bugün bir amlı için ne yaptın

36.

0

http://www.sweetymarie.com/?id=1060308

okulunagasi
31.05.2011 19:20

···

#40518665 şikayet

35.

0

yapmadığım şey kalmadı amuha koyim

merkez kirk kuvveti
31.05.2011 19:19

···

#40518485 şikayet

34.

0

@8 ağır ekşici detected

gel bayan ayir bayan
31.05.2011 19:13

···

#40517783 şikayet

33.

0

düşünüp çektim pampa olrmu

sakinamamadafaka
31.05.2011 19:04

···

#40516797 şikayet

32.

0

çikolota verdim

not: kardeşim

sephiroth
31.05.2011 18:51

···

#40515223 şikayet

31.

+1

otobuse binerken oncelik verdim, gulumsedi, tesekkur etti

chumbucket
31.05.2011 18:48

···

#40514854 şikayet

30.

+1 -1

dıbına kürekle vurdum. sonrada biber gazı atıp kaçtım. en son gördüğümde dıbını ovuşturarak koşuyodu.

prof dr haydar dumen
31.05.2011 18:46

···

#40514660 şikayet

29.

0

rezil etsende verdim şukunu bin

arthurcarlos
31.05.2011 18:44

···

#40514435 şikayet

28.

0

@27 gülümsedim bin

sevisekmipanpa
31.05.2011 18:43

···

#40514357 şikayet

27.

0

Tümünü Göster

annoying cucumber
31.05.2011 18:39

···

#40513825 şikayet

26.

0

gibik başlık

sefilius
31.05.2011 18:37

···

#40513613 şikayet

25.

0

he 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.[15][16] 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.[17] 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.[18]
in 1931 lemaître went further and suggested that the evident expansion in forward time required that the universe contracted backwards in time, and would continue to do so until it could contract no further, bringing all the mass of the universe into a single point, a "primeval atom" where and when the fabric of time and space comes into existence.[19]
starting in 1924, hubble painstakingly developed a series of distance indicators, the forerunner of the cosmic distance ladder, using the 100-inch (2,500 mm) 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.[8][20] lemaître had already shown that this was expected, given the cosmological principle.[21]
during the 1930s other ideas were proposed as non-standard cosmologies to explain hubble's observations, including the milne model,[22] the oscillatory universe (originally suggested by friedmann, but advocated by albert einstein and richard tolman)[23] and fritz zwicky's tired light hypothesis.[24]
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.[25] the other was lemaître's big bang theory,[notes 1] advocated and developed by george gamow, who introduced big bang nucleosynthesis (bbn)[26] and whose associates, ralph alpher and robert herman, predicted the cosmic microwave background radiation (cmb).[27] 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.[28][notes 2] 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[29] secured the big bang as the best theory of the origin and evolution of the cosmos. 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.
huge strides in big bang cosmology have been made since the late 1990s as a result of major advances in telescope technology as well as the analysis of copious data from satellites such as cobe,[30] the hubble space telescope and wmap.[31] 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.
overview

timeline of the big bang
main article: timeline of the big bang
a graphical timeline is available at
graphical 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.[32] this singularity signals the breakdown of general relativity. how closely we can extrapolate towards the singularity is debated—certainly not earlier than the planck epoch. this singularity is sometimes called "the big bang",[33] but the term can also refer to the early hot, dense phase is itself,[34][notes 3] 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, the universe has a calculated age of 13.75 ± 0.11 billion years.[35] the agreement of these three independent measurements strongly supports the λcdm model that describes in detail the contents of the universe.
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, 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.[36] after inflation stopped, the universe consisted of a quark–gluon plasma, as well as all other elementary particles.[37] 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. 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.[38]
the universe continued to grow in size 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.[39] 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.[40] 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.[41]

the hubble ultra deep field showcases galaxies from an ancient era when the universe was younger, denser, and warmer according to the big bang theory.
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. 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[42]), and is estimated to make up about 23% of the matter/energy of the universe, while baryonic matter makes up about 4.6%.[35] 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.[35]
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 .

Tümünü Göster

hukukcugeldidagilinbeyler
31.05.2011 18:36

···

#40513487 şikayet

24.

