Cosmology Definition and 943 Threads

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. Quarlep

    Calculating Surface Density of the Universe Using the Shell Model

    You know friedmann equations derived from kinetic energy and potantial energy conservation.I found these shell model for universe.Here I am curious about something. This shell is like a surface of sphere isn't it.I mean it has only surface and that surface mass is m.And we made our equations...
  2. L

    The average density of halo of non-baryonic dark matter?

    I've got a homework question that I'm particularly stuck on: Suppose that the halo, assumed spherical, of non-baryonic dark matter surrounding our galaxy has mass ~ 5 x10^12 M solar and radius 0.1 Mpc. What it its average density in Kg m-3? I think that I need to use the formula...
  3. N

    Schools Graduate School Guidance. I want to be a cosmologist

    I had a lot of trouble in my early undergraduate career and had received some really bad grades. I retook a lot of courses and after 6 years, I am finally graduating with good marks in my third and fourth year courses and I believe I have an overall good understanding of undergraduate physics. I...
  4. C

    Minnesota or Carnegie Mellon for particle cosmology

    Now that I have pretty much given up on Columbia, but still will have somewhere to go, I will try to make the best of what I have. Since Carnegie Mellon actually earmarks spots for waitlistees, rather than using it to fill up the class when too many No's have been recorded (like WUSTL, which I...
  5. P

    Engineering Which path should I choose? (Computer Engineering, Math, Cosmology ?)

    I am currently computer engineering student(second year). Well its not like I don't like computer engineering.but somtimes I think I should have chosen another path.I am pretty good at mathematics.I like to solve maths problems.I am also fascinated about cosmology.I like electronics as well.I...
  6. wolram

    B What Is the Evidence for Dark Matter and Dark Energy?

    To date AFAIK Dark matter and Dark energy are mathematical anomalies, What is the evidence for their existence and what is the latest thoughts as to what these hypothetical enteritis are?
  7. T

    Covariance betw scalar amplitude & spectral index in Planck?

    I am reading some of "Planck 2013 results. XXII. Constraints on inflation." The paper is full of values for various inflationary parameters under various models, with their confidence intervals. For instance, in Table 5 on page 13, the authors report that — for a model including both running of...
  8. N

    Physics The Future of "Lone Physicists" - Researching Physics Alone?

    Hello everyone, just a quick question: I have heard that it is impossible to do research in physics by yourself anymore. I heard that "The days of Einstein are gone" and that nowadays in physics, especially string and quantum relativity research, everyone publishes in groups. I feel like this is...
  9. marcus

    What can you learn about cosmology from Google calculator?

    Before I say, I just want to mention that the Danish words for 15 and 18 are femten and atten Atten sounds a bit like the English word "eighteen". So that is where we get our metric prefixes femto- for 10-15 and atto- for 10-18. When you do cosmology the most common quantity, or one of the...
  10. H

    Scott Dodelson Modern Cosmology 4.2

    Hi guys, I recently started reading/working through Scott Dodelson's Modern Cosmology in preparation for a Masters course I'm taking next year and one of the exercises has stumped me and (arghhh!) its not one of the solved ones in the back! It is in Chapter 4 (The Boltzmann equations) and is...
  11. T

    Gravitational waves in cosmology?

    The usual calculations for gravitational waves linearize the GR equations around the background solution of flat space time ( g = Minkowski metric matrix ) empty of matter and energy ( T = 0 ) What happens in cosmology, when one must linearize the GR equations about the FRW metric matrix with...
  12. H

    Required backround for quantum cosmology

    Hello every body. I want to learn about quantum cosmology but I always find lot of difficulties :confused:. I have a very usual background :frown: on Quantum Mechanics and General Relativity. What are the required specific topics of QM or GR that i should learn before I can learn about Quantum...
  13. U

    Does a Closed Universe Satisfy the FRW Equations?

