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113-547: Observations made by Edwin Hubble during the 1930s–1950s found that galaxies appeared to be moving away from each other, leading to the currently accepted Big Bang theory. This suggests that the universe began very dense about 13.787 billion years ago , and it has expanded and (on average) become less dense ever since. Confirmation of the Big Bang mostly depends on knowing the rate of expansion, average density of matter, and

226-626: A Bachelor of Science degree by 1910. For a year he was also a student laboratory assistant for the physicist Robert Millikan , a future Nobel Prize winner. Hubble also became a member of the Kappa Sigma fraternity. A Rhodes Scholar , he spent three years at The Queen's College, Oxford studying jurisprudence instead of science (as a promise to his dying father), and later added studies in literature and Spanish, eventually earning his master's degree. In 1909, Hubble's father moved his family from Chicago to Shelbyville, Kentucky , so that

339-415: A cyclic model , which is also known as an oscillatory universe. The universe could then consist of an infinite sequence of finite universes, with each finite universe ending with a Big Crunch that is also the Big Bang of the next universe. A problem with the cyclic universe is that it does not reconcile with the second law of thermodynamics , as entropy would build up from oscillation to oscillation and cause

452-504: A disc , have an edge or boundary. Spaces that have an edge are difficult to treat, both conceptually and mathematically. Namely, it is difficult to state what would happen at the edge of such a universe. For this reason, spaces that have an edge are typically excluded from consideration. However, there exist many finite spaces, such as the 3-sphere and 3-torus , that have no edges. Mathematically, these spaces are referred to as being compact without boundary. The term compact means that it

565-425: A peer-reviewed scientific journal until 1929. Hubble's findings fundamentally changed the scientific view of the universe. Supporters state that Hubble's discovery of nebulae outside of our galaxy helped pave the way for future astronomers. Although some of his more renowned colleagues simply scoffed at his results, Hubble ended up publishing his findings on nebulae. This published work earned him an award titled

678-519: A closed universe. The current Hubble constant defines a rate of acceleration of the universe not large enough to destroy local structures like galaxies, which are held together by gravity, but large enough to increase the space between them. A steady increase in the Hubble constant to infinity would result in all material objects in the universe, starting with galaxies and eventually (in a finite time) all forms, no matter how small, disintegrating into unbound elementary particles , radiation and beyond. As

791-415: A distance at least d apart. A finite universe is a bounded metric space, where there is some distance d such that all points are within distance d of each other. The smallest such d is called the diameter of the universe, in which case the universe has a well-defined "volume" or "scale". Assuming a finite universe, the universe can either have an edge or no edge. Many finite mathematical spaces, e.g.,

904-474: A flat or hyperbolic universe implies an infinite universe; however, the correct statement is that a flat universe that is also simply connected implies an infinite universe. For example, Euclidean space is flat, simply connected, and infinite, but there are tori that are flat, multiply connected, finite, and compact (see flat torus ). In general, local to global theorems in Riemannian geometry relate

1017-498: A given current observer) is a roughly spherical region extending about 46 billion light-years in all directions (from that observer, the observer being the current Earth, unless specified otherwise). It appears older and more redshifted the deeper we look into space. In theory, we could look all the way back to the Big Bang , but in practice, we can only see up to the cosmic microwave background (CMB) (roughly 370 000 years after

1130-491: A negative energy density and positive pressure, would cause even an open universe to re-collapse to a big crunch. If the average density of the universe exactly equals the critical density so that Ω = 1 {\displaystyle \Omega =1} , then the geometry of the universe is flat: as in Euclidean geometry , the sum of the angles of a triangle is 180 degrees and parallel lines continuously maintain

1243-475: A portion of the universe would be destroyed by the Big Slurp while most of the universe would still be unaffected because galaxies located further than 4,200 megaparsecs (13 billion light-years ) away from each other are moving away from each other faster than the speed of light while the Big Slurp itself cannot expand faster than the speed of light. To place this in context, the size of the observable universe

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1356-400: A possible ultimate fate of the universe. Alexander Friedmann proposed several solutions in 1922, as did Georges Lemaître in 1927. In some of these solutions, the universe has been expanding from an initial singularity which was, essentially, the Big Bang. In 1929, Edwin Hubble published his conclusion, based on his observations of Cepheid variable stars in distant galaxies, that

1469-403: A repulsive quantum force causes re-expansion. In simple terms, this theory states that the universe will continuously repeat the cycle of a Big Bang, followed by a Big Crunch. Each possibility described so far is based on a simple form for the dark energy equation of state. However, as the name is meant to imply, little is now known about the physics of dark energy . If the theory of inflation

1582-418: A sphere. The sum of the angles of a triangle exceeds 180 degrees and there are no parallel lines; all lines eventually meet. The geometry of the universe is, at least on a very large scale, elliptic . In a closed universe, gravity eventually stops the expansion of the universe, after which it starts to contract until all matter in the universe collapses to a point, a final singularity termed the " Big Crunch ",

