Friday, 6 April 2012

Sejarah Ilmu Kosmologi

Name Author and date Classification Remarks
Hindu cosmology Hindu Rigveda (2000  BC) Cyclical or oscillating, Infinite in time One cycle of existence is around 311 trillion years and the life of one universe around 8 billion years. This Universal cycle is preceded by an infinite number of universes and to be followed by another infinite number of universes. Includes an infinite number of universes at one given time.
Jain cosmology Jain Agamas (written around 500 AD as per the teachings of Mahavira 599-527 BC) Cyclical or oscillating, eternal and finite Jain cosmology considers the loka, or universe, as an uncreated entity, existing since infinity, the shape of the universe as similar to a man standing with legs apart and arm resting on his waist. This Universe, according to Jainism, is broad at the top, narrow at the middle and once again becomes broad at the bottom.
Babylonian cosmology Babylonian literature (c. 3000 BC) Flat earth floating in infinite "waters of chaos" The Earth and the Heavens form a unit within infinite "waters of chaos"; the earth is flat and circular, and a solid dome (the "firmament") keeps out the outer "chaos"-ocean.
Eleatic cosmology Parmenides (c.515 BC) Finite and spherical in extent The Universe is unchanging, uniform, perfect, necessary, timeless, and neither generated nor perishable. Void is impossible. Plurality and change are products of epistemic ignorance derived from sense experience. Temporal and spatial limits are arbitrary and relative to the Parmenidean whole.
Biblical cosmology Genesis creation narrative (c.500 BC) Flat earth floating in infinite "waters of chaos" Based on Babylonian cosmology. The Earth and the Heavens form a unit within infinite "waters of chaos"; the earth is flat and circular, and a solid dome (the "firmament") keeps out the outer "chaos"-ocean.
Atomist universe Anaxagoras (500–428 BC) & 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.[5]
Stoic universe Stoics (300 BC – 200 AD) 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 BC) Geocentric, static, steady state, finite extent, infinite time Spherical earth is surrounded by concentric celestial spheres. Universe exists unchanged throughout eternity. Contains a fifth element, called aether (later known as quintessence), added to the four Classical elements.
Aristarchean universe Aristarchus (circa 280 BC) 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.
Ptolemaic model (based on Aristotelian universe) Ptolemy (2nd century AD) 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.
Medieval universe Medieval philosophers (500–1200) Finite in time A 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 There exists an infinite outer space beyond the known world, and God has the power to fill the vacuum with an infinite number of universes.
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 stationary 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 (1473–1543) Heliocentric with circular planetary orbits First clearly described heliocentric model, in 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.
Bruno's cosmology Giordano Bruno (1548-1600) Infinite extent, infinite time, homogenous, isotropic, non-hierarchical Rejects the idea of a hierarchical universe. Earth and Sun have no special properties in comparison with the other heavenly bodies. The void between the stars is filled with aether, and matter is composed of the same four elements (water, earth, fire, and air) everywhere, and is atomistic, animistic and intelligent.
Keplerian Johann Kepler (1571–1630) Heliocentric with elliptical planetary orbits Kepler's discoveries, marrying mathematics and physics, provided the foundation for our present conception of the Solar system, but distant stars were still seen as objects in a thin, fixed celestial sphere.
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 18th century 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 universe 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, a.k.a. 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.
The original Big Bang. a.k.a. 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 (a.k.a. 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) Hermann 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.

Sumber: Wikipedia

No comments: