Cosmology
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The fine-tuned Universe is the proposition that the conditions that allow life in the Universe can only occur when certain universal fundamental physical constants lie within a very narrow range, so that if any of several fundamental constants were only slightly different, the Universe would be unlikely to be conducive to the establishment and development of matter , astronomical structures, elemental diversity, or life as it is presently understood. [ 1 ] The existence and extent of fine-tuning in the Universe is a matter of dispute in the scientific community. [ citation needed ] The proposition is also discussed among philosophers , theologians , creationists , and intelligent design proponents. Physicist Paul Davies has asserted that "There is now broad agreement among physicists and cosmologists that the Universe is in several respects ‘fine-tuned' for life".
Fine-tuned Universe
Are We Living Inside a Black Hole?
Black Hole Concept Wikimedia Commons Scientists trying to explain the universe’s accelerating expansion usually point to dark energy, which seems to be pushing everything apart. But an Indiana University professor has a new theory, reports New Scientist : We’re inside a black hole that exists in another universe.
In July the European Space Agency released a new map showing the universe in its infancy, 13.7 billion years ago—just 300,000 years after the Big Bang. In this full-sky image, created with data from the new Planck space telescope , red and orange areas represent primordial lumps that gave rise to giant clusters of galaxies. The blue and white zones comprise very different signals, mostly emissions from relatively nearby clouds of gas and dust in our galaxy. Planck scientists plan to strip out those local features to get an even clearer picture of the early evolution of the cosmos. A full release of data is coming in two years.
#7: The Map of Everything | Cosmology
#46: Do Physical Laws Vary From Place to Place? | Cosmology
Since the days of Isaac Newton, a bedrock principle of physics has been that the basic properties of the universe (the laws of gravity and the speed of light, for instance) are the same in all locations, at all times. So scientists were intrigued by the announcement last August that one of the so-called constants of nature might not be so constant after all. John Webb , an astronomer at the University of New South Wales in Australia, was studying the fine-structure constant, which governs the strength of the force between charged particles, in a large number of distant galaxies. Using data from the Very Large Telescope in Chile, he and his colleagues found a slight but notable variation in the constant: It increased one part per million for every billion light-years farther they looked. Odder still, an earlier survey in the Northern Hemisphere indicated that the constant decreased with distance, suggesting a possible asymmetry in the universe.
The visible edge of the universe is, by definition, the most distant thing that we can see.
#76: What Lies Beyond the Edge of the Universe | Cosmology
#83: Mammoth Star Is the Biggest One Ever Seen | Stars
Last year British astronomers identified the most massive star ever seen: a behemoth weighing 265 times as much as our sun, so huge that it challenges astronomers’ models of how stars are born.
Microwave radiation map hints at other universes - space - 17 December 2010
Update on 16 August 2011 : The researchers ran additional statistical checks on the CMB data, looking at the probability that the bubbles would appear anywhere on the sky. Lead author Stephen Feeney says: "The current data favour no bubble collisions. However, a non-zero number of bubble collisions is still allowed, and there are four patches in the WMAP data where [signals of possible bubble universes] are higher than anything we expect from systematic errors due to instrumental effects, foreground-removal artefacts etc.Holographic principle
The holographic principle is a property of quantum gravity and string theories which states that the description of a volume of space can be thought of as encoded on a boundary to the region—preferably a light-like boundary like a gravitational horizon . First proposed by Gerard 't Hooft , it was given a precise string-theory interpretation by Leonard Susskind [ 1 ] who combined his ideas with previous ones of 't Hooft and Charles Thorn . [ 1 ] [ 2 ] As pointed out by Raphael Bousso , [ 3 ] Thorn observed in 1978 that string theory admits a lower dimensional description in which gravity emerges from it in what would now be called a holographic way. In a larger and more speculative sense, the theory suggests that the entire universe can be seen as a two-dimensional information structure "painted" on the cosmological horizon , such that the three dimensions we observe are only an effective description at macroscopic scales and at low energies .
Entropic force
Diffusion from a microscopic and macroscopic point of view. Initially, there are solute molecules on the left side of a barrier (purple line) and none on the right. The barrier is removed, and the solute diffuses to fill the whole container. Top: A single molecule moves around randomly. Middle: With more molecules, there is a statistical trend that the solute fills the container more and more uniformly. Bottom: With an enormous number of solute molecules, all randomness is gone: The solute appears to move smoothly and deterministically from high-concentration areas to low-concentration areas.
An ideal chain (or freely-jointed chain ) is the simplest model to describe a polymer . It only assumes a polymer as a random walk and neglects any kind of interactions among monomers . Although it is simple, its generality gives us some insights about the physics of polymers. In this model, monomers are rigid rods of a fixed length l , and their orientation is completely independent of the orientations and positions of neighbouring monomers, to the extent that two monomers can co-exist at the same place. [ edit ] The model N monomers form the polymer, whose total unfolded length is:
Ideal chain
Inflation (cosmology)
In physical cosmology , cosmic inflation , cosmological inflation or just inflation is the theorized extremely rapid exponential expansion of the early universe by a factor of at least 10 78 in volume, driven by a negative-pressure vacuum energy density. [ 1 ] The inflationary epoch comprises the first part of the electroweak epoch following the grand unification epoch . It lasted from 10 −36 seconds after the Big Bang to sometime between 10 −33 and 10 −32 seconds. Following the inflationary period, the universe continued to expand, but at a slower rate. The term "inflation" is also used to refer to the hypothesis that inflation occurred, to the theory of inflation, or to the inflationary epoch . The inflationary hypothesis was originally proposed in 1980 by American physicist Alan Guth , who named it "inflation". [ 2 ] It was also proposed by Katsuhiko Sato in 1981. [ 3 ]Metric expansion of space
The metric expansion of space is the increase of the distance between two distant parts of the universe with time . It is an intrinsic expansion whereby the scale of space itself is changed . That is, a metric expansion is defined by an increase in distance between parts of the universe even without those parts "moving" anywhere. This is not the same as any usual concept of motion, or any kind of expansion of objects "outward" into other "preexisting" space, or any kind of explosion of matter which is commonly experienced on earth.In physical cosmology and astronomy , dark energy is a hypothetical form of energy that permeates all of space and tends to accelerate the expansion of the universe . [ 1 ] Dark energy is the most accepted hypothesis to explain observations since the 1990s that indicate that the universe is expanding at an accelerating rate . In the standard model of cosmology , dark energy currently accounts for 68.3% of the total mass–energy of the universe. [ 2 ] Two proposed forms for dark energy are the cosmological constant , a constant energy density filling space homogeneously, [ 3 ] and scalar fields such as quintessence or moduli , dynamic quantities whose energy density can vary in time and space. Contributions from scalar fields that are constant in space are usually also included in the cosmological constant. The cosmological constant is physically equivalent to vacuum energy .