1695-472: A spontaneous entropy decrease by the Poincaré recurrence theorem , thermal fluctuations , and the fluctuation theorem . The heat death scenario is compatible with any of the three spatial models, but it requires that the universe reaches an eventual temperature minimum. Without dark energy, it could occur only under a flat or hyperbolic geometry. With a positive cosmological constant, it could also occur in

1808-441: A sufficiently large spatial scale. Global structure covers the geometry and the topology of the whole universe—both the observable universe and beyond. While the local geometry does not determine the global geometry completely, it does limit the possibilities, particularly a geometry of a constant curvature. The universe is often taken to be a geodesic manifold , free of topological defects ; relaxing either of these complicates

1921-469: A third place in a single high school track and field meet in 1906, and he played a variety of positions on the basketball court, from center to shooting guard . Hubble led the University of Chicago's basketball team to their first Big Ten Conference title in 1907 . Hubble's studies at the University of Chicago were concentrated on mathematics , astronomy and philosophy , which resulted in

2034-456: A three-dimensional analog of an infinitely extended saddle shape. There are a great variety of hyperbolic 3-manifolds , and their classification is not completely understood. Those of finite volume can be understood via the Mostow rigidity theorem . For hyperbolic local geometry, many of the possible three-dimensional spaces are informally called "horn topologies", so called because of the shape of

2147-459: A true vacuum at any moment. In order to best understand the false vacuum collapse theory, one must first understand the Higgs field which permeates the universe. Much like an electromagnetic field , it varies in strength based upon its potential. A true vacuum exists so long as the universe exists in its lowest energy state, in which case the false vacuum theory is irrelevant. However, if the vacuum

2260-481: A universe with zero curvature, the local geometry is flat . The most familiar such global structure is that of Euclidean space, which is infinite in extent. Flat universes that are finite in extent include the torus and Klein bottle . Moreover, in three dimensions, there are 10 finite closed flat 3-manifolds, of which 6 are orientable and 4 are non-orientable. These are the Bieberbach manifolds . The most familiar

2373-441: A variety of methods. In 1929 Hubble examined the relationship between these distances and their radial velocities as determined from their redshifts . All of his estimated distances are now known to be too small, by up to a factor of about 7. This was due to factors such as the fact that there are two kinds of Cepheid variables or confusing bright gas clouds with bright stars. However, his distances were more or less proportional to

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2486-505: Is life . This scenario has gained ground as the most likely fate. In this scenario, stars are expected to form normally for 10 to 10 (1–100 trillion) years, but eventually the supply of gas needed for star formation will be exhausted. As existing stars run out of fuel and cease to shine, the universe will slowly and inexorably grow darker. Eventually black holes will dominate the universe, but they will disappear over time as they emit Hawking radiation . Over infinite time, there could be

2599-615: Is a catch-all term for any hypothesized field with negative pressure, usually with a density that changes as the universe expands. Some cosmologists are studying whether dark energy which varies in time (due to a portion of it being caused by a scalar field in the early universe) can solve the crisis in cosmology . Upcoming galaxy surveys from the Euclid , Nancy Grace Roman and James Webb space telescopes (and data from next-generation ground-based telescopes ) are expected to further develop our understanding of dark energy (specifically whether it

2712-454: Is a quantity describing how the geometry of a space differs locally from flat space. The curvature of any locally isotropic space (and hence of a locally isotropic universe) falls into one of the three following cases: Curved geometries are in the domain of non-Euclidean geometry . An example of a positively curved space would be the surface of a sphere such as the Earth. A triangle drawn from

2825-466: Is best understood as a constant energy intrinsic to space, as a time varying quantum field or as something else entirely). 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 7.5 billion years after

2938-405: Is constantly created. These two theories were active contenders until the 1965 discovery, by Arno Allan Penzias and Robert Woodrow Wilson , of the cosmic microwave background radiation, a fact that is a straightforward prediction of the Big Bang theory, and one that the original Steady State theory could not account for. As a result, the Big Bang theory quickly became the most widely held view of

3051-453: Is currently about 46 billion light years in all directions from earth. The universe is thought to be that size or larger. Choosing among these rival scenarios is done by 'weighing' the universe, for example, measuring the relative contributions of matter , radiation , dark matter , and dark energy to the critical density . More concretely, competing scenarios are evaluated against data on galaxy clustering and distant supernovas , and on

3164-430: Is defined primarily by its curvature , while the global geometry is characterised by its topology (which itself is constrained by curvature). General relativity explains how spatial curvature (local geometry) is constrained by gravity . The global topology of the universe cannot be deduced from measurements of curvature inferred from observations within the family of homogeneous general relativistic models alone, due to

3277-414: Is finite in extent ("bounded") and complete . The term "without boundary" means that the space has no edges. Moreover, so that calculus can be applied, the universe is typically assumed to be a differentiable manifold . A mathematical object that possesses all these properties, compact without boundary and differentiable, is termed a closed manifold . The 3-sphere and 3-torus are both closed manifolds. In

