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6,000 | European operations were from RAF Mildenhall, England. There were two routes. One was along the Norwegian west coast and up the Kola Peninsula, which contained several large naval bases belonging to the Soviet Navy's Northern Fleet. Over the years, there were several emergency landings in Norway, four in Bodø and two o... | https://en.wikipedia.org/wiki?curid=55245 |
6,001 | Swedish Air Force fighter pilots have managed to lock their radar on an SR-71 on multiple occasions within shooting range. Target illumination was maintained by feeding target location from ground-based radars to the fire-control computer in the JA 37 Viggen interceptor. The most common site for the lock-on was the thi... | https://en.wikipedia.org/wiki?curid=55245 |
6,002 | On 29 June 1987, an SR-71 was on a mission around the Baltic Sea to spy on Soviet postings when one of the engines exploded. The aircraft, which was at 20 km altitude, quickly lost altitude and turned 180° to the left and turned over Gotland to search for the Swedish coast. Thus, Swedish airspace was violated, whereupo... | https://en.wikipedia.org/wiki?curid=55245 |
6,003 | One widely conventional view, and probably the best-known view, of the reasons for the SR-71's retirement in 1989—a view that the Air Force itself offered to the Congress—was that besides being very expensive, the SR-71 had become redundant anyway, among other reconnaissance methods that were ever-evolving. However, an... | https://en.wikipedia.org/wiki?curid=55245 |
6,004 | Graham noted that in the 1970s and early 1980s, SR-71 squadron and wing commanders were often promoted into higher positions as general officers within the USAF structure and the Pentagon. (In order to be selected into the SR-71 program in the first place, a pilot or navigator (RSO) had to be a top-quality USAF officer... | https://en.wikipedia.org/wiki?curid=55245 |
6,005 | The USAF may have seen the SR-71 as a bargaining chip to ensure the survival of other priorities. Also, the SR-71 program's "product", which was operational and strategic intelligence, was not seen by these generals as being very valuable to the USAF. The primary consumers of this intelligence were the CIA, NSA, and DI... | https://en.wikipedia.org/wiki?curid=55245 |
6,006 | The SR-71, while much more capable than the Lockheed U-2 in terms of range, speed, and survivability, suffered the lack of a data link, which the U-2 had been upgraded to carry. This meant that much of the SR-71's imagery and radar data could not be used in real time, but had to wait until the aircraft returned to base... | https://en.wikipedia.org/wiki?curid=55245 |
6,007 | In 1988, Congress was convinced to allocate $160,000 to keep six SR-71s and a trainer model in flyable storage that could become flightworthy within 60 days. However, the USAF refused to spend the money. While the SR-71 survived attempts to retire it in 1988, partly due to the unmatched ability to provide high-quality ... | https://en.wikipedia.org/wiki?curid=55245 |
6,008 | The SR-71 program's main operational capabilities came to a close at the end of fiscal year 1989 (October 1989). The 1st Strategic Reconnaissance Squadron (1 SRS) kept its pilots and aircraft operational and active, and flew some operational reconnaissance missions through the end of 1989 and into 1990, due to uncertai... | https://en.wikipedia.org/wiki?curid=55245 |
6,009 | Due to unease over political situations in the Middle East and North Korea, the U.S. Congress re-examined the SR-71 beginning in 1993. Rear Admiral Thomas F. Hall addressed the question of why the SR-71 was retired, saying it was under "the belief that, given the time delay associated with mounting a mission, conductin... | https://en.wikipedia.org/wiki?curid=55245 |
6,010 | Macke told the committee that they were "flying U-2s, RC-135s, [and] other strategic and tactical assets" to collect information in some areas. Senator Robert Byrd and other senators complained that the "better than" successor to the SR-71 had yet to be developed at the cost of the "good enough" serviceable aircraft. T... | https://en.wikipedia.org/wiki?curid=55245 |
6,011 | Congress's disappointment with the lack of a suitable replacement for the Blackbird was cited concerning whether to continue funding imaging sensors on the U-2. Congressional conferees stated the "experience with the SR-71 serves as a reminder of the pitfalls of failing to keep existing systems up-to-date and capable i... | https://en.wikipedia.org/wiki?curid=55245 |