-1

he 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.[15][16] 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.[17] 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.[18]
in 1931 lemaître went further and suggested that the evident expansion in forward time required that the universe contracted backwards in time, and would continue to do so until it could contract no further, bringing all the mass of the universe into a single point, a "primeval atom" where and when the fabric of time and space comes into existence.[19]
starting in 1924, hubble painstakingly developed a series of distance indicators, the forerunner of the cosmic distance ladder, using the 100-inch (2,500 mm) 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.[8][20] lemaître had already shown that this was expected, given the cosmological principle.[21]
during the 1930s other ideas were proposed as non-standard cosmologies to explain hubble's observations, including the milne model,[22] the oscillatory universe (originally suggested by friedmann, but advocated by albert einstein and richard tolman)[23] and fritz zwicky's tired light hypothesis.[24]
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.[25] the other was lemaître's big bang theory,[notes 1] advocated and developed by george gamow, who introduced big bang nucleosynthesis (bbn)[26] and whose associates, ralph alpher and robert herman, predicted the cosmic microwave background radiation (cmb).[27] 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.[28][notes 2] 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[29] secured the big bang as the best theory of the origin and evolution of the cosmos. 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.
huge strides in big bang cosmology have been made since the late 1990s as a result of major advances in telescope technology as well as the analysis of copious data from satellites such as cobe,[30] the hubble space telescope and wmap.[31] 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.
overview

timeline of the big bang
main article: timeline of the big bang
a graphical timeline is available at
graphical 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.[32] this singularity signals the breakdown of general relativity. how closely we can extrapolate towards the singularity is debated—certainly not earlier than the planck epoch. this singularity is sometimes called "the big bang",[33] but the term can also refer to the early hot, dense phase is itself,[34][notes 3] 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, the universe has a calculated age of 13.75 ± 0.11 billion years.[35] the agreement of these three independent measurements strongly supports the λcdm model that describes in detail the contents of the universe.
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, 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.[36] after inflation stopped, the universe consisted of a quark–gluon plasma, as well as all other elementary particles.[37] 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. 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.[38]
the universe continued to grow in size 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.[39] 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.[40] 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.[41]

the hubble ultra deep field showcases galaxies from an ancient era when the universe was younger, denser, and warmer according to the big bang theory.
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. 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[42]), and is estimated to make up about 23% of the matter/energy of the universe, while baryonic matter makes up about 4.6%.[35] 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.[35]
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 .

Tümünü Göster

hukukcugeldidagilinbeyler
31.05.2011 18:36

···

#40513469 şikayet

23.

-1

he 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.[15][16] 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.[17] 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.[18]
in 1931 lemaître went further and suggested that the evident expansion in forward time required that the universe contracted backwards in time, and would continue to do so until it could contract no further, bringing all the mass of the universe into a single point, a "primeval atom" where and when the fabric of time and space comes into existence.[19]
starting in 1924, hubble painstakingly developed a series of distance indicators, the forerunner of the cosmic distance ladder, using the 100-inch (2,500 mm) 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.[8][20] lemaître had already shown that this was expected, given the cosmological principle.[21]
during the 1930s other ideas were proposed as non-standard cosmologies to explain hubble's observations, including the milne model,[22] the oscillatory universe (originally suggested by friedmann, but advocated by albert einstein and richard tolman)[23] and fritz zwicky's tired light hypothesis.[24]
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.[25] the other was lemaître's big bang theory,[notes 1] advocated and developed by george gamow, who introduced big bang nucleosynthesis (bbn)[26] and whose associates, ralph alpher and robert herman, predicted the cosmic microwave background radiation (cmb).[27] 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.[28][notes 2] 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[29] secured the big bang as the best theory of the origin and evolution of the cosmos. 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.
huge strides in big bang cosmology have been made since the late 1990s as a result of major advances in telescope technology as well as the analysis of copious data from satellites such as cobe,[30] the hubble space telescope and wmap.[31] 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.
overview

timeline of the big bang
main article: timeline of the big bang
a graphical timeline is available at
graphical 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.[32] this singularity signals the breakdown of general relativity. how closely we can extrapolate towards the singularity is debated—certainly not earlier than the planck epoch. this singularity is sometimes called "the big bang",[33] but the term can also refer to the early hot, dense phase is itself,[34][notes 3] 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, the universe has a calculated age of 13.75 ± 0.11 billion years.[35] the agreement of these three independent measurements strongly supports the λcdm model that describes in detail the contents of the universe.
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, 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.[36] after inflation stopped, the universe consisted of a quark–gluon plasma, as well as all other elementary particles.[37] 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. 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.[38]
the universe continued to grow in size 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.[39] 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.[40] 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.[41]

the hubble ultra deep field showcases galaxies from an ancient era when the universe was younger, denser, and warmer according to the big bang theory.
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. 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[42]), and is estimated to make up about 23% of the matter/energy of the universe, while baryonic matter makes up about 4.6%.[35] 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.[35]
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 .

