Cosmology

Cosmology (from Greek κοσμολογία - κόσμος, kosmos, "universe"; and -λογία, -logia, "study"), in strict usage, refers to the study of the Universe in its totality as it now is (or at least as it can be observed now), and by extension, humanity's place in it. Though the word cosmology is recent (first used in 1730 in Christian Wolff's Cosmologia Generalis), study of the universe has a long history involving science, philosophy, esotericism, and religion. (See Cosmogony for the study of origins of the Universe.)

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Cosmology compared with cosmogony

Cosmology is the study of the structure and changes in the present universe, while the scientific field of cosmogony is concerned with the origin of the universe. Observations about our present universe may not only allow predictions to be made about the future, but they also provide clues to events that happened long ago when...the cosmos began. So—the work of cosmologists and cosmogonists overlaps.

– National Aeronautics and Space Administration (NASA) [1]

Disciplines

In recent times, physics and astrophysics have played a central role in shaping the understanding of the universe through scientific observation and experiment; or what is known as physical cosmology shaped through both mathematics and observation in the analysis of the whole universe. In other words, in this discipline, which focuses on the universe as it exists on the largest scale and at the earliest moments, it is generally understood to begin with the Big Bang (possibly combined with cosmic inflation) – an expansion of space from which the universe itself is thought to have emerged ~13.7±0.2×109 (13.7 billion) years ago.[2] From its violent beginnings and until its various speculative ends, cosmologists propose that the history of the universe has been governed entirely by physical laws. Theories of an impersonal universe governed by physical laws were first proposed by Roger Bacon . Later Dmitry Grinevich supported Bacon's proposed laws through some experiments that he performed involving different physical laws. Between the domains of religion and science, stands the philosophical perspective of metaphysical cosmology. This ancient field of study seeks to draw intuitive conclusions about the nature of the universe, man, God and/or their relationships based on the extension of some set of presumed facts borrowed from spiritual experience and/or observation.

But metaphysical cosmology has also been observed as the placing of man in the universe in relationship to all other entities. This is demonstrated by the observation made by Marcus Aurelius of a man's place in that relationship: "He who does not know what the world is does not know where he is, and he who does not know for what purpose the world exists, does not know who he is, nor what the world is."[3] This is the purpose of the ancient metaphysical cosmology.

Cosmology is often an important aspect of the creation myths of religions that seek to explain the existence and nature of reality. In some cases, views about the creation (cosmogony) and destruction (eschatology) of the universe play a central role in shaping a framework of religious cosmology for understanding humanity's role in the universe.

A more contemporary distinction between religion and philosophy, esoteric cosmology is distinguished from religion in its less tradition-bound construction and reliance on modern "intellectual understanding" rather than faith, and from philosophy in its emphasis on spirituality as a formative concept.

There are many historical cosmologies:

"… the universe itself acts on us as a random, inefficient, and yet in the long run effective, teaching machine. …our way of looking at the universe has gradually evolved through a natural selection of ideas." —Steven Weinberg[4]

