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Big Bang
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Early universe
Components · Structure
The Big Bang theory is the prevailing cosmological model for the universe from the earliest known periods through its subsequent large-scale evolution.[1][2][3] It states that the universe was in a very high density state and then expanded.[4][5] If the known laws of physics are extrapolated beyond where they are valid there is a singularity. Modern measurements place this moment at approximately 13.8 billion years ago, which is thus considered the age of the universe.[6] After the initial expansion, the universe cooled sufficiently to allow the formation of subatomic particles, and later simple atoms. Giant clouds of these primordial elements later coalesced through gravity to form stars and galaxies.
In the mid-20th century, three British astrophysicists, Stephen Hawking, George F. R. Ellis, and Roger Penrose turned their attention to the theory of relativity and its implications regarding our notions of time. In 1968 and 1970, they published papers in which they extended Einstein's theory of general relativity to include measurements of time and space.[7][8] According to their calculations, time and space had a finite beginning that corresponded to the origin of matter and energy.
Since Georges Lemaître first noted, in 1927, that an expanding universe might be traced back in time to an originating single point, scientists have built on his idea of cosmic expansion. While the scientific community was once divided between supporters of two different expanding universe theories, the Big Bang and the Steady State theory, accumulated empirical evidence provides strong support for the former.[9] In 1929, from analysis of galactic redshifts, Edwin Hubble concluded that galaxies are drifting apart, important observational evidence consistent with the hypothesis of an expanding universe. In 1964, the cosmic microwave background radiation was discovered, which was crucial evidence in favor of the Big Bang model, since that theory predicted the existence of background radiation throughout the universe before it was discovered. More recently, measurements of the redshifts of supernovae indicate that the expansion of the universe is accelerating, an observation attributed to dark energy.[10] The known physical laws of nature can be used to calculate the characteristics of the universe in detail back in time to an initial state of extreme density and temperature.[11][12][13]
- 1 Overview
- 2 Timeline of the Big Bang
- 3 Underlying assumptions
- 4 History
- 5 Observational evidence
- 6 Related issues in physics
- 7 Problems
- 8 The future according to the Big Bang theory
- 9 Before: Speculative physics beyond the Big Bang theory
- 10 Religious and philosophical interpretations
- 11 See also
- 12 Notes
- 13 References
- 14 Further reading
- 15 External links
|External Timeline
| A graphical timeline is available at
Graphical timeline of the Big Bang
Hubble observed that the distances to faraway galaxies were strongly correlated with their redshifts. This was interpreted to mean that all distant galaxies and clusters are receding away from our vantage point with an apparent velocity proportional to their distance: that is, the farther they are, the faster they move away from us, regardless of direction.[18] Assuming the Copernican principle (that the Earth is not the center of the universe), the only remaining interpretation is that all observable regions of the universe are receding from all others. Since we know that the distance between galaxies increases today, it must mean that in the past galaxies were closer together. The continuous expansion of the universe implies that the universe was denser and hotter in the past.
Large particle accelerators can replicate the conditions that prevailed after the early moments of the universe, resulting in confirmation and refinement of the details of the Big Bang model. However, these accelerators can only probe so far into high energy regimes. Consequently, the state of the universe in the earliest instants of the Big Bang expansion is still poorly understood and an area of open investigation and indeed, speculation.
The first subatomic particles included protons, neutrons, and electrons. Though simple atomic nuclei formed within the first three minutes after the Big Bang, thousands of years passed before the first electrically neutral atoms formed. The majority of atoms produced by the Big Bang were hydrogen, along with helium and traces of lithium. Giant clouds of these primordial elements later coalesced through gravity to form stars and galaxies, and the heavier elements were synthesized either within stars or during supernovae.
The Big Bang theory offers a comprehensive explanation for a broad range of observed phenomena, including the abundance of light elements, the cosmic microwave background, large scale structure, and Hubble's Law.[19] The framework for the Big Bang model relies on Albert Einstein's theory of general relativity and on simplifying assumptions such as homogeneity and isotropy of space. The governing equations were formulated by Alexander Friedmann, and similar solutions were worked on by Willem de Sitter. Since then, astrophysicists have incorporated observational and theoretical additions into the Big Bang model, and its parametrization as the Lambda-CDM model serves as the framework for current investigations of theoretical cosmology. The Lambda-CDM model is the standard model of Big Bang cosmology, the simplest model that provides a reasonably good account of various observations about the universe.
Timeline of the Big Bang
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.[20] This singularity signals the breakdown of general relativity and thus, all the laws of physics. How closely we can extrapolate towards the singularity is debated—certainly no closer than the end of the Planck epoch. This singularity is sometimes called "the Big Bang",[21] but the term can also refer to the early hot, dense phase itself,[22][notes 1] which can be considered the "birth" of our universe. Based on measurements of the expansion using Type Ia supernovae, measurements of temperature fluctuations in the cosmic microwave background, and measurements of the correlation function of galaxies[citation needed], the universe has an estimated age of 13.798 ± 0.037 billion years.[23] The agreement of these three independent measurements strongly supports the ΛCDM model that describes in detail the contents of the universe.
Inflation and baryogenesis
The earliest phases of the Big Bang are subject to much speculation. In the most common models the universe was filled homogeneously and isotropically with an incredibly high energy density and huge temperatures and pressures and was very rapidly expanding and cooling. Approximately 10−37 seconds into the expansion, a phase transition caused a cosmic inflation, during which the universe grew exponentially.[24] After inflation stopped, the universe consisted of a quark–gluon plasma, as well as all other elementary particles.[25] Temperatures were so high that the random motions of particles were at relativistic speeds, and particle–antiparticle pairs of all kinds were being continuously created and destroyed in collisions.[4] At some point an unknown reaction called baryogenesis violated the conservation of baryon number, leading to a very small excess of quarks and leptons over antiquarks and antileptons—of the order of one part in 30 million. This resulted in the predominance of matter over antimatter in the present universe.[26]
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.[27] After about 10−11 seconds, the picture becomes less speculative, since particle energies drop to values that can be attained in particle physics experiments. At about 10−6 seconds, quarks and gluons combined to form baryons such as protons and neutrons. The small excess of quarks over antiquarks led to a small excess of baryons over antibaryons. The temperature was now no longer high enough to create new proton–antiproton pairs (similarly for neutrons–antineutrons), so a mass annihilation immediately followed, leaving just one in 1010 of the original protons and neutrons, and none of their antiparticles. A similar process happened at about 1 second for electrons and positrons. After these annihilations, the remaining protons, neutrons and electrons were no longer moving relativistically and the energy density of the universe was dominated by photons (with a minor contribution from neutrinos).