3390-464: Is longer in one dimension than the others. Scientists test these models by looking for novel implications – phenomena not yet observed but necessary if the model is accurate. For instance, a small closed universe would produce multiple images of the same object in the sky, though not necessarily of the same age. As of 2024, current observational evidence suggests that the observable universe is spatially flat with an unknown global structure. The curvature

3503-459: Is measured as ρ critical = 9.47 × 10  kg⋅m . From these values, within experimental error, the universe seems to be spatially flat. Another way to measure Ω is to do so geometrically by measuring an angle across the observable universe. This can be done by using the CMB and measuring the power spectrum and temperature anisotropy . For instance, one can imagine finding a gas cloud that

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3616-468: Is not in its lowest energy state (a false vacuum ), it could tunnel into a lower-energy state. This is called vacuum decay . This has the potential to fundamentally alter the universe: in some scenarios, even the various physical constants could have different values, severely affecting the foundations of matter , energy , and spacetime . It is also possible that all structures will be destroyed instantaneously, without any forewarning. However, only

3729-589: Is not in thermal equilibrium due to being so large that light speed cannot propagate the thermal information. Knowing this propagation speed, we then know the size of the gas cloud as well as the distance to the gas cloud, we then have two sides of a triangle and can then determine the angles. Using a method similar to this, the BOOMERanG experiment has determined that the sum of the angles to 180° within experimental error, corresponding to Ω total ≈ 1.00 ± 0.12 . These and other astronomical measurements constrain

3842-511: Is spatially flat to within a 0.4% margin of error of the curvature density parameter with an unknown global topology. It is currently unknown whether the universe is simply connected like euclidean space or multiply connected like a torus. To date, no compelling evidence has been found suggesting the topology of the universe is not simply connected, though it has not been ruled out by astronomical observations. The universe's structure can be examined from two angles: The observable universe (of

3955-422: Is the quotient of the 3-sphere by the binary icosahedral group , which is very close to icosahedral symmetry , the symmetry of a soccer ball. This was proposed by Jean-Pierre Luminet and colleagues in 2003 and an optimal orientation on the sky for the model was estimated in 2008. A hyperbolic universe, one of a negative spatial curvature, is described by hyperbolic geometry, and can be thought of locally as

4068-404: Is the aforementioned 3-torus universe . In the absence of dark energy, a flat universe expands forever but at a continually decelerating rate, with expansion asymptotically approaching zero. With dark energy, the expansion rate of the universe initially slows down, due to the effect of gravity, but eventually increases. The ultimate fate of the universe is the same as that of an open universe in

4181-418: Is true, the universe went through an episode dominated by a different form of dark energy in the first moments of the Big Bang, but inflation ended, indicating an equation of state more complex than those assumed 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 difficult to predict or parameterize. As

4294-581: The American Association for the Advancement of Science that results from a six-year survey with the Mt. Wilson telescope did not support the expanding universe theory. According to a Los Angeles Times article reporting on Hubble's remarks, "The nebulae could not be uniformly distributed, as the telescope shows they are, and still fit the explosion idea. Explanations which try to get around what

4407-606: The Andromeda Nebula and Triangulum Nebula . His observations, made in 1924, proved conclusively that these nebulae were much too distant to be part of the Milky Way and were, in fact, entire galaxies outside our own; thus today they are no longer considered nebulae . This was first hypothesized as early as 1755 when Immanuel Kant 's General History of Nature and Theory of the Heavens appeared. Hubble's hypothesis

4520-556: The Milky Way . He used the strong direct relationship between a classical Cepheid variable 's luminosity and pulsation period (discovered in 1908 by Henrietta Swan Leavitt ) for scaling galactic and extragalactic distances . Hubble confirmed in 1929 that the recessional velocity of a galaxy increases with its distance from Earth, a behavior that became known as Hubble's law , although it had been proposed two years earlier by Georges Lemaître . The Hubble law implies that

4633-533: The United States declared war on Germany in 1917 during World War I , Hubble rushed to complete his Ph.D. dissertation so he could join the military. Hubble volunteered for the United States Army and was assigned to the newly created 86th Division , where he served in the 2nd Battalion, 343rd Infantry Regiment. He rose to the rank of major, and was found fit for overseas duty on July 9, 1918;

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4746-526: The pseudosphere , a canonical model of hyperbolic geometry. An example is the Picard horn , a negatively curved space, colloquially described as "funnel-shaped". When cosmologists speak of the universe as being "open" or "closed", they most commonly are referring to whether the curvature is negative or positive, respectively. These meanings of open and closed are different from the mathematical meaning of open and closed used for sets in topological spaces and for

4859-452: The redshift -distance relation, and published observational support for it, two years before the discovery of Hubble's law. Although he used the term "velocities" in his paper (and "apparent radial velocities" in the introduction), he later expressed doubt about interpreting these as real velocities. In 1931 he wrote a letter to the Dutch cosmologist Willem de Sitter expressing his opinion on