Historical cosmologies

Name Author and date Classification Remarks
Babylonian cosmology Babylonian literature (1900-1200 B.C.) Plurality of heavens and earths The Earth and heavens are a "spatial whole, even one of round shape," revolving around the "cult-place of the deity" rather than the Earth,[5] and there is a plurality of heavens and earths.[6]
Brahmanda (Hindu Cosmology) Hindu Rigveda (1500-1200 B.C.) Cyclical or oscillating, Infinite in time The universe sustains for around 311 trillion and 40 billion years that is 100 years of the cosmic creator Brahma. There is a smaller period of unmanifestation in around 4 billion years that is one day in the life of Brahma. The universe cycles between expansion and total collapse. After one cycle of the life of Brahma another universe follows up to an infinite number each of which exists for a time period of 311 trillion and 40 billion years. It also speaks of an infinite number of universes at one given point of time. Universe expanded from a concentrated form —a point called a Bindu. The universe, as a living entity, is bound to the perpetual cycle of birth, death, and rebirth.
Atomist universe Anaxagoras (500-428 B.C.) & later Epicurus Infinite in extent The universe contains only two things: an infinite number of tiny seeds, or atoms, and the void of infinite extent. All atoms are made of the same substance, but differ in size and shape. Objects are formed from atom aggregations and decay back into atoms. Incorporates Leucippus’ principle of causality: ”nothing happens at random; everything happens out of reason and necessity.” The universe was not ruled by gods.
Pythagorean Universe Philolaus (d. 390 BC) Existence of a "Central Fire" at the center of the Universe. At the center of the Universe is a central fire, around which the Earth, Sun, Moon and Planets revolve uniformly. The sun revolves around the central fire once a year, the stars are immobile. The earth in its motion maintains the same hidden face towards the central fire, hence it is never seen. This is the first known non-geocentric model of the Universe.[7]
Stoic universe Stoics (300 B.C. - 200 A.D.) Island universe The cosmos is finite and surrounded by an infinite void. It is in a state of flux, as it pulsates in size and periodically passes through upheavals and conflagrations.
Aristotelian universe Aristotle (384-322 B.C.) Geocentric, static, steady state, finite extent, infinite time Spherical earth is surrounded by concentric celestial spheres. Universe exists unchanged throughout eternity. Contains a 5th element called aether (later known as quintessence).
Aristarchean universe Aristarchus (circa 280 B.C.) Heliocentric Earth rotates daily on its axis and revolves annually about the sun in a circular orbit. Sphere of fixed stars is centered about the sun.
Seleucian universe Seleucus of Seleucia (circa 190 B.C.) Heliocentric Modifications to the Aristarchean universe, with the inclusion of the tide phenomenon to explain heliocentrism.
Ptolemaic model (based on Aristotelian universe) Ptolemy (2nd century A.D.) Geocentric Universe orbits about a stationary Earth. Planets move in circular epicycles, each having a center that moved in a larger circular orbit (called an eccentric or a deferent) around a center-point near the Earth. The use of equants added another level of complexity and allowed astronomers to predict the positions of the planets. The most successful universe model of all time, using the criterion of longevity. Almagest (the Great System).
Aryabhatan model Aryabhata (499) Geocentric or Heliocentric The Earth rotates and the planets move in elliptical orbits, possibly around either the Earth or the Sun. It is uncertain whether the model is geocentric or heliocentric due to planetary orbits given with respect to both the Earth and the Sun.
Abrahamic universe Medieval philosophers (500-1200) Finite in time The universe that is finite in time and has a beginning is proposed by the Christian philosopher, John Philoponus, who argues against the ancient Greek notion of an infinite past. Logical arguments supporting a finite universe are developed by the early Muslim philosopher, Alkindus; the Jewish philosopher, Saadia Gaon; and the Muslim theologian, Algazel.
Multiversal cosmology Fakhr al-Din al-Razi (1149–1209) Multiverse, multiple worlds & universes Al-Razi rejects the idea of an Earth-centered universe and, in the context of his commentary on the Qur'anic verse, "All praise belongs to God, Lord of the Worlds," proposes that the universe has more than "a thousand thousand worlds beyond this world such that each one of those worlds be bigger and more massive than this world as well as having the like of what this world has," [8] and that there could be an infinite number of universes.[9]
Maragha models Maragha school (1259–1528) Geocentric Various modifications to Ptolemaic model and Aristotelian universe, including rejection of equant and eccentrics at Maragheh observatory, and introduction of Tusi-couple by Al-Tusi. Alternative models later proposed, including the first accurate lunar model by Ibn al-Shatir, a model rejecting stationery Earth in favour of Earth's rotation by Ali Kuşçu, and planetary model incorporating "circular inertia" by Al-Birjandi.
Nilakanthan model Nilakantha Somayaji (1444–1544) Geocentric and Heliocentric A universe in which the planets orbit the Sun and the Sun orbits the Earth, similar to the later Tychonic system.
Copernican universe Nicolaus Copernicus (1543) Heliocentric The geocentric Maragha model of Ibn al-Shatir adapted to meet the requirements of the ancient heliocentric Aristarchean universe in his De revolutionibus orbium coelestium.
Tychonic system Tycho Brahe (1546–1601) Geocentric and Heliocentric A universe in which the planets orbit the Sun and the Sun orbits the Earth, similar to the earlier Nilakanthan model.
Static Newtonian Sir Isaac Newton (1642–1727) Static (evolving), steady state, infinite Every particle in the universe attracts every other particle. Matter on the large scale is uniformly distributed. Gravitationally balanced but unstable.
Cartesian Vortex universe René Descartes

17th century

 Static (evolving), steady state, infinite A system of huge swirling whirlpools of aethereal or fine matter produces what we would call gravitational effects. His vacuum was not empty. All space was filled with matter that swirled around in large and small vortices.
Hierarchical universe Immanuel Kant, Johann Lambert 1700s Static (evolving), steady state, infinite Matter is clustered on ever larger scales of hierarchy. Matter is endlessly being recycled.
Einstein Universe with a cosmological constant Albert Einstein 1917 Static (nominally). Bounded (finite) “Matter without motion.” Contains uniformly distributed matter. Uniformly curved spherical space; based on Riemann’s hypersphere. Curvature is set equal to Λ. In effect Λ is equivalent to a repulsive force which counteracts gravity. Unstable.
De Sitter universe Willem de Sitter 1917 Expanding flat space.

