Misplaced Pages

#394605

75-695: This is the timeline of the Stelliferous era but also partly charts the Primordial era , and charts more of the Degenerate era of the heat death scenario. The scale is 10 × log 10 ⁡ { t } {\displaystyle 10\times \log _{10}\{t\}} where { t } {\displaystyle \{t\}} is the time since the Big Bang expressed in years. For example, 10 billion years after

150-478: A galaxy exchange kinetic energy in a process called dynamical relaxation , making their velocity distribution approach the Maxwell–Boltzmann distribution . Dynamical relaxation can proceed either by close encounters of two stars or by less violent but more frequent distant encounters. In the case of a close encounter, two brown dwarfs or stellar remnants will pass close to each other. When this happens,

225-409: A quasar , as long as enough matter is present there. In an expanding universe with decreasing density and non-zero cosmological constant , matter density would reach zero, resulting in most matter except black dwarfs , neutron stars , black holes , and planets ionizing and dissipating at thermal equilibrium . The following timeline assumes that protons do decay. The subsequent evolution of

300-632: A combined mass of more than the Chandrasekhar limit of about 1.4 solar masses happen to merge. The resulting object will then undergo runaway thermonuclear fusion, producing a Type Ia supernova and dispelling the darkness of the Degenerate Era for a few weeks. Neutron stars could also collide , forming even brighter supernovae and dispelling up to 6 solar masses of degenerate gas into the interstellar medium. The resulting matter from these supernovae could potentially create new stars. If

375-502: A false vacuum ; 95% confidence interval is 10 to 10 years due in part to uncertainty about the top quark mass. In 10 years, cold fusion occurring via quantum tunneling should make the light nuclei in stellar-mass objects fuse into iron-56 nuclei (see isotopes of iron ). Fission and alpha particle emission should make heavy nuclei also decay to iron, leaving stellar-mass objects as cold spheres of iron, called iron stars . Before this happens, however, in some black dwarfs

450-484: A final heat death of the universe. Infinite expansion does not constrain the overall spatial curvature of the universe . It can be open (with negative spatial curvature), flat, or closed (positive spatial curvature), although if it is closed, sufficient dark energy must be present to counteract the gravitational forces or else the universe will end in a Big Crunch . Observations of the Cosmic microwave background by

525-436: A finite scale factor. If the current vacuum state is a false vacuum , the vacuum may decay into an even lower-energy state. Presumably, extreme low- energy states imply that localized quantum events become major macroscopic phenomena rather than negligible microscopic events because even the smallest perturbations make the biggest difference in this era, so there is no telling what will or might happen to space or time. It

600-489: A general relativity-based theory called the conformal cyclic cosmology in which the universe expands until all the matter decays and is turned to light. Since nothing in the universe would have any time or distance scale associated with it, it becomes identical with the Big Bang (resulting in a type of Big Crunch that becomes the next Big Bang, thus starting the next cycle). Penrose and Gurzadyan suggested that signatures of conformal cyclic cosmology could potentially be found in

675-421: A half-life comparable to that of protons. Planets (substellar objects) would decay in a simple cascade process from heavier elements to hydrogen and finally to photons and leptons while radiating energy. If the proton does not decay at all, then stellar objects would still disappear, but more slowly. See § Future without proton decay below. Shorter or longer proton half-lives will accelerate or decelerate

750-502: A process called 'stellar ignition' occurs, and its lifetime as a star will properly begin. Stars of very low mass will eventually exhaust all their fusible hydrogen and then become helium white dwarfs . Stars of low to medium mass, such as our own sun , will expel some of their mass as a planetary nebula and eventually become white dwarfs ; more massive stars will explode in a core-collapse supernova , leaving behind neutron stars or black holes . In any case, although some of

825-477: A rough proportionality between the red shift of an object and its distance. Hubble plotted a trend line from 46 galaxies, studying and obtaining the Hubble Constant , which he deduced to be 500 km/s/Mpc, nearly seven times than what it is considered today, but still giving the proof that the universe was expanding and was not a static object. After Hubble's discovery was published, Einstein abandoned