4972-470: The "apparent velocities" in question are usually thought of as an increase in proper distance that occurs due to the expansion of the universe . Light traveling through an expanding metric will experience a Hubble-type redshift, a mechanism somewhat different from the Doppler effect , although the two mechanisms become equivalent descriptions related by a coordinate transformation for nearby galaxies. In

5085-424: The 1930s, Hubble was involved in determining the distribution of galaxies and spatial curvature . These data seemed to indicate that the universe was flat and homogeneous, but there was a deviation from flatness at large redshifts. According to Allan Sandage , Hubble believed that his count data gave a more reasonable result concerning spatial curvature if the redshift correction was made assuming no recession. To

5198-417: The 1980 documentary Cosmos: A Personal Voyage by astronomer Carl Sagan , Hubble's life and work are portrayed on screen in episode 10, "The Edge of Forever". The play Creation's Birthday , written by Cornell physicist Hasan Padamsee, tells Hubble's life story. Shape of the universe In physical cosmology , the shape of the universe refers to both its local and global geometry. Local geometry

5311-402: The 1990s and early 2000s, empirical methods for determining the global topology using measurements on scales that would show multiple imaging were proposed and applied to cosmological observations. In the 2000s and 2010s, it was shown that, since the universe is inhomogeneous as shown in the cosmic web of large-scale structure , acceleration effects measured on local scales in the patterns of

5424-495: The 86th Division moved overseas, but never saw combat as it was broken up and its personnel used as replacements in other units. After the end of World War I, Hubble spent a year at University of Cambridge , where he renewed his studies of astronomy. In 1919, Hubble was offered a staff position at the Carnegie Institution for Science 's Mount Wilson Observatory, near Pasadena, California , by George Ellery Hale ,

5537-565: The American Association Prize and five hundred dollars from Burton E. Livingston of the Committee on Awards. Hubble also devised the most commonly used system for classifying galaxies , grouping them according to their appearance in photographic images. He arranged the different groups of galaxies in what became known as the Hubble sequence. Hubble went on to estimate the distances to 24 extra-galactic nebulae, using

5650-400: The Big Bang theory, specifically that the universe tunneled into existence and had a finite density consistent with quantum mechanics, before evolving in a manner governed by classical physics. Also, if the universe is closed, this theory would predict that once this universe collapses it will spawn another universe in an event similar to the Big Bang after a universal singularity is reached or

5763-502: The Big Bang, but at these scales unknown quantum effects need to be considered (see Quantum gravity ). Recent evidence suggests that this scenario is unlikely but has not been ruled out, as measurements have been available only over a relatively short period of time and could reverse in the future. This scenario allows the Big Bang to occur immediately after the Big Crunch of a preceding universe. If this happens repeatedly, it creates

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5876-555: The Big Bang, that the expansion rate of the universe has probably been increasing, commensurate with the Open Universe theory. However, measurements made by the Wilkinson Microwave Anisotropy Probe suggest that the universe is either flat or very close to flat. If Ω > 1 {\displaystyle \Omega >1} , the geometry of space is closed like the surface of

5989-615: The Chief of the External Ballistics Branch of the Ballistic Research Laboratory during which he directed a large volume of research in exterior ballistics which increased the effective firepower of bombs and projectiles. His work was facilitated by his personal development of several items of equipment for the instrumentation used in exterior ballistics, the most outstanding development being

6102-423: The amount of dark matter and dark energy that the universe contains. The theoretical scientific exploration of the ultimate fate of the universe became possible with Albert Einstein 's 1915 theory of general relativity . General relativity can be employed to describe the universe on the largest possible scale. There are several possible solutions to the equations of general relativity, and each solution implies

6215-414: The analysis considerably. A global geometry is a local geometry plus a topology. It follows that a topology alone does not give a global geometry: for instance, Euclidean 3-space and hyperbolic 3-space have the same topology but different global geometries. As stated in the introduction, investigations within the study of the global structure of the universe include: One of the unanswered questions about

6328-512: The anisotropies in the cosmic microwave background . Edwin Hubble Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an American astronomer. He played a crucial role in establishing the fields of extragalactic astronomy and observational cosmology . Hubble proved that many objects previously thought to be clouds of dust and gas and classified as " nebulae " were actually galaxies beyond

6441-759: The astronomer Mario Livio reported in Nature that a letter he found in the Lemaître archive demonstrated that the redaction had been made by Lemaître himself, who apparently saw no point in publishing scientific content which had already been reported in 1929 by Hubble. However, the fact remains that Lemaître published the law in French, two years prior to Hubble. During Hubble's life the Nobel Prize in Physics did not cover work done in astronomy. Hubble spent much of

6554-404: The average matter density of the universe divided by a critical value of that density. This selects one of three possible geometries depending on whether Ω {\displaystyle \Omega } is equal to, less than, or greater than 1 {\displaystyle 1} . These are called, respectively, the flat, open and closed universes. These three adjectives refer to