Steady state. Λ > 0

 “Motion without matter.” Only apparently static. Based on Einstein’s General Relativity. Space expands with constant acceleration. Scale factor (radius of universe) increases exponentially, i.e. constant inflation.
MacMillan William Duncan MacMillan 1920s Static &

steady state

 New matter is created from radiation. Starlight is perpetually recycled into new matter particles.
Friedmann universe of spherical space Alexander Friedmann 1922 Spherical expanding space.

k= +1 ; no Λ

 Positive curvature. Curvature constant k = +1

Expands then recollapses. Spatially closed (finite).
Friedmann universe of hyperbolic space Alexander Friedmann 1924 Hyperbolic expanding space.

k= -1 ; no Λ

 Negative curvature. Said to be infinite (but ambiguous). Unbounded. Expands forever.
Dirac large numbers hypothesis Paul Dirac 1930s Expanding Demands a large variation in G, which decreases with time. Gravity weakens as universe evolves.
Friedmann zero-curvature, aka the Einstein-DeSitter universe Einstein & DeSitter 1932 Expanding flat space.

k= 0 ; Λ = 0 Critical density

 Curvature constant k = 0. Said to be infinite (but ambiguous). ‘Unbounded cosmos of limited extent.’ Expands forever. ‘Simplest’ of all known universes. Named after but not considered by Friedmann. Has a deceleration term q =½ which means that its expansion rate slows down.
Georges Lemaître

the original Big Bang. aka Friedmann-Lemaître Model

 Georges Lemaître 1927-29 Expansion

Λ > 0 Λ > |Gravity|

 Λ is positive and has a magnitude greater than Gravity. Universe has initial high density state (‘primeval atom’). Followed by a two stage expansion. Λ is used to destabilize the universe. (Lemaître is considered to be the father of the big bang model.)
Oscillating universe

(aka Friedmann-Einstein; was latter’s 1st choice after rejecting his own 1917 model)

 Favored by Friedmann

1920s

 Expanding and contracting in cycles Time is endless and beginningless; thus avoids the beginning-of-time paradox. Perpetual cycles of big bang followed by big crunch.
Eddington Arthur Eddington 1930 First Static

then Expands

 Static Einstein 1917 universe with its instability disturbed into expansion mode; with relentless matter dilution becomes a DeSitter universe. Λ dominates gravity.
Milne universe of kinematic relativity Edward Milne, 1933, 1935;

