What is Cosmological: Definition and 432 Discussions

Cosmology (from Greek κόσμος, kosmos "world" and -λογία, -logia "study of") is a branch of astronomy concerned with the studies of the origin and evolution of the universe, from the Big Bang to today and on into the future. It is the scientific study of the origin, evolution, and eventual fate of the universe. Physical cosmology is the scientific study of the universe's origin, its large-scale structures and dynamics, and its ultimate fate, as well as the laws of science that govern these areas.The term cosmology was first used in English in 1656 in Thomas Blount's Glossographia, and in 1731 taken up in Latin by German philosopher Christian Wolff, in Cosmologia Generalis.Religious or mythological cosmology is a body of beliefs based on mythological, religious, and esoteric literature and traditions of creation myths and eschatology.
Physical cosmology is studied by scientists, such as astronomers and physicists, as well as philosophers, such as metaphysicians, philosophers of physics, and philosophers of space and time. Because of this shared scope with philosophy, theories in physical cosmology may include both scientific and non-scientific propositions, and may depend upon assumptions that cannot be tested. Cosmology differs from astronomy in that the former is concerned with the Universe as a whole while the latter deals with individual celestial objects. Modern physical cosmology is dominated by the Big Bang theory, which attempts to bring together observational astronomy and particle physics; more specifically, a standard parameterization of the Big Bang with dark matter and dark energy, known as the Lambda-CDM model.
Theoretical astrophysicist David N. Spergel has described cosmology as a "historical science" because "when we look out in space, we look back in time" due to the finite nature of the speed of light.

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  1. N

    Meaning of cosmological constant ?

    Incredibly much has been written about the cosmological constant and all its implications on the evolution of the universe. I want to ask however a more basic question about it. The cosmological constant has the dimension of 1/R^2. So supposing this constant is non-zero, its value points to the...
  2. T

    Schwarzchild solution with cosmological constant

    How do we solve for it? I still don't know much about non linear equations. Unfortunately, this reduces to R=-4(cosmos constant) which is not a system thus making simplicfication difficult. I'm assuming that we can still use the previous arguments and assume that the metric coompontents Gtt and...
  3. D

    The link between the cosmological constant and the higgs field

    I have read that the current expansion of the universe could be due to a bare positive cosmological constant along with a negative cosmological constant due to the false vacuum of the higgs field. Currently this negative CC is not enough to cancel the positive cc but with time this can be...
  4. marcus

    Where is the Cosmological Event Horizon in the LCDM model?

    this is a case where it could be very helpful if someone (Pervect? Wallace? hellfire?) who has the numbers handy could tell us how far away the CEH is at present according to the usual LCDM model I don't know the exact figure. I think it is somewhere around 16 Gly. that is, slightly further...
  5. W

    Dark Energy, the Cosmological Constant, General Relativity and you

    So there has been a few threads over the last few days where the whole issue of dark energy and/or the cosmological constant has been discussed in the context of whether it is a valid 'solution' to GR or if it violates some principle of relativity or even insults Einsteins 'legacy', whatever...
  6. jal

    Dynamical coherent states and physical solutions of quantum cosmological bounces

    http://arxiv.org/PS_cache/gr-qc/pdf/0703/0703144.pdf Dynamical coherent states and physical solutions of quantum cosmological bounces Martin Bojowald_ 29 march 2007 I could ask a lot of question ... however, one for now What does he mean by "squeezing"? jal
  7. Garth

    Are the Cosmological Coincidences Just a Matter of Chance?

    One problem in the standard \LambdaCDM model is the near equality to an OOM of the densities of baryonic matter (4%), non-baryonic Dark Matter (23%) and Dark Energy (73%). The coincidence is more striking if it is realized that the proportion of DE, if due to the cosmological constant, will grow...
  8. wolram

    Standard cosmological pardigram

    http://background.uchicago.edu/~whu/araa/node3.html I found this site, would it be a good reference?
  9. P

    What is the true nature of our expanding universe?

    lets say we have a ball with no air in it, so it is no bigger than a dot. now we attach a pump to it that pumps air into this very elastic ball at a relativistic speed. 1) there are an infinite number of 2-dimensional universes within the ball. all of them are of course at some radial...
  10. M

    Cosmological Red Shift: How Does z Change With Time?

