Observable universe
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Posted on March 22, 2011 by Ashley Corbion . Cosmology sometimes seems mysterious: you often hear about dark matter, dark energy , big bang , multiverse , extra dimensions … I think we can undoubtedly say that our Universe is weird… And fascinating. A problem with some of these yet to be explained mysteries is that the models created to describe them are mainly purely theoretical, without being testable. This is particularly true with theories involving extra dimensions (who said string theory?..). Other theories even explore the possibility of lower dimensionality, in which the Universe had a smaller number of spatial dimensions in the past. Recently, physicists Jonas Mureika from Loyola Marymount University in Los Angeles, California, and Dejan Stojkovic from SUNY at Buffalo in Buffalo, New York, have proposed an interesting way to investigate lower dimensions of the Universe.
The vanishing dimensions of the Universe
Laser Space Telescope Could Test for Vanishing Dimensions
The universe may have started out with fewer dimensions than the three we live in, and could still collapse down to one dimension at extremely high energies. The idea could solve some of the thorniest problems in particle physics and, unlike more popular models like string theory, can be tested with the next generation of space telescopes , according to a new study March 11 in Physical Review Letters . The problems arise from the standard model of particle physics, which successfully explains most of the universe but breaks down as it reaches the high energies that existed shortly after the Big Bang. The standard model still can’t explain why the expansion of the universe is accelerating, for example, or how to knit together the physics of extremely large and extremely small objects. Most theoretical physicists have assumed the limitations mean some strange new physics come into play at high energies, perhaps involving exotic new particles and extra, invisible dimensions of space.
ScienceDaily (Apr. 20, 2011) — Did the early universe have just one spatial dimension? That's the mind-boggling concept at the heart of a theory that University at Buffalo physicist Dejan Stojkovic and colleagues proposed in 2010. They suggested that the early universe -- which exploded from a single point and was very, very small at first -- was one-dimensional (like a straight line) before expanding to include two dimensions (like a plane) and then three (like the world in which we live today). The theory, if valid, would address important problems in particle physics. Now, in a new paper in Physical Review Letters , Stojkovic and Loyola Marymount University physicist Jonas Mureika describe a test that could prove or disprove the "vanishing dimensions" hypothesis.
Primordial weirdness: Did the early universe have one dimension? Scientists outline test for theory
Some scientists believe that, as the universe gets older and larger, it adds more dimensions. Cute theory. But how does this help solve pressing questions of of physics? And how can it be tested? One of the crazier theories of physics is the idea of Vanishing Dimensions. It should, technically, be the idea of Appearing Dimensions, since it proposes that, as the universe aged and grew, it added more and more dimensions.
Did the early universe have only one dimension?
A member of the Local Group of galaxies, irregular galaxy Sextans A is 4.3 million light-years distant. The bright Milky Way foreground stars appear yellowish in this view. Beyond them lie the stars of Sextans A with young blue star clusters clearly visible. Distribution of the iron content (in logarithmic scale) in four dwarf neighbouring galaxies of the Milky Way.
Local Group
Milky Way
The Milky Way is the galaxy that contains the Earth . [ 10 ] [a] This name derives from its appearance as a dim "milky" glowing band arching across the night sky, in which the naked eye cannot distinguish individual stars. The term "Milky Way" is a translation of the Classical Latin via lactea , from the Hellenistic Greek γαλαξίας κύκλος (pr. galaxías kýklos , "milky circle"). [ 11 ] [ 12 ] [ 13 ] The Galaxy has this appearance because it is a disk-shaped structure that is being viewed from inside. Earth is located within the Galactic plane of this disk, around two thirds of the way out from the center, on the inner edge of a spiral-shaped concentration of gas and dust called the Orion–Cygnus Arm . The concept of this faint band of light being made up of stars was proven in 1610 when Galileo Galilei used his telescope to resolve it into individual stars.
The Canis Major Dwarf Galaxy is a hypothetical galaxy in the Local Group , located in the same part of the sky as the constellation Canis Major . The galaxy contains a relatively high percentage of red giant stars , and is thought to contain an estimated one billion stars in all. The Canis Major Dwarf Galaxy is classified as an irregular galaxy and is now thought to be the closest neighbouring galaxy to our location in the Milky Way , being located about 25,000 light-years away from our Solar System [ 2 ] and 42,000 light-years from the Galactic Center . It has a roughly elliptical shape and is thought to contain as many stars as the Sagittarius Dwarf Elliptical Galaxy , the previous contender for closest galaxy to our location in the Milky Way. [ edit ] Discovery The galaxy was first discovered in November 2003 by an international team of French, Italian, British and Australian astronomers .