William H. McCrea, 1930s

 Kinematic expansion with NO space expansion Rejects general relativity and the expanding space paradigm. Gravity not included as initial assumption. Obeys cosmological principle & rules of special relativity. The Milne expanding universe consists of a finite spherical cloud of particles (or galaxies) that expands WITHIN flat space which is infinite and otherwise empty. It has a center and a cosmic edge (the surface of the particle cloud) which expands at light speed. His explanation of gravity was elaborate and unconvincing. For instance, his universe has an infinite number of particles, hence infinite mass, within a finite cosmic volume.
Friedmann-Lemaître-Robertson-Walker class of models Howard Robertson, Arthur Walker, 1935 Uniformly expanding Class of universes that are homogenous and isotropic. Spacetime separates into uniformly curved space and cosmic time common to all comoving observers. The formulation system is now known as the FLRW or Robertson-Walker metrics of cosmic time and curved space.
Steady-state expanding (Bondi & Gold) Herman Bondi, Thomas Gold 1948 Expanding, steady state, infinite Matter creation rate maintains constant density. Continuous creation out of nothing from nowhere. Exponential expansion. Deceleration term q = -1.
Steady-state expanding (Hoyle) Fred Hoyle 1948 Expanding, steady state; but unstable Matter creation rate maintains constant density. But since matter creation rate must be exactly balanced with the space expansion rate the system is unstable.
Ambiplasma Hannes Alfvén 1965 Oskar Klein Cellular universe, expanding by means of matter-antimatter annihilation Based on the concept of plasma cosmology. The universe is viewed as meta-galaxies divided by double layers —hence its bubble-like nature. Other universes are formed from other bubbles. Ongoing cosmic matter-antimatter annihilations keep the bubbles separated and moving apart preventing them from interacting.
Brans-Dicke Carl H. Brans; Robert H. Dicke Expanding Based on Mach’s principle. G varies with time as universe expands. "But nobody is quite sure what Mach’s principle actually means."
Cosmic inflation Alan Guth 1980 Big Bang with modification to solve horizon problem and flatness problem. Based on the concept of hot inflation. The universe is viewed as a multiple quantum flux —hence its bubble-like nature. Other universes are formed from other bubbles. Ongoing cosmic expansion kept the bubbles separated and moving apart preventing them from interacting.
Eternal Inflation (a multiple universe model) Andreï Linde 1983 Big Bang with cosmic inflation A multiverse, based on the concept of cold inflation, in which inflationary events occur at random each with independent initial conditions; some expand into bubble universes supposedly like our entire cosmos. Bubbles nucleate in a spacetime foam.
Cyclic model Paul Steinhardt; Neil Turok 2002 Expanding and contracting in cycles; M theory. Two parallel orbifold planes or M-branes collide periodically in a higher dimensional space. With quintessence or dark energy
Cyclic model Lauris Baum;Paul Frampton 2007 Solution of Tolman's entropy problem Phantom dark energy fragments universe

into large number of disconnected patches. Our patch contracts containing only dark energy with zero entropy.

Table Notes: the term "static" simply means not expanding and not contracting. Symbol G represents Newton's gravitational constant; Λ (Lambda) is the cosmological constant.

Physical cosmology

Main article: Physical cosmology

Physical cosmology is the branch of physics and astrophysics that deals with the study of the physical origins and evolution of the Universe. It also includes the study of the nature of the Universe on its very largest scales. In its earliest form it was what is now known as celestial mechanics, the study of the heavens. The Greek philosophers Aristarchus of Samos, Aristotle and Ptolemy proposed different cosmological theories. In particular, the geocentric Ptolemaic system was the accepted theory to explain the motion of the heavens until Nicolaus Copernicus, and subsequently Johannes Kepler and Galileo Galilei proposed a heliocentric system in the 16th century. This is known as one of the most famous examples of epistemological rupture in physical cosmology.

With Isaac Newton and the 1687 publication of Principia Mathematica, the problem of the motion of the heavens was finally solved. Newton provided a physical mechanism for Kepler's laws and his law of universal gravitation allowed the anomalies in previous systems, caused by gravitational interaction between the planets, to be resolved. A fundamental difference between Newton's cosmology and those preceding it was the Copernican principle that the bodies on earth obey the same physical laws as all the celestial bodies. This was a crucial philosophical advance in physical cosmology.

Modern scientific cosmology is usually considered to have begun in 1917 with Albert Einstein's publication of his final modification of general relativity in the paper "Cosmological Considerations of the General Theory of Relativity," (although this paper was not widely available outside of Germany until the end of World War I). General relativity prompted cosmogonists such as Willem de Sitter, Karl Schwarzschild and Arthur Eddington to explore the astronomical consequences of the theory, which enhanced the growing ability of astronomers to study very distant objects. Prior to this (and for some time afterwards), physicists assumed that the Universe was static and unchanging. In parallel to this dynamic approach to cosmology, a debate was unfolding regarding the nature of the cosmos itself. On the one hand, Mount Wilson astronomer Harlow Shapley championed the model of a cosmos made up of the Milky Way star system only. Heber D. Curtis, on the other hand, suggested spiral nebulae were star systems in their own right, island universes. This difference of ideas came to a climax with the organization of the Great Debate at the meeting of the (US) National Academy of Sciences in Washington on 26 April 1920. The resolution of the debate on the structure of the cosmos came with the detection of novae in the Andromeda galaxy by Edwin Hubble in 1923 and 1924. Their distance established spiral nebulae well beyond the edge of the Milky Way and has galaxies of their own. Subsequent modeling of the universe explored the possibility that the cosmological constant introduced by Einstein in his 1917 paper may result in an expanding universe, depending on its value. Thus the big bang model was proposed by the Belgian priest Georges Lemaître in 1927 which was subsequently corroborated by Edwin Hubble's discovery of the red shift in 1929 and later by the discovery of the cosmic microwave background radiation by Arno Penzias and Robert Woodrow Wilson in 1964. These findings were a first step to rule out some of many alternative physical cosmologies.