    I know that the variation of cosmological red shift with the distance is given by z= H_0 l (1+\frac{1}{2} (1+q_0) H_0 l) Where l is the luminosity distance, H_0 is the Hubble parameter at the corrent epoch and q_0 is the deceleration parameter. I would like to know how does z...
  11. stevebd1

    Calculating Critical Density and Cosmological Constant

    I'm currently looking into the values for the 'critical density' and 'cosmological constant', I managed to calculate a figure for the critical density which was close to the generally accepted figure, with lambda I came up with an astronomically small number which I later realized after...
  12. Q

    Is the Hyperboloid Model Truly Homogeneous and Isotropic?

    Hi: The principle states that : the universe is homogeneous and isotropic. Then we have three solutions often depicted as i) Sphere ii) Plane iii) Hyperboloid I can understand that the sphere and plane is homogeneous and isotropic, but the iii) does not seems to be. There seems to be a...
  13. Loren Booda

    Cosmological geometries that may function as blackbodies

    Of closed, flat and open universes, which have the potential to act as a blackbody?
  14. M

    How does the cosmological event horizon change the matter density?

    I'm told that the cosmological event horizon produces a temperature at every point of space similar to how a black hole event horizon produces a radiation near its surface. If there exists a temperature, then there must be particles to produce that temperature. They must be baryons since normal...
  15. marcus

    The Status of Cosmological Natural Selection (Smolin rebuts Vilenkin)

    The status of cosmological natural selection Lee Smolin 25 pages "The problem of making predictions from theories that have landscapes of possible low energy parameters is reviewed. Conditions for such a theory to yield falsifiable predictions for doable experiments are given. It is shown...
  16. L

    Schwarzschild metric, cosmological constant

    From an https://www.physicsforums.com/showthread.php?t=140501", a new question comes to me. Is there a known generalisation of the Schwarzschild geometry when the cosmological constant is positive? Are there still black-holes in this case? Are there small modifications to the Newtonian...
  17. M

    Figuring out the units for the cosmological constant

    How does one figure out the units of measure for the cosmological constant? In the Einstein Field Equation: \[Rab - \frac{1}{2}Rgab + \Lambda gab = 8\pi Tab\] Lambda is a constant but the units of measure for gab and Tab differ for each combination of indices. For example T00 is an...
  18. marcus

    Penrose: Outrageous Solution to Big Bang Cosmology Puzzle

    Penrose: Before the Big Bang--Outrageous Solution to a Profound Cosmological Puzzle a video of a talk given at Perimeter Institute recently by Sir Roger Penrose Before the Big Bang: an Outrageous Solution to a Profound Cosmological Puzzle go here...
  19. T

    Calculation of the Cosmological Constant

    Hallo, perhaps you remind our last paper (gr-qc/0511089) about the local characteristics of differential structures. Meanwhile we examined the global characteristics and found a way to compute the cosmological constant. It would be nice to hear your opinion about it! See...
  20. B

    A positive cosmological constant * SUSY/string theory

    lee smolin claims that SUSY/string theory can account for negative (anti-DS) and zero cosmological constant, but not a positive de-sitter constant, which is what has been observed. he also claims the kodama state in LQG has a good semiclassical limit that is GR, and incorporates a small...
  21. M

    A fix for the Cosmological Constant problem?

    I hear that the calculated value of the vacuum energy using QFT is 120 orders of magnitude more than what is observed for the cosmological constant (or vacuum energy). But I wonder if this calculation was done in a very slow locally expanding spacetime. Or was it done with a strictly...
  22. M

    Entropy of Cosmological Event Horizon

    Has anyone got a reference to the entropy of the cosmological event horizon? Is this entropy an upper limit of the entropy inside (like a black hole) or a lower limit? I'm entertaining the idea that a shrinking cosmological event horizon puts a shrinking upper bound on the entropy inside it...
  23. Loren Booda

    Planck - stelactic - cosmological black hole symmetry?

