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

    What is the role of gravity in the cosmological redshift?

    I’ve made several efforts to provide a simple description of how the cosmological redshift works. Each has been closer to the mark than its predecessor, and now I think I’ve got it nailed. The premise underlying the redshift is simply that a photon must travel at a local velocity of c through...
  2. tom.stoer

    Solution to the Cosmological Constant, Zero-Point Energy, P.D. Mannheim

    Has anybody studied this paper? http://arxiv.org/abs/0909.0212v4 Comprehensive Solution to the Cosmological Constant, Zero-Point Energy, and Quantum Gravity Problems Philip D. Mannheim (Submitted on 1 Sep 2009 (v1), last revised 7 Jan 2010 (this version, v4)) Abstract: We present a...
  3. edpell

    Cosmological constant or dark energy or vaccum denisty/energy/energy density

    Are these five names cosmological constant, dark energy, vacuum density, vacuum energy, vacuum energy density names for the same thing?
  4. Q

    Exploring the Possibilities of Integrating Cosmological Theories

    Hi! This is my first post. I have a question of cosmological importance - literally and figuratively. The Standard Model is the most accepted theory of (almost) everything, yet is unable to make sense of gravity. String Theory can explain it all theoretically through quantitative...
  5. F

    Is the Cosmological Constant the Same as Dark Energy?

    What does this paragraph mean? I read it somewhere that a relatively newer observation renewed the concept of "cosmological constant", and it was connected with "dark energy", again, can anyone provide detailed information on that? Wasn't "cosmological constant" proved erroneous long ago...
  6. S

    What is the Role of the Cosmological Constant in the Expansion of the Universe?

    E proposed cosmological constant to prove the universe is stationary. Some others suggested Universe is contracting, while some others suggested Universe is exanding and for either of them cosmological constant was considered responsible. Today when this is discovered universe is expanding with...
  7. D

    Decaying cosmological constant

    The following is from a research paper: doi:10.1088/0034-4885/68/4/R04 The structure of the world from pure numbers F J Tipler Department of Mathematics and Department of Physics, Tulane University, New Orleans, LA 70118, USA Received 21 September 2004 Published 15 March 2005 Online...
  8. I

    Unit transformation of Cosmological Constant ?

    Question : How to unit transformation of Cosmological Constant? 10-47 GeV4 ===> ? eV or, x eV ===> ? GeV4 1) How compair ( X ) GeV4 with ( Y ) eV ? 2) How compair ( 10-29 g/cm3) with (Y eV)? please, easely explain to me! and, have a nice day!
  9. F

    Susskind on the cosmological constant.

    I am watching a lecture by Susskind on his book The Cosmic Landscape. And he is going on about how "tuned" and unlikely it is. Largely based on work done by Weinberg. He said it was one of the biggest surprises in science and can't be ignored. How fine tuned the cosmological constant is. Is...
  10. B

    Difference between Dark Energy and Cosmological Constant

    Can someone remind me what the difference between the Cosmological Constant (\Lambda) and Dark Energy (DE)? Doesn't DE (with w = -1) show up in the Einstein's field equations in exactly the same way as \Lambda does? (In case your an expert, I was trying to understand the conclusion of...
  11. marcus

    Cosmological footprints of LQG (Aurelien Barrau and Julien Grain)

    It's important to be able to test LQG with observations, most likely using new data on the microwave Background (CMB) collected by instruments such as the Planck spacecraft . It turned out to be impossible to derive a prediction of dispersion (energy dependent speed of light) at least so...
  12. P

    Human observer & cosmological interpretations

    Hi! This is my first time on here and my first post. I don't do professional work in this field but it has been a keen interest of mine over the years. Anyway, if someone can share some insights, I would really appreciate it greatly! Given the divide between classical physics and quantum...
  13. N

    Misconceptions re: Cosmological Redshift

    Apparently my recent thread on the cosmological redshift assumed more general insight into this subject than is the case. So the purpose of this thread is to help dispel some popular misconceptions about the cosmological redshift and hopefully spur a vigorous discussion. This thread is NOT...
  14. N

    Cosmological Constant and Planck Length in relativity

    There seems to be a difference in the way relativity views Planck length as frame dependent and the cosmological constant, an energy density?, as invariant...Any insights appreciated! There is a well known contradiction between relativity and the Planck length: Wikipedia explains the...
  15. N

    The Mechanism of the Cosmological Redshift

    It is well established that the cosmological redshift causes both the wavelength and the separation of photons to increase in proportion with the increase in the cosmic scale factor a. The traditional explanation for the mechanism of the redshift is that ‘expanding space’ progressively forces...
  16. K

    What exactly is cosmological inflation?

