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Topic: Big Bang nucleosynthesis

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Big Bang

Nucleosynthesis

Helium

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Timeline of the Universe

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	Big Bang nucleosynthesis - Wikipedia, the free encyclopedia
		One feature of BBN is that the physical laws and constants that govern the behavior of matter at these energies are very well understood, and hence BBN lacks some of the speculative uncertainties that characterize earlier periods in the life of the universe.
		Big Bang nucleosynthesis predicts about 25% helium-4, and this number is extremely insensitive to the initial conditions of the universe.
		The problem was that while the concentration of deuterium in the universe is consistent with the Big Bang model as a whole, it is too high to be consistent with a model that presumes that most of the universe consists of protons and neutrons.
	en.wikipedia.org /wiki/Big_Bang_nucleosynthesis (2022 words)

	Nucleosynthesis - Wikipedia, the free encyclopedia
		The subsequent nucleosynthesis of the elements occurs primarily either by nuclear fusion or nuclear fission.
		Big Bang nucleosynthesis occurred within the first three minutes of the universe and is responsible for most of the helium-4 and deuterium in the universe.
		The 4He, 3He, 2H and 7Li nuclei are fused in the cooling of the Big Bang from the primordial nucleons, which were created by the cooling of the quark-gluon plasma.
	en.wikipedia.org /wiki/Nucleosynthesis (586 words)

	WMAP Cosmology101: Formation of the Elements
		The Big Bang theory predicts that the early universe was a very hot place.
		One second after the Big Bang, the temperature of the universe was roughly 10 billion degrees and was filled with a sea of neutrons, protons, electrons, anti-electrons (positrons), photons and neutrinos.
		The predicted abundance of deuterium, helium and lithium depends on the density of ordinary matter in the early universe, as shown in the figure at left.
	map.gsfc.nasa.gov /m_uni/uni_101bbtest2.html (433 words)

	Big Bang: How Did the Universe Begin? (Site not responding. Last check: 2007-11-07)
		The big bang is not like an explosion of matter in otherwise empty space; rather, space itself began with the big bang and carried matter with it as it expanded.
		Based on theories of the big bang nucleosynthesis, physicists in the mid-1960s calculated that roughly 1/4 of mass was converted into helium in the beginning, while the rest remained as hydrogen.
		Despite the high temperature at the beginning, the big bang nucleosynthesis could create deuterium because the expansion of the universe lowered the density and temperature so quickly that there was hardly time for the deuterium to decay.
	www.ugcs.caltech.edu /~yukimoon/BigBang/BigBang.htm (3052 words)

	Big Bang Cosmology Primer
		Furthermore, the cosmic microwave background (CMB), a theoretical prediction about photons left over from the big bang, was discovered in the 1960's and mapped out by a team at Berkeley in the early 1990's.
		A possible explanation is that right after the big bang the Universe began a period of exaggerated outward expansion, with particles flying outward faster than the current speed of light.
		Big bang nucleosynthesis limits the total number of baryons to be a fraction of the Universes total mass.
	cosmology.berkeley.edu /Education/IUP/Big_Bang_Primer.html (1809 words)

	Big Bang Theory Busted By 33 Top Scientists
		The big bang today relies on a growing number of hypothetical entities, things that we have never observed-- inflation, dark matter and dark energy are the most prominent examples.
		Yet the big bang is not the only framework available for understanding the history of the universe.
		As a result, the dominance of the big bang within the field has become self-sustaining, irrespective of the scientific validity of the theory.
	www.rense.com /general53/bbng.htm (879 words)

	Big Bang Nucleosynthesis Activity (Site not responding. Last check: 2007-11-07)
		Gamow, Alpher, Bethe and Herman (1948) proposed the hot Big Bang as a means to produce all of the elements.
		About 1 second after the Big Bang, quarks condense to form baryons: the proton to neutron ratio was 7:1.
		About 1 second after the Big Bang, the temperature is slightly less than the neutron-proton mass difference, these weak reactions become slower than the expansion rate of the Universe, and the neutron:proton ratio freezes out at about 1:6.
	geology.wcupa.edu /mgagne/ess355/bbns.html (1212 words)

	Big Bang - EvoWiki
		The "Big Bang" marks the beginning point of the universe from which all time, space, matter, and energy originated.
		The term "Big Bang" was coined by Fred Hoyle in an attempt to mock the theory; however, the term caught on and was quickly adopted by proponents of the theory.
		Constraints from Big Bang nucleosynthesis suggest that only about 6% of the Universe's matter is baryonic matter; this means that nearly all of the dark matter is nonbaryonic, most likely Weakly Interacting Massive Particles (WIMP's).
	wiki.cotch.net /index.php/Big_Bang (2039 words)