SECTION 10

#1732791155395

900-510: A set of equations showing that the end of the universe depends on its density . It could either expand or contract rather than stay stable. With enough matter, gravity could stop the universe's expansion and eventually reverse it. This reversal would result in the universe collapsing on itself, not too dissimilar to a black hole . The ending of the Big Crunch would get filled with radiation from stars and high-energy particles ; when this

975-465: A singular point, and if we're in an infinite universe with infinite stars, would infinite forces in every direction not affect all of those stars? This question is known as Bentley's paradox , an early predecessor of the Big Crunch. Although, it is now known that stars move around and are not static. Albert Einstein favored an unchanging model of the universe. He collaborated in 1917 with Dutch astronomer Willem de Sitter to help demonstrate that

1050-405: A smaller, denser galaxy. Since encounters are more frequent in this denser galaxy, the process then accelerates. The result is that most objects (90% to 99%) are ejected from the galaxy, leaving a small fraction (maybe 1% to 10%) which fall into the central supermassive black hole . It has been suggested that the matter of the fallen remnants will form an accretion disk around it that will create

1125-498: A universe in a state of constant Big Bangs and Big Crunches. Cyclic universes were briefly considered by Albert Einstein in 1931. He hypothesized that there was a universe before the Big Bang, which ended in a Big Crunch, which could create a Big Bang as a reaction. Our universe could be in a cycle of expansion and contraction, a cycle possibly going on infinitely. There are more modern models of Cyclic universes as well. The Ekpyrotic model , formed by Paul Steinhardt , states that

1200-445: Is condensed and blueshifted to higher energy, it would be intense enough to ignite the surface of stars before they collide. In the final moments, the universe would be one large fireball with a near-infinite temperature, and at the absolute end, neither time, nor space would remain. The Big Crunch scenario hypothesized that the density of matter throughout the universe is sufficiently high that gravitational attraction will overcome

1275-449: 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 correct, 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 much more complicated than those assumed so far for present-day dark energy. It

1350-452: Is negligible at low spacetime curvature, but that rises very rapidly in the Planck regime , overwhelming classical gravity and resolving singularities of general relativity . Once the singularities are resolved the conceptual paradigm of cosmology changes, forcing one to revisit the standard issues—such as the horizon problem—from a new perspective. Under this model, due to quantum geometry,

1425-436: Is now an almost pure vacuum (possibly accompanied with the presence of a false vacuum ). The expansion of the universe slowly causes itself to cool down to absolute zero . The universe now reaches an even lower energy state than the earlier one mentioned. Whatever event happens beyond this era is highly speculative. It is possible that a Big Rip event may occur far off into the future. This singularity would take place at

1500-446: Is perceived that the laws of "macro-physics" will break down, and the laws of quantum physics will prevail. The universe could possibly avoid eternal heat death through random quantum tunneling and quantum fluctuations , given the non-zero probability of producing a new Big Bang creating a new universe in roughly 10 years. Big Crunch The hypothesis dates back to 1922, with Russian physicist Alexander Friedmann creating

1575-495: 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 Gregory Laughlin divided

SECTION 20

#1732791155395

1650-408: Is true as well, the accelerating expansion of the Universe would inverse to contraction within the cosmic near-future of the next 100 million years. According to an Andrei-Ijjas-Steinhardt study, the scenario fits "naturally with cyclic cosmologies and recent conjectures about quantum gravity ". The study suggests that the slow contraction phase would "endure for a period of order 1 billion y before

1725-469: The Adler–Bell–Jackiw anomaly , virtual black holes , or higher-dimension supersymmetry possibly with a half-life of under 10 years. 2018 estimate of Standard Model lifetime before collapse of a false vacuum ; 95% confidence interval is 10 to 10 years due in part to uncertainty about the top quark mass. Although protons are stable in standard model physics, a quantum anomaly may exist on