6,012 | Retired USAF Colonel Jay Murphy was made the Program Manager for Lockheed's reactivation plans. Retired USAF Colonels Don Emmons and Barry MacKean were put under government contract to remake the plane's logistic and support structure. Still-active USAF pilots and Reconnaissance Systems Officers (RSOs) who had worked w... | https://en.wikipedia.org/wiki?curid=55245 |
6,013 | The reactivation met much resistance: the USAF had not budgeted for the aircraft, and UAV developers worried that their programs would suffer if money was shifted to support the SR-71s. Also, with the allocation requiring yearly reaffirmation by Congress, long-term planning for the SR-71 was difficult. In 1996, the USA... | https://en.wikipedia.org/wiki?curid=55245 |
6,014 | NASA operated the two last airworthy Blackbirds until 1999. All other Blackbirds have been moved to museums except for the two SR-71s and a few D-21 drones retained by the NASA Dryden Flight Research Center (later renamed the Armstrong Flight Research Center). | https://en.wikipedia.org/wiki?curid=55245 |
6,015 | The SR-71 was the world's fastest and highest-flying air-breathing operational manned aircraft throughout its career and it still holds that record. On 28 July 1976, SR-71 serial number 61-7962, piloted by then Captain Robert Helt, broke the world record: an "absolute altitude record" of . Several aircraft have exceede... | https://en.wikipedia.org/wiki?curid=55245 |
6,016 | The SR-71 also holds the "speed over a recognized course" record for flying from New York to London—distance , , and an elapsed time of 1 hour 54 minutes and 56.4 seconds—set on 1 September 1974, while flown by USAF pilot James V. Sullivan and Noel F. Widdifield, reconnaissance systems officer (RSO). This equates to an... | https://en.wikipedia.org/wiki?curid=55245 |
6,017 | On 26 April 1971, 61-7968, flown by majors Thomas B. Estes and Dewain C. Vick, flew over in 10 hours and 30 minutes. This flight was awarded the 1971 Mackay Trophy for the "most meritorious flight of the year" and the 1972 Harmon Trophy for "most outstanding international achievement in the art/science of aeronautics". | https://en.wikipedia.org/wiki?curid=55245 |
6,018 | When the SR-71 was retired in 1990, one Blackbird was flown from its birthplace at USAF Plant 42 in Palmdale, California, to go on exhibit at what is now the Smithsonian Institution's Steven F. Udvar-Hazy Center in Chantilly, Virginia. On 6 March 1990, Lt. Col. Raymond E. and Lt. Col. Joseph T. Vida piloted SR-71 S/N 6... | https://en.wikipedia.org/wiki?curid=55245 |
6,019 | These four speed records were accepted by the National Aeronautic Association (NAA), the recognized body for aviation records in the United States. Additionally, "Air & Space/Smithsonian" reported that the USAF clocked the SR-71 at one point in its flight reaching . After the Los Angeles–Washington flight, on 6 March 1... | https://en.wikipedia.org/wiki?curid=55245 |
6,020 | Speculation existed regarding a replacement for the SR-71, including a rumored aircraft codenamed Aurora. The limitations of reconnaissance satellites, which take up to 24 hours to arrive in the proper orbit to photograph a particular target, make them slower to respond to demand than reconnaissance planes. The fly-ove... | https://en.wikipedia.org/wiki?curid=55245 |
6,021 | On 1 November 2013, media outlets reported that Skunk Works has been working on an unmanned reconnaissance airplane it has named SR-72, which would fly twice as fast as the SR-71, at Mach 6. However, the USAF is officially pursuing the Northrop Grumman RQ-180 UAV to assume the SR-71's strategic ISR role. | https://en.wikipedia.org/wiki?curid=55245 |
6,022 | Twelve SR-71s were lost and one pilot died in accidents during the aircraft's service career. Eleven of these accidents happened between 1966 and 1972. | https://en.wikipedia.org/wiki?curid=55245 |
6,023 | After completion of all USAF and NASA SR-71 operations at Edwards AFB, the SR-71 Flight Simulator was moved in July 2006 to the Frontiers of Flight Museum at Love Field Airport in Dallas, Texas. | https://en.wikipedia.org/wiki?curid=55245 |
6,024 | 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 earliest known periods through its subsequent large-scale form. These models offer... | https://en.wikipedia.org/wiki?curid=4116 |