    Homework Statement (a) Show that the equations satisfy FRW equations. (b) Show the metric when ##\eta## is taken as time Homework EquationsThe Attempt at a Solution [/B] The FRW equation is: 3 \left( \frac{\dot a}{a} \right)^2 = 8\pi G \rho Using ##\frac{da}{dt} = \frac{da}{d\eta}...
  14. P

    Cosmology books for high school students

    Is there any book, on cosmology, or anything related (Not too deep) recommended for a high school students interest basis. Thank you.
  15. G

    Cosmology from Quantum Potential

    I am not sure where to find people who may understand the following paper but I figured someone here might be interested and or educated enough to weigh in on this subject. I tried with my local astronomical society and haven't heard anything back from them. This idea is interesting to me but I...
  16. Amrator

    Is Cosmology a Branch of Physics or Astronomy?

    I have always considered cosmologists to be physicists because I noticed that cosmologists usually apply (Correct me if I'm wrong) general relativity. They seem to take approaches similar to those of physicists. Astronomy is the study of celestial objects, while cosmology is the study of the...
  17. BilboBombadillo

    Self teaching physics with poor math skills?

    Ahoy there. I am twenty years old, and have (as a result of my interest in cosmology and astronomy, and the natural sciences) developed a keen appreciation for mathematics (in physics, primarily). I have always had an interest in the sciences, but lackluster teachers and personal disinterest...
  18. B

    Not sure where my research interests lie in undergrad?

    Hello, I am currently studying astrophysics in my undergrad. I am concerned with the fact that I do not know what field I want to explore during grad school yet. I am in my junior year and will probably finish my undergrad in five years due to double majoring in math as well. I realize I have...
  19. E

    What are the important numbers in Cosmology?

    What are the important numbers in cosmology that dictates the very fate of the universe? I searched through Google and one site states that they are 13 constants; http://www.popularmechanics.com/flight/g163/13-most-important-numbers-in-the-universe/ What could be the possible consequences if...
  20. Mastermind01

    What is the History of the Universe and How Can I Learn More?

    Hello, this is my first post. I am a 15 year old from India just finishing my 1st year in high school. One of my friends recommended to me the world science U website - http://www.worldscienceu.com/courses/master_class I watched Max Tegmarks' History of the universe -...
  21. Greg Bernhardt

    What topics are covered in the University of Arizona's Cosmology Video Lectures?

    Series of Lectures on Astrophysics and Cosmology This is part 1 of 12 in the series. Click the youtube link to select another video in the series.
  22. H

    Can taste perception be influenced by packaging? A blind trial study.

    ...of physics on both quantum and cosmic scales. I am a chemical engineer and avid programmer who has always had an interest in fundamental physics, but this will be my first effort to truly pursue that passion. And I make beer for a living. :)
  23. T

    First cosmology computer simulations

    I understand that the first cosmological computer simulations Did not have DM Only gas dynamics on expanding grids And, that those sims produced no structure of any kind No LSS Only vast expanses of nearly uniform space plasma Devoid of any clumps Essentially reminiscent of the real...
  24. L

    Is the gravitational constant actually a variable?

    Hi, as an engineer i don't have much formal training in theoretical physics so bare with me. As most of you know, we can only understand 4% of our universe with the current models we have. The rest of the 96% is dark matter and dark energy (23% and 73%, respectively). Could these unexplained...
  25. B

    Is Quantum Cosmology a Viable Path to Understanding the Universe?

    I just finished reading a book called Three Roads to Quantum Gravity, and in it the author mentioned a few arguments surrounding quantum cosmology. He did not seem too fond of it, but to me (relatively inexperienced) combining the two makes a lot of sense. What are your thoughts on it?
  26. D

    Baryon acoustic oscillations and sound horizon

    I'm having some trouble understand this correctly, so I was hoping someone could enlighten me a bit :) Okay, so in the early Universe most of the hydrogen and helium was formed, and then kept in equilibrium, and ionized via photons. So we have a plasma of baryonic matter, including dark matter...
  27. D

    Boltzmann equation for the early Universe

    I'm currently reading about the Boltzmann equation, used for the early Universe. The equation I end up with, after some simplifications is the following: \begin{equation} a^{-3}\frac{d}{dt}\left(n_1a^3\right) = n_1^{(0)}n_2^{(0)}\langle\sigma v\rangle\left[\frac{n_3 n_4}{n_3^{(0)}n_4^{(0)}} -...
  28. binbagsss

    Comoving Observers Concepts cosmology

    I have read 'comoving observers are a special set of freely-falling observers' . I have the following definitions: Comoving Frame: "defined at a time t is the inertial frame in which the accelerated observer is instantaneously at rest at t=t0. (Thus the term 'comoving frame' actually refers to...
  29. K

    What are the topological properties of the FLRW model?