A few minutes into the expansion, when the temperature was about a billion (one thousand million; 109; SI prefix giga-) kelvin and the density was about that of air, neutrons combined with protons to form the universe's deuterium and helium nuclei in a process called Big Bang nucleosynthesis.[28] Most protons remained uncombined as hydrogen nuclei. As the universe cooled, the rest mass 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); hence the radiation decoupled from matter and continued through space largely unimpeded. This relic radiation is known as the cosmic microwave background radiation.[29] The chemistry of life may have begun shortly after the Big Bang, 13.8 billion years ago, during a habitable epoch when the universe was only 10–17 million years old.[30][31][32]
Structure formation
Over a long period of time, the slightly denser regions of the nearly uniformly distributed matter gravitationally attracted nearby matter and thus grew even denser, forming gas clouds, stars, galaxies, and the other astronomical structures observable today.[4] The details of this process depend on the amount and type of matter in the universe. The four possible types of matter are known as cold dark matter, warm dark matter, hot dark matter, and baryonic matter. The best measurements available (from WMAP) show that the data is well-fit by a Lambda-CDM model in which dark matter is assumed to be cold (warm dark matter is ruled out by early reionization[33]), and is estimated to make up about 23% of the matter/energy of the universe, while baryonic matter makes up about 4.6%.[34] In an "extended model" which includes hot dark matter in the form of neutrinos, then if the "physical baryon density" Ωbh2 is estimated at about 0.023 (this is different from the 'baryon density' Ωb expressed as a fraction of the total matter/energy density, which as noted above is about 0.046), and the corresponding cold dark matter density Ωch2 is about 0.11, the corresponding neutrino density Ωvh2 is estimated to be less than 0.0062.[34]
Cosmic acceleration
Independent lines of evidence from Type Ia supernovae and the CMB imply that the universe today is dominated by a mysterious form of energy known as dark energy, which apparently permeates all of space. The observations suggest 73% of the total energy density of today's universe is in this form. When the universe was very young, it was likely infused with dark energy, but with less space and everything closer together, gravity predominated, and it was slowly braking the expansion. But eventually, after numerous billion years of expansion, the growing abundance of dark energy caused the expansion of the universe to slowly begin to accelerate. Dark energy in its simplest formulation takes the form of the cosmological constant term in Einstein's field equations of general relativity, but its composition and mechanism are unknown and, more generally, the details of its equation of state and relationship with the Standard Model of particle physics continue to be investigated both observationally and theoretically.[10]
All of this cosmic evolution after the inflationary epoch can be rigorously described and modelled by the ΛCDM model of cosmology, which uses the independent frameworks of quantum mechanics and Einstein's General Relativity. There is no well-supported model describing the action prior to 10−15 seconds or so. Apparently a new unified theory of quantum gravitation is needed to break this barrier. Understanding this earliest of eras in the history of the universe is currently one of the greatest unsolved problems in physics.
Underlying assumptions
The Big Bang theory depends on two major assumptions: the universality of physical laws and the cosmological principle. The cosmological principle states that on large scales the universe is homogeneous and isotropic.
These ideas were initially taken as postulates, but today there are efforts 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 10−5.[36] Also, general relativity has passed stringent tests on the scale of the Solar System and binary stars.[notes 2]
If the large-scale universe appears isotropic as viewed from Earth, 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 level of 10−5 via observations of the CMB. The universe has been measured to be homogeneous on the largest scales at the 10% level.[37]
Expansion of space
General relativity describes spacetime by a metric, which determines the distances that separate nearby points. The points, which can be galaxies, stars, or other objects, themselves are specified using a coordinate chart or "grid" that is laid down over all spacetime. The cosmological principle implies that the metric should be homogeneous and isotropic on large scales, which uniquely singles out the Friedmann–Lemaître–Robertson–Walker metric (FLRW metric). This metric contains a scale factor, which describes how the size of the universe changes with time. This enables a convenient choice of a coordinate system to be made, called comoving coordinates. In this coordinate system the grid expands along with the universe, and objects that are moving only due to the expansion of the universe remain at fixed points on the grid. While their coordinate distance (comoving distance) remains constant, the physical distance between two such comoving points expands proportionally with the scale factor of the universe.[38]
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 distance between two comoving points. In other words, the Big Bang is not an explosion in space, but rather an expansion of space.[4] Because the FLRW metric assumes a uniform distribution of mass and energy, it applies to our universe only on large scales—local concentrations of matter such as our galaxy are gravitationally bound and as such do not experience the large-scale expansion of space.[39]
An important feature of the Big Bang spacetime is the presence of 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 had time to reach us. This places a limit or a past horizon on the most distant objects that can be observed. Conversely, because space is expanding, and more distant objects are receding ever more quickly, light emitted by us today may never "catch up" to very distant objects. This defines a future horizon, which limits the events in the future that we will be able to influence. The presence of either type of horizon depends on the details of the FLRW model that describes our universe. 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 to accelerate, there is a future horizon as well.[40]
English astronomer Fred Hoyle is credited with coining the term "Big Bang" during a 1949 BBC radio broadcast. 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.[41][42][43]:129
The Big Bang theory 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 Earth. He did not grasp the cosmological implications of this fact, and indeed at the time it was highly controversial whether or not these nebulae were "island universes" outside our Milky Way.[45][46] Ten years later, Alexander Friedmann, a Russian cosmologist and mathematician, derived the Friedmann equations from Albert Einstein's equations of general relativity, showing that the universe might be expanding in contrast to the static universe model advocated by Einstein at that time.[47] In 1924 Edwin Hubble's measurement of the great distance to the nearest spiral nebulae showed that these systems were indeed other galaxies. Independently deriving Friedmann's equations in 1927, Georges Lemaître, a Belgian physicist and Roman Catholic priest, proposed that the inferred recession of the nebulae was due to the expansion of the universe.[48]
In 1931 Lemaître went further and suggested that the evident expansion of the universe, if projected back in time, meant that the further in the past the smaller the universe was, until at some finite time in the past all the mass of the universe was concentrated into a single point, a "primeval atom" where and when the fabric of time and space came into existence.[49]
Starting in 1924, Hubble painstakingly developed a series of distance indicators, the forerunner of the cosmic distance ladder, using the Script error: No such module "convert". Hooker telescope at Mount Wilson Observatory. This allowed him to estimate distances to galaxies whose redshifts had already been measured, mostly by Slipher. In 1929 Hubble discovered a correlation between distance and recession velocity—now known as Hubble's law.[18][50] Lemaître had already shown that this was expected, given the cosmological principle.[10]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.[51] This perception was enhanced by the fact that the originator of the Big Bang theory, Monsignor Georges Lemaître, was a Roman Catholic priest.[52] Arthur Eddington agreed with Aristotle that the universe did not have a beginning in time, viz., that matter is eternal. A beginning in time was "repugnant" to him.[53][54] Lemaître, however, thought that
If the world has begun with a single quantum, the notions of space and time would altogether fail to have any meaning at the beginning; they would only begin to have a sensible meaning when the original quantum had been divided into a sufficient number of quanta. If this suggestion is correct, the beginning of the world happened a little before the beginning of space and time.[55]
During the 1930s other ideas were proposed as non-standard cosmologies to explain Hubble's observations, including the Milne model,[56] the oscillatory universe (originally suggested by Friedmann, but advocated by Albert Einstein and Richard Tolman)[57] and Fritz Zwicky's tired light hypothesis.[58]
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.[59] The other was Lemaître's Big Bang theory, advocated and developed by George Gamow, who introduced big bang nucleosynthesis (BBN)[60] and whose associates, Ralph Alpher and Robert Herman, predicted the cosmic microwave background radiation (CMB).[61] Ironically, it was Hoyle who coined the phrase that came to be applied to Lemaître's theory, referring to it as "this big bang idea" during a BBC Radio broadcast in March 1949.[43]:129[notes 3] For a while, support was split between these two theories. Eventually, the observational evidence, most notably from radio source counts, began to favor Big Bang over Steady State. The discovery and confirmation of the cosmic microwave background radiation in 1964[63] secured the Big Bang as the best theory of the origin and evolution of the universe. Much of the current work in cosmology includes understanding how galaxies form in the context of the Big Bang, understanding the physics of the universe at earlier and earlier times, and reconciling observations with the basic theory.
