In recent times, physics and astrophysics have come to play a central role in shaping what is now known as physical cosmology, i.e. the understanding of the Universe through scientific observation and experiment. This discipline, which focuses on the Universe as it exists on the largest scales and at the earliest times, begins by arguing for the big bang, a sort of cosmic explosion from which the Universe itself is said to have erupted ~13.7 ± 0.2 billion (109) years ago. After its violent beginnings and until its very end, scientists then propose that the entire history of the Universe has been an orderly progression governed by physical laws.

In between the doctrines of religion and science, stands the philosophical perspective of metaphysical cosmology. This ancient field of study seeks to draw logical conclusions about the nature of the Universe, man, god and/or their connections based on the extension of some set of presumed facts borrowed from religion and/or observation.

Cosmology is often an important aspect of the origin beliefs of religions and mythologies that seek to explain the existence and nature of the 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.

Physical cosmology

Physical cosmology is the branch of physics and astrophysics that deals with the study of the physical origins of the Universe and 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 Tycho Brahe, 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 may be considered to begin in 1915 with Albert Einstein's publication of his general theory of relativity and the growing ability of astronomers to study very distant objects. Prior to this, physicists had assumed that the Universe was static and unchanging. However, the general theory of relativity was not amenable to a static Universe. Thus the big bang theory was proposed by the Belgian priest Georges Lemaître in 1927 and rapidly confirmed 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.

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 theory. This has led many to refer to modern times as the "Golden age of cosmology."

Plasma cosmology

Plasma cosmology is a cosmological model based on the electromagnetic properties of astrophysical plasmas. Plasma cosmology explains the large scale structure and evolution of the universe, from galaxy formation to the cosmic microwave background by invoking electromagnetic phenomena associated with laboratory plasmas.

Plasma, electrically conducting gas in which electrons are stripped away from atoms and can move freely, makes up the stars and the interstellar medium. Astrophysicists agree that electromagnetic effects are important in stars, galactic discs, quasars and active galactic nuclei but in the standard big bang model the formation of structure is dominated by gravitational effects. Plasma cosmology asserts that the universe has no beginning, whereas in the big bang model the universe, as we know it, has existed for only a finite time.

The basic assumptions of plasma cosmology are, 1) since the universe is nearly all plasma, electromagnetic forces are equal in importance with gravitation on all scales. 2) since we never see effects without causes, we have no reason to assume an origin in time for the universe—an effect without a cause. Thus this approach, in contrast to certain interpretations of the Big Bang cosmology, does not permit any beginning for the universe. 3) unlike the steady state theory, the universe is not changeless. Rather, since every part of the universe we observe is evolving, it assumes that the universe itself is evolving as well.

Plasma cosmology also differs from big bang cosmology methodologically. Its advocates emphasize the links between physical processes observable in laboratories on Earth and those that govern the cosmos. Plasma cosmology is explained as much as possible in terms of known physics, using the theoretical and experimental results of laboratory plasma physics in cosmological applications. Proponents contrast this with the Big bang theory which has over the course of its existence required the introduction of such features as inflation, dark matter and dark energy that have not been detectable yet in laboratory experiments. read more about Plasma Universe

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:

What is the origin of the Universe? What is its first cause? Is its existence necessary? (see monism, pantheism, emanationism and creationism)
What are the ultimate material components of the Universe? (see mechanism, dynamism, hylomorphism, atomism)

What is the ultimate reason for the existence of the Universe? Does the cosmos have a purpose?

Religious cosmology

Many world religions have origins beliefs that explain the beginnings of the Universe and life. Often these are derived from scriptural teachings and held to be part of the faith's dogma, but in some cases these are also extended through the use of philosophical and metaphysical arguments.
In some origin beliefs, 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.

Both Christianity and Judaism rely on the Genesis narrative as a scriptural account of cosmology. See also Biblical cosmology and Tzimtzum.
Islam relies on understanding from the Qu'ran as its major source for explaining cosmology.

Certain adherents of Buddhism, Hinduism (See also Hindu cosmology) and Jainism believe that the Universe passes through endless cycles of creation and destruction, each cycle lasting for trillions of years (e.g. 331 trillion years, or the life-span of Brahma, according to Hinduism), and each cycle with sub-cycles of local creation and destruction (e.g. 4.32 billion years, or a day of Brahma, according to Hinduism). The Vedic (Hindu) view of the world sees one true divine principle self-projecting as the divine word, 'birthing' the cosmos that we know from the monistic Hiranyagarbha or Golden Womb.

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 sometimes difficult to distinguish where religion or philosophy end and esotericism 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 Gnosticism, Tantra (especially Kashmir Shaivism), Kabbalah, Sufism, Surat Shabda Yoga, Theosophy, Anthroposophy, the Fourth Way teaching of Gurdjieff and Ouspensky, the teachings of Patrizia Norelli-Bachelet, Gnostic circle and in The Rosicrucian Cosmo-Conception.