6,025 | Crucially, these models are compatible with the Hubble–Lemaître law—the observation that the farther away a galaxy is, the faster it is moving away from Earth. Extrapolating this cosmic expansion backwards in time using the known laws of physics, the models describe an increasingly concentrated cosmos preceded by a sin... | https://en.wikipedia.org/wiki?curid=4116 |
6,026 | There remain aspects of the observed universe that are not yet adequately explained by the Big Bang models. After its initial expansion, the universe cooled sufficiently to allow the formation of subatomic particles, and later atoms. The unequal abundances of matter and antimatter that allowed this to occur is an unexp... | https://en.wikipedia.org/wiki?curid=4116 |
6,027 | The Big Bang models offer a comprehensive explanation for a broad range of observed phenomena, including the abundances of the light elements, the CMB, large-scale structure, and Hubble's law. The models depend on two major assumptions: the universality of physical laws and the cosmological principle. The universality ... | https://en.wikipedia.org/wiki?curid=4116 |
6,028 | These ideas were initially taken as postulates, but later efforts were made to test each of them. For example, the first assumption has been tested by observations showing that largest possible deviation of the fine-structure constant over much of the age of the universe is of order 10. Also, general relativity has pas... | https://en.wikipedia.org/wiki?curid=4116 |
6,029 | The large-scale universe appears isotropic as viewed from Earth. If it is indeed isotropic, the cosmological principle can be derived from the simpler Copernican principle, which states that there is no preferred (or special) observer or vantage point. To this end, the cosmological principle has been confirmed to a lev... | https://en.wikipedia.org/wiki?curid=4116 |
6,030 | The expansion of the Universe was inferred from early twentieth century astronomical observations and is an essential ingredient of the Big Bang models. Mathematically, general relativity describes spacetime by a metric, which determines the distances that separate nearby points. The points, which can be relative to ga... | https://en.wikipedia.org/wiki?curid=4116 |
6,031 | The Big Bang is not an explosion of matter moving outward to fill an empty universe. Instead, space itself expands with time everywhere and increases the physical distances between comoving points. In other words, the Big Bang is not an explosion "in space", but rather an expansion "of space". Because the FLRW metric a... | https://en.wikipedia.org/wiki?curid=4116 |
6,032 | An important feature of the Big Bang spacetime is the presence of particle horizons. Since the universe has a finite age, and light travels at a finite speed, there may be events in the past whose light has not yet had time to reach us. This places a limit or a "past horizon" on the most distant objects that can be obs... | https://en.wikipedia.org/wiki?curid=4116 |
6,033 | Our understanding of the universe back to very early times suggests that there is a past horizon, though in practice our view is also limited by the opacity of the universe at early times. So our view cannot extend further backward in time, though the horizon recedes in space. If the expansion of the universe continues... | https://en.wikipedia.org/wiki?curid=4116 |
6,034 | Some processes in the early universe occurred too slowly, compared to the expansion rate of the universe, to reach approximate thermodynamic equilibrium. Others were fast enough to reach thermalization. The parameter usually used to find out whether a process in the very early universe has reached thermal equilibrium i... | https://en.wikipedia.org/wiki?curid=4116 |
6,035 | According to the Big Bang models, the universe at the beginning was very hot and very compact, and since then it has been expanding and cooling down. | https://en.wikipedia.org/wiki?curid=4116 |
6,036 | Extrapolation of the expansion of the universe backwards in time using general relativity yields an infinite density and temperature at a finite time in the past. This irregular behavior, known as the gravitational singularity, indicates that general relativity is not an adequate description of the laws of physics in t... | https://en.wikipedia.org/wiki?curid=4116 |
6,037 | This primordial singularity is itself sometimes called "the Big Bang", but the term can also refer to a more generic early hot, dense phase of the universe. In either case, "the Big Bang" as an event is also colloquially referred to as the "birth" of our universe since it represents the point in history where the unive... | https://en.wikipedia.org/wiki?curid=4116 |