	[No title] (Site not responding. Last check: 2007-11-07)
		Big Bang Nucleosynthesis (BBN) refers to an epoch in the early universe when the light elements were synthesized, the so-called nuclear age of cosmology.
		Primordial nucleosynthesis and the cosmic radiation background are both sensitive to the amount of ordinary matter there is in the universe.
		Plotted in the figure are the light element abundances predicted by primordial nucleosynthesis against its one free parameter, the baryon-to-photon ratio.
	www.physics.uiuc.edu /People/Faculty/profiles/Wandelt/BBN.htm (969 words)

	The Big Bang Model
		One of the primary successes of the Big Bang theory is its explanation for the chemical composition of the universe.
		After that, about three and a half minutes after the starting point, the temperature and density dropped so much that collisions between particles were rare, and of such low energy that the electric forces of repulsion between positively-charged nuclei prevented fusion.
		Big Bang tutorial from the Center for Astrophysics and Space Sciences at the University of San Diego.
	spiff.rit.edu /classes/phys240/lectures/bb/bb.html (2208 words)

	Big bang nucleosynthesis (Site not responding. Last check: 2007-11-07)
		The isotopes produced in big bang nucleosynthesis (BBN) are D, He-3, He-4, and Li-7.
		Standard big-bang nucleosynthesis (SBBN) assumes the standard model of particle physics and a homogenous and isotropic early universe.
		BBN can be used to constrain possible nonstandard features of cosmology or particle physics.
	www.physics.helsinki.fi /~hitu_kh/bbn.shtml (179 words)

	An universe without Big Bang (Site not responding. Last check: 2007-11-07)
		This model is opposed to the standard model of Hot Big Bang and all its prolongations.
		This model is without expansion of the universe, without recession of the galaxies, without inflationary universe, with a different origin of the Cosmic Microwave Background Radiation,without primordial nucleosynthesis (Big Bang Nucleosynthesis) of the light elements.
		The essential concepts of the expanding universe, the law of Hubble (v = HD), the primordial explosion, the redshifts, subjected to an analysis criticizes, are disputed.
	www.freazer.com /perso/redshifts (402 words)

	Big Bang Nucleosynthesis (Site not responding. Last check: 2007-11-07)
		Light elements (namely deuterium, helium, and lithium) were produced in the first few minutes of the Big Bang, while elements heavier than helium are thought to have their origins in the interiors of stars which formed much later in the history of the Universe.
		Roughly three minutes after the Big Bang itself, the temperature of the Universe rapidly cooled from its phenomenal 10^32 Kelvin to approximately 10^9 Kelvin.
		The Big Bang Nucleosynthesis theory predicts that roughly 25% the mass of the Universe consists of Helium.
	astro.berkeley.edu /~mwhite/darkmatter/bbn.html (645 words)

	The Big Bang (Site not responding. Last check: 2007-11-07)
		The net result of the early nuclear reactions Big Bang Nucleosynthesis is to transform all of the neutrons, along with the necessary protons, into Helium nuclei plus traces of
		This is because the Universe is expanding and the density decreasing as nuclear reactions are occurring.
		The strongest evidence that something like the Big Bang really happened is the Cosmic Background Radiation predicted by Cosmologist George Gamov in 1948 and discovered by Arno Penzias and Robert Wilson of Bell Labs in 1965.
	cassfos02.ucsd.edu /public/tutorial/BB.html (1168 words)

	Science and Reason: The Big Bang
		The big bang theory of the initial state and subsequent development of the universe was originated around 1931 by Georges Lemaître and further developed in the 1940s by George Gamow and his students Ralph Alpher and Robert Herman.
		the theory of the big bang – the notion that at some point in time about 14 billion years ago (by current reckoning), all matter in the observable universe was in a state of extremely high density and temperature, and subsequently "exploded", resulting in the expansion we still see today.
		One consequence of the homogeneity condition is that the big bang event (if such existed, which isn't in fact absolutely required in all versions of the model) didn't happen at one particular point in space.
	www.scienceandreason.net /oq/oq-co008.htm (20702 words)

	Big Bang Nucleosynthesis (Site not responding. Last check: 2007-11-07)
		Big bang nucleosynthesis and new physics (Groningen, 2005)
		Big bang nucleosynthesis and physics beyond the standard model (1996)
		Nucleosynthesis bounds on a time-varying cosmological `constant' (1996)
	www-thphys.physics.ox.ac.uk /users/SubirSarkar/bbn.html (137 words)