6667-551: The beginning of the known universe. It derives from the oscillatory universe or cyclic repetition interpretation of the Big Bang where the first cosmological event was the result of the collapse of a previous universe. According to one version of the Big Bang theory of cosmology, in the beginning the universe was infinitely dense. Such a description seems to be at odds with other more widely accepted theories, especially quantum mechanics and its uncertainty principle . Therefore, quantum mechanics has given rise to an alternative version of

6780-452: The big bang) as anything beyond that is opaque . Studies show that the observable universe is isotropic and homogeneous on the largest scales. If the observable universe encompasses the entire universe, we might determine its structure through observation. However, if the observable universe is smaller, we can only grasp a portion of it, making it impossible to deduce the global geometry through observation. Different mathematical models of

6893-528: The boys' basketball team. After a year of high-school teaching, he entered graduate school with the help of his former professor from the University of Chicago to study astronomy at the university's Yerkes Observatory , where he received his Ph.D. in 1921. His dissertation was titled "Photographic Investigations of Faint Nebulae". At Yerkes, he had access to its 40-inch refractor built in 1897, as well as an innovative 26-inch (61 cm) reflector. After

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7006-563: The bulk of his correspondence, photographs, notebooks, observing logbooks, and other materials, are held by the Huntington Library in San Marino, California. They were donated by his wife Grace Burke Hubble upon her death in 1980. In 2011, the journal Nature reported claims that Hubble might have played a role in the redaction of key parts of the 1931 English translation of Lemaître's 1927 paper, which formulated what

7119-577: The completion of the 100-inch (2.5 m) Hooker Telescope , then the world's largest. At that time, the prevailing view of the cosmos was that the universe consisted entirely of the Milky Way galaxy. Using the Hooker Telescope at Mount Wilson , Hubble identified Cepheid variables , a standard candle discovered by Henrietta Swan Leavitt . Comparing their apparent luminosity to their intrinsic luminosity gives their distance from Earth. Hubble found Cepheids in several nebulae , including

7232-470: The critical energy density. Data from the 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 (predominantly photons and neutrinos ), and dark energy or the cosmological constant : The actual value for critical density value

7345-453: The curvature of the universe can be determined by measuring the average density of matter within it, assuming that all matter is evenly distributed (rather than the distortions caused by 'dense' objects such as galaxies). This assumption is justified by the observations that, while the universe is "weakly" inhomogeneous and anisotropic (see the large-scale structure of the cosmos ), it is on average homogeneous and isotropic when analyzed at

7458-418: The energy density, scale factor and expansion rate become infinite, the universe ends as what is effectively a singularity. In the special case of phantom dark energy , which has supposed negative kinetic energy that would result in a higher rate of acceleration than other cosmological constants predict, a more sudden big rip could occur. The Big Crunch hypothesis is a symmetric view of the ultimate fate of

7571-433: The equator to a pole will have at least two angles equal 90°, which makes the sum of the 3 angles greater than 180°. An example of a negatively curved surface would be the shape of a saddle or mountain pass. A triangle drawn on a saddle surface will have the sum of the angles adding up to less than 180°. General relativity explains that mass and energy bend the curvature of spacetime and is used to determine what curvature

7684-427: The eventual heat death of the universe. Current evidence also indicates the universe is not closed . This has caused cosmologists to abandon the oscillating universe model. A somewhat similar idea is embraced by the cyclic model , but this idea evades heat death because of an expansion of the branes that dilutes entropy accumulated in the previous cycle. The Big Bounce is a theorized scientific model related to

7797-419: The existence of locally indistinguishable spaces with varying global topological characteristics. For example; a multiply connected space like a 3 torus has everywhere zero curvature but is finite in extent, whereas a flat simply connected space is infinite in extent (such as Euclidean space ). Current observational evidence ( WMAP , BOOMERanG , and Planck for example) imply that the observable universe

7910-539: The family could live in a small town, ultimately settling in nearby Louisville . His father died in the winter of 1913, while Edwin was still in England. In the following summer, Edwin returned home to care for his mother, two sisters, and younger brother, along with his brother William. The family moved once more to Everett Avenue, in Louisville's Highlands neighborhood, to accommodate Edwin and William. Hubble

8023-562: The founder and director of the observatory. Hubble remained on staff at Mount Wilson until his death in 1953. Shortly before his death, Hubble became the first astronomer to use the newly completed giant 200-inch (5.1 m) reflector Hale Telescope at the Palomar Observatory near San Diego, California. Hubble also worked as a civilian for United States Army at Aberdeen Proving Ground in Maryland during World War II as

8136-408: The geometry of space is open , i.e., negatively curved like the surface of a saddle. The angles of a triangle sum to less than 180 degrees, and lines that do not meet are never equidistant; they have a point of least distance and otherwise grow apart. The geometry of such a universe is hyperbolic . Even without dark energy, a negatively curved universe expands forever, with gravity negligibly slowing