    Like nested dolls, these black holes appear coexisting concentrically where the central stelactic (stellar-galactic) black hole mediates a symmetry between the other two. For instance, consider how stelactic Hawking radiation manifests under inversion of its event horizon. The events within...
  24. MathematicalPhysicist

    Theories without the use of cosmological principle.

    are there theories in cosmology which do not incorporate/use the cosmological principle?
  25. E

    The cosmological principle in simple models of the universe

    NOTE: Taken from another thread on a similar subject: https://www.physicsforums.com/showthread.php?t=125698 "An infinite amount of space with matter uniformly distributed throughout", is not a claim of infinite matter – at least it shouldn't be. If matter is assumed to be inside of a greater...
  26. Robert100

    Common misconceptions of cosmological horizons and superluminal expansion

    I recently came across this paper on arXiv.org http://arxiv.org/abs/astro-ph/0310808 Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the Universe Authors: Tamara M. Davis, Charles H. Lineweaver Comments: To appear in Publications of...
  27. P

    A Birkhoff's theorem with cosmological constant

    Birkhoff's theorem says that any vacuum solution of Einstein's equations must be static, and asymptotically flat. One of the consequences of Birkhoff's theorem is that the gravitational field inside any spherical shell of matter is zero, even if the shell is expanding. But what happens if...
  28. P

    Birkhoff's theorem with cosmological constant

    Birkhoff's theorem says that any vacuum solution of Einstein's equations must be static, and asymptotically flat. One of the consequences of Birkhoff's theorem is that the gravitational field inside any spherical shell of matter is zero, even if the shell is expanding. But what happens if...
  29. P

    Cosmological expansion effects

    In another thread, someone was talking about cosmological expansion effects on planetary orbits. (Actually it was about lunar orbits, but I think planetary orbits are more to the point). Through a somewhat round-about path, I eventually got to thinking about the following question. Suppose we...
  30. H

    Exploring the Cosmological Frame of CMB

    How to understand that the cosmic microwave background (CMB) can define a cosmological frame? Cheers!
  31. S

    'Cyclic universe' can explain cosmological constant

    http://www.newscientistspace.com/article/dn9114-cyclic-universe-can-explain-cosmological-constant.html" I thought Einstein abondend the cosmological constant after they found out the uninverse is expanding. Why are they interestead in it again?
  32. R

    Accelerating expansion and the Cosmological Constant

    Einstein’s Cosmological Constant was inserted into his General Relativity equations to make the universe static, neither expanding nor contracting, as most physicists believed it was at that time, as his equations showed that the universe is unstable and would eventually contract into a single...
  33. wolram

    Casimir Effect Confronts Cosmological Constant

    I thought this the right place to post this, from the little i can understand it seems interesting. http://arxiv.org/abs/astro-ph/0604265 Casimir Effect confronts Cosmological Constant Authors: Gaurang Mahajan, Sudipta Sarkar, T. Padmanabhan Comments: revtex4; four pages; 5 figs It has...
  34. M

    Cosmological Event Horizon during Inflation

    The newly release WMAP data supports the Inflation model that the universe expanded from subatomic scales to Astronomic scales in a fraction of a second. If so, then what would have been the distance from each point where space would have been expanding at the speed of light, approximately? Thanks.
  35. Chronos

    A Cosmological Pot Sticker

    I was thinking about posting this in the cosmology forum, but, concluded the more philosophically inclined souls would have more fun with it: http://www.arxiv.org/abs/astro-ph/0602280 Issues in the Philosophy of Cosmology A thought provoking paper, IMHO.
  36. B

    Cosmological Constant and the like

    I have a few questions that have been piling up. 1. Einstein introduced the cosmoligical constant to demand a static universe like so, G + (Lambda * metric tensor) = T If you were to calculate the perihelion precession of mercury, bending of starlight etc. with this additional term would...
  37. T

    Difference between particle horizon and cosmological event horizon?