Tümünü Göster

hukukcugeldidagilinbeyler
31.05.2011 18:36

···

#40513446 şikayet

22.

0

he 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.[15][16] 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.[17] 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.[18]
in 1931 lemaître went further and suggested that the evident expansion in forward time required that the universe contracted backwards in time, and would continue to do so until it could contract no further, bringing all the mass of the universe into a single point, a "primeval atom" where and when the fabric of time and space comes into existence.[19]
starting in 1924, hubble painstakingly developed a series of distance indicators, the forerunner of the cosmic distance ladder, using the 100-inch (2,500 mm) 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.[8][20] lemaître had already shown that this was expected, given the cosmological principle.[21]
during the 1930s other ideas were proposed as non-standard cosmologies to explain hubble's observations, including the milne model,[22] the oscillatory universe (originally suggested by friedmann, but advocated by albert einstein and richard tolman)[23] and fritz zwicky's tired light hypothesis.[24]
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.[25] the other was lemaître's big bang theory,[notes 1] advocated and developed by george gamow, who introduced big bang nucleosynthesis (bbn)[26] and whose associates, ralph alpher and robert herman, predicted the cosmic microwave background radiation (cmb).[27] 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.[28][notes 2] 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[29] secured the big bang as the best theory of the origin and evolution of the cosmos. 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.
huge strides in big bang cosmology have been made since the late 1990s as a result of major advances in telescope technology as well as the analysis of copious data from satellites such as cobe,[30] the hubble space telescope and wmap.[31] 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.
overview

timeline of the big bang
main article: timeline of the big bang
a graphical timeline is available at
graphical 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.[32] this singularity signals the breakdown of general relativity. how closely we can extrapolate towards the singularity is debated—certainly not earlier than the planck epoch. this singularity is sometimes called "the big bang",[33] but the term can also refer to the early hot, dense phase is itself,[34][notes 3] 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, the universe has a calculated age of 13.75 ± 0.11 billion years.[35] the agreement of these three independent measurements strongly supports the λcdm model that describes in detail the contents of the universe.
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, 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.[36] after inflation stopped, the universe consisted of a quark–gluon plasma, as well as all other elementary particles.[37] 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. 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.[38]
the universe continued to grow in size 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.[39] 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.[40] 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.[41]

the hubble ultra deep field showcases galaxies from an ancient era when the universe was younger, denser, and warmer according to the big bang theory.
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. 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[42]), and is estimated to make up about 23% of the matter/energy of the universe, while baryonic matter makes up about 4.6%.[35] 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.[35]
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 .

Tümünü Göster

hukukcugeldidagilinbeyler
31.05.2011 18:36

···

#40513430 şikayet

21.

0

he 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.[15][16] 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.[17] 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.[18]
in 1931 lemaître went further and suggested that the evident expansion in forward time required that the universe contracted backwards in time, and would continue to do so until it could contract no further, bringing all the mass of the universe into a single point, a "primeval atom" where and when the fabric of time and space comes into existence.[19]
starting in 1924, hubble painstakingly developed a series of distance indicators, the forerunner of the cosmic distance ladder, using the 100-inch (2,500 mm) 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.[8][20] lemaître had already shown that this was expected, given the cosmological principle.[21]
during the 1930s other ideas were proposed as non-standard cosmologies to explain hubble's observations, including the milne model,[22] the oscillatory universe (originally suggested by friedmann, but advocated by albert einstein and richard tolman)[23] and fritz zwicky's tired light hypothesis.[24]
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.[25] the other was lemaître's big bang theory,[notes 1] advocated and developed by george gamow, who introduced big bang nucleosynthesis (bbn)[26] and whose associates, ralph alpher and robert herman, predicted the cosmic microwave background radiation (cmb).[27] 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.[28][notes 2] 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[29] secured the big bang as the best theory of the origin and evolution of the cosmos. 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.
huge strides in big bang cosmology have been made since the late 1990s as a result of major advances in telescope technology as well as the analysis of copious data from satellites such as cobe,[30] the hubble space telescope and wmap.[31] 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.
overview