8249-445: The great telescope sees, he said, fail to stand up. The explosion, for example, would have had to start long after the earth was created, and possibly even after the first life appeared here." (Hubble's estimate of what we now call the Hubble constant would put the Big Bang only 2 billion years ago.) Hubble married Grace Lillian (Burke) Leib (1889–1980), daughter of John Patrick and Luella (Kepford) Burke, on February 26, 1924. Hubble

8362-576: The greater their relative speed of separation. If interpreted that way, Hubble's measurements on 46 galaxies lead to a value for the Hubble constant of 500 km/s/Mpc, which is much higher than the currently accepted values of 74 km/s/Mpc (cosmic distance ladder method) or 68 km/s/Mpc ( CMB method ) due to errors in their distance calibrations. Yet the reason for the redshift remained unclear. Georges Lemaître predicted on theoretical grounds based on Einstein's equations for general relativity

8475-475: The high-speed clock camera, which made possible the study of the characteristics of bombs and low-velocity projectiles in flight. The results of his studies were credited with greatly improving design, performance, and military effectiveness of bombs and rockets. For his work there, he received the Legion of Merit award. Edwin Hubble's arrival at Mount Wilson Observatory, California, in 1919 coincided roughly with

8588-575: The later part of his career attempting to have astronomy considered part of physics, instead of being a separate science. He did this largely so that astronomers—including himself—could be recognized by the Nobel Committee for their valuable contributions to astrophysics . This campaign was unsuccessful in Hubble's lifetime, but shortly after his death, the Nobel Prize Committee decided that astronomical work would be eligible for

8701-514: The local geometry to the global geometry. If the local geometry has constant curvature, the global geometry is very constrained, as described in Thurston geometries . The latest research shows that even the most powerful future experiments (like the SKA ) will not be able to distinguish between a flat, open and closed universe if the true value of cosmological curvature parameter is smaller than 10 . If

8814-531: The mathematical meaning of open and closed manifolds, which gives rise to ambiguity and confusion. In mathematics, there are definitions for a closed manifold (i.e., compact without boundary) and open manifold (i.e., one that is not compact and without boundary). A "closed universe" is necessarily a closed manifold. An "open universe" can be either a closed or open manifold. For example, in the Friedmann–Lemaître–Robertson–Walker (FLRW) model,

8927-431: The movements of galaxies should, in principle, reveal the global topology of the universe. The curvature of the universe places constraints on the topology. If the spatial geometry is spherical , i.e., possess positive curvature, the topology is compact. For a flat (zero curvature) or a hyperbolic (negative curvature) spatial geometry, the topology can be either compact or infinite. Many textbooks erroneously state that

9040-437: The nature of dark energy and dark matter remain enigmatic, even hypothetical, the possibilities surrounding their coming role in the universe are unknown. There are also some possible events, such as the Big Slurp, which would seriously harm the universe, although the universe as a whole would not be completely destroyed as a result. This theory posits that the universe currently exists in a false vacuum and that it could become

9153-419: The opposite of the Big Bang . If, however, the universe contains dark energy, then the resulting repulsive force may be sufficient to cause the expansion of the universe to continue forever—even if Ω > 1 {\displaystyle \Omega >1} . This is the case in the currently accepted Lambda-CDM model , where dark energy is found through observations to account for roughly 68% of

9266-452: The origin of the universe. Einstein and his contemporaries believed in a static universe . When Einstein found that his general relativity equations could easily be solved in such a way as to allow the universe to be expanding at the present and contracting in the far future, he added to those equations what he called a cosmological constant  ⁠— ⁠essentially a constant energy density, unaffected by any expansion or contraction ⁠— ⁠whose role

9379-485: The overall geometry of the universe , and not to the local curving of spacetime caused by smaller clumps of mass (for example, galaxies and stars ). If the primary content of the universe is inert matter, as in the dust models popular for much of the 20th century, there is a particular fate corresponding to each geometry. Hence cosmologists aimed to determine the fate of the universe by measuring Ω {\displaystyle \Omega } , or equivalently

9492-414: The physical properties of the mass–energy in the universe. There is a strong consensus among cosmologists that the shape of the universe is considered "flat" ( parallel lines stay parallel) and will continue to expand forever. Factors that need to be considered in determining the universe's origin and ultimate fate include the average motions of galaxies, the shape and structure of the universe, and

9605-554: The physics prize. However, the Nobel prize is not awarded posthumously. On March 6, 2008, the United States Postal Service released a 41-cent stamp honoring Hubble on a sheet titled "American Scientists" designed by artist Victor Stabin . His citation reads: Often called a "pioneer of the distant stars", astronomer Edwin Hubble (1889–1953) played a pivotal role in deciphering the vast and complex nature of

9718-441: The rate at which the expansion was decelerating. Starting in 1998, observations of supernovas in distant galaxies have been interpreted as consistent with a universe whose expansion is accelerating . Subsequent cosmological theorizing has been designed so as to allow for this possible acceleration, nearly always by invoking dark energy , which in its simplest form is just a positive cosmological constant. In general, dark energy