1800-680: The Big Bang , the Milky Way and the Andromeda galaxy will collide with one another and merge into one large galaxy based on current evidence. Up until 2012, there was no way to confirm whether the possible collision was going to happen or not. In 2012, researchers came to the conclusion that the collision is definite after using the Hubble Space Telescope between 2002 and 2010 to track the motion of Andromeda. This results in

1875-414: The Big Bang , the first star formed. Since then, stars have formed by the collapse of small, dense core regions in large, cold molecular clouds of hydrogen gas. At first, this produces a protostar , which is hot and bright because of energy generated by gravitational contraction . After the protostar contracts for a while, its core could become hot enough to fuse hydrogen, if it exceeds critical mass,

1950-527: The Big Bounce , in which after the big crunch destroys the universe, it does a sort of bounce, causing another big bang. This could potentially repeat forever in a phenomenon known as a cyclic universe. Richard Bentley, a churchman and scholar, sent a letter to Isaac Newton in preparation for a lecture on Newton's theories and the rejection of atheism : If we're in a finite universe and all stars attract each other together, would they not all collapse to

2025-655: The Local Supercluster will be redshifted to such an extent that even gamma rays they emit will have wavelengths longer than the size of the observable universe of the time. Therefore, these galaxies will no longer be detectable in any way. By 10 (100 trillion) years from now, star formation will end, leaving all stellar objects in the form of degenerate remnants . If protons do not decay , stellar-mass objects will disappear more slowly, making this era last longer . By 10 (100 trillion) years from now, star formation will end. This period, known as

2100-546: The Local Supercluster will pass behind the cosmological horizon . It will then be impossible for events in the Local Supercluster to affect other galaxies. Similarly, it will be impossible for events after 150 billion years, as seen by observers in distant galaxies, to affect events in the Local Supercluster. However, an observer in the Local Supercluster will continue to see distant galaxies, but events they observe will become exponentially more redshifted as

2175-545: The Wilkinson Microwave Anisotropy Probe and the Planck mission suggest that the universe is spatially flat and has a significant amount of dark energy . In this case, the universe might 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

2250-452: The cosmic microwave background ; as of 2020, these have not been detected. There are also some flaws with this model as well: skeptics pointed out that in order to match up an infinitely large universe to an infinitely small universe, that all particles must lose their mass when the universe gets old. Penrose presented evidence of CCC in the form of rings that had uniform temperature in the CMB,

2325-512: The electroweak level, which can cause groups of baryons (protons and neutrons) to annihilate into antileptons via the sphaleron transition. Such baryon/lepton violations have a number of 3 and can only occur in multiples or groups of three baryons, which can restrict or prohibit such events. No experimental evidence of sphalerons has yet been observed at low energy levels, though they are believed to occur regularly at high energies and temperatures. After 10  years, black holes will dominate

Graphical timeline of the Stelliferous Era - Misplaced Pages Continue

2400-535: The universe will continue forever. The prevailing theory is that the universe will cool as it expands, eventually becoming too cold to sustain life. For this reason, this future scenario once popularly called " Heat Death " is now known as the "Big Chill" or "Big Freeze". If dark energy —represented by the cosmological constant , a constant energy density filling space homogeneously, or scalar fields , such as quintessence or moduli , dynamic quantities whose energy density can vary in time and space—accelerates

2475-413: The "Degenerate Era", will last until the degenerate remnants finally decay. The least-massive stars take the longest to exhaust their hydrogen fuel (see stellar evolution ). Thus, the longest living stars in the universe are low-mass red dwarfs , with a mass of about 0.08 solar masses ( M ☉ ), which have a lifetime of over 10 (10 trillion) years. Coincidentally, this is comparable to

2550-399: The Big Bang (13.8 billion years ago) is 10 × log 10 ⁡ { 10 , 000 , 000 , 000 } = 10 × 10 = 100 {\displaystyle 10\times \log _{10}\{10,000,000,000\}=10\times 10=100} . Future of an expanding universe#The Stelliferous Era Current observations suggest that the expansion of

