What is Cosmology: Definition and 917 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.

View More On Wikipedia.org
Recent contents Top users
  1. L

    Exploring the Intersection of Art and Physics: A Humanities Perspective

    Hi, I'm a new member. I joined this forum because I'm interested with astrophysics and cosmology. I'm actually in the field of the Humanities, currently taking up my Master's in Art History. I like physics because I think it is where art and science beautifully intersect. I started to see the...
  2. A

    I Entropy of the last scattering surface and today's universe?

    Hi, I am quite confused about followed question, I think scientist think the last scattering surface was dense plasma at the temperature of 3000K. If the today's universe much cooler and less dense then "the last scattering surface" how can anyone says entropy increased by time? Isn't universe...
  3. K

    What are Kaustov's areas of interest in physics?

    Hello everyone.. Myself Kaustov from NIT Trichy, pursuing BTech. in production technology. Very much interested to be a part of physics forum. I have knowledge on Theoretical Astrophysics and Cosmology and also Particle physics. Very much interested to be part of all the discussions and to help...
  4. H

    Other Publishing as an Independent: A Guide

    Lets say I have a new Idea and maybe it has scientific value maybe not, that's not the topic now. I want to put this idea out there and I've already talked myself into trying to publish rather than posting. Maybe I would post, it depends on how it gets rejected. I'm sure not many like me try...
  5. andrewkirk

    I MUST every possible thing happen in a Tegmark L1 Multiverse?

    I've been looking at one of Max Tegmark's articles about his 'Mathematical Universe' hypothesis, here on arXiv. As a preliminary, note that Tegmark's framework has four 'levels' of multiverses, with each level being an infinite collection of multiverses at the level below it. The second or...
  6. V

    Show metric perturbation transformation

    Homework Statement Consider following transformation: Transformation: $$X^{\mu}\rightarrow \tilde{X^{\mu}}= X^{\mu}+\xi^{\mu}(\eta, \vec{x})$$ where ##\xi^0=T, \xi^i=L_i## Show transformation of metric perturbation ##B_i\rightarrow \tilde{B_i}=B_i+\partial_iT-\partial_{\eta}L_i## Homework...
  7. J

    Programs European Cosmology groups for PhD

    Hi, I am planning to apply to some PhD programs in Cosmology in Europe. I've already identified some potential groups, but I'm sure that I'm still missing a few. I am interested in Cosmology in general (not a particular aspect/research area of it). Could you kindly inform me of any European...
  8. N

    Suggestion for cosmology overview

    I was wondering if I could get suggestions for good general-background book on cosmology and the development/evolution of the universe. This is for myself, and I'll leave any more specifics to the topics open as I'd be look into whatever suggestions I receive. I'm a biophysicist, and back in...
  9. L

    I Paul Steinhardt's cyclic model

    Hello. I think I don't understand very well the Paul Steinhardt's cyclic model of Universe(s). According to Paul Steinhardt, 2 universes get closer. Then, there's the big bounce, which products effects like a big bang. If 2 universes get closer, they have a (relative) speed ( speed is the...
  10. J

    Relativity Is Gravitation by Misner, Throne, Wheeler outdated?

    Hi! With the re-release of the textbook "Gravitation" by Misner, Thorne and Wheeler, I was wondering if it is worth buying and if it's outdated. Upon checking the older version at the library, I found that the explanations and visualization techniques in the sections on differential(Riemannian)...
  11. C

    B Electroweak spontaneous symmetry breaking

    This is a question that I have tried to pose several times without any success but, anyway, I would like to try again for the very last time. Asume for a moment that EW-SSB (electroweak spontaneous symmetry breaking) actually happened in our early universe. Imagine that our Standard Model of...
  12. D

    I Understanding the 2nd Term of the Friedmann Equation: Replacing U with -kc^2

    while deriving the friedmann equation using Newtonian Mechanics the 2nd term of the r.h.s is coming to be 2^U/(r^2*a^2) where U is a constt,but it is replaced by -kc^2/(r^2*a^2)?
  13. D

    B What is dark energy in the fabric of space-time?

    I know that according to Einstein's theory of relativity, space-time is like a fabric which can be pliable. Gravity is the shape, or the warping of that fabric. In this analogy, what would dark energy (the unknown form of energy that is causing the universe to expand) be?
  14. D

    Other What are possible research questions to pursue in cosmology?

    Hi all! I am currently trying to figure out a possible original research question that I can pursue in