos. Charles K. Kao (1933) is a Chinese-born Hong

neg: Cosmological constant constant to be equal to zero. That changed with the surprising discovery in 1998 that the expansion of the universe is accelerating, implying the possibility of a positive nonzero value for the cosmological constant. Since the 1990s, studies have shown that around 68% of the mass–energy density of the universe can be attributed to so-called dark energy. The cosmological constant Λ is the simplest possible explanation for dark energy, and is used in the current standard model of cosmology known as the ΛCDM model. While dark energy is poorly understood at a fundamental level, the main required properties of dark

neg: Dark Energy Survey DES makes it an ideal probe for finding more dwarf or ‘satellite’ galaxies around our Milky Way Galaxy. The number of dwarf galaxies gives important information about the evolution of galaxies and structure in the universe. Cosmological simulations have tended to predict many more dwarf galaxies around large galaxies than we see around our Milky Way Galaxy, leading to what is known as the missing satellite problem. Dwarf galaxies are also interesting in that they appear to be the most dark matter dominated objects in the universe, based on their mass to light ratio. This makes them interesting targets for

neg: Physics beyond the Standard Model These phases could potentially create a surplus of leptons over anti-leptons in the early universe, a process known as leptogenesis. This asymmetry could then at a later stage be converted in an excess of baryons over anti-baryons, and explain the matter-antimatter asymmetry in the universe. The light neutrinos are disfavored as an explanation for the observation of dark matter, due to considerations of large-scale structure formation in the early universe. Simulations of structure formation show that they are too hot—i.e. their kinetic energy is large compared to their mass—while formation of structures similar to the galaxies in our universe requires

neg: Ultimate fate of the universe 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 effect of gravity, but eventually increases. The ultimate fate of the universe is the same as an open universe. The fate of the universe is 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

neg: Hydrogen Intensity and Real-time Analysis eXperiment neighboring meerKAT radio telescope and its eponymous animal. The nature of the dark energy and dark matter are among the greatest unsolved mysteries in modern cosmology.<ref name="albrecht/etal"></ref> It has been known since the late 1920s, with the discovery of Hubble's law, that the universe is expanding, but for most of the 20th century it was assumed that this was a decelerating expansion, following a hot big bang. However, in the late 1990s it was discovered that the expansion of the universe is in fact accelerating. Dark energy is the hypothesized form of energy which causes this acceleration, however little is

neg: Dark energy viscosity. In the Friedmann–Lemaître–Robertson–Walker metric, it can be shown that a strong constant negative pressure in all the universe causes an acceleration in the expansion if the universe is already expanding, or a deceleration in contraction if the universe is already contracting. This accelerating expansion effect is sometimes labeled "gravitational repulsion". In standard cosmology, there are three components of the universe: matter, radiation, and dark energy. Matter is anything whose energy density scales with the inverse cube of the scale factor, i.e., ρ ∝ a, while radiation is anything which scales to the inverse fourth power of the scale factor

neg: Dark Energy Survey Standard ruler to constrain cosmology, and in particular, the evolution of dark energy. Measurements of BAO form a key part of the observation program of the Dark Energy Survey. Before roughly 380,000 years after the big bang, the universe was a hot, dense plasma consisting almost entirely of photons, electrons and protons (the last two of these components are often referred to collectively as baryons, although technically this is a misnomer). The high temperature of the universe during this epoch prevented electrons and protons from combining to form neutral atoms. A consequence of the high degree of ionization of the

neg: Scale factor (cosmology) eventually dominate the energy density of the Universe. Recent measurements of the change in Hubble constant with time, based on observations of distant supernovae, show this acceleration in expansion rate, indicating the presence of such dark energy. For a dark-energy-dominated universe, the evolution of the scale factor in the Friedmann–Lemaître–Robertson–Walker metric is easily obtained solving the Friedmann equations: Here, the coefficient "H" in the exponential, the Hubble constant, is This exponential dependence on time makes the spacetime geometry identical to the de Sitter Universe, and only holds for a positive sign of the cosmological constant, the sign that was observed

neg: Dark energy any, exists between dark energy and inflation. Even after inflationary models became accepted, the cosmological constant was thought to be irrelevant to the current universe. Nearly all inflation models predict that the total (matter+energy) density of the universe should be very close to the critical density. During the 1980s, most cosmological research focused on models with critical density in matter only, usually 95% cold dark matter and 5% ordinary matter (baryons). These models were found to be successful at forming realistic galaxies and clusters, but some problems appeared in the late 1980s: in particular, the model required a value for

neg: Void (astronomy) the evolution of a void's shape is in part the result of the expansion of the universe. Since this acceleration is believed to be caused by dark energy, studying the changes of a void's shape over a period of time can further refine the Quintessence + Cold Dark Matter ("QCDM") model and provide a more accurate dark energy equation of state. Additionally the abundance of voids is a promising way to constrain the dark energy equation of state. Cosmic voids contain a mix of galaxies and matter that is slightly different than other regions in the universe. This unique mix

neg: Dark Energy Survey from distant galaxies was emitted. If the expansion rate of the universe is speeding up due to dark energy, then the size of the universe increases more rapidly with time than if the expansion were slowing down. Using supernovae, we cannot quite measure the size of the universe versus time. Instead we can measure the size of the universe (at the time the star exploded) and the distance to the supernova. With the distance to the exploding supernova in hand, astronomers can use the value of the speed of light along with the theory of General Relativity to determine how

neg: Future Circular Collider reach and higher precision are necessary. The Future Circular Collider (FCC) study develops options for potential high-energy frontier circular colliders at CERN for the post-LHC era that will open up new horizons in the field of fundamental physics. Among other things, it plans to study dark matter, which accounts for approximately 25% of the visible universe, make precise measurements of the Higgs boson, and explore beyond the Standard Model theories. A Future Circular Collider could open a window for exploring the unknown 95% of the Universe: What is dark matter? Are there supersymmetric particles? Are there other fundamental interactions? The

neg: Quintessence: The Search for Missing Mass in the Universe of the mass and energy of the universe resides in empty space, an idea now widely known as "dark energy". Furthermore, Krauss has formulated a model in which the universe could have potentially come from "nothing," as outlined in his later book "A Universe from Nothing". Whether our universe is ever-expanding depends on the amount and properties of matter, but there is too little visible matter around us to explain the behavior we can see—over 90% of the universe consists of the missing mass or dark matter, which Krauss termed "the fifth essence." In this book Krauss demonstrates how the

neg: Dark fluid than expected. This implied that the Universe was not only expanding, but accelerating its expansion. The theory of dark energy was created to explain this phenomenon. The traditional approach to modeling the effects of gravity assumes that general relativity is as valid at cosmological scales as it is in the Solar System, where its predictions have been more accurately tested. Not changing the rules of gravity, however, implies the presence of dark matter and dark energy in parts of the Universe where the curvature of the space-time manifold is far less than that in the Solar System. It is phenomenologically

neg: Bharat Ratra Ratra was a postdoctoral fellow at the Stanford Linear Accelerator Center, Princeton University, the California Institute of Technology and the Massachusetts Institute of Technology. He joined Kansas State University in 1996 as an assistant professor of physics. He was promoted to associate professor in 2001 and professor in 2004. Ratra has worked in a number of areas of cosmology and astroparticle and early universe physics. In 1988, Ratra and Jim Peebles of Princeton University proposed the first dynamical dark energy scalar field, or quintessence, model. Dark energy is the leading candidate for the mechanism that is responsible for causing the