Significant progress in Big Bang cosmology have 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 COBE,[64] the Hubble Space Telescope and WMAP.[65] Cosmologists now have fairly precise and accurate measurements of many of the parameters of the Big Bang model, and have made the unexpected discovery that the expansion of the universe appears to be accelerating.
Observational evidence
"[The] big bang picture is too firmly grounded in data from every area to be proved invalid in its general features."
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 nucleosynthesis. More recent evidence includes observations of galaxy formation and evolution, and the distribution of large-scale cosmic structures,[67] These are sometimes called the "four pillars" of the Big Bang theory.[68]
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 subjected to the most active laboratory investigations.[69] Remaining issues include the cuspy halo problem and the dwarf galaxy problem of cold dark matter. Dark energy is also an area of intense interest for scientists, but it is not clear whether direct detection of dark energy will be possible.[70] Inflation and baryogenesis remain more speculative features of current Big Bang models. Viable, quantitative explanations for such phenomena are still being sought. These are currently unsolved problems in physics.
Hubble's law and the expansion of space
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 lines or absorption lines corresponding to atoms of the chemical elements interacting with the light. These redshifts are uniformly isotropic, distributed evenly among the observed objects in all directions. If the redshift is interpreted as a Doppler shift, the recessional velocity of the object can be calculated. For some galaxies, it is possible to estimate distances via the cosmic distance ladder. When the recessional velocities are plotted against these distances, a linear relationship known as Hubble's law is observed:[18]
- v = H0D,
- v is the recessional velocity of the galaxy or other distant object,
- D is the comoving distance to the object, and
- H0 is Hubble's constant, measured to be 70.4Script error: No such module "Su". km/s/Mpc by the WMAP probe.[34]
Hubble's law has two possible explanations. Either we are at the center of an explosion of galaxies—which is untenable given the Copernican principle—or the universe is uniformly expanding everywhere. This universal expansion was predicted from general relativity by Alexander Friedmann in 1922[47] and Georges Lemaître in 1927,[48] well before Hubble made his 1929 analysis and observations, and it remains the cornerstone of the Big Bang theory as developed by Friedmann, Lemaître, Robertson, and Walker.
The theory requires the relation v = HD to hold at all times, where D is the comoving distance, v is the recessional velocity, and v, H, and D vary as the universe expands (hence we write H0 to denote the present-day Hubble "constant"). For distances much smaller than the size of the observable universe, the Hubble redshift can be thought of as the Doppler shift corresponding to the recession velocity v. However, the redshift is not a true Doppler shift, but rather the result of the expansion of the universe between the time the light was emitted and the time that it was detected.[71]
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,[18] supporting the Cosmological principle that the universe looks the same in all directions, along with much other evidence. If the redshifts were the result of an explosion from a center distant from us, they would not be so similar in different directions.
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.[72] Radiation from the Big Bang was demonstrably warmer at earlier times throughout the universe. Uniform cooling of the cosmic microwave background over billions of years is explainable only if the universe is experiencing a metric expansion, and excludes the possibility that we are near the unique center of an explosion.
Cosmic microwave background radiation
In 1964 Arno Penzias and Robert Wilson serendipitously discovered the cosmic background radiation, an omnidirectional signal in the microwave band.[63] Their discovery provided substantial confirmation of the general CMB predictions: the radiation was found to be consistent with an almost perfect black body spectrum in all directions; this spectrum has been redshifted by the expansion of the universe, and today corresponds to approximately 2.725 K. This tipped the balance of evidence in favor of the Big Bang model, and Penzias and Wilson were awarded a Nobel Prize in 1978.
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 372±14Lua error: Unmatched close-bracket at pattern character 67.,[33] the mean free path for a photon becomes long enough to reach the present day and the universe becomes transparent.
In 1989 NASA launched the Cosmic Background Explorer satellite (COBE). Its findings were consistent with predictions regarding the CMB, finding a residual temperature of 2.726 K (more recent measurements have revised this figure down slightly to 2.725 K) and providing the first evidence for fluctuations (anisotropies) in the CMB, at a level of about one part in 105.[64] John C. Mather and George Smoot were awarded the Nobel Prize for their leadership in this work. 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 anisotropies.[77][78][79]
In early 2003 the first results of the Wilkinson Microwave Anisotropy Probe (WMAP) 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.[65] The Planck space probe was launched in May 2009. Other ground and balloon based cosmic microwave background experiments are ongoing.
Abundance of primordial elements
Using the Big Bang model it is possible to calculate the concentration of helium-4, helium-3, deuterium, and lithium-7 in the universe as ratios to the amount of ordinary hydrogen.[28] The relative abundances depend on a single parameter, the ratio of photons to baryons. This value can be calculated independently from the detailed structure of CMB fluctuations. The ratios predicted (by mass, not by number) are about 0.25 for 4He/H, about 10−3 for 2H/H, about 10−4 for 3He/H and about 10−9 for 7Li/H.[28]
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 4He, and off by a factor of two for 7Li; in the latter two cases there are substantial systematic uncertainties. Nonetheless, the general consistency with abundances predicted by Big Bang nucleosynthesis is strong evidence for the Big Bang, as the theory is the only known explanation for the relative abundances of light elements, and it is virtually impossible to "tune" the Big Bang to produce much more or less than 20–30% helium.[80] Indeed there is no obvious reason outside of the Big Bang that, for example, the young universe (i.e., before star formation, as determined by studying matter supposedly free of stellar nucleosynthesis products) should have more helium than deuterium or more deuterium than 3He, and in constant ratios, too.[81]:182-185
Galactic evolution and distribution
Detailed observations of the morphology and distribution of galaxies and quasars are in agreement with the current state of the Big Bang theory. 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 been forming, such as galaxy clusters and superclusters. 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 distances but shortly after the Big Bang. These observations are strong arguments against the steady-state model. Observations of star formation, galaxy and quasar distributions and larger structures agree well with Big Bang simulations of the formation of structure in the universe and are helping to complete details of the theory.[82][83]
Primordial gas clouds
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. These two clouds of gas contain no elements heavier than hydrogen and deuterium.[84][85] Since the clouds of gas have no heavy elements, they likely formed in the first few minutes after the Big Bang, during Big Bang nucleosynthesis. Their composition matches the composition predicted from Big Bang nucleosynthesis. This provides direct evidence that there was a period in the history of the universe before the formation of the first stars, when most ordinary matter existed in the form of clouds of neutral hydrogen.[citation needed]
Other lines of evidence
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.[86]
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.[87] This prediction also implies that the amplitude of the Sunyaev–Zel'dovich effect in clusters of galaxies does not depend directly on redshift. Observations have found this to be roughly true, but this effect depends on cluster properties that do change with cosmic time, making precise measurements difficult.[88][89]
On 17 March 2014, astronomers at the Harvard-Smithsonian Center for Astrophysics announced the apparent detection of primordial gravitational waves, which, if confirmed, may provide strong evidence for inflation and the Big Bang.[14][15][16][17] However, on 19 June 2014, lowered confidence in confirming the findings was reported;[90][91][92] and on 19 September 2014, even more lowered confidence.[93][94]
Related issues in physics
Baryon asymmetry
It is not yet understood why the universe has more matter than antimatter.[95] 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 made almost entirely of matter. A process called baryogenesis was hypothesized to account for the asymmetry. For baryogenesis to occur, the Sakharov conditions must be satisfied. These require that baryon number is not conserved, that C-symmetry and CP-symmetry are violated and that the universe depart from thermodynamic equilibrium.[96] All these conditions occur in the Standard Model, but the effect is not strong enough to explain the present baryon asymmetry.