6,038 | Despite being extremely dense at this time—far denser than is usually required to form a black hole—the universe did not re-collapse into a singularity. Commonly used calculations and limits for explaining gravitational collapse are usually based upon objects of relatively constant size, such as stars, and do not apply... | https://en.wikipedia.org/wiki?curid=4116 |
6,039 | The earliest phases of the Big Bang are subject to much speculation, since astronomical data about them are not available. In the most common models the universe was filled homogeneously and isotropically with a very high energy density and huge temperatures and pressures, and was very rapidly expanding and cooling. Th... | https://en.wikipedia.org/wiki?curid=4116 |
6,040 | At approximately 10 seconds into the expansion, a phase transition caused a cosmic inflation, during which the universe grew exponentially, unconstrained by the light speed invariance, and temperatures dropped by a factor of 100,000. This concept is motivated by the flatness problem, where the density of matter and ene... | https://en.wikipedia.org/wiki?curid=4116 |
6,041 | Inflation stopped at around the 10 to 10 seconds mark, with the universe's volume having increased by a factor of at least 10. Reheating occurred until the universe obtained the temperatures required for the production of a quark–gluon plasma as well as all other elementary particles. Temperatures were so high that the... | https://en.wikipedia.org/wiki?curid=4116 |
6,042 | The universe continued to decrease in density and fall in temperature, hence the typical energy of each particle was decreasing. Symmetry-breaking phase transitions put the fundamental forces of physics and the parameters of elementary particles into their present form, with the electromagnetic force and weak nuclear f... | https://en.wikipedia.org/wiki?curid=4116 |
6,043 | A few minutes into the expansion, when the temperature was about a billion kelvin and the density of matter in the universe was comparable to the current density of Earth's atmosphere, neutrons combined with protons to form the universe's deuterium and helium nuclei in a process called Big Bang nucleosynthesis (BBN). M... | https://en.wikipedia.org/wiki?curid=4116 |
6,044 | As the universe cooled, the rest energy density of matter came to gravitationally dominate that of the photon radiation. After about 379,000 years, the electrons and nuclei combined into atoms (mostly hydrogen), which were able to emit radiation. This relic radiation, which continued through space largely unimpeded, is... | https://en.wikipedia.org/wiki?curid=4116 |
6,045 | Over a long period of time, the slightly denser regions of the uniformly distributed matter gravitationally attracted nearby matter and thus grew even denser, forming gas clouds, stars, galaxies, and the other astronomical structures observable today. The details of this process depend on the amount and type of matter ... | https://en.wikipedia.org/wiki?curid=4116 |
6,046 | In an "extended model" which includes hot dark matter in the form of neutrinos, then the "physical baryon density" formula_1 is estimated at 0.023. (This is different from the 'baryon density' formula_2 expressed as a fraction of the total matter/energy density, which is about 0.046.) The corresponding cold dark matter... | https://en.wikipedia.org/wiki?curid=4116 |
6,047 | 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 appears to homogeneously permeate all of space. Observations suggest that 73% of the total energy density of the present day universe is in this form. W... | https://en.wikipedia.org/wiki?curid=4116 |
6,048 | Dark energy in its simplest formulation is modeled by a cosmological constant term in Einstein field equations of general relativity, but its composition and mechanism are unknown. More generally, the details of its equation of state and relationship with the Standard Model of particle physics continue to be investigat... | https://en.wikipedia.org/wiki?curid=4116 |
6,049 | All of this cosmic evolution after the inflationary epoch can be rigorously described and modeled by the lambda-CDM model of cosmology, which uses the independent frameworks of quantum mechanics and general relativity. There are no easily testable models that would describe the situation prior to approximately 10 secon... | https://en.wikipedia.org/wiki?curid=4116 |