    What is the difference between particle horizon and cosmological event horizon?
  38. N

    Does the Cosmological Argument prove God's Existence?

    This is my first post here, so I appologise in advance if this is the wrong forum. Anyway, I was interested to see if this was a generally held opinion. My philosophy course didn't really go into much detail (alas, only Higher level (in Scotland)) I think that the cosmological argument goes as...
  39. P

    Vacuum with cosmological constant

    I was thinking about constraints on the stress-energy tensor of the vacuum, and came to an interesting conclusion that the vacuum itself should only be isotropic in one rest frame if there is a cosmological constant. If we start with a vacuum that is homogeneous and isotropic in some cartesian...
  40. marcus

    The Cosmological Parameters 2005

    this just came out http://arxiv.org/abs/astro-ph/0601168 it is an update, as of year-end 2005, of the best estimates of the values of the main cosmological parameters like the Hubble parameter and the dark energy density (or cosm. const.) and the Omega number which is used to indicate how...
  41. turbo

    Addressing Impossibilities in the Standard Cosmological Model

    some examples: 1) inflation that turns on, then magically switches off simultaneously in causally-disconnected parts of the universe. 2) DM 3) DE 4) cosmological expansion that slowed nicely for billions of years, then accelerated (again, simultaneously in causally-disconnected parts of the...
  42. Loren Booda

    Upon the initial cosmological singularity

    What perspective can one take concerning the origin of the universe in the big bang model? Can a collapsed observer occupy the singularity itself, or is there a higher dimensional "superspace" (John Archibald Wheeler) one shares apart from it? Might an observer possesses properties beyond...
  43. P

    Cosmological Constant: Unravelling the Mysteries of Dark Matter

    Einstein introduced the cosmological constant to keep a static universe But we know the universe is expanding due to dark matter? The exstistence of dark matter promotes the cosmoloigcal constant again. How does that make sense? Static universe: need cosmological constant...
  44. Loren Booda

    Entanglement of common cosmological origin?

    Could entanglement arise from the continuity of the initial universal singularity?
  45. K

    Cosmological Constant: What & Why?

    what is cosmological constant?Why it is introduced by Enstien.?
  46. J

    Quantum Gravity with a Positive Cosmological Constant

    Hi, I have been reading the paper "Quantum Gravity with a Positive Cosmological Constant" by Lee Smolin (http://arxiv.org/abs/hep-th/0209079), and am having some trouble making the constants in Part I, Sections 2, 3, and 4 match with what I would calculate them to be when I try to go through...
  47. wolram

    Quasars non cosmological red shift.

    http://arxiv.org/PS_cache/astro-ph/pdf/0506/0506115.pdf Title: On quasar host galaxies as tests of non-cosmological redshifts Authors: E. Zackrisson Comments: 9 pages, 4 figures Journal-ref: MNRAS 359 (2005), 1193 Despite a general consensus in the astronomical community that all...
  48. G

    GR & The Cosmological Constant

    When we approach a calculation in relativity, do we have to change the cosmological constant in order to work with bigger dimensions? Because i know we are limited to seeing 1, 2 and 3 dimensions, i was just curious if you wanted to figure out an answer using an equation based on a bigger...
  49. Loren Booda

    Convergent cosmological evolution

    There are many examples of convergent evolution here on Earth, such as the separate development of wings on birds, bats and insects. I propose that the midpoint of evolution be marked by an equivalence between convergent and divergent adaptations. For the universe as a...
  50. wolram

    Dopplerian Redshifts: Alternative Cosmological Paradigm?

    http://arxiv.org/abs/astro-ph/0505310 Authors: Michael A. Ivanov Comments: 20 pages, 4 figures, LaTeX. Contribution to the 1st Crisis in Cosmology Conference (CCC-1), which will be held in Moncao, Portugal, 23-25 June 2005 If gravitons are super-strong interacting particles and the...
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