Dark energy
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 negative pressure, dubbed "dark energy".[10] Dark energy, though speculative, solves numerous problems. Measurements of the cosmic microwave background indicate that the universe is very nearly spatially flat, and therefore according to general relativity the universe must have almost exactly the critical density of mass/energy. But the mass density of the universe can be measured from its gravitational clustering, and is found to have only about 30% of the critical density.[10] Since theory suggests that dark energy does not cluster in the usual way it is the best explanation for the "missing" energy density. Dark energy also helps to explain two geometrical measures of the overall curvature of the universe, one using the frequency of gravitational lenses, and the other using the characteristic pattern of the large-scale structure as a cosmic ruler.
Negative pressure is believed to be a property of vacuum energy, but the exact nature and existence of dark energy remains one of the great mysteries of the Big Bang. Possible candidates include a cosmological constant and quintessence. 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 1% neutrinos.[34] According to theory, the energy density in matter decreases with the expansion of the universe, but the dark energy density remains constant (or nearly so) as the universe expands. Therefore matter made up a larger fraction of the total energy of the universe in the past than it does today, but its fractional contribution will fall in the far future as dark energy becomes even more dominant.
Dark matter
During the 1970s and 80s, 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 interact with normal baryonic matter. In addition, the assumption that the universe is mostly normal matter led to predictions that were strongly inconsistent with observations. In particular, the universe today is far more lumpy and contains far less deuterium than can be accounted for without dark matter. While dark matter has always been controversial, it is inferred by various observations: the anisotropies in the CMB, galaxy cluster velocity dispersions, large-scale structure distributions, gravitational lensing studies, and X-ray measurements of galaxy clusters.[97]
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.[98]
Globular cluster age
In the mid-1990s observations of globular clusters appeared to be inconsistent with the Big Bang theory. Computer simulations that matched the observations of the stellar populations of globular clusters suggested that they were about 15 billion years old, which conflicted with the 13.8 billion year age of the universe. This issue was partially resolved in the late 1990s when new computer simulations, which included the effects of mass loss due to stellar winds, indicated a much younger age for globular clusters.[99] There remain some questions as to how accurately the ages of the clusters are measured, but it is clear that observations of globular clusters no longer appear inconsistent with the Big Bang theory.
There are generally considered to be three outstanding problems with the Big Bang theory: the horizon problem, the flatness problem, and the magnetic monopole problem. The most common answer to these problems is inflationary theory; however, since this creates new problems, other options have been proposed, such as the Weyl curvature hypothesis.[100][101]
Horizon problem
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.[102] The observed isotropy of the CMB is problematic in this regard: if the universe had been dominated by radiation or matter at all times up to the epoch of last scattering, the particle horizon at that time would correspond to about 2 degrees on the sky. There would then be no mechanism to cause wider regions to have the same temperature.[81]:191–202
A resolution to this apparent inconsistency is offered by inflationary 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 than previously assumed, so that regions presently on opposite sides of the observable universe are well inside each other's particle horizon. The observed isotropy of the CMB then follows from the fact that this larger region was in causal contact before the beginning of inflation.[24]:180–186
Heisenberg's uncertainty principle predicts that during the inflationary phase there would be quantum thermal fluctuations, which would be magnified to cosmic scale. These fluctuations serve as the seeds of all current structure in the universe.[81]:207 Inflation predicts that the primordial fluctuations are nearly scale invariant and Gaussian, which has been accurately confirmed by measurements of the CMB.[103]:sec 6
If inflation occurred, exponential expansion would push large regions of space well beyond our observable horizon.[24]:180–186
Flatness problem
The flatness problem (also known as the oldness problem) is an observational problem associated with a Friedmann–Lemaître–Robertson–Walker metric.[102] 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 the critical density, in which case space is said to be flat. The problem is that any small departure from the critical density grows with time, and yet the universe today remains very close to flat.[notes 4] Given that a natural timescale for departure from flatness might be the Planck time, 10−43 seconds,[4] the fact that the universe has reached neither a heat death nor a Big Crunch after billions of years requires an explanation. For instance, even at the relatively late age of a few minutes (the time of nucleosynthesis), the universe density must have been within one part in 1014 of its critical value, or it would not exist as it does today.[104]
Magnetic monopoles
The magnetic monopole objection was raised in the late 1970s. Grand unification theories 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, given that no monopoles have been found. This problem is also resolved by cosmic inflation, which removes all point defects from the observable universe, in the same way that it drives the geometry to flatness.[102]
The future according to the Big Bang theory
Before observations of dark energy, cosmologists considered two scenarios for the future of the universe. If the mass density of the universe were greater than the critical density, then the universe would reach a maximum size and then begin to collapse. It would become denser and hotter again, ending with a state similar to that in which it started—a Big Crunch.[40] Alternatively, if the density in the universe were equal to or below the critical density, the expansion would slow down but never stop. Star formation would cease with the consumption of interstellar gas in each galaxy; stars would burn out leaving white dwarfs, neutron stars, and black holes. Very gradually, collisions between these would result in mass accumulating into larger and larger black holes. The average temperature of the universe would asymptotically approach absolute zero—a Big Freeze.[105] Moreover, if the proton were unstable, then baryonic matter would disappear, leaving only radiation and black holes. Eventually, black holes would evaporate by emitting Hawking radiation. The entropy of the universe would increase to the point where no organized form of energy could be extracted from it, a scenario known as heat death.[106]:sec VI.D
Modern observations of accelerating expansion imply that more and more of the currently visible universe will pass beyond our event horizon and out of contact with us. The eventual result is not known. The ΛCDM model of the universe contains dark energy in the form of a cosmological constant. This theory suggests that only gravitationally bound systems, such as galaxies, will remain together, and they too will be subject to heat death as the universe expands and cools. Other explanations of dark energy, called phantom energy theories, suggest that ultimately galaxy clusters, stars, planets, atoms, nuclei, and matter itself will be torn apart by the ever-increasing expansion in a so-called Big Rip.[107]
Before: Speculative physics beyond the Big Bang theory
While the Big Bang model is well established in cosmology, it is likely to be refined. The Big Bang Theory, built upon the equations of classical general relativity, indicates a singularity at the origin of cosmic time; this infinite energy density is regarded as impossible in physics. Still, it is known that the equations are not applicable before the time when universe cooled down to the Planck temperature, and this conclusion depends on various assumptions, of which some could never be experimentally verified.
One proposed refinement to avoid this would-be singularity is to develop a correct treatment of quantum gravity.[108]
It is not known what could have preceded the hot dense state of the early universe or how and why it originated, though speculation abounds in the field of cosmogony.
Some proposals, each of which entails untested hypotheses, are:
- Models including the Hartle–Hawking no-boundary condition, in which the whole of space-time is finite; the Big Bang does represent the limit of time but without any singularity.[109]
- Big Bang lattice model, states that the universe at the moment of the Big Bang consists of an infinite lattice of fermions, which is smeared over the fundamental domain so it has rotational, translational and gauge symmetry. The symmetry is the largest symmetry possible and hence the lowest entropy of any state.[110]
- Brane cosmology models, in which inflation is due to the movement of branes in string theory; the pre-Big Bang model; the ekpyrotic model, in which the Big Bang is the result of a collision between branes and the cyclic model, a variant of the ekpyrotic model in which collisions occur periodically. In the latter model the Big Bang was preceded by a Big Crunch and the universe cycles from one process to the other.[111][112][113][114]
- Eternal inflation, in which universal inflation ends locally here and there in a random fashion, each end-point leading to a bubble universe, expanding from its own big bang.[115][116]
Proposals in the last two categories, see the Big Bang as an event in either a much larger and older universe or in a multiverse.
Religious and philosophical interpretations
As a description of the origin of the universe, the Big Bang has significant bearing on religion and philosophy.[117][118] As a result, it has become one of the liveliest areas in the discourse between science and religion.[119] Some believe the Big Bang implies a creator,[120][121] and some see its mention in their holy books,[122] while others argue that Big Bang cosmology makes the notion of a creator superfluous.[118][123]
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The second section discusses the classic tests of the Big Bang theory that make it so compelling as the likely valid description of our universe.
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- Kolb, E.; Turner, M. (1988). The Early Universe. Addison–Wesley. ISBN 0-201-11604-9.
- Masters, Ken (Ed.) (2015). Origins: Before the Big Bang. Lulu.com. ISBN 978-1-312-75326-6.
- Ostriker, Jeremiah P.; Mitton, Simon (2013). Heart of Darkness: Unraveling the mysteries of the invisible Universe. Princeton, NJ: Princeton University Press. ISBN 978-0-691-13430-7.
- Peacock, J. (1999). Cosmological Physics. Cambridge University Press. ISBN 0-521-42270-1.
- Woolfson, M. (2013). Time, Space, Stars and Man: The Story of Big Bang (2nd edition). World Scientific Publishing. ISBN 978-1-84816-933-3.
Further reading
- For an annotated list of textbooks and monographs, see physical cosmology.
- Alpher, R. A.; Herman, R. (1988). "Reflections on early work on 'big bang' cosmology". Physics Today 8 (8): 24–34. Bibcode:1988PhT....41h..24A. doi:10.1063/1.881126.
- "Cosmic Journey: A History of Scientific Cosmology". American Institute of Physics.
- Barrow, J. D. (1994). The Origin of the Universe. Weidenfeld & Nicolson. ISBN 0-297-81497-4.
- Davies, P. C. W. (1992). The Mind of God: The scientific basis for a rational world. Simon & Schuster. ISBN 0-671-71069-9.
- Feuerbacher, B.; Scranton, R. (2006). "Evidence for the Big Bang". TalkOrigins.
- Mather, J. C.; Boslough, J. (1996). The very first light: the true inside story of the scientific journey back to the dawn of the Universe. Basic Books. p. 300. ISBN 0-465-01575-1.
- Riordan, Michael; Zajc, William (May 2006). "The First Few Microseconds" (PDF). Scientific American.
- Singh, S. (2004). <span />Big Bang: The origins of the universe<span />. Fourth Estate. ISBN 0-00-716220-0.
- "Misconceptions about the Big Bang" (PDF). Scientific American. March 2005.
- Weinberg, S. (1993). The First Three Minutes: A Modern View Of The Origin Of The Universe. Basic Books. ISBN 0-465-02437-8.
External links
Find more about
Big Bang
at Wikipedia's sister projects
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- big-bang model at Encyclopædia Britannica
- The Story of the Big Bang - STFC funded project explaining the history of the universe in easy-to-understand language
- Big Bang Cosmology WMAP
- The Big Bang - NASA Science
- Big bang model with animated graphics
- Cosmology at DMOZ
- Evidence for the Big Bang
- Universe
- A Cosmic History of the Universe
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I am currently looking for a Beta, so if anyone can get back to me on that, I would be very grateful. The beta boards banned me the day I got an account so... meh.
My favorite character in the HP series is Voldemort, just cause he's so plain evil and not afraid to admit it.
I also beta. Email me at nhdgal at gmail dot com.

subset: commoncrawl


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Poet Robert Hass on Brenda Hillman's Academy of American Poets Fellowship Award
Leah Garchik reports in SF Gate:
Poet Robert Hass attended last Friday's Academy of American Poets awards ceremonies at the New School in New York, where a $25,000 Academy Fellowship to a midcareer poet was given, as well as a Wallace Stevens Award of S100,000 for lifetime achievement. With its "leaves starting to turn and litter the sidewalks in front of the brownstones," Manhattan "looked like a New Yorker drawing of autumn in New York," e-mailed Hass. "Inside, the auditorium was jammed with the poets of the city and it was Northern California night.
"The fellowship went to Brenda Hillman of Kensington and Inverness and it was presented by Sharon Olds (living in New York, born in Children's Hospital in S.F., grown up in Berkeley) and the W.S. Prize went to our heroic Gary Snyder of Nevada City, the award presented by Jane Hirshfield of Mill Valley. So the audience listened to these brilliant poems of the Sierra foothills and the Point Reyes coast and then went out into the cool Manhattan night."


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The Dallas Cowboys couldn't complete what would have been a stunning comeback after falling behind 23-0 at home, and their eventual 29-24 home loss to the New York Giants on Sunday all but ensures the reigning Super Bowl champions will repeat as NFC East champions.
Tony Romo led a valiant rally, but his four interceptions and wide receiver Dez Bryant's inability to stay inbounds on a potential game-winning Hail Mary gave the Giants a split in the division series. Instead of Dallas (3-4) getting a sweep and moving a half-game behind New York (6-2), it's now a solid 2½-game deficit.
As a bonus for the Giants, the Philadelphia Eagles (3-4) and Washington Redskins (3-5) fell hard in blowout losses earlier in the afternoon. Mathematically speaking, New York's East competitors are alive, but they will not be able to clean up their messes well enough to challenge the Giants, who won't need to sweat out December this time before locking up the division.
Even worse for the Cowboys, Eagles and Redskins is the fact that the Giants are a much better all-around team than last season.
Their pass rush is healthy and rolling, and their secondary has done a good job of overcoming injuries. The running game has come to life with a combination of Ahmad Bradshaw and Andre Brown. Then there's Eli Manning, who's just been, well, Eli Manning—unflappable as ever, even when his offense is frustratingly settling for field goals and not putting an opponent away like it usually does in the fourth quarter.
The Giants don't make the critical mistakes that the other NFC East teams continually do. They protect the ball and are rarely undisciplined under Tom Coughlin. They close out games with the poise you expect from champions.
The Cowboys don't protect the ball. They rack up penalties at the worst times, and Romo can't quite get them over the hump in big games against tough teams.
The Redskins' defense can't stop anybody, negating the potential heroics of dynamic rookie quarterback Robert Griffin III.
The Eagles have no clue what they're doing on either side of the ball, and their win over the Giants earlier in the season seems like a fluky exception to the rule that they're not really a good team.
The Giants knew that defending their title would be hard with heavyweights such as the San Francisco 49ers, Green Bay Packers and Atlanta Falcons in the NFC. But they probably never imagined that they would have complete control of the East before the end of October.
A tale of two Norths
The Chicago Bears (6-1) and Baltimore Ravens (5-2) are in first place in the two North divisions. But both teams should be nervous about their leads heading into the second half of the season.
The Bears have the better record but have the bigger reason to worry. With more shoddy pass protection for Jay Cutler, their offense limped along before the Bears eked out a 23-22 home win over the Carolina Panthers. Once again, it required the defense to make a big play—a touchdown by cornerback Tim Jennings off a Cam Newton interception—to bail them out.
Chicago already has lost to the second-place Packers (5-3) and has tricky games the next three weeks (at Tennessee, vs. Houston, at San Francisco) while Green Bay has an easier time (vs. Arizona, a bye, at Detroit). Aaron Rodgers and his teammates are dealing with some key injuries, but the Packers have enough depth to keep pushing forward to the point that they can surpass the Bears before the teams' Week 15 rematch at Chicago.
For the Ravens, it's simple. If they plan to win the AFC North again, despite mounting defensive injuries, they must take care of business against surging archrival Pittsburgh (4-3) head-to-head. The teams face off twice in a twice in a three-week span, on Nov. 18 at Pittsburgh and Dec. 2 at Baltimore.
The Ravens, who had a bye in Week 8, need to sort out some offensive problems. The Steelers, led by quarterback Ben Roethlisberger, stayed in a groove on that side of the ball by picking apart Washington in a 27-12 home victory. More important, Pittsburgh's Troy Polamalu-less defense had its best performance of the season in silencing Griffin (177 yards passing, 8 yards rushing).
The Ravens still are very talented, and they should be a well-adjusted team that's ready to rebound when they get back to action against Cleveland in Week 9. But they know that to have any shot at the Super Bowl, they need to maintain a top-two playoff seed. It's a must then that they to regain their early-season momentum before Week 11, because it's clear the Steelers are playing better football at the moment.
Wild wild-card race ahead
Let's figure that the respective runners-up in the two North divisions (Bears or Packers, Ravens or Steelers) can fall back on getting the top wild card—the No. 5 seed—in each conference. The No. 6 seeds, however, are completely up for grabs. Here's handicapping the surprise mix of clubs battling for the second wild card in both conferences.
Vikings (5-3). Christian Ponder isn't playing well, and the Seahawks' defense awaits him in Week 9 at Seattle. With two games left against both the Packers and Bears, it doesn't bode well for Minnesota.
Cardinals (4-3). They can't protect John Skelton or Kevin Kolb, and the 49ers' defense will deliver the latest knockout punch on Monday night before the Packers follow suit.
Seahawks (4-4). They'll hang around for the duration because of their defense. And with the Vikings and New York Jets coming to town the next two weeks, the Seahawks will likely pad their win total nicely before their Week 11 bye.
Eagles (3-4). As messy as their current situation is, they're always capable of getting hot in a hurry. Dangerous until they're officially eliminated.
Cowboys (3-4). See what we wrote about the Eagles, whom they still play twice.
Buccaneers (3-4). Josh Freeman and Doug Martin have the Bucs' offense buzzing, but their pass defense is a liability. That will hurt in their toughest remaining games—against Peyton Manning's Broncos and two vs. the high-flying Falcons.
Lions (3-4). Now that Matthew Stafford is back on track, last season's No. 6 seed should be confident it can make a second half run similar to its first half run in 2011. Of the seven contenders for the final wild card, Detroit has the best quarterback situation.
Dolphins (4-3) and Colts (4-3). The NFL gods knew what they were doing, as Miami travels to Indianapolis in a key matchup of rookie quarterbacks Ryan Tannehill and Andrew Luck in Week 9. It's just easier to like Luck (and his team) at home and, really, anywhere going forward coming off his great comeback performance at Tennessee.
Chargers (3-4). The ugly 7-6 loss at Cleveland was painful for both Philip Rivers and Norv Turner. Can they pick up the pieces against the Chiefs and Buccaneers before a rematch with the Broncos? We wouldn't bank on it.
Bills (3-4). They are too uneven offensively and too porous defensively to consider a possible playoff team.
Bengals (3-4). With the Broncos and Giants up next, it will become clear that Marvin Lewis' team won't be making a second consecutive playoff trip.
Raiders (3-4). Carson Palmer and Darren McFadden have given Oakland a balanced offense that's capable of keeping the team in games against anyone. Other than matchups against the Ravens and Broncos, the rest of the Raiders' games are winnable. It begins with a critical swing game Sunday against the NFC version of them—Tampa Bay.
Injury report
Dolphins QB Ryan Tannehill (quadriceps). Tannehill is expected to return for a Week 9 passing duel with fellow rookie Andrew Luck in Indianapolis. And given the game now has big wild-card implications, he'll do everything he can to rebound well.
Chiefs QB Brady Quinn (concussion). Former starter Matt Cassel played well against the Raiders in relief and is expected to start Thursday at San Diego. At this point, it doesn't matter which quarterback Kansas City plays for the rest of '12, because the '13 draft is where the team will find its next starter.
Steelers S Ryan Clark (concussion). Pittsburgh's defense already has been trying to hold up with fellow safety Troy Polamalu on the shelf with a calf injury. But it would really miss Clark, its stay-at-home cover man, in a Week 9 matchup with Eli Manning and the Giants.
Giants S Antrel Rolle (head). Rolle was getting his head injury checked out on Sunday night. Just like Clark is key to Pittsburgh, New York would like to have Rolle on the field against red-hot Ben Roethlisberger and the Steelers.


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Looking for a way to get the word out? Main Street Russellville is still accepting registrations for the chili cookoff and for nonprofit, commercial, political and arts and crafts vendors. Chili cooks can show what they've got at the CASI sanctioned Chili Cookoff, and vendors can display their wares in a family-oriented atmosphere.
You can also participate in the Fall Fest 5K/1K Run/Walk, the Tour de Pumpkin Bike Ride, Car & Truck Show, Old Fashioned Pie and Cake Contest, Canine Capers Dog Show, and Children's Costume Contest. Start your day with the Friends of the Depot Omelet Breakfast at the American Legion Hut. Come be a part of the fun.
If you are interested in registering for a booth or participating in the chili cookoff or other event, please contact Main Street Russellville at 967-1437, P.O. Box 694, Russellville, AR 72811. You can download all applications on our website at www.mainstreetrussellville.com.
The Downtown Fall Festival & Chili Cookoff is another project of Main Street Russellville, a 501 (c)(3) non-profit organization whose mission is the redevelopment and revitalization of the historic heart of the city.