Pythagorean views

Pythagorean thought was dominated by mathematics, but it was also profoundly mystical. In the area of cosmology there is less agreement about what Pythagoras himself actually taught, but most scholars believe that the Pythagorean idea of the transmigration of the soul is too central to have been added by a later follower of Pythagoras. On the other hand it is impossible to determine the origin of the Pythagorean account of substance. It seems that the Pythagorean account begins with Anaximander's account of the ultimate substance of things as "the boundless," by Anaximander called the "apeiron." On the other hand, the Pythagorean account says that it is through the notion of the "limit" that the "boundless" takes form.

Pythagoras wrote nothing down, and relying on the writings of Parmenides, Empedocles, Philolaus and Plato (people either considered Pythagoreans, or whose works are thought deeply indebted to Pythagoreanism) results in a very diverse picture in which it is difficult to ascertain what the common unifying Pythagorean themes were. Relying on Philolaus, whom all scholar's agree should be highly representative of the Pythagorean school, one has a very intricate picture. Aristotle explains how the Pythagoreans (by which he meant the circle around Philolaus) developed Anaximander's ideas about the apeiron and the peiron, the unlimited and limited, by writing that:

"… for they [the Pythagoreans] plainly say that when the one had been constructed, whether out of planes or of surface or of seed or of elements which they cannot express, immediately the nearest part of the unlimited began to be drawn in and limited by the limit."

Continuing with:

"The Pythagoreans, too, held that void exists, and that it enters the heaven from the unlimited breath – it, so to speak, breathes in void. The void distinguishes the natures of things, since it is the thing that separates and distinguishes the successive terms in a series. This happens in the first case of numbers; for the void distinguishes their nature."

When the apeiron is inhaled by the perion it causes separation, which also apparently means that it "separates and distinguishes the successive terms in a series." Instead of an undiffrentiated whole we have a living whole of inter-connected parts separated by "void" between them. This inhalation of the apeiron is also what makes the world mathematical, not just possible to describe using math, but truly mathematical since it shows numbers and reality to be upheld by the same principle: both the continuum of numbers (that is yet a series of successive terms, separated by void) and the field of reality, the cosmos - both are a play of emptiness and form, apeiron and peiron. What really sets this apart from Anaximander's original ideas is that this play of apeiron and peiron must take place according to harmonia (harmony), about which Stobaeus commentated:

"About nature and harmony this is the position. The being of the objects, being eternal, and nature itself admit of divine, not human, knowledge – except that it was not possible for any of the things that exist and are known by us to have come into being, without there existing the being of those things from which the universe was composed, the limited and the unlimited. And since these principles existed being neither alike nor of the same kind, it would have been impossible for them to be ordered into a universe if harmony had not supervened – in whatever manner this came into being. Things that were alike and of the same kind had no need of harmony, but those that were unlike and not of the same kind and of unequal order – it was necessary for such things to have been locked together by harmony, if they are to be held together in an ordered universe."

A musical scale presupposes an unlimited continuum of pitches, which must be limited in some way in order for a scale to arise. The crucial point is that not just any set of limiters will do. We cannot just pick pitches at random along the continuum and produce a scale that will be musically pleasing. The diatonic scale, also known as "Pythagorean," is such that the ratio of the highest to the lowest pitch is 2:1, which produces the interval of an octave. That octave is in turn divided into a fifth and a fourth, which have the ratios of 3:2 and 4:3 respectively and which, when added, make an octave. If we go up a fifth from the lowest note in the octave and then up a fourth from there, we will reach the upper note of the octave. Finally the fifth can be divided into three whole tones, each corresponding to the ratio of 9:8 and a remainder with a ratio of 256:243 and the fourth into two whole tones with the same remainder. This is a good example of a concrete applied use of Philolaus’ reasoning. In Philolaus' terms the fitting together of limiters and unlimiteds involves their combination in accordance with ratios of numbers (harmony). Similarly the cosmos and the individual things in the cosmos do not arise by a chance combination of limiters and unlimiteds; the limiters and unlimiteds must be fitted together in a "pleasing" (harmonic) way in accordance with number for an order to arise.

Pythagorean mysticism

The Pythagoreans are known for their theory of the transmigration of souls, and also for their theory that numbers constitute the true nature of things. They performed purification rites and followed and developed various rules of living which they believed would enable their soul to achieve a higher rank among the gods. Much of their mysticism concering the soul seem inseparable from the Orphic tradition. The Orphics included various purifactory rites and practices as well as incubatory rites of descent into the underworld. Apart from being linked with this Pythagoras is also closely linked with Pherekydes of Syros, the man ancient commentators tend to credit as the first Greek to teach a transmigration of souls. Ancient commentators agree that Pherekydes was Pythagoras' most intimate teacher. Pherekydes axpunded his teaching on the soul in terms of a pentemychos ("five-nooks," or "five hidden cavities") - The most likely origin of the Pythagorean use of the pentagram, used by them as a symbol of recognition among members and as a symbol of inner health (ugieia).

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Cosmos", Wikipedia article "Cosmology", Wikipedia article "Plasma Universe" and Wikipedia article "Pythagoreanism".