Ekpyrotic universe The ekpyrotic universe, or ekpyrotic scenario, is a cosmological model of the origin and shape of the universe. The name comes from a Stoic term ekpyrosis (Ancient Greek ἐκπύρωσις ekpurōsis) meaning conflagration or in Stoic usage "conversion into fire".[1] The ekpyrotic model of the universe is an alternative to the standard cosmic inflation model for the very early universe; both models accommodate the standard Big Bang Lambda-CDM model of our universe.[2][3] The ekpyrotic model is a precursor to, and part of, some cyclic models. The ekpyrotic model came out of work by Neil Turok and Paul Steinhardt and maintains that the universe did not start in a singularity, but came about from the collision of two branes. This collision avoids the primordial singularity and superluminal expansion of spacetime while preserving nearly scale-free density fluctuations and other features of the observed universe. See also[edit] Notes and references[edit] Further reading[edit] P.
Brane cosmology Brane cosmology refers to several theories in particle physics and cosmology related to string theory, superstring theory and M-theory. Brane and bulk[edit] The central idea is that the visible, four-dimensional universe is restricted to a brane inside a higher-dimensional space, called the "bulk" (also known as "hyperspace"). If the additional dimensions are compact, then the observed universe contains the extra dimensions, and then no reference to the bulk is appropriate. In the bulk model, at least some of the extra dimensions are extensive (possibly infinite), and other branes may be moving through this bulk. Why gravity is weak and the cosmological constant is small[edit] Some versions of brane cosmology, based on the large extra dimension idea, can explain the weakness of gravity relative to the other fundamental forces of nature, thus solving the so-called hierarchy problem. Models of brane cosmology[edit] The authors discussed the possibility that the Universe has See also[edit]
Philosophy of physics Centuries ago, the study of causality, and of the fundamental nature of space, time, matter, and the universe were part of metaphysics. Today the philosophy of physics is essentially a part of the philosophy of science. Physicists utilize the scientific method to delineate the universals and constants governing physical phenomena, and the philosophy of physics reflects on the results of this empirical research. Purpose of physics[edit] According to Niels Bohr, the purpose of physics is:[1] not to disclose the real essence of phenomena but only to trackdown (...) relations between the manifold aspects of experience. Many, particularly realists, find this minimal formulation an inadequate formulation of the purpose of physics, which they view as providing, in addition, a deeper world picture. Philosophy of space and time[edit] Time[edit] Time, in many philosophies, is seen as change. Time travel[edit] A second, similar type of time travel is permitted by general relativity. Space[edit] Elsewhere:
Category:Physical cosmology Physical cosmology is the scholarly and academic study of questions about the ultimate fate of the universe. The subject matter of this field is studied using scholarly methodology, including the scientific method and reason. It is studied by scientists, such as astronomers, and theoretical physicists; and academic philosophers, such as metaphysicians, philosophers of physics, and philosophers of space and time. Subcategories This category has the following 14 subcategories, out of 14 total. Pages in category "Physical cosmology" The following 200 pages are in this category, out of 219 total. (previous 200) (next 200)(previous 200) (next 200) Hindu cycle of the universe See also Hindu units of measurement. This is similar to the Cyclical Universe Theory in physical cosmology. The Big Bang is described as the birth of the universe (Brahma), the life of the universe then follows (Vishnu), and the Big Crunch would be described as the destruction of the universe (Shiva). In a number of stories from the Puranas the continual creation and destruction of the universe is equated to the outwards and inwards breaths of the gigantic cosmic Maha Vishnu. Hindu thesis of creation[edit] Initially everything was unmanifested and was one without a second . In vishnu purana ,It is stated that the purusha(GOD) manifests himself into three forms to maintain the material realm or the manifested realm . Karnodakasayi Vishnu expands himself as Garbhodakasayivisnu and enters into each universe and from Garbhodakasayivisnu originates bhrama from the naval . Hindu viewpoint of modern cosmology[edit] Even string theory finds a place in the Hindu texts. The end of the universe[edit]
Drake equation The Drake equation is a probabilistic argument used to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way galaxy. The equation was written in 1961 by Frank Drake not for purposes of quantifying the number of civilizations,[1] but intended as a way to stimulate scientific dialogue at the world's first SETI meeting, in Green Bank, West Virginia. The equation summarizes the main concepts which scientists must contemplate when considering the question of other radio-communicative life.[1] The Drake equation has proved controversial since several of its factors are currently unknown, and estimates of their values span a very wide range. This has led critics to label the equation a guesstimate, or even meaningless. History[edit] In September 1959, physicists Giuseppe Cocconi and Philip Morrison published an article in the journal Nature with the provocative title "Searching for Interstellar Communications The equation[edit] The Drake equation is: where: .
Libertarianism (metaphysics) The term "libertarianism" in a metaphysical or philosophical sense was first used by late Enlightenment free-thinkers to refer to those who believed in free will, as opposed to determinism.[9] The first recorded use was in 1789 by William Belsham in a discussion of free will and in opposition to "necessitarian" (or determinist) views.[10][11] Metaphysical and philosophical contrasts between philosophies of necessity and libertarianism continued in the early 19th century.[12] Explanations of libertarianism that do not involve dispensing with physicalism require physical indeterminism, such as probabilistic subatomic particle behavior – theory unknown to many of the early writers on free will. Physical determinism, under the assumption of physicalism, implies there is only one possible future and is therefore not compatible with libertarian free will. Nozick puts forward an indeterministic theory of free will in Philosophical Explanations.[6]
Category:Cosmology There are two very different senses in which the term "Cosmology" is used. Physical cosmology is the scholarly and academic study of questions about the ultimate fate of the universe. The subject matter of this field is studied using scholarly methodology, including the scientific method and reason. It is studied by scientists, such as astronomers and theoretical physicists; and academic philosophers, such as metaphysicians, philosophers of physics, and philosophers of space and time.Religious cosmology (or mythological cosmology) is a body of beliefs based on the historical, mythological, religious, and esoteric literature and theories about eschatology (i.e. the end of the world), including such theories, as for instance apocalypticism. Subcategories This category has the following 3 subcategories, out of 3 total. Pages in category "Cosmology" The following 19 pages are in this category, out of 19 total.
Hindu cosmology In Hindu cosmology the universe is cyclically created and destroyed. The Hindu literature, such as Vedas, Puranas, cites the creation of universe. They describe the aspects of evolution, astronomy, etc. Description[edit] The Hindu cosmology and timeline is the closest to modern scientific timelines[1] and even more which might indicate that the Big Bang is not the beginning of everything,[2] but just the start of the present cycle preceded by an infinite number of universes and to be followed by another infinite number of universes.[3] The Rig Veda questions the origin of the cosmos in: "Neither being (sat) nor non-being was as yet. Large scale structure of the Universe according to one Hindu cosmology. Map 2: Intermediate neighbourhood of the Earth according to one Hindu cosmology. Map 3: Local neighbourhood of the Earth according to one Hindu cosmology. Overview of Yugas: Further elaborations from the Vedic texts[edit] Rig Veda[edit] The Puranas[edit] Multiverse in Hinduism[edit] See also[edit]