Canis Major Dwarf Galaxy
Andromeda Galaxy
The Andromeda Galaxy ( / æ n ˈ d r ɒ m ə d ə / ) is a spiral galaxy approximately 2.6 million light-years (2.5 × 10 19 km) from Earth [ 4 ] in the Andromeda constellation . It is also known as Messier 31 , M31 , or NGC 224 , and is often referred to as the Great Andromeda Nebula in older texts. The Andromeda Galaxy is the nearest spiral galaxy to our galaxy ( Milky Way ), but not the closest galaxy overall. It gets its name from the area of the sky in which it appears, the Andromeda constellation, which was named after the mythological princess Andromeda .
A star is a massive, luminous sphere of plasma held together by gravity . At the end of its lifetime, a star can also contain a proportion of degenerate matter . The nearest star to Earth is the Sun , which is the source of most of the energy on Earth. Other stars are visible from Earth during the night, when they are not obscured by atmospheric phenomena, appearing as a multitude of fixed luminous points because of their immense distance. Historically, the most prominent stars on the celestial sphere were grouped together into constellations and asterisms , and the brightest stars gained proper names. Extensive catalogues of stars have been assembled by astronomers, which provide standardized star designations .
Portal: Star
A supernova (abbreviated SN, plural SNe after supernovae) is a stellar explosion that is more energetic than a nova . It is pronounced / ˌ s uː p ər ˈ n oʊ v ə / with the plural supernovae / ˌ s uː p ər ˈ n oʊ v iː / or supernovas . Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy , before fading from view over several weeks or months. During this short interval a supernova can radiate as much energy as the Sun is expected to emit over its entire life span. [ 1 ] The explosion expels much or all of a star's material [ 2 ] at a velocity of up to 30,000 km/s (10% of the speed of light ), driving a shock wave [ 3 ] into the surrounding interstellar medium . This shock wave sweeps up an expanding shell of gas and dust called a supernova remnant .
Supernova
Eta Carinae , in the constellation of Carina, one of the nearer candidates for a future hypernova Hypernova (pl. hypernovae ), also known as a type 1c Supernova , refers to an immensely large star that collapses at the end of its lifespan. Until the 1990s, it referred specifically to an explosion with an energy of over 100 supernovae (over 10 48 joules ); such explosions are believed to be the origin of long-duration gamma-ray bursts . [ 1 ] After the 1990s, the term came to be used to describe the supernovae of the most massive stars, the hypergiants , which have masses from 100 to over 300 times that of the Sun . Decaying 56 Ni , a short-lived isotope of nickel , is believed to provide much of a hypernova's light. [ 2 ]
Hypernova
Magnetar
Artist's conception of a magnetar, with magnetic field lines A magnetar is a type of neutron star with an extremely powerful magnetic field , the decay of which powers the emission of high-energy electromagnetic radiation , particularly X-rays and gamma rays . [ 1 ] The theory regarding these objects was proposed by Robert Duncan and Christopher Thompson in 1992, but the first recorded burst of gamma rays thought to have been from a magnetar was detected on March 5, 1979. [ 2 ] During the following decade, the magnetar hypothesis has become widely accepted as a likely explanation for soft gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs). [ edit ] Description Little is known about the physical structure of magnetars because none are sufficiently close to Earth to facilitate study. Like other neutron stars , magnetars are around 20 kilometres (12 mi) in diameter but have a greater mass than the Sun .Observable universe
Visualization of the 93 billion light year – or 28 billion parsec – three-dimensional observable universe. The scale is such that the fine grains of light represent collections of large numbers of superclusters . The Virgo Supercluster – home of Milky Way – is marked at the center, but is too small to be seen in the image. In Big Bang cosmology , the observable universe consists of the galaxies and other matter that humans can in principle observe from Earth in the present day, because light (or other signals) from those objects has had time to reach us since the beginning of the cosmological expansion. Assuming the universe is isotropic , the distance to the edge of the observable universe is roughly the same in every direction—that is, the observable universe is a spherical volume (a ball ) centered on the observer, regardless of the shape of the universe as a whole.The universe is commonly defined as the totality of everything that exists , [ 1 ] including all matter and energy , the planets , stars , galaxies , and the contents of intergalactic space . [ 2 ] [ 3 ] Definitions and usage vary and similar terms include the cosmos , the world and nature . Scientific observation of earlier stages in the development of the universe, which can be seen at great distances, suggests that the universe has been governed by the same physical laws and constants throughout most of its extent and history. There are various multiverse theories, in which physicists have suggested that our universe might be one among many universes that likewise exist. [ 4 ] [ 5 ] History Throughout recorded history, several cosmologies and cosmogonies have been proposed to account for observations of the universe. The earliest quantitative geocentric models were developed by the ancient Greek philosophers .