    What exactly is cosmological inflation? Just a hypothesis that the rate of expansion is increasing? What is negative-pressure vacuum energy density? If the universe is expanding faster than the speed of light, how do any photons reach us from anywhere other than our sun? Thanks in advance!
  17. C

    An unmodelled component in astronomical and cosmological spectral shift

    The standard model of accelerating expansion is successful in matching parameters to observation, but substantial observational problems with both CDM and MOND are now well reported in the literature. While there is no true reconciliation between general relativity and quantum mechanics, science...
  18. M

    Cosmological Constant: Significance & "God" Particle

    can someone tell me about the cosmological constant,its significance and 'god' particle?
  19. D

    Do the cosmological expansion affect binding systems

    It is known that in result of the cosmological expansion the distances between galaxies increase according Hubble law v=H*r. Distant SNeIa show that the dark energy accelerates the expansion. I heard in a scientific popular transmission that in result of the acceleration of expansion, every...
  20. Ranku

    What is the force of the cosmological constant?

    I have read that "the cosmological constant introduces a force of repulsion between bodies. The force increases in (simple) proportion to the distance between them." Is this description accurate? Is there a classical formula of the force of the cosmological constant like that of gravitational force?
  21. N

    Cosmological Constant and the Colapse of the Universe

    I was wondering if someone would mind talking a little about why the cosmological constant was introduced and what it actually means for the universe to collapse according to Einstein's Universe. I was reading up on Wikiepdia (not the greatest source, I know) in the Static Universe entry and it...
  22. M

    Einstein field eqns, with cosmological const, Newtonian limit

    Homework Statement This question is a slightly customised version of Q18(a) P212 of Schutz Prove that G_{\alpha \beta} + \Lambda g_{\alpha \beta} = 8 \pi T_{\alpha \beta} in the Newtonian limit reduces to \nabla^2 \phi = 4\pi \rho + \Lambda (I found this result in another text...
  23. H

    Mathamatical Description of the Cosmological Principle

    I think this belongs here, while not relativistic, is is about objects moving relative to one another. Summery: This stems from the description of 'Dark Energy' in a mathamatical context to show that you can place a 'center of the universe' at any point in space, and the accelaration vector...
  24. P

    Cosmological Constant or Quintessence

    Hi! I have more questions. 1st. Is there any diference between Cosmological Constant and quintessence? 2nd. If there is, which is? I've only understood that cosmological constant is the energy of the vacuum but I don't know what quitessence is, so please, could somebody tell me if...
  25. E

    Does the calculated large cosmological constant in falsify QFT?

    QFT it is possible to calculate the energy density of empty space. It is known to be around 10^50 orders to large. Does the calculated large cosmological constant in falsify QFT? Or does GR have to be re-done with a higher energy density
  26. wolram

    A Realistic Cosmological Model: 90 Years of Development

    arXiv:0811.2402 [ps, pdf, other] Title: A Realistic Cosmological Model Based on Observations and Some Theory Developed Over the Last 90 Years Authors: Geoffrey Burbidge Comments: 21 pages, conference Subjects: Astrophysics (astro-ph) This meeting is entitled "A Century of Cosmology."...
  27. L

    Vacuum solution with nonzero cosmological constant

    Consider the vacuum solution to Einstein's equations with non-zero cosmological constant. Following Carroll, we can find the equation for the radial geodesic with the aid of killing vectors. It takes the standard form: E = T + V. But, with non-zero cosmological constant V(r) now has a term...
  28. wolram

    Cosmological Inflation: Theory and Observations

    arXiv:0810.3022 [pdf, other] Title: Cosmological Inflation: Theory and Observations Authors: Daniel Baumann (Harvard), Hiranya V. Peiris (Cambridge) Comments: 18 pages, 12 figures. Invited review to appear in Advanced Science Letters Special Issue on Quantum Gravity, Cosmology and Black...
  29. nicksauce

    Solution of Friedmann equation w/ Cosmological Constant

    Homework Statement Solve for the age of the universe as a function of scale factor in a cosmology with \Omega_{M}=0.3, \Omega_{\Lambda}=0.7.Homework Equations The Attempt at a Solution (\frac{\dot{a}}{a})^2=H_0^2(0.3a^{-3}+0.7) \frac{da}{a\sqrt{0.3a^{-3}+0.7}}=H_0dt At this point, Maple seems...
  30. marcus

    Exploring a New Cosmological Paradigm: Peter & Pinto-Neto's Non-Singular Bounce

    It's been pointed out already at Cosmo forum that a revolution, or at least a minor insurrection, is brewing in cosmology. This paper is part of that. It comes from a different direction compared to some of the other research in nonsingular cosmology. For instance it is not specifically a Loop...
  31. I

    Alternative hypoteses for cosmological redshift

    I heard there are many alternative hypoteses for cosmological redshift, e g Fred Hoyle' s variation of mass and tired light. There are other ones? Thanks.
  32. wolram

    Kinematic Origin of Cosmological Redshift: Bunn & Hogg

    arXiv:0808.1081 (cross-list from physics.pop-ph) [ps, pdf, other] Title: The kinematic origin of the cosmological redshift Authors: Emory F. Bunn, David W. Hogg Comments: 14 pages. Submitted to Am. J. Phys Subjects: Popular Physics (physics.pop-ph); Astrophysics (astro-ph); General...
  33. J

    Superluminal Recession & Cosmological Redshift

    I'm taking the liberty of revising and restating this topic which started in a separate thread. Comments are welcome. A lively debate is underway today by mainstream cosmologists as to whether the expansion of the universe implies that empty space between galaxies is also expanding. When...
  34. N

    Technical question: vanishing of the cosmological constant in Randall Sundrum 1

    This is a very technical question so I don't really expect someone to have the answer unless they have actually worked with or studied the RS models. They say that the value of the brane tensions in model 1 (which are related to the bulk cosmological constant) are such that the 4D...
  35. J

    Do Cosmological Tidal Forces Prove the Expansion of Space?

