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Cosmic inflation

2007-10-02T18:46:56Z

Love: started article, bulked it out. next step: add the proposed mechanism

In the field of [[Cosmology]], '''cosmic inflation''' is a theory which posits that in the first 10-35 of a second after the [[Big Bang]], the universe underwent a period of rapid, exponential inflation, with it increasing in size by a factor of at least 1026. It was first proposed by [[Alan Guth]] of [[MIT]], in 1981. The theory accounts for many objections to the Big Bang model. <ref>http://physicsworld.com/cws/article/print/24768</ref> <ref>http://www.symmetrymagazine.org/cms/?pid=1000045</ref>

=Problems with the Big Bang model=

==The Flatness problem==

The [[critical density]] of the universe is the density at which the universe's rate of expansion will slow down, and eventually reach a rate of zero, as the age of the universe becomes very, very large. Densities above or below this would lead to the universe eventually collapsing back on itself during to gravity, or expanding at an every increasing rate, respectively. <ref>http://www.daviddarling.info/encyclopedia/C/critical_density.html</ref>Today's best estimates of the universe's density place it staggeringly close to the critical density - the universe is described as being almost "flat", since the shape of the universe's geometry is decided by its density - hence the name of ''the flatness problem''. If the universe's density is extrapolated back until just after the [[Big Bang]], it is found to be exceedingly close to 1 - given that it can take any value, this value leading to a perfectly "flat" universe seems unlikely to have been chosen at random. <ref>http://www.daviddarling.info/encyclopedia/C/critical_density.html</ref>

The explanation offered by cosmic inflation is that the period of exponential expansion which occured essentially "ironed out" any small creases in the early universe, leading to the visible universe's shape being flat.

==The Horizon problem==

In accordance with the [[Cosmological principle]], the observable universe is seen to be both homogeneous and isotropic on large scales (that is, the "same", no matter where you are, or where you look). <ref>http://csep10.phys.utk.edu/astr162/lect/cosmology/cp.html</ref> Given the vast size of the observable universe, and the finite age of the universe, there is no reason for the universe to be so "smooth" - there has not been enough time for light to travel between two points at opposite ends of the universe, and so they are not causally connected, and there should be no reason for them to have such similar properties.

Cosmic inflation offers an explanation, in that the universe expanded by such a large amount, over such a small time, so the entire visible universe is in fact a very small portion of the early universe (in causal contact with surrounding points at that time) which was expanded into everything seen today.

==The Magnetic Monopole problem==

Several physical theories, such as [[General Relativity]] and some [[Grand Unified Theories]] predict the existence of particles called [[magnetic monopoles]], as well as the [[magnetic dipoles]] easily observed in nature. However, no monopoles have ever been observed, and given the success of other aspects of the Standard Model, this was unexpected.<ref>http://superstringtheory.com/cosmo/cosmo4.html</ref>

However, if the magnetic monopoles were created ''before'' the period of expansion posited by cosmic inflation as is expected, they would have been diluted throughout the universe, since the distance between two neighbouring particles would have been increased by such a huge factor, so there may only be one monopole (if that) present in the entire visible universe.

Big Bang theory

2007-10-02T17:56:13Z

Love: added alternative explanation of starlight problem

[[Image:Universe expansion.png|right|thumb|250px|According to the Big Bang theory, the universe emerged from an extremely dense and hot state called the ''original singularity''.]]
[[Image:End of universe.jpg|right|thumb|250px|According to the Big Bang theory, the 3 possible geometry of the universe depends on value of the ''[[cosmological constant]]''.]]
The '''Big Bang Theory''' is the current dominant scientific theory explaining the acceleration of matter throughout the Universe. Big bang theories are actually a ''class'' of scientific models that describe the Universe as expanding from a very hot, dense state approximately 13.7 billion years ago<ref>[http://map.gsfc.nasa.gov/m_uni/uni_101age.html WMAP Cosmology 101: Age of the Universe]</ref> (although this number has changed several times throughout recent history). It was first proposed by [[Georges-Henri Lemaitre]] and evidence for the expansion was observed by [[Edwin Hubble]]<ref>Hubble, E. Proceedings of the National Academy of Sciences of the United States of America, Volume 15, Issue 3, pp. 168-173.</ref>. Later [[George Gamow]] predicted that the Big Bang would leave an observable microwave background radiation (or CMBR). This radiation was subsequently discovered by Arno Penzias and Robert Wilson at [[Bell Labs]] and found to be close to that predicted by Gamow (Gamow predicted a background radiation level equivalent to a roughly 3 K black body object, and the observed level is that of a 2.725 K body). Pensiaz and Wilson were awarded a Nobel Prize in 1978 for their work.

The term "Big Bang" implies an explosion of matter into pre-existing space, but the theory actually indicates that space is dynamic and more space is constantly created in the interstices between particles as the density of the universe falls. In other words, the Big Bang describes the expansion of space and time. Big Bang theorists state that the Hubble [[redshift]] is a consequence of this stretching of the fabric of space.