6,050 | English astronomer Fred Hoyle is credited with coining the term "Big Bang" during a talk for a March 1949 BBC Radio broadcast, saying: "These theories were based on the hypothesis that all the matter in the universe was created in one big bang at a particular time in the remote past." However, it did not catch on until... | https://en.wikipedia.org/wiki?curid=4116 |
6,051 | It is popularly reported that Hoyle, who favored an alternative "steady-state" cosmological model, intended this to be pejorative, but Hoyle explicitly denied this and said it was just a striking image meant to highlight the difference between the two models. Helge Kragh writes that the evidence for the claim that it w... | https://en.wikipedia.org/wiki?curid=4116 |
6,052 | The term itself is a misnomer as it implies the occurrence of an explosion. However, an explosion implies expansion from a center point out into the surrounding space. Rather than expanding "into" space, the Big Bang was the expansion/stretching "of" space itself, everywhere simultaneously (not from a single point), ca... | https://en.wikipedia.org/wiki?curid=4116 |
6,053 | The Big Bang models developed from observations of the structure of the universe and from theoretical considerations. In 1912, Vesto Slipher measured the first Doppler shift of a "spiral nebula" (spiral nebula is the obsolete term for spiral galaxies), and soon discovered that almost all such nebulae were receding from... | https://en.wikipedia.org/wiki?curid=4116 |
6,054 | In 1924, American astronomer Edwin Hubble's measurement of the great distance to the nearest spiral nebulae showed that these systems were indeed other galaxies. Starting that same year, Hubble painstakingly developed a series of distance indicators, the forerunner of the cosmic distance ladder, using the Hooker telesc... | https://en.wikipedia.org/wiki?curid=4116 |
6,055 | Independently deriving Friedmann's equations in 1927, Georges Lemaître, a Belgian physicist and Roman Catholic priest, proposed that the recession of the nebulae was due to the expansion of the universe. He inferred the relation that Hubble would later observe, given the cosmological principle. In 1931, Lemaître went f... | https://en.wikipedia.org/wiki?curid=4116 |
6,056 | In the 1920s and 1930s, almost every major cosmologist preferred an eternal steady-state universe, and several complained that the beginning of time implied by the Big Bang imported religious concepts into physics; this objection was later repeated by supporters of the steady-state theory. This perception was enhanced ... | https://en.wikipedia.org/wiki?curid=4116 |
6,057 | During the 1930s, other ideas were proposed as non-standard cosmologies to explain Hubble's observations, including the Milne model, the oscillatory universe (originally suggested by Friedmann, but advocated by Albert Einstein and Richard C. Tolman) and Fritz Zwicky's tired light hypothesis. | https://en.wikipedia.org/wiki?curid=4116 |
6,058 | After World War II, two distinct possibilities emerged. One was Fred Hoyle's steady-state model, whereby new matter would be created as the universe seemed to expand. In this model the universe is roughly the same at any point in time. The other was Lemaître's Big Bang theory, advocated and developed by George Gamow, w... | https://en.wikipedia.org/wiki?curid=4116 |
6,059 | In 1968 and 1970, Roger Penrose, Stephen Hawking, and George F. R. Ellis published papers where they showed that mathematical singularities were an inevitable initial condition of relativistic models of the Big Bang. Then, from the 1970s to the 1990s, cosmologists worked on characterizing the features of the Big Bang u... | https://en.wikipedia.org/wiki?curid=4116 |
6,060 | In the mid-1990s, observations of certain globular clusters appeared to indicate that they were about 15 billion years old, which conflicted with most then-current estimates of the age of the universe (and indeed with the age measured today). This issue was later resolved when new computer simulations, which included t... | https://en.wikipedia.org/wiki?curid=4116 |
6,061 | Significant progress in Big Bang cosmology has been made since the late 1990s as a result of advances in telescope technology as well as the analysis of data from satellites such as the Cosmic Background Explorer (COBE), the Hubble Space Telescope and WMAP. Cosmologists now have fairly precise and accurate measurements... | https://en.wikipedia.org/wiki?curid=4116 |