9831-458: The rate of expansion. With dark energy, the expansion not only continues but accelerates. The ultimate fate of an open universe with dark energy is either universal heat death or a " 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 cosmological constant , which would correspond to

9944-430: The same distance. Measurements from the Wilkinson Microwave Anisotropy Probe have confirmed the universe is flat within a 0.4% margin of error. In the absence of dark energy, a flat universe expands forever but at a continually decelerating rate, with expansion asymptotically approaching zero. With dark energy, the expansion rate of the universe initially slows, due to the effects of gravity, but eventually increases, and

10057-473: The sense that space will continue expanding forever. A flat universe can have zero total energy . A positively curved universe is described by elliptic geometry , and can be thought of as a three-dimensional hypersphere , or some other spherical 3-manifold (such as the Poincaré dodecahedral space ), all of which are quotients of the 3-sphere. Poincaré dodecahedral space is a positively curved space, colloquially described as "soccerball-shaped", as it

10170-399: The spatial curvature to be very close to zero, although they do not constrain its sign. This means that although the local geometries of spacetime are generated by the theory of relativity based on spacetime intervals , we can approximate 3-space by the familiar Euclidean geometry . The Friedmann–Lemaître–Robertson–Walker (FLRW) model using Friedmann equations is commonly used to model

10283-428: The theoretical interpretation of the redshift-distance relation: Mr. Humason and I are both deeply sensible of your gracious appreciation of the papers on velocities and distances of nebulae. We use the term 'apparent' velocities to emphasize the empirical features of the correlation. The interpretation, we feel, should be left to you and the very few others who are competent to discuss the matter with authority. Today,

10396-631: The total energy content of the universe. According to the Lambda-CDM model, the universe would need to have an average matter density roughly seventeen times greater than its measured value today in order for the effects of dark energy to be overcome and the universe to eventually collapse. This is in spite of the fact that, according to the Lambda-CDM model, any increase in matter density would result in Ω > 1 {\displaystyle \Omega >1} . If Ω < 1 {\displaystyle \Omega <1} ,

10509-418: The true distances, and combining his distances with measurements of the redshifts of the galaxies by Vesto Slipher , and by his assistant Milton L. Humason , he found a roughly linear relationship between the distances of the galaxies and their radial velocities (corrected for solar motion), a discovery that later became known as Hubble's law. This meant that the greater the distance between any two galaxies,

10622-531: The true value of the cosmological curvature parameter is larger than 10 we will be able to distinguish between these three models even now. Final results of the Planck mission, released in 2018, show the cosmological curvature parameter, 1 − Ω = Ω K = − Kc / a H , to be 0.0007 ± 0.0019 , consistent with a flat universe. (i.e. positive curvature: K = +1 , Ω K < 0 , Ω > 1 , negative curvature: K = −1 , Ω K > 0 , Ω < 1 , zero curvature: K = 0 , Ω K = 0 , Ω = 1 ). In

10735-460: The ultimate fate of the universe becomes the same as that of an open universe. The fate of the universe may be determined by its density. The preponderance of evidence to date, based on measurements of the rate of expansion and the mass density, favors a universe that will continue to expand indefinitely, resulting in the "Big Freeze" scenario below. However, observations are not conclusive, and alternative models are still possible. The heat death of

10848-469: The universe has by using a value called the density parameter , represented with Omega ( Ω ). The density parameter is the average density of the universe divided by the critical energy density, that is, the mass energy needed for a universe to be flat. Put another way, Scientists could experimentally calculate Ω to determine the curvature two ways. One is to count all the mass–energy in the universe and take its average density, then divide that average by

10961-556: The universe is expanding. A decade before, the American astronomer Vesto Slipher had provided the first evidence that the light from many of these nebulae was strongly red-shifted, indicative of high recession velocities. Hubble's name is most widely recognized for the Hubble Space Telescope , which was named in his honor, with a model prominently displayed in his hometown of Marshfield, Missouri . Edwin Hubble

11074-561: The universe is whether it is infinite or finite in extent. For intuition, it can be understood that a finite universe has a finite volume that, for example, could be in theory filled with a finite amount of material, while an infinite universe is unbounded and no numerical volume could possibly fill it. Mathematically, the question of whether the universe is infinite or finite is referred to as boundedness . An infinite universe (unbounded metric space) means that there are points arbitrarily far apart: for any distance d , there are points that are of

11187-415: The universe must be either expanding or contracting. Unable to believe what his own equations were telling him, Einstein introduced a cosmological constant (a " fudge factor ") to the equations to avoid this "problem". When Einstein learned of Hubble's redshifts, he immediately realized that the expansion predicted by general relativity must be real, and in later life, he said that changing his equations

11300-446: The universe was expanding. From then on, the beginning of the universe and its possible end have been the subjects of serious scientific investigation. In 1927, Georges Lemaître set out a theory that has since come to be called the Big Bang theory of the origin of the universe. In 1948, Fred Hoyle set out his opposing Steady State theory in which the universe continually expanded but remained statistically unchanged as new matter