2625-510: The Big Bang could have been caused by two parallel orbifold planes, referred to as branes colliding in a higher-dimensional space. The four-dimension universe lies on one of the branes. The collision corresponds to the Big Crunch, then a Big Bang. The matter and radiation around us today are quantum fluctuations from before the branes. After several billion years, the universe has reached its modern state, and it will start contracting in another several billion years. Dark energy corresponds to

2700-678: The Big Bang is replaced by the Big Bounce with no assumptions or any fine tuning. The approach of effective dynamics has been used extensively in loop quantum cosmology to describe physics at the Planck scale, and also the beginning of the universe. Numerical simulations have confirmed the validity of effective dynamics, which provides a good approximation of the full loop quantum dynamics. It has been shown when states have very large quantum fluctuations at late times, meaning they do not lead to macroscopic universes as described by general relativity, but

2775-559: The CMB becomes hotter than M-type stars (about 500,000 years before the Big Crunch in Davies' model), they would no longer be able to radiate away their heat and would cook themselves until they evaporate; this continues for successively hotter stars until O-type stars boil away about 100,000 years before the Big Crunch. In the last minutes, the temperature of the universe would be so great that atoms and atomic nuclei would break up and get sucked up into already coalescing black holes . At

2850-425: The Local Supercluster becomes causally impossible. 8 × 10 (800 billion) years from now, the luminosities of the different galaxies, approximately similar until then to the current ones thanks to the increasing luminosity of the remaining stars as they age, will start to decrease, as the less massive red dwarf stars begin to die as white dwarfs . 2 × 10 (2 trillion) years from now, all galaxies outside

2925-472: The Milky Way and the Andromeda Galaxy, are gravitationally bound to each other. It is expected that between 10 (100 billion) and 10 (1 trillion) years from now, their orbits will decay and the entire Local Group will merge into one large galaxy. Assuming that dark energy continues to make the universe expand at an accelerating rate, in about 150 billion years all galaxies outside

3000-475: The basis of modern cosmology". After this discovery, Einstein's and Newton's models of a contracting, yet static universe were dropped for the expanding universe model. A hypothesis called " Big Bounce " proposes that the universe could collapse to the state where it began and then initiate another Big Bang, so in this way, the universe would last forever but would pass through phases of expansion (Big Bang) and contraction (Big Crunch). This means that there may be

3075-575: The black hole's mass decreases, its temperature increases, becoming comparable to the Sun 's by the time the black hole mass has decreased to 10 kilograms. The hole then provides a temporary source of light during the general darkness of the Black Hole Era. During the last stages of its evaporation, a black hole will emit not only massless particles, but also heavier particles, such as electrons , positrons , protons , and antiprotons . After all

Graphical timeline of the Stelliferous Era - Misplaced Pages Continue

3150-489: The black holes have evaporated (and after all the ordinary matter made of protons has disintegrated, if protons are unstable), the universe will be nearly empty. Photons , leptons , baryons , neutrinos , electrons , and positrons will fly from place to place, hardly ever encountering each other. Gravitationally , the universe will be dominated by dark matter , electrons , and positrons (not protons ). By this era, with only very diffuse matter remaining, activity in

3225-677: The combined mass is not above the Chandrasekhar limit but is larger than the minimum mass to fuse carbon (about 0.9  M ☉ ), a carbon star could be produced, with a lifetime of around 10 (1 million) years. Also, if two helium white dwarfs with a combined mass of at least 0.3  M ☉ collide, a helium star may be produced, with a lifetime of a few hundred million years. Finally, brown dwarfs could form new stars by colliding with each other to form red dwarf stars, which can survive for 10 (10 trillion) years, or by accreting gas at very slow rates from

3300-410: The cosmological constant. In their simplest form, the equations generated a model of the universe that expanded or contracted. Contradicting what was observed, hence the creation of the cosmological constant. After the confirmation that the universe was expanding, Einstein called his assumption that the universe was static his "biggest mistake". In 1931, Einstein visited Hubble to thank him for "providing