6,062 | The earliest and most direct observational evidence of the validity of the theory are the expansion of the universe according to Hubble's law (as indicated by the redshifts of galaxies), discovery and measurement of the cosmic microwave background and the relative abundances of light elements produced by Big Bang nucle... | https://en.wikipedia.org/wiki?curid=4116 |
6,063 | Precise modern models of the Big Bang appeal to various exotic physical phenomena that have not been observed in terrestrial laboratory experiments or incorporated into the Standard Model of particle physics. Of these features, dark matter is currently the subject of most active laboratory investigations. Remaining iss... | https://en.wikipedia.org/wiki?curid=4116 |
6,064 | Observations of distant galaxies and quasars show that these objects are redshifted: the light emitted from them has been shifted to longer wavelengths. This can be seen by taking a frequency spectrum of an object and matching the spectroscopic pattern of emission or absorption lines corresponding to atoms of the chemi... | https://en.wikipedia.org/wiki?curid=4116 |
6,065 | Hubble's law has two possible explanations. Either we are at the center of an explosion of galaxies—which is untenable under the assumption of the Copernican principle—or the universe is uniformly expanding everywhere. This universal expansion was predicted from general relativity by Friedmann in 1922 and Lemaître in 1... | https://en.wikipedia.org/wiki?curid=4116 |
6,066 | The theory requires the relation formula_9 to hold at all times, where formula_7 is the proper distance, "v" is the recessional velocity, and formula_6, formula_12, and formula_7 vary as the universe expands (hence we write formula_8 to denote the present-day Hubble "constant"). For distances much smaller than the size... | https://en.wikipedia.org/wiki?curid=4116 |
6,067 | That space is undergoing metric expansion is shown by direct observational evidence of the cosmological principle and the Copernican principle, which together with Hubble's law have no other explanation. Astronomical redshifts are extremely isotropic and homogeneous, supporting the cosmological principle that the unive... | https://en.wikipedia.org/wiki?curid=4116 |
6,068 | Measurements of the effects of the cosmic microwave background radiation on the dynamics of distant astrophysical systems in 2000 proved the Copernican principle, that, on a cosmological scale, the Earth is not in a central position. Radiation from the Big Bang was demonstrably warmer at earlier times throughout the un... | https://en.wikipedia.org/wiki?curid=4116 |
6,069 | In 1964, Arno Penzias and Robert Wilson serendipitously discovered the cosmic background radiation, an omnidirectional signal in the microwave band. Their discovery provided substantial confirmation of the big-bang predictions by Alpher, Herman and Gamow around 1950. Through the 1970s, the radiation was found to be app... | https://en.wikipedia.org/wiki?curid=4116 |
6,070 | The "surface of last scattering" corresponding to emission of the CMB occurs shortly after "recombination", the epoch when neutral hydrogen becomes stable. Prior to this, the universe comprised a hot dense photon-baryon plasma sea where photons were quickly scattered from free charged particles. Peaking at around , the... | https://en.wikipedia.org/wiki?curid=4116 |
6,071 | In 1989, NASA launched COBE, which made two major advances: in 1990, high-precision spectrum measurements showed that the CMB frequency spectrum is an almost perfect blackbody with no deviations at a level of 1 part in 10, and measured a residual temperature of 2.726 K (more recent measurements have revised this figure... | https://en.wikipedia.org/wiki?curid=4116 |
6,072 | During the following decade, CMB anisotropies were further investigated by a large number of ground-based and balloon experiments. In 2000–2001, several experiments, most notably BOOMERanG, found the shape of the universe to be spatially almost flat by measuring the typical angular size (the size on the sky) of the ani... | https://en.wikipedia.org/wiki?curid=4116 |
6,073 | In early 2003, the first results of the Wilkinson Microwave Anisotropy Probe were released, yielding what were at the time the most accurate values for some of the cosmological parameters. The results disproved several specific cosmic inflation models, but are consistent with the inflation theory in general. The "Planc... | https://en.wikipedia.org/wiki?curid=4116 |