	Physics News Update Number 247 - PROBLEMS WITH BIG-BANG NUCLEOSYNTHESIS? (Site not responding. Last check: 2007-11-07)
		A long with the expansion of the universe and the cosmic microwave background, the most prominent artifact of the big bang is the synthesis of several species of light nuclei, namely D, He-4, He-3, and Li-7, only seconds after the explosion.
		Cosmologies which make predictions of the amount of early nucleosynthesis must account for the present-day abundances of these nuclei, consisting of the primordial inventory plus any that may have been manufactured (or destroyed) in the cores of stars.
		Although the measurement uncertainties are still considerable, the observed abundances of He-4 and D seems to be at odds with the main big bang model.
	www.aip.org /enews/physnews/1995/split/pnu247-1.htm (310 words)

	Glossary
		The cosmic microwave background, big bang nucleosynthesis, and the observed Hubble expansion of the Universe are considered proof of the big bang theory.
		Lighter elements, such as Hydrogen, Helium and Lithium, were formed as a result of the big bang in a process called big bang nucleosynthesis.
		Observable radiation (in the microwave portion of the electromagnetic spectrum) left over from the big bang, the cosmic microwave background is considered proof of the big bang.
	cosmology.berkeley.edu /Education/IUP/GlossaryA_E.htm (798 words)

	The universe is the poor man’s particle accelerator \| Cosmic Variance (Site not responding. Last check: 2007-11-07)
		Schramm was an enormously influential figure in contemporary cosmology, one of the prime movers in bringing together particle physics and astrophysics in the study of the early universe.
		Between a few seconds and a few minutes after the Big Bang, the universe was a nuclear reactor, converting nucleons (neutrons and protons) into nuclei of helium, lithium, and deuterium.
		And BBN assures us that Einstein’s general relativity works without modification in the very early universe; in particular, we know that Newton’s constant of gravitation had the same value then as it does now to within about twenty percent.
	cosmicvariance.com /2005/12/19/the-universe-is-the-poor-mans-particle-accelerator (1425 words)

	Nucleosynthesis
		By the time the universe was three minutes old the process had basically stopped and the relative abundances of the elements was fixed at ratios that didn't change for very long time: 75% hydrogen, 25% helium, with trace amounts of deuterium (hydrogen-2), helium-3, and lithium-7.
		Big Bang nucleosynthesis produced no elements heavier than lithium.
		Almost all the hydrogen and helium present in the universe today (and some of the lithium) were created in the first three minutes after the big bang.
	www.hypertextbook.com /physics/modern/nucleosynthesis (683 words)

	Ned Wright's Cosmology Tutorial - Part 1
		Another piece of evidence in favor of the Big Bang is the abundance of the light elements, like hydrogen, deuterium (heavy hydrogen), helium and lithium.
		The theory of Big Bang Nucleosynthesis predicts that about 1/4 of the mass of the Universe should be helium, which is very close to what is observed.
		The abundance of deuterium is inversely related to the density of nucleons in the Universe, and the observed value of the deuterium abundance suggests that there is one nucleon for every 4 cubic meters of space in the the Universe.
	www.astro.ucla.edu /~wright/cosmo_01.htm (1560 words)

	The Big Bang theory (Site not responding. Last check: 2007-11-07)
		Standard Big Bang Nucleosynthesis refers to an exceptionally simple and beautiful model of the early universe.
		The standard Big Bang model of cosmology is the simplest (i.e., it has the fewest adjustable parameters) and is based on the
		In the context of Big Bang cosmology there are a number of "free parameters" that are not fixed
	users.rcn.com /metanoia/fas/bigbang.html (297 words)

	3.4 Nucleosynthesis (Site not responding. Last check: 2007-11-07)
		seconds after the Big Bang) are in good agreement with the standard model of our Universe (see § 2.2).
		However, it is interesting to investigate other more general models to assert the role of shear and curvature on the nucleosynthesis process.
		He increases with increasing shear; this is due to time scale effects and the competition between dissipation and enhanced reaction rates from photon heating and neutrino blue shifts.
	relativity.livingreviews.org /Articles/lrr-1998-9/node9.html (321 words)

	Baryon Density Constraint (Site not responding. Last check: 2007-11-07)
		The yield of Big Bang nucleosynthesis, however, depends strongly upon the density of protons and neutrons in the early Universe.
		The reaction rates for the protons and neutrons (and therefore the yields of Big Bang nucleosynthesis) can be changed by making different assumptions about the baryon density in the Universe.
		This is a nice state of affairs as it then makes it very easy to think about how changes in the baryon density of the Universe change the outcome of Big Bang nucleosynthesis.
	zebu.uoregon.edu /~imamura/123/lecture-8/limits.html (286 words)

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