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The UTeach Model Documents
Main Document
The UTeach Model
written by
Michael Marder
As part of an NSF funded Math and Science Partnership grant, we have developed and implemented a yearlong series of science content courses for future elementary teachers based on Physics and Everyday Thinking (PET). The geology and biology courses continue the theme of energy and interactions developed through PET and the pedagogical model mimics PET. The courses are taught on five campuses, three community colleges that feed Western Washington University, and the Northwest Indian College. Student learning results for both inservice and preservice teachers are positive. We have documented positive changes in elementary classroom science instruction and student achievement as well as differences in preservice students in science teaching methods courses.
This file is available in multiple formats: .pptx, .pdf
- Download UTeach model - Marder.pptx - 3245kb Powerpoint Document
- Download UTeach model - Marder.pdf - 2962kb Adobe PDF Document
Published October 10, 2008
Last Modified November 6, 2008
This file is included in the full-text index.
This file has previous versions.


text: E 325 Computing for Environmental Scientists (1-3 cr.) P: MATH-M 118 or M 119; K 300 or equivalent; SPEA-E 272. Survey of computing applications to environmental issues. Personal computing emphasized. Application of spreadsheets, graphics, simple statistics, and BASIC programming to environmental science issues. Manipulation and interpretation of real data, case studies, and projects. Many software packages used.


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Published on October 14th, 2010 | by Kilduff Kolleen6
How-to: Recycled Paper Envelopes
Often when I need cards, I find myself making them from paper and scraps of supplies I have around my office instead of purchasing them. But for some reason I usually purchase envelopes for these cards. I have plenty of paper that usually gets put in the recycle bin, and I wondered why I was buying more paper in the form of an envelope? So I worked up a template to make easy envelopes from a standard size piece of paper, therefore envelopes can me made from most magazines that would usually be placed in the recycling bin.
Here's how:
- 2-3 pieces of magazine or newspaper approx. 8.5" x 11"
- Scissors and/or exacto knife
- Paper glue
- Printer (to print templates)
- Pencil
- Bonefolder or butter knife
- Ruler
1. Download the Envelopetemplate and print it out full size (a scale has been placed on each jpg to help with printing at the correct proportions).
Next >>
6 Responses to How-to: Recycled Paper Envelopes
I highly appreciate the idea of reuing scraps of paper, however, one thing strikes me in this tutorial: why would you print 2 templates and THEN tracing it onto 2 other (to be reused) sheets of paper? These instructions result in using 4 (FOUR) sheets of paper to make an envelop that usually exists out of ONE sheet of paper. You could at least try (if possible) to print the template directly on the sheets of paper to be reused.
Anna, I noticed that, too, but I thought that I would print the template onto heavy cardstock so that I could use it multiple times. Of course, I can't tell if that would be possible because the templates won't open on my computer.
I disagree that printing directly onto the paper to be reused is best. If you're going to be making many envelopes (and we use a similar method and have made many (at least a couple a week) without the template wearing out) over time using two extra pieces of paper seems like a small amount in the end. What about ink (and the cartridges it goes in?) Never mind that you can use the templates for an envelope if you are ever done with them.
Thanks for the tutorial. We make these regularly but it's nice to have another size template around for when we make another size card. And I had not thought of making my own mailing label. Thanks for cluing me in!
I can't find a link for the third template. It didn't show as a link in the article. Could you provide it, please? I have never made envelopes before, but have always wanted to do it. So now is my chance!
My mom makes cards and envelopes from scraps- back when I was a teen and loved writing to pen pals (before email took over) I used to make my own envelopes from pages of fashion magazines. They were bright, colorful and stylish 🙂


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Discussion in 'Science Fiction & Fantasy' started by Obiwanshinobi, Jan 30, 2011.
Why does my post get the bomb?????
You know, Supes has decided to renounce his American citizenship before the U.N., in Action #900.
I'm sure that's entirely coincidental to any desire Warners might have to "internationalize" the character a bit before they release a big budget movie that'll need to do good foreign box office.
I think there ought to be a law that people insulting other people's appearances on the internet are obliged to post a picture of themselves to compare with.
^ Dennis that was in a back up story and is unclear if that is actually going to be touched upon in either of the two books.
TRUTH... JUSTICE... All that stuff.
Still remember how many Americans were so totally upset about Superman Returns because of this.
Superman is already pretty international anyways as as Justice League member who respond to global threats. Clark Kent is still a US citizen it's just Superman who is revoking his to better serve the role. That's what I got from the story. I doubt Cornell will use this in Action Comics if it is an ongoing thread.
It will be forgotten and never brought up again just like dozens of other shock value comic stories.
The thing is thought it wasn't a shock value story. It was like a two or three page back up story (actually longer than that) in a milestone issue. It just happened to be picked up by one of the comic news sites and went viral. Sigh.
And why wouldn't it? It's the most unique and "newsworthy" thing that there would be to report on.
Has FOX News fussed about it yet?
Whether it's touched on frequently or not doesn't have much to do with whether it's "in continuity" or not; for example, how often do they refer back to the story decades ago in which the United Nations issued Superman blanket permission to go anywhere in the world, into any country without carrying papers (on the odd notion that the U.N. could do that kind of thing)?
Yet, Clark Kent still has his citizenship...
I guess I'm not looking at it as being newsworthy as others are lol.
I'm not even American and I thought it was pretty lame how they glossed over the line like that, apparently to make Superman sound more "international". I know, it doesn't really matter since he's an alien so he doesn't technically belong to any earth nationality, but I like the idea of him being represented as an American hero.
I thought it was pretty cool how he flew to the White House at the end of "Superman II" to put back the flag Zod and co. had knocked down and promise the U.S. President "I won't let you down again".
Maybe some people think patriotism in movies is lame these days (possibly because America pushed it so hard after 9/11), but I think it's a good thing for superhero movies. Unlike others, I didn't mind all the pro New York stuff in the Spider-Man movies.
They don't make the decision because someone says "that's lame." It's strictly their idea of how to maximize box office.
Because it isn't newsworthy!
I didn't (and still don't) mind it in the first one, because it seems natural. By 3, it is just overdone and shoved down the audience's throat (particularly at the end where everyone is just watching and cheering Spidey on as he gets the shit kicked out of him - it is like they are watching a movie).
NPR, Huffington Post, FOX News...in fact, this is the only thing that's getting Action #900 any real mainstream press coverage. It's newsworthy where the simple publication of a so-called "milestone comic" isn't, and one has to wonder whether that's another reason that they did it - the free advertising may pump up their sales a bit for at least a monty.
I don't know...call me crazy, but when I turn on the news, I don't typically expect to learn what fictional characters are doing.
Okay - in 2011, you're crazy...or at least not paying attention. You may as well say that when you turn on the news you don't expect to hear what project Lindsay Lohan just got dropped from. Walter Cronkite has been neither a senior editor nor anchor at CBS for some decades now.
DC and Marvel have managed to generate this kind of mainstream media attention more than once in the last few years with stunt plotting - the last time, I believe, was the death of Steve Rogers. One doesn't imagine that this late in the day they're naive to the potential news value of this kind of story event when they cook it up.
^ ^Indeed, besides which this has nothing to do with "Man of Steel" and should have been posted in the Action Comics thread (which someone did). Again another reason why I'm so dismissive of this is because this was a back up story. I feel for Cornell a bit who told one of the best Luthor/Superman stories that has been done in a long, long time and it gets ignored because of this.