Observations of distant supernovae indicate that the Universe is actually undergoing accelerated expansion<ref>Riess, A. G., et al. The Astronomical Journal, Volume 116, Issue 3, pp. 1009-1038.</ref><ref>Perlmutter, S., et al. The Astrophysical Journal, Volume 517, Issue 2, pp. 565-586.</ref> and galaxy surveys<ref>[http://www.sdss.org/dr5/ Sloan Digital Sky Survey]</ref><ref>Tegmark, M., et al. Physical Review D, vol. 74, Issue 12.</ref> and recent observations of the microwave background<ref>[http://map.gsfc.nasa.gov/ Wilkinson Microwave Anisotropy Probe]</ref><ref>See, for example, http://arxiv.org/abs/astro-ph/0603449</ref> have corroborated these claims. Conventional wisdom is that the acceleration is caused by some sort of [[dark energy]], which has not yet been directly observed.

== Big Bang Theory Dissent Letter ==
The Big Bang Theory has had many dissenters including the British astronomer Sir [[Fred Hoyle]], the Nobel Prize winner [[Hannes Alfven]], and astronomers [[Geoffrey Burbidge]] and [[Halton Arp]]. <ref>http://www.icr.org/article/343/</ref> It was Hoyle who sarcastically coined the term during a radio broadcast.

In 2004, a ‘Open Letter to the Scientific Community’ disputing the big bang theory was signed by 33 scientists and has been published on the internet and in the science journal [[New Scientist]]. <ref>http://www.answersingenesis.org/docs2004/0601skepticism.asp</ref> <ref>http://www.newscientist.com/article/mg18224482.900</ref> The dissent letter has subsequently been signed by hundreds of individuals around the world. <ref>http://www.cosmologystatement.org/</ref> Professional cosmologists are actively creating models (some of which contradict the Big Bang scenario) and collecting data that probe the specific nature of the earliest observable aspects of the Universe.

==Starlight Problem for the Big Bang Theory==
The [[starlight problem]] is an argument against the Big Bang Theory. <ref>http://www.answersingenesis.org/creation/v25/i4/lighttravel.asp</ref> The [[creation science]] organization [[Answers in Genesis]] has stated the following regarding the starlight problem for the Big Bang Theory and the work of [[Charles W. Misner]] is cited who published his work in ''[[Physical Review Letters]]'':
{{cquote|The problem is this: even assuming the big bang timescale, there has not been enough time for light to travel between widely separated regions of space. So, how can the different regions of the current [cosmic microwave background] CMB have such precisely uniform temperatures if they have never communicated with each other? This is a light-travel–time problem.<ref>http://www.answersingenesis.org/creation/v25/i4/lighttravel.asp</ref>}}

However, a theory first put forward by [[Alan Guth]], of [[MIT]], named [[cosmic inflation]] offers an alternative explanation: during the universe's first 10-35 of a second, a period of rapid, exponential inflation occured, expanding the universe by a factor of at least 1026. This allows for the uniformity of the [[CMBR]] - the vast distances were in thermodynamical contact before the rapid inflation. <ref>http://www.symmetrymagazine.org/cms/?pid=1000045</ref> <ref>http://physicsworld.com/cws/article/print/24768</ref>

==Creationist and Theistic Evolutionary Views==
Young earth creationist scientists contest the Big Bang Theory stating that it is scientifically unsound.
<ref name="BB Critique">Thompson, Bert, Harrub, Brad, and May, Branyon [http://www.apologeticspress.org/modules.php?name=Read&cat=1&itemid=22 The Big Bang Theory—A Scientific Critique] ''Apologetics Press'', May 2003 - 23[5]:32-34,36-47.</ref>
<ref>Brown, Walt, 2001, [http://www.creationscience.com/onlinebook/AstroPhysicalSciences16.html Big Bang?]</ref><ref>http://www.apologeticspress.org/articles/309</ref><ref>http://www.apologeticspress.org/articles/2047</ref><ref>http://www.icr.org/article/343/</ref>

Some Old Earth Creationists and Theistic Evolutionists argue that the Big Bang is in fact mentioned in the Bible. <ref>[http://www.reasons.org/resources/fff/2000issue03/index.shtml#big_bang_the_bible_taught_it_first http://www.reasons.org/resources/fff/2000issue03/index.shtml#big_bang_the_bible_taught_it_first]</ref> Some Christian apologists who believe in an old earth, such as [[William Craig]] use the Big Bang as an apologetic, arguing that it proves that the universe had a beginning. <ref>Strobel, Lee. ''The Case for a Creator''. Zondervan, 2004. </ref>

==References==
{{reflist|2}}

[[Category:Astronomy]]

Neodymium

2007-10-02T00:10:15Z

Love: thought i'd get the ball rolling

This element can be used to make [[magnets]].