    The team of Francis, Barnes, James & Lewis have published several very helpful papers in recent years about the expansion of space (with their names in various orders.) I suggested in a recent thread about their Radar Ranging article that they are trending away from explaining particle...
  36. N

    Cosmological Constant Problem

    I am new to the world of theoretical physics and was wondering if anyone can explain "vacuum energy" to me? What does it have to do with the expansion of our universe? Something about a "cosmological constant" is also involved. If someone can give me a concise and accurate version of what...
  37. Fra

    Logic of E-H action, ricci scalar, cosmological constant?

    Logic of E-H action, ricci scalar, cosmological constant?? This crazy thread is mean to stimulate some reflections on the logic of Einsteins Equations. It would be interesting if those who have any ideas can join. Maybe it could be enlightning? The common way of thinking about GR is that we...
  38. F

    Cosmological Friction: Exploring the Force

    What is the force of "friction" (for want of a better word) between the two four-dimensional universes that have come together to create our three-dimensional surface (universe). As a three-dimensional analog think of two rectangular solids moving toward each other. One is moving right...
  39. marcus

    Calculating the cosmological constant from scratch

    Here is a fun thing to try The Google calculator knows the values of pi, the speed of light c, Newton's G and stuff like that. So you can easily make it calculate the cosmological constant from a few familiar facts. You have to know that the usual estimate of the Hubble parameter is 71...
  40. R

    Cosmological Constant in mks units

    Hey folks, I'm writing a pop-sci article for a journal and one of the referees wants me to give the cosmological const in mks units instead of GeV. I just wanted to check with anyone in the know if the following looks correct. First, the accepted value of lambda (order of mag)...
  41. K

    Ray of light travelling through universe (applying cosmological principle)

    cosmological principle states that, on large spatial scales, universe is homogeneous and isotropic. in other words, universe looks the same in every direction and that is true for every point of view. there are some challanges to this principle, but for this discussion, I will assume it is...
  42. A

    Stability of cosmological models

    to those experts in the field of cosmology i was wondering if " large scale structures can be formed in stable cosmological models" or should i say that " large scale structures cannot be formed in those cosmological models that are stable with respect to gravitational or other curvature...
  43. C

    Acceptable cosmological discussions

    Hello, I am a new arrival to this forum. It was mentioned at another forum. So I came over registered and would love to see the prevailing Cosmological discussions. The post that brought me here, was this one below: Posted: Sat Jan 05, 2008 8:08 am Post subject: Physics Forum...
  44. L

    Is the Cosmological Arrow of Time Linked to the Thermodynamic Arrow of Time?

    Is the cosmological arrow of time just a special case of the thermodynamic arrow of time, where the universe is the isolated system?
  45. E

    Cosmological constant as a perfect fluid

    Hi everyone, If anyone could point me in the right direction with this problem I'd really appreciate it. "Show that the cosmological constant can be interpreted as a perfect fluid having an equation of state w=-1." I have a rough idea of how to do the second part of the proof: if the...
  46. E

    Cosmological constant as a perfect fluid

    Hi everyone, If anyone could point me in the right direction with this problem I'd really appreciate it. "Show that the cosmological constant can be interpreted as a perfect fluid having an equation of state w=-1." I have a rough idea of how to do the second part of the proof: if the...
  47. E

    Cosmological constant as a fluid

    Hi everyone, If anyone could point me in the right direction with this problem I'd really appreciate it. "Show that the cosmological constant can be interpreted as a perfect fluid having an equation of state w=-1." I have a rough idea of how to do the second part of the proof: if the...
  48. Peter Morgan

    Are there cosmological models in which Planck's constant varies?

    If we take Planck's constant to be a measure of quantum fluctuations, which seems natural in the world-view of https://www.physicsforums.com/showthread.php?t=204567", then it also seems natural to ask whether Planck's constant might vary over cosmological scales, just as temperature is a measure...
  49. Q

    Is the cosmological prinicple wrong? Is Big Bang wrong?

    This is a big hole in the sky. Although you can't see it with the naked eye it actually covers almost 3 degrees of the sky, and to put that into perspective the full Moon covers about half a degree! Until recently no-one was sure how big or far away this void was but the latest calculations...
  50. R

    G from cosmological measurements

    okay, good. actually at another time i was staring at the more general equation and had a few questions regarding it. so 1/H is the Hubble Time and about the age of the universe (maybe a milli-smidgen longer). this has been measured independently (from astronomical observation), right? and...
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