3375-486: The effective dynamics departs from quantum dynamics near bounce and the later universe. In this case, the effective dynamics will overestimate the density at bounce, but it will still capture qualitative aspects extremely well. If a form of quintessence driven by a scalar field evolving down a monotonically decreasing potential that passes sufficiently below zero is the (main) explanation of dark energy and current data (in particular observational constraints on dark energy)

3450-448: The expansion of the universe, then the space between clusters of galaxies will grow at an increasing rate. Redshift will stretch ancient ambient photons (including gamma rays) to undetectably long wavelengths and low energies. 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,

3525-435: The expansion that began with the Big Bang. The FLRW cosmology can predict whether the expansion will eventually stop based on the average energy density , Hubble parameter , and cosmological constant . If the expansion stopped, then contraction will inevitably follow, accelerating as time passes and finishing the universe in a kind of gravitational collapse , turning the universe into a black hole. Experimental evidence in

3600-520: The force between the branes, allowing for problems, like the flatness and monopole in the previous models to be fixed. The cycles can also go infinitely into the past and the future, and an attractor allows for a complete history of the universe. This fixes the problem of the earlier model of the universe going into heat death from entropy buildup. The new model avoids this with a net expansion after every cycle, stopping entropy buildup. There are still some flaws in this model, however. The basis of

3675-571: The formation of Milkdromeda (also known as Milkomeda ). 22 billion years in the future is the earliest possible end of the Universe in the Big Rip scenario, assuming a model of dark energy with w = −1.5 . False vacuum decay may occur in 20 to 30 billion years if the Higgs field is metastable. The galaxies in the Local Group , the cluster of galaxies which includes

3750-405: The galaxy approaches the horizon until time in the distant galaxy seems to stop. The observer in the Local Supercluster never observes events after 150 billion years in their local time, and eventually all light and background radiation lying outside the Local Supercluster will appear to blink out as light becomes so redshifted that its wavelength has become longer than the physical diameter of

3825-446: The horizon. Technically, it will take an infinitely long time for all causal interaction between the Local Supercluster and this light to cease. However, due to the redshifting explained above, the light will not necessarily be observed for an infinite amount of time, and after 150 billion years, no new causal interaction will be observed. Therefore, after 150 billion years, intergalactic transportation and communication beyond

SECTION 50

#1732791155395

3900-421: The idea being that these rings would be the signature in our aeon—An aeon being the current cycle of the universe that we're in—was caused by spherical gravitational waves caused by colliding black holes from our previous aeon. Loop quantum cosmology is a model of the universe that proposes a "quantum-bridge" between expanding and contracting universes. In this model quantum geometry creates a brand-new force that

3975-515: The late 1990s and early 2000s (namely the observation of distant supernovas as standard candles ; and the well-resolved mapping of the cosmic microwave background ) led to the conclusion that the expansion of the universe is not getting slowed by gravity but is instead accelerating . The 2011 Nobel Prize in Physics was awarded to researchers who contributed to this discovery. The Big Crunch hypothesis also leads into another hypothesis known as

4050-595: The length of time over which star formation takes place. Once star formation ends and the least-massive red dwarfs exhaust their fuel, nuclear fusion will cease. The low-mass red dwarfs will cool and become black dwarfs . The only objects remaining with more than planetary mass will be brown dwarfs , with mass less than 0.08  M ☉ , and degenerate remnants ; white dwarfs , produced by stars with initial masses between about 0.08 and 8 solar masses; and neutron stars and black holes , produced by stars with initial masses over 8  M ☉ . Most of

4125-417: The mass of this collection, approximately 90%, will be in the form of white dwarfs. In the absence of any energy source, all of these formerly luminous bodies will cool and become faint. The universe will become extremely dark after the last stars burn out. Even so, there can still be occasional light in the universe. One of the ways the universe can be illuminated is if two carbon – oxygen white dwarfs with

4200-482: The model, branes, are still not understood completely by string theorists, and the possibility that the scale invariant spectrum could be destroyed from the big crunch. While cosmic inflation and the general character of the forces—or the collision of the branes in the Ekpyrotic model—required to make vacuum fluctuations is known. A candidate from particle physics is missing. Physicist Roger Penrose advanced

4275-528: The past and future history of an expanding universe into five eras. The first, the Primordial Era , is the time in the past just after the Big Bang when stars had not yet formed. The second, the Stelliferous Era , includes the present day and all of the stars and galaxies now seen. It is the time during which stars form from collapsing clouds of gas . In the subsequent Degenerate Era ,

4350-729: The process is expected to lower their Chandrasekhar limit resulting in a supernova in 10 years. Non-degenerate silicon has been calculated to tunnel to iron in approximately 10 years. Quantum tunneling should also turn large objects into black holes , which (on these timescales) will instantaneously evaporate into subatomic particles. Depending on the assumptions made, the time this takes to happen can be calculated as from 10 years to 10 years. Quantum tunneling may also make iron stars collapse into neutron stars in around 10 years. With black holes having evaporated, nearly all baryonic matter will have now decayed into subatomic particles (electrons, neutrons, protons, and quarks). The universe

4425-537: The process. This means that after 10 years (the maximum proton half-life used by Adams & Laughlin (1997)), one-half of all baryonic matter will have been converted into gamma ray photons and leptons through proton decay. Given our assumed half-life of the proton, nucleons (protons and bound neutrons) will have undergone roughly 1,000 half-lives by the time the universe is 10 years old. This means that there will be roughly 0.5 (approximately 10 ) as many nucleons; as there are an estimated 10 protons currently in

4500-485: The proton does not decay according to the theories described above, then the Degenerate Era will last longer, and will overlap or surpass the Black Hole Era. On a time scale of 10 years solid matter is theorized to potentially rearrange its atoms and molecules via quantum tunneling , and may behave as liquid and become smooth spheres due to diffusion and gravity. Degenerate stellar objects can potentially still experience proton decay, for example via processes involving

4575-427: The remaining interstellar medium until they have enough mass to start hydrogen burning as red dwarfs. This process, at least on white dwarfs, could induce Type Ia supernovae. Over time, the orbits of planets will decay due to gravitational radiation , or planets will be ejected from their local systems by gravitational perturbations caused by encounters with another stellar remnant . Over time, objects in

SECTION 60

#1732791155395

4650-592: The star's matter may be returned to the interstellar medium , a degenerate remnant will be left behind whose mass is not returned to the interstellar medium. Therefore, the supply of gas available for star formation is steadily being exhausted. The Andromeda Galaxy is approximately 2.5 million light years away from our galaxy, the Milky Way galaxy, and they are moving towards each other at approximately 300 kilometers (186 miles) per second. Approximately five billion years from now, or 19 billion years after

4725-559: The stars will have burnt out, leaving all stellar-mass objects as stellar remnants — white dwarfs , neutron stars , and black holes . In the Black Hole Era , white dwarfs, neutron stars, and other smaller astronomical objects have been destroyed by proton decay , leaving only black holes. Finally, in the Dark Era , even black holes have disappeared, leaving only a dilute gas of photons and leptons . This future history and

4800-420: The theory of general relativity would work with a static model; Willem demonstrated that his equations could describe a very simple universe. Finding no problems initially, scientists adapted the model to describe the universe. They ran into a different form of Bentley's paradox. The theory of general relativity also described the universe as restless. Einstein realized that for a static universe to exist—which

4875-448: The time of the Big Crunch, all the matter in the universe would be crushed into an infinitely hot, infinitely dense singularity similar to the Big Bang . The Big Crunch may be followed by another Big Bang, creating a new universe. In The Restaurant at the End of the Universe , a novel by Douglas Adams , the concept is that a restaurant, Milliways, is set up to allow patrons to observe

4950-573: The timeline below assume the continued expansion of the universe. If space in the universe begins to contract, subsequent events in the timeline may not occur because the Big Crunch , the collapse of the universe into a hot, dense state similar to that after the Big Bang, will prevail. The observable universe is currently 1.38 × 10 (13.8 billion) years old. This time lies within the Stelliferous Era. About 155 million years after