11413-408: The universe's global geometry can be constructed, all consistent with current observations and general relativity. Hence, it is unclear whether the observable universe matches the entire universe or is significantly smaller, though it is generally accepted that the universe is larger than the observable universe. The universe may be compact in some dimensions and not in others, similar to how a cuboid

11526-477: The universe, also known as the Big Freeze (or Big Chill), is a scenario under which continued expansion results in a universe that asymptotically approaches absolute zero temperature. Under this scenario, the universe eventually reaches a state of maximum entropy in which everything is evenly distributed and there are no energy gradients —which are needed to sustain information processing, one form of which

11639-556: The universe. His meticulous studies of spiral nebulae proved the existence of galaxies other than our own Milky Way. Had he not died suddenly in 1953, Hubble would have won that year's Nobel Prize in Physics. (The assertion that he would have won the Nobel Prize in 1953 is likely false, although he was nominated for the prize that year. ) The other scientists on the "American Scientists" sheet include Gerty Cori , biochemist; Linus Pauling , chemist, and John Bardeen , physicist. In

11752-403: The universe. Just as the theorized Big Bang started as a cosmological expansion, this theory assumes that the average density of the universe will be enough to stop its expansion and the universe will begin contracting. The result is unknown; a simple estimation would have all the matter and spacetime in the universe collapse into a dimensionless singularity back into how the universe started with

11865-441: The universe. The FLRW model provides a curvature of the universe based on the mathematics of fluid dynamics , that is, modeling the matter within the universe as a perfect fluid. Although stars and structures of mass can be introduced into an "almost FLRW" model, a strictly FLRW model is used to approximate the local geometry of the observable universe. Another way of saying this is that, if all forms of dark energy are ignored, then

11978-592: The very end of his writings, he maintained this position, favouring (or at the very least keeping open) the model where no true expansion exists, and therefore that the redshift "represents a hitherto unrecognized principle of nature." There were methodological problems with Hubble's survey technique that showed a deviation from flatness at large redshifts. In particular, the technique did not account for changes in luminosity of galaxies due to galaxy evolution . Earlier, in 1917, Albert Einstein had found that his newly developed theory of general relativity indicated that

12091-511: Was "the biggest blunder of [his] life". In fact, Einstein apparently once visited Hubble and tried to convince him that the universe was expanding. Hubble also discovered the asteroid 1373 Cincinnati on August 30, 1935. In 1936 he wrote The Observational Approach to Cosmology and The Realm of the Nebulae which explained his approaches to extra-galactic astronomy and his view of the subject's history. In December 1941, Hubble reported to

12204-629: Was a dutiful son, who despite his intense interest in astronomy since boyhood, acquiesced to his father's request to study law, first at the University of Chicago and later at Oxford. In this time, he also took some math and science courses. After the death of his father in 1913, Edwin returned to the Midwest from Oxford but did not have the motivation to practice law. Instead, he proceeded to teach Spanish, physics and mathematics at New Albany High School in New Albany , Indiana, where he also coached

12317-550: Was born in 1889 to Virginia Lee Hubble (née James) (1864–1934) and John Powell Hubble, an insurance executive, in Marshfield, Missouri, and moved to Wheaton , Illinois, in 1900. In his younger days, he was noted more for his athletic prowess than his intellectual abilities, although he did earn good grades in every subject except spelling. Edwin was a gifted athlete, playing baseball , football , and running track in both high school and college. He won seven first places and

12430-405: Was later called Hubble's law and also gave observational evidence. Historians quoted in the article were skeptical that the redactions were part of a campaign to ensure Hubble retained priority. However, the observational astronomer Sidney van den Bergh published a paper suggesting that while the omissions may have been made by a translator, they may still have been deliberate. In November 2011,

12543-662: Was opposed by many in the astronomy establishment of the time, in particular by Harvard University –based Harlow Shapley . Despite the opposition, Hubble, then a thirty-five-year-old scientist, had his findings first published in The New York Times on November 23 , 1924, then presented them to other astronomers at the January 1, 1925, meeting of the American Astronomical Society . Hubble's results for Andromeda were not formally published in

12656-632: Was raised as a Protestant Christian, but some of his later statements suggest uncertainty. Hubble had a heart attack in July 1949 while on vacation in Colorado . He was cared for by his wife and continued on a modified diet and work schedule. He died of cerebral thrombosis (a blood clot in his brain) on September 28, 1953, in San Marino , California. No funeral was held for him, and his wife never revealed his burial site. Hubble's papers comprising

12769-450: Was to offset the effect of gravity on the universe as a whole in such a way that the universe would remain static. However, after Hubble announced his conclusion that the universe was expanding, Einstein would write that his cosmological constant was "the greatest blunder of my life." An important parameter in fate of the universe theory is the density parameter , omega ( Ω {\displaystyle \Omega } ), defined as

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