6,074 | Using the Big Bang model, it is possible to calculate the concentration of the isotopes helium-4 (He), helium-3 (He), deuterium (H), and lithium-7 (Li) in the universe as ratios to the amount of ordinary hydrogen. The relative abundances depend on a single parameter, the ratio of photons to baryons. This value can be c... | https://en.wikipedia.org/wiki?curid=4116 |
6,075 | The measured abundances all agree at least roughly with those predicted from a single value of the baryon-to-photon ratio. The agreement is excellent for deuterium, close but formally discrepant for He, and off by a factor of two for Li (this anomaly is known as the cosmological lithium problem); in the latter two case... | https://en.wikipedia.org/wiki?curid=4116 |
6,076 | Detailed observations of the morphology and distribution of galaxies and quasars are in agreement with the current state of the Big Bang models. A combination of observations and theory suggest that the first quasars and galaxies formed about a billion years after the Big Bang, and since then, larger structures have be... | https://en.wikipedia.org/wiki?curid=4116 |
6,077 | Populations of stars have been aging and evolving, so that distant galaxies (which are observed as they were in the early universe) appear very different from nearby galaxies (observed in a more recent state). Moreover, galaxies that formed relatively recently, appear markedly different from galaxies formed at similar ... | https://en.wikipedia.org/wiki?curid=4116 |
6,078 | In 2011, astronomers found what they believe to be pristine clouds of primordial gas by analyzing absorption lines in the spectra of distant quasars. Before this discovery, all other astronomical objects have been observed to contain heavy elements that are formed in stars. Despite being sensitive to carbon, oxygen, an... | https://en.wikipedia.org/wiki?curid=4116 |
6,079 | The age of the universe as estimated from the Hubble expansion and the CMB is now in good agreement with other estimates using the ages of the oldest stars, both as measured by applying the theory of stellar evolution to globular clusters and through radiometric dating of individual Population II stars. It is also in g... | https://en.wikipedia.org/wiki?curid=4116 |
6,080 | The prediction that the CMB temperature was higher in the past has been experimentally supported by observations of very low temperature absorption lines in gas clouds at high redshift. This prediction also implies that the amplitude of the Sunyaev–Zel'dovich effect in clusters of galaxies does not depend directly on r... | https://en.wikipedia.org/wiki?curid=4116 |
6,081 | Future gravitational-wave observatories might be able to detect primordial gravitational waves, relics of the early universe, up to less than a second after the Big Bang. | https://en.wikipedia.org/wiki?curid=4116 |
6,082 | As with any theory, a number of mysteries and problems have arisen as a result of the development of the Big Bang models. Some of these mysteries and problems have been resolved while others are still outstanding. Proposed solutions to some of the problems in the Big Bang model have revealed new mysteries of their own.... | https://en.wikipedia.org/wiki?curid=4116 |
6,083 | It is not yet understood why the universe has more matter than antimatter. It is generally assumed that when the universe was young and very hot it was in statistical equilibrium and contained equal numbers of baryons and antibaryons. However, observations suggest that the universe, including its most distant parts, is... | https://en.wikipedia.org/wiki?curid=4116 |
6,084 | Measurements of the redshift–magnitude relation for type Ia supernovae indicate that the expansion of the universe has been accelerating since the universe was about half its present age. To explain this acceleration, general relativity requires that much of the energy in the universe consists of a component with large... | https://en.wikipedia.org/wiki?curid=4116 |
6,085 | 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 univer... | https://en.wikipedia.org/wiki?curid=4116 |
6,086 | 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 matter, 4.6% regular matter and less than... | https://en.wikipedia.org/wiki?curid=4116 |