timeline of the big bang
main article: timeline of the big bang
a graphical timeline is available at
graphical 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.[32] this singularity signals the breakdown of general relativity. how closely we can extrapolate towards the singularity is debated—certainly not earlier than the planck epoch. this singularity is sometimes called "the big bang",[33] but the term can also refer to the early hot, dense phase is itself,[34][notes 3] 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, the universe has a calculated age of 13.75 ± 0.11 billion years.[35] the agreement of these three independent measurements strongly supports the λcdm model that describes in detail the contents of the universe.
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, 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.[36] after inflation stopped, the universe consisted of a quark–gluon plasma, as well as all other elementary particles.[37] 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. 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.[38]
the universe continued to grow in size 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.[39] 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.[40] 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.[41]

the hubble ultra deep field showcases galaxies from an ancient era when the universe was younger, denser, and warmer according to the big bang theory.
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. 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[42]), and is estimated to make up about 23% of the matter/energy of the universe, while baryonic matter makes up about 4.6%.[35] 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.[35]
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 .

Tümünü Göster

hukukcugeldidagilinbeyler
31.05.2011 18:36

···

#40513415 şikayet

20.

0

he 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.[15][16] 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.[17] 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.[18]
in 1931 lemaître went further and suggested that the evident expansion in forward time required that the universe contracted backwards in time, and would continue to do so until it could contract no further, bringing all the mass of the universe into a single point, a "primeval atom" where and when the fabric of time and space comes into existence.[19]
starting in 1924, hubble painstakingly developed a series of distance indicators, the forerunner of the cosmic distance ladder, using the 100-inch (2,500 mm) 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.[8][20] lemaître had already shown that this was expected, given the cosmological principle.[21]
during the 1930s other ideas were proposed as non-standard cosmologies to explain hubble's observations, including the milne model,[22] the oscillatory universe (originally suggested by friedmann, but advocated by albert einstein and richard tolman)[23] and fritz zwicky's tired light hypothesis.[24]
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.[25] the other was lemaître's big bang theory,[notes 1] advocated and developed by george gamow, who introduced big bang nucleosynthesis (bbn)[26] and whose associates, ralph alpher and robert herman, predicted the cosmic microwave background radiation (cmb).[27] 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.[28][notes 2] 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[29] secured the big bang as the best theory of the origin and evolution of the cosmos. 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.
huge strides in big bang cosmology have been made since the late 1990s as a result of major advances in telescope technology as well as the analysis of copious data from satellites such as cobe,[30] the hubble space telescope and wmap.[31] 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.
overview

timeline of the big bang
main article: timeline of the big bang
a graphical timeline is available at
graphical 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.[32] this singularity signals the breakdown of general relativity. how closely we can extrapolate towards the singularity is debated—certainly not earlier than the planck epoch. this singularity is sometimes called "the big bang",[33] but the term can also refer to the early hot, dense phase is itself,[34][notes 3] 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, the universe has a calculated age of 13.75 ± 0.11 billion years.[35] the agreement of these three independent measurements strongly supports the λcdm model that describes in detail the contents of the universe.
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, 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.[36] after inflation stopped, the universe consisted of a quark–gluon plasma, as well as all other elementary particles.[37] 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. 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.[38]
the universe continued to grow in size 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.[39] 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.[40] 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.[41]

the hubble ultra deep field showcases galaxies from an ancient era when the universe was younger, denser, and warmer according to the big bang theory.
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. 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[42]), and is estimated to make up about 23% of the matter/energy of the universe, while baryonic matter makes up about 4.6%.[35] 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.[35]
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 .

Tümünü Göster

hukukcugeldidagilinbeyler
31.05.2011 18:35

···

#40513389 şikayet

19.

0

yanımdan geçerken onun zütüne baktım sonra kıllı göbeğimi kaşıdım ve yere harita şeklinde bir balgam fırlattım

hic5
31.05.2011 18:35

···

#40513378 şikayet

18.