    So, I was trying to do a derivation of my own for the FLRW metric, since I couldn't understand the one Wald had. The spatial slice M is a connected Riemannian manifold which is everywhere isotropic. That is, in every point p\in M and unit vectors in v_1,v_2\in T_p\left(M\right) there is an...
  30. twistor

    Is the Weyl Curvature Hypothesis a Viable Alternative to Inflation?

    Hello guys. I was thinking about alternatives to inflation, especially old ones (such as the hawking-hartle state and imaginary time) and I remebered a theory put foward by Penrose, in which his relatively new CCC is based. Called the Weyl Curvature Hypothesis. No idea of what it is. Could you...
  31. D

    Calculate the age of the Universe at a temperature

    Homework Statement I've been told to calculate the age of the Universe at T = 1 \, \text{MeV}, assuming that a(t=0)=0. Homework Equations Now, I've already calculated the value of H at that temperature, which was around H(1\,\text{MeV}) \approx 0.6 \,\text{s}^{-1}. I've also shown, that in a...
  32. V

    Big Bang: A True Singularity That is Coordinate Independent

    Consider a flat Robertson-Walker metric. When we say that there is a singularity at $$t=0$$ Clearly it is a coordinate dependent statement. So it is a "candidate" singularity. In principle there is "another coordinate system" in which the corresponding metric has no singularity as we...
  33. D

    Calculating energy density in the early Universe

    Homework Statement I've been told to calculate the energy density in the early Universe. It states that it is completely dominated by neutrinos (3 species), photons, electrons, and positrons. Homework EquationsThe Attempt at a Solution Now, I've found an equation to calculate the energy...
  34. WineRedPsy

    Cosmology or Theoretical Physics?

    I don't really have to look into this just yet but it bothers me. I quite like cosmology and stuff like such. Universal topology and relativity and sum of histories and stuff. Fun! I really would like to study any theoretical physics though, it just strikes my fancy particularly. I figure I'd...
  35. W

    Unranked/low ranked graduate programs in theoretical cosmology/hep-th or astro?

    I'm applying for graduate school but am from a basically unknown state school. My stats can be found here: http://www.physicsgre.com/viewtopic.php?f=21&t=5735. I am looking for a low ranked or unranked theoretical cosmology/hep-th school or a similarly ranked observational astronomy program...
  36. V

    Upper Energy Limit in Field Theory: Exploring Quantum Gravity

    I see that we use dimensional analysis involving constants of nature to obtain the Planck length and then apply the uncertainty principle to find the corresponding Planck mass-energy. But the energy and length scales were found by invoking a "particle" interpretation of fundamental entities of...
  37. T

    Proton-electron mass ratio; changed? how much?

    On the subject of our 'finely turned universe', I have read that the proton-electron mass ratio can not deviate more than 1:1037. In other readings, the allowable deviation was stated as 1% ("If the neutron were very slightly less massive, then it could not decay without energy input. If its...
  38. V

    Topology of Relativity: Implications of Niels Bohr's Arguments

    I have seen in the online Stanford Encyclopedia of Philosophy in the entry on Copenhagen Interpretation of Quantum Mechanics that Niels Bohr had argued that the theory of relativity is not a literal representation of the universe: "Neither does the theory of relativity, Bohr argued, provide us...
  39. m4r35n357

    Cosmology Chapter Mistake: Reflections on Relativity

    http://mathpages.com/rr/s7-01/7-01.htm I am completely unable to follow the following sequence of working between equations 2 and 3. AFAIK the final answer is correct, but the intermediate steps seem to be a "casserole of nonsense". I would appreciate feedback from anyone who can follow this...
  40. TumblingDice

