cosmology theory Comparison Table

Astronomy View all facts Glossary Help

abstraction > hypothesis > theory > astronomy theory > cosmology theory

Next astronomy theory: galaxy theory Up: astronomy theory Previous astronomy theory: stellar theory

cosmology theory comparison table

Subject has volume has momentum has material has velocity has mass has extent has angular momentum has definition has location has synonym has temperature has antonym

big bang One of three standard Big Bang models that were formulated by Friedmann and Lemaitre of an isotropic and homogeneous universe composed of expanding matter and radiation. In these models space is unbounded. Friedmann-Lemaitre universe big crunch

big crunch One hypothesized future for the universe in which the current expansion stops, reverses, and results in all space and all matter collapsing together; a reversal of the big bang. big bang

cosmic string Some contemporary cosmological theories suggest that boundaries were formed between different regions of the universe at the moment of creation. These boundaries survive today as "cosmic strings", incredibly thin but very massive strings many light years in length. or center of gravity

de Sitter model A geometrical model (1917) of an empty universe, based on Einstein's field equations.

Eddington-Lemaitre universe A cosmological model in which the cosmological constant plays a crucial role by allowing an initial phase that is identical to the Einstein static universe. After an arbitrarily long time, the universe begins to expand. The difficulty with this model is that the initiation of galaxy formation may actually cause a collapse rather than initiate an expansion of the universe.

Hoyle-Narlikar theory A reformulation of the general theory of relativity that incorporates and extends Mach's principle (q.v.). In this theory, the inertial mass of a particle is a function of the masses of all other particles, multiplied by a coupling constant which is a function of cosmic epoch. In cosmologies based on this theory, the gravitational constant G decreases strongly with time.

Hubble law A relation which states that recessional speed is proportional to distance for a homogeneous and isotropic universe. Galaxies moving away from us with a speed precisely following this relation are said to follow the Hubble flow. Because the actual universe is not precisely homogeneous, with lumpiness arising from clustering of galaxies and voids of empty space, the motions of actual galaxies deviate somewhat from the Hubble flow.

kinematic relativity Theory proposed by Edward Milne as a viable alternative to Einstein's general theory of relativity, and based generally on kinematics (the science of pure motion, without reference to matter or force), from which Milne successfully derived new systems of dynamics and electrodynamics.

Klein-Alfvén cosmology A cosmological model in which the early universe is depicted as a giant collapsing spherical cloud of matter and antimatter. When a critical density is reached, the matter and antimatter begin to annihilate, the resulting release of radiation and energy causing the universe to expand. There are many difficulties with this model of the expanding universe, which is largely discredited on observational grounds.

static universe A universe whose radius of curvature is constant and independent of time, as in the Einstein universe.

Steady State Theory A cosmological theory propounded by Bondi, Gold, and Hoyle in which the Universe has no beginning and no end and maintains the same mean density, in the face of its observed expansion, by the continuous creation of matter at the current rate of 2.8 × 10^-46 g cm^-3 s^-1 (or roughly one nucleon per cubic kilometer per year). Discovery of the microwave background has persuaded most astronomers to reject the steady-state theory.

tired light The hypothesis that light may be degraded in energy, thereby increasing in wavelength and becoming redshifted, during its passage through intergalactic space. This would provide an alternative to the Big Bang model in accounting for the redshifts of distant galaxies. However, there is no evidence for any such tired-light effect.

Twistor Theory Model of the Universe proposed by Roger Penrose, based on the application of complex numbers (involving (-1)^1/2) used in calculations in the microscopic world of atoms and quantum theory to the macroscopic ordinary world of physical laws and relativity. The result is an eight-dimensional concept of reality that although complicated is possibly a more logical understanding of the constitution of the Universe.

variable-mass theory A theory of Hoyle and Narlikar in which the masses of fundamental particles are assumed to vary with time in a manner that precisely accounts for the Hubble redshift law.

Next astronomy theory: galaxy theory Up: astronomy theory Previous astronomy theory: stellar theory

Subject	has volume	has momentum	has material	has velocity	has mass	has extent	has angular momentum	has definition	has location	has synonym	has temperature	has antonym
big bang								One of three standard Big Bang models that were formulated by Friedmann and Lemaitre of an isotropic and homogeneous universe composed of expanding matter and radiation. In these models space is unbounded.		Friedmann-Lemaitre universe		big crunch
big crunch								One hypothesized future for the universe in which the current expansion stops, reverses, and results in all space and all matter collapsing together; a reversal of the big bang.				big bang
cosmic string								Some contemporary cosmological theories suggest that boundaries were formed between different regions of the universe at the moment of creation. These boundaries survive today as "cosmic strings", incredibly thin but very massive strings many light years in length.	or center of gravity
de Sitter model								A geometrical model (1917) of an empty universe, based on Einstein's field equations.
Eddington-Lemaitre universe								A cosmological model in which the cosmological constant plays a crucial role by allowing an initial phase that is identical to the Einstein static universe. After an arbitrarily long time, the universe begins to expand. The difficulty with this model is that the initiation of galaxy formation may actually cause a collapse rather than initiate an expansion of the universe.
Hoyle-Narlikar theory								A reformulation of the general theory of relativity that incorporates and extends Mach's principle (q.v.). In this theory, the inertial mass of a particle is a function of the masses of all other particles, multiplied by a coupling constant which is a function of cosmic epoch. In cosmologies based on this theory, the gravitational constant G decreases strongly with time.
Hubble law								A relation which states that recessional speed is proportional to distance for a homogeneous and isotropic universe. Galaxies moving away from us with a speed precisely following this relation are said to follow the Hubble flow. Because the actual universe is not precisely homogeneous, with lumpiness arising from clustering of galaxies and voids of empty space, the motions of actual galaxies deviate somewhat from the Hubble flow.
kinematic relativity								Theory proposed by Edward Milne as a viable alternative to Einstein's general theory of relativity, and based generally on kinematics (the science of pure motion, without reference to matter or force), from which Milne successfully derived new systems of dynamics and electrodynamics.
Klein-Alfvén cosmology								A cosmological model in which the early universe is depicted as a giant collapsing spherical cloud of matter and antimatter. When a critical density is reached, the matter and antimatter begin to annihilate, the resulting release of radiation and energy causing the universe to expand. There are many difficulties with this model of the expanding universe, which is largely discredited on observational grounds.
static universe								A universe whose radius of curvature is constant and independent of time, as in the Einstein universe.
Steady State Theory								A cosmological theory propounded by Bondi, Gold, and Hoyle in which the Universe has no beginning and no end and maintains the same mean density, in the face of its observed expansion, by the continuous creation of matter at the current rate of 2.8 × 10^-46 g cm^-3 s^-1 (or roughly one nucleon per cubic kilometer per year). Discovery of the microwave background has persuaded most astronomers to reject the steady-state theory.
tired light								The hypothesis that light may be degraded in energy, thereby increasing in wavelength and becoming redshifted, during its passage through intergalactic space. This would provide an alternative to the Big Bang model in accounting for the redshifts of distant galaxies. However, there is no evidence for any such tired-light effect.
Twistor Theory								Model of the Universe proposed by Roger Penrose, based on the application of complex numbers (involving (-1)^1/2) used in calculations in the microscopic world of atoms and quantum theory to the macroscopic ordinary world of physical laws and relativity. The result is an eight-dimensional concept of reality that although complicated is possibly a more logical understanding of the constitution of the Universe.
variable-mass theory								A theory of Hoyle and Narlikar in which the masses of fundamental particles are assumed to vary with time in a manner that precisely accounts for the Hubble redshift law.