Recent observations made by the COBE and WMAP satellites observing this background radiation have effectively, in many scientists' eyes, transformed cosmology from a highly speculative science into a predictive science, as these observations matched predictions made by a theory called Cosmic inflation, which is a modification of the standard big bang model. This has led many to refer to modern times as the "Golden age of cosmology."[10]

Metaphysical cosmology

In philosophy and metaphysics, cosmology deals with the world as the totality of space, time and all phenomena. Historically, it has had quite a broad scope, and in many cases was founded in religion. The ancient Greeks did not draw a distinction between this use and their model for the cosmos. However, in modern use it addresses questions about the Universe which are beyond the scope of science. It is distinguished from religious cosmology in that it approaches these questions using philosophical methods (e.g. dialectics). Modern metaphysical cosmology tries to address questions such as:

Religious cosmology

Many cultures have creation stories that explain the beginnings of the Universe and life. Often these are derived from scriptural teachings or held as the dogma of a particular faith. In some cases these are extended through philosophical and metaphysical arguments.

In some creation stories, the universe was created by a direct act of a god or gods who are also responsible for the creation of humanity (see creationism). In many cases, religious cosmologies also foretell the end of the Universe, either through another divine act or as part of the original design.

Large scale structure of the Universe according to one Hindu cosmology.

Many religions accept the findings of physical cosmology, in particular the Big Bang, and some, such as the Roman Catholic Church, have embraced it as suggesting a philosophical first cause. Others have tried to use the methodology of science to advocate for their own religious cosmology, as in intelligent design or creationist cosmologies.

Esoteric cosmology

Many esoteric and occult teachings involve highly elaborate cosmologies. These constitute a "map" of the Universe and of states of existences and consciousness according to the worldview of that particular doctrine. Such cosmologies cover many of the same concerns also addressed by religious and philosophical cosmology, such as the origin, purpose, and destiny of the Universe and of consciousness and the nature of existence. For this reason it is difficult to distinguish where religion or philosophy end and esotericism and/or occultism begins.

Common themes addressed in esoteric cosmology are emanation, involution, evolution, epigenesis, planes of existence, hierarchies of spiritual beings, cosmic cycles (e.g., cosmic year, Yuga), yogic or spiritual disciplines, and references to altered states of consciousness. Examples of esoteric cosmologies can be found in modern Theosophy, Anthroposophy, Gnosticism, Tantra (especially Kashmir Shaivism), Kabbalah, or Sufism.

See also

Notes

  1. ↑ http://genesismission.jpl.nasa.gov/educate/scimodule/Cosmogony/CosmogonyPDF/CosCosmolTT.pdf
  2. ↑ "First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations". http://arXiv.org/abs/astro-ph/0302209. Retrieved 2003. 
  3. ↑ "The thoughts of Marcus Aurelius Antonius viii. 52". http://www.gutenberg.org/files/15877/15877-h/15877-h.htm#viii._52. 
  4. ↑ Weinberg, Steven. 1992. Dreams of a Final Theory (Pantheon Books, NY) p158. ISBN 0-679-41923-3
  5. ↑ Norriss S. Hetherington (1993), Cosmology: historical, literary, philosophical, religious, and scientific perspectives, Taylor & Francis, p. 46, ISBN 0815309341 
  6. ↑ Norriss S. Hetherington (1993), Cosmology: historical, literary, philosophical, religious, and scientific perspectives, Taylor & Francis, p. 44, ISBN 0815309341 
  7. ↑ Boyer, C. A History of Mathematics. Wiley, p. 54.
  8. ↑ Adi Setia (2004), "Fakhr Al-Din Al-Razi on Physics and the Nature of the Physical World: A Preliminary Survey", Islam & Science 2, http://findarticles.com/p/articles/mi_m0QYQ/is_2_2/ai_n9532826/, retrieved 2010-03-02 
  9. ↑ John Cooper (1998), "al-Razi, Fakhr al-Din (1149-1209)", Routledge Encyclopedia of Philosophy (Routledge), http://www.muslimphilosophy.com/ip/rep/H044.htm, retrieved 2010-03-07 
  10. ↑ Alan Guth is reported to have made this very claim in an Edge Foundation interview EDGE

References

External links