    Alan Guth:Inflationary Cosmology live stream 10/31

    Just saw this. "Learn inflationary cosmology from the guy who invented it." Live stream Friday, 10/31, at 2pm EDT (11am PDT) here: http://new.livestream.com/accounts/4044190/AlanGuthLivestream
  41. R

    Number Density of Photons (Cosmology)

    Homework Statement Given the maximum possible number density of stars in the present universe, assume that they have been radiating light for 10 billion years at a solar rate of ##3.9 \times 10^{26} \ W##. Photons emitted all have a restframe wavelength of 500 nm. Find a crude upper bound for...
  42. R

    Cosmology Questions: Show Max Size in Expanding Universe w/o Quotes

    Homework Statement (a)[/B] From the continuity equation show that if ##P=\omega \rho## and ##\omega > -1/3##, show that an expanding universe will eventually reach a maximum size. Take ##k=1## (closed universe). (b) Show that if ##\omega <-1##, the energy density ##\rho## will increase as the...
  43. anorlunda

    Photon's History: Quantum Expression for Energy Loss with Scale Factor Increase

    I know that QM and GR have not net been combined, so perhaps this is a foolish question, but I'll try anyhow. A photon traveling in the vacuum, has energy h/λ. That energy is fixed. It never varies in any circumstances (true?) except one. That one is the expansion of space time; i.e. the...
  44. K

    Cosmological Expansion: Estimating Present Horizon Length

    Homework Statement If light traveled a distance L = H_{eq}^{-1} at M-R equality, how large does this distance expand to at present? (in Mpc) Homework Equations z_{eq} = 3500 \Omega_m = 0.32 at present \rho_c = 3.64 \times 10^{-47} GeV^4 present critical density The Attempt at a...
  45. C

    Ohio State vs. WUSTL vs. Notre Dame for particle cosmology theory?

    First off, my supervisor has connections at both, albeit under different forms: my supervisor postdocked at Ohio State, while he personally knows a professor at WUSTL and another research collaborator I worked with and that writes me a LOR knows another professor at WUSTL (connections at WUSTL...
  46. C

    Event Horizon Properties for Incoming Matter Explained

    Dear all, In one of his lectures,Prof. Susskind mentioned that the event horizon "bulges" forward to meet any incoming radiation or matter; and it is a property of Einstein field equations. I have not come across any such property, and if it exists, shouldn't it belong to the Schwarzschild(or...
  47. S

    Is the Big Bang replaced with a Big Bounce in String-Inspired Cosmology?

    We have made a third film in our "Before the Big Bang" series for youtube. Our first centred around an interview with Abhay Ashtekar and focused on LQC Our second Sir Roger Pernose on CCC This fetaures an interview with Gabrielle Veneziano (founder of string theory), Ali Nayeri ( who works...
  48. wolram

    Is Supersymmetry still viable in cosmology?

    Is Supersymmetry still viable in cosmology, given that so far no supersymmetric particles have been found. From Wiki. SUSY is often criticized in that its greatest strength and weakness is that it is not falsifiable, because its breaking mechanism and the minimum mass above which it is...
  49. julcab12

    Big Bang, Blowup, and Modular Curves: Algebraic Geometry in Cosmology

    http://arxiv.org/abs/1402.2158 Big Bang, Blowup, and Modular Curves: Algebraic Geometry in Cosmology Yuri I. Manin, Matilde Marcolli (Submitted on 10 Feb 2014 (v1), last revised 9 Jul 2014 (this version, v3)) We introduce some algebraic geometric models in cosmology related to the...
  50. ChrisVer

    Problem in Dodelson Modern Cosmology

    Could you please confirm my idea of how to deal with the problem question [b] in the attachment? In case of a non-relativistic neutrino, the energy density will be given by: \rho = m_{\nu} n And if we adopt a perturbation, then n \rightarrow n_{0} [1+ x ] So in general what he asks from...
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