5025-423: The trajectories of the objects involved in the close encounter change slightly, in such a way that their kinetic energies are more nearly equal than before. After a large number of encounters, then, lighter objects tend to gain speed while the heavier objects lose it. Because of dynamical relaxation, some objects will gain just enough energy to reach galactic escape velocity and depart the galaxy, leaving behind

5100-463: The universe are predicted to continue to grow. Larger black holes of up to 10 (100 trillion) M ☉ may form during the collapse of superclusters of galaxies. Even these would evaporate over a timescale of 10 to 10 years. Hawking radiation has a thermal spectrum . During most of a black hole's lifetime, the radiation has a low temperature and is mainly in the form of massless particles such as photons and hypothetical gravitons . As

5175-753: The universe depends on the possibility and rate of proton decay . Experimental evidence shows that if the proton is unstable, it has a half-life of at least 10 years. Some of the Grand Unified theories (GUTs) predict long-term proton instability between 10 and 10 years, with the upper bound on standard (non-supersymmetry) proton decay at 1.4 × 10 years and an overall upper limit maximum for any proton decay (including supersymmetry models) at 6 × 10 years. Recent research showing proton lifetime (if unstable) at or exceeding 10 –10 year range rules out simpler GUTs and most non-supersymmetry models. Neutrons bound into nuclei are also suspected to decay with

5250-538: The universe transitions to a new phase of expansion". Paul Davies considered a scenario in which the Big Crunch happens about 100 billion years from the present. In his model, the contracting universe would evolve roughly like the expanding phase in reverse. First, galaxy clusters , and then galaxies, would merge, and the temperature of the cosmic microwave background (CMB) would begin to rise as CMB photons get blueshifted . Stars would eventually become so close together that they begin to collide with each other. Once

5325-872: The universe will eventually tail off dramatically (compared with previous eras), with very low energy levels and very large time scales, with events taking a very long time to happen if they ever happen at all. Electrons and positrons drifting through space will encounter one another and occasionally form positronium atoms. These structures are unstable, however, and their constituent particles must eventually annihilate. However, most electrons and positrons will remain unbound. Other low-level annihilation events will also take place, albeit extremely slowly. The universe now reaches an extremely low-energy state. If protons do not decay, stellar-mass objects will still become black holes , although even more slowly. The following timeline that assumes proton decay does not take place. 2018 estimate of Standard Model lifetime before collapse of

5400-439: The universe will slowly and inexorably grow darker. According to theories that predict proton decay , the stellar remnants left behind will disappear, leaving behind only black holes , which themselves eventually disappear as they emit Hawking radiation . Ultimately, if the universe reaches thermodynamic equilibrium , a state in which the temperature approaches a uniform value, no further work will be possible, resulting in

5475-465: The universe, none will remain at the end of the Degenerate Age. Effectively, all baryonic matter will have been changed into photons and leptons . Some models predict the formation of stable positronium atoms with diameters greater than the observable universe's current diameter (roughly 6 × 10 metres) in 10 years, and that these will in turn decay to gamma radiation in 10 years. If

5550-437: The universe. They will slowly evaporate via Hawking radiation . A black hole with a mass of around 1  M ☉ will vanish in around 2 × 10 years. As the lifetime of a black hole is proportional to the cube of its mass, more massive black holes take longer to decay. A supermassive black hole with a mass of 10 (100 billion) M ☉ will evaporate in around 2 × 10 years. The largest black holes in

5625-681: Was observed at the time—an anti-gravity would be needed to counter the gravity contracting the universe together, adding an extra force that would ruin the equations in the theory of relativity. In the end, the cosmological constant , the name for the anti-gravity force, was added to the theory of relativity. Edwin Hubble working in the Mount Wilson Observatory took measurements of the distances of galaxies and paired them with Vesto Silpher and Milton Humason 's measurements of red shifts associated with those galaxies. He discovered

#394605