-1

he 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.[15][16] 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.[17] 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.[18]
in 1931 lemaître went further and suggested that the evident expansion in forward time required that the universe contracted backwards in time, and would continue to do so until it could contract no further, bringing all the mass of the universe into a single point, a "primeval atom" where and when the fabric of time and space comes into existence.[19]
starting in 1924, hubble painstakingly developed a series of distance indicators, the forerunner of the cosmic distance ladder, using the 100-inch (2,500 mm) 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.[8][20] lemaître had already shown that this was expected, given the cosmological principle.[21]
during the 1930s other ideas were proposed as non-standard cosmologies to explain hubble's observations, including the milne model,[22] the oscillatory universe (originally suggested by friedmann, but advocated by albert einstein and richard tolman)[23] and fritz zwicky's tired light hypothesis.[24]
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.[25] the other was lemaître's big bang theory,[notes 1] advocated and developed by george gamow, who introduced big bang nucleosynthesis (bbn)[26] and whose associates, ralph alpher and robert herman, predicted the cosmic microwave background radiation (cmb).[27] 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.[28][notes 2] 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[29] secured the big bang as the best theory of the origin and evolution of the cosmos. 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.
huge strides in big bang cosmology have been made since the late 1990s as a result of major advances in telescope technology as well as the analysis of copious data from satellites such as cobe,[30] the hubble space telescope and wmap.[31] 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.
overview

timeline of the big bang
main article: timeline of the big bang
a graphical timeline is available at
graphical 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.[32] this singularity signals the breakdown of general relativity. how closely we can extrapolate towards the singularity is debated—certainly not earlier than the planck epoch. this singularity is sometimes called "the big bang",[33] but the term can also refer to the early hot, dense phase is itself,[34][notes 3] 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, the universe has a calculated age of 13.75 ± 0.11 billion years.[35] the agreement of these three independent measurements strongly supports the λcdm model that describes in detail the contents of the universe.
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, 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.[36] after inflation stopped, the universe consisted of a quark–gluon plasma, as well as all other elementary particles.[37] 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. 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.[38]
the universe continued to grow in size 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.[39] 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.[40] 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.[41]

the hubble ultra deep field showcases galaxies from an ancient era when the universe was younger, denser, and warmer according to the big bang theory.
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. 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[42]), and is estimated to make up about 23% of the matter/energy of the universe, while baryonic matter makes up about 4.6%.[35] 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.[35]
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 .

Tümünü Göster

hukukcugeldidagilinbeyler
31.05.2011 18:35

···

#40513365 şikayet

17.

0

he 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.[15][16] 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.[17] 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.[18]
in 1931 lemaître went further and suggested that the evident expansion in forward time required that the universe contracted backwards in time, and would continue to do so until it could contract no further, bringing all the mass of the universe into a single point, a "primeval atom" where and when the fabric of time and space comes into existence.[19]
starting in 1924, hubble painstakingly developed a series of distance indicators, the forerunner of the cosmic distance ladder, using the 100-inch (2,500 mm) 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.[8][20] lemaître had already shown that this was expected, given the cosmological principle.[21]
during the 1930s other ideas were proposed as non-standard cosmologies to explain hubble's observations, including the milne model,[22] the oscillatory universe (originally suggested by friedmann, but advocated by albert einstein and richard tolman)[23] and fritz zwicky's tired light hypothesis.[24]
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.[25] the other was lemaître's big bang theory,[notes 1] advocated and developed by george gamow, who introduced big bang nucleosynthesis (bbn)[26] and whose associates, ralph alpher and robert herman, predicted the cosmic microwave background radiation (cmb).[27] 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.[28][notes 2] 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[29] secured the big bang as the best theory of the origin and evolution of the cosmos. 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.
huge strides in big bang cosmology have been made since the late 1990s as a result of major advances in telescope technology as well as the analysis of copious data from satellites such as cobe,[30] the hubble space telescope and wmap.[31] 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.
overview

timeline of the big bang
main article: timeline of the big bang
a graphical timeline is available at
graphical 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.[32] this singularity signals the breakdown of general relativity. how closely we can extrapolate towards the singularity is debated—certainly not earlier than the planck epoch. this singularity is sometimes called "the big bang",[33] but the term can also refer to the early hot, dense phase is itself,[34][notes 3] 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, the universe has a calculated age of 13.75 ± 0.11 billion years.[35] the agreement of these three independent measurements strongly supports the λcdm model that describes in detail the contents of the universe.
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, 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.[36] after inflation stopped, the universe consisted of a quark–gluon plasma, as well as all other elementary particles.[37] 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. 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.[38]
the universe continued to grow in size 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.[39] 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.[40] 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.[41]

the hubble ultra deep field showcases galaxies from an ancient era when the universe was younger, denser, and warmer according to the big bang theory.
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. 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[42]), and is estimated to make up about 23% of the matter/energy of the universe, while baryonic matter makes up about 4.6%.[35] 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.[35]
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 .

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