I know it happens, but I still think it is kinda silly. I mean, really, nothing else happened in the world that major news outlets need to talk about what fictional things are happening to fictional characters?
Then again, if it's Fox News...
Separate names with a comma.


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That's a monolever frame R65, so with the exception of the engine itself, it is the same as the R80 monolever from the same year - including the final drive ratio..
BMWs in my garage: 1982 R65LS, 1978 R100/7
Thanks mang.
I have only had three airheads, so my sample is small. 84 R100, 83 R80ST and this R65 mono... but as far as motors are concerned this 650 is the smoothest out of the lot. The only drawback is that it runs out of steam on the highway.. But she is a real sweetheart... The 650 motor sips gas so the range is quite nice.
I love your R65. There is something very appealing to me about the monolever R65 and R80's. Probably the fact I like that 60 years of airhead boxer refinement is found in them coupled w/ my belief that the 650 to 800cc boxer motor is the perfect size!
Thanks for the R65 pic, the bike that inspired me to paint my R80 wheels black (then the 80 was promptly stolen by my wife)!
my 1993 R100RS- last of the RS Airhead series, limited production, one of 38 imported (apparently)
Too many nice looking old airheads. I need to stop looking at these or build a bigger garage.
Purchased new in October 1973 from Bob Wyckoff, Sport Spot, North Haledon, NJ- Wixom fairing and bags, restoration by Chris Harris, Manchester, NH. Currently 14,000 miles on bike - now ride in seacoast area of NH.
Forgot to mention that Chris Harris operates Affordable Beemer Services in Manchester, NH


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During his extended battle with mylodisplacia, Carl Sagan wrote something to the effect of, "I would almost recommend almost dying to everybody. It's a character building experience like no other. You get a much clearer perspective of what's important and what isn't, the preciousness and beauty of life. I say almost because of the irreducible and essential element of risk". I've actually had a similar epiphany, but being so much more vindictive than Sagan, I'm employing it in a different way. I'm finding it's just as therapeutic though.
I'm not putting up with tedious self-absorbed leaching sociopaths any more. I'm sure you know the type, the human remura, every thing is about them, their relationships, their boss, their family, their terrible life, their aches and pains, and everyone is against them. If they call you there is a 50/50 chance it's for a ride in the middle of rush hour or an emergency "loan" that you'll never see again, etc.
I'm not talking about people who are down on their luck for a few months, or who suffer horrible accidents or fall prey to terrible disease or are single-handedly raising five children. I'm talking about the manipulative lazy jackasses who are perpetually in crisis, year after year after year, who prey like experts on your generosity to bail them out of those crises which are almost always entirely of their own making. They are usually unwilling to do the simplest thing, like get a goddamn job even if it isn't an ideal six figure dream position, but are more than happy to suck down your hard-earned loot, food, cable, use you for rides and anything else they can get out of you.
Fuck them. I've methodically told them, in a reasonably kind diplomatic way, that I have a real health issue to deal with and I won't be able to provide them one-sided, non stop 24/7 emotional and financial support for the foreseeable future. It was three people I've known for thirty plus years, and they confirmed my judgement when not a single one of them gave a goddamn about my heart attack. All three fired back with variations of "You were never a true friend" alternating with how their latest self inflicted latest crisis is the worst ever and pleas for me to not make their burden heavier.
Like wise I reached out to every personal friend, every ex girl friend and every extended relative I've not kept in touch with or had some stupid falling out with telling them how much I valued knowing them. The criteria: every one of these people has, through strength of character and decency, proven themselves time and time again to be caring compassionate human beings, who genuinely like me, and who have collectively made my life so much better than it would have otherwise been. The mere possibility of having gone through life and never having met them, never having done the fun things I've done with them, frightens me. Another thing that unites them, they too get used right and left by the moochers and predators of the world.
This may seem like common sense, but that's what it took for me to appreciate those who love me and want the best for me, and kick the few remaining louts posing as people who care to the curb. It's not easy, users are skilled at what they do, they know how to manipulate you, they know your buttons, they know exactly how to guilt you. Folks, if you have someone in your life that fits into either category, good or bad, I can tell you, laying it on the line feels good, real real fucking good, It's such an affirming, self esteem building experience I would almost recommend it to anyone, almost, if not for the irreducible and essential element of risk.
I'll be writing more traditional science and political content soon folks. I beat the widow maker and heart problems won't be a major theme going forward. Thanks for all the emails and comments!


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Danny Valencia: Mom has game, too
Third baseman always supported by baseball-loving mom
My mom has always been into baseball. She watches a lot of games, and she reads a lot of baseball books, including books about the mechanics of baseball. She really took a liking to the game itself, and she has always taken it really seriously.
She has become very smart, very intelligent about baseball. It is sort of weird to hear about baseball details from your mother. Mostly she talks to me about my approach at the plate and my swing. We talk about my using right field when I have two strikes. We talk about hitting the ball to right-center and waiting for a good pitch to hit. Those are the things she has always been tough on me about.
When I was younger, it was very unique relating to the other kids I played and grew up with. Some would mess with me, saying things like my mom knew more about baseball and our team than our coach did. It was weird to see some of the guys go up and ask her for advice. It stopped once I got to high school. She has always been tough on me, but I would listen. She was as much of my coach as she was my mother.
The website Wikipedia says that she was one of my two hitting coaches when I was a kid. That is not entirely true, but I guess it is what it is.
Now that I am up in the big leagues, she follows me closely and she follows the Twins closely from her home in Florida. She has the baseball TV package. and when she is not watching our games, she is watching the games of the guys I played with in college. She is always watching games and keeping up with those teams. She also does a good job of following some of my friends who are in the Minor Leagues.
Overall, my mother has been very supportive of me and my endeavors. She has always expected a lot from me, and she is someone I really care about and listen when she says something. She is my mom -- I love her -- and she is always trying to help. She just probably goes about it differently than most moms.
I also know that she is very proud of me. She is happy to watch me on TV and tell her friends that she raised a son who plays in the Majors.
Twins third baseman Danny Valencia had a solid first full season in the big leagues in 2011, hitting .246 with 15 homers and 72 RBIs in 154 games. In 2010 -- his rookie year -- he hit .311 in 85 contests.
This story was not subject to the approval of Major League Baseball or its clubs.


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I am looking for a photo or two of an early 60s era R 50 that can accompany a blog post I am composing about an 81-year-old former rider I met the other day while waiting at a car repair place. If you have a picture you would be willing to share, I'll credit you as the source.
Dave Delgardo


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Quote:Make one yourself after several years of a metalwork class
Quote: Sorry, but that is just a ridiculous thing to say. You've obviously got no knowledge or concept of how Japanese swords are made. If you have nothing worthwhile to contribute, please just read other people's posts!
Quote:I say this because It would seem folly to put your trust in anything you haven't made yourself.
Quote:Would you rather put your life behind a blade you made yourself or someone elses?
Quote:well in his defense I do like that Call of Duty quote he gave.. but ya Im confident that making a katana is quite a bit more difficult than a few years in a general metalworking class...
Quote:Any Sword of any kind. If you do not know the results of endless painstaking days, folding and hammering, melting and molding firsthand, you have no idea how much of a defense that sword will give you.
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