6,087 | 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 extending to more exotic forms of quintessence or other modified gravity schemes. A cosmological constant problem, sometimes called the "most embarrassing p... | https://en.wikipedia.org/wiki?curid=4116 |
6,088 | During the 1970s and the 1980s, various observations showed that there is not sufficient visible matter in the universe to account for the apparent strength of gravitational forces within and between galaxies. This led to the idea that up to 90% of the matter in the universe is dark matter that does not emit light or i... | https://en.wikipedia.org/wiki?curid=4116 |
6,089 | Indirect evidence for dark matter comes from its gravitational influence on other matter, as no dark matter particles have been observed in laboratories. Many particle physics candidates for dark matter have been proposed, and several projects to detect them directly are underway. | https://en.wikipedia.org/wiki?curid=4116 |
6,090 | Additionally, there are outstanding problems associated with the currently favored cold dark matter model which include the dwarf galaxy problem and the cuspy halo problem. Alternative theories have been proposed that do not require a large amount of undetected matter, but instead modify the laws of gravity established... | https://en.wikipedia.org/wiki?curid=4116 |
6,091 | The horizon problem results from the premise that information cannot travel faster than light. In a universe of finite age this sets a limit—the particle horizon—on the separation of any two regions of space that are in causal contact. The observed isotropy of the CMB is problematic in this regard: if the universe had ... | https://en.wikipedia.org/wiki?curid=4116 |
6,092 | A resolution to this apparent inconsistency is offered by inflation theory in which a homogeneous and isotropic scalar energy field dominates the universe at some very early period (before baryogenesis). During inflation, the universe undergoes exponential expansion, and the particle horizon expands much more rapidly t... | https://en.wikipedia.org/wiki?curid=4116 |
6,093 | Heisenberg's uncertainty principle predicts that during the inflationary phase there would be quantum thermal fluctuations, which would be magnified to a cosmic scale. These fluctuations served as the seeds for all the current structures in the universe. Inflation predicts that the primordial fluctuations are nearly sc... | https://en.wikipedia.org/wiki?curid=4116 |
6,094 | If inflation occurred, exponential expansion would push large regions of space well beyond our observable horizon. | https://en.wikipedia.org/wiki?curid=4116 |
6,095 | A related issue to the classic horizon problem arises because in most standard cosmological inflation models, inflation ceases well before electroweak symmetry breaking occurs, so inflation should not be able to prevent large-scale discontinuities in the electroweak vacuum since distant parts of the observable universe... | https://en.wikipedia.org/wiki?curid=4116 |
6,096 | The magnetic monopole objection was raised in the late 1970s. Grand unified theories (GUTs) predicted topological defects in space that would manifest as magnetic monopoles. These objects would be produced efficiently in the hot early universe, resulting in a density much higher than is consistent with observations, gi... | https://en.wikipedia.org/wiki?curid=4116 |
6,097 | The flatness problem (also known as the oldness problem) is an observational problem associated with a FLRW. The universe may have positive, negative, or zero spatial curvature depending on its total energy density. Curvature is negative if its density is less than the critical density; positive if greater; and zero at... | https://en.wikipedia.org/wiki?curid=4116 |
6,098 | The problem is that any small departure from the critical density grows with time, and yet the universe today remains very close to flat. Given that a natural timescale for departure from flatness might be the Planck time, 10 seconds, the fact that the universe has reached neither a heat death nor a Big Crunch after bi... | https://en.wikipedia.org/wiki?curid=4116 |
6,099 | One of the common misconceptions about the Big Bang model is that it fully explains the origin of the universe. However, the Big Bang model does not describe how energy, time, and space were caused, but rather it describes the emergence of the present universe from an ultra-dense and high-temperature initial state. It ... | https://en.wikipedia.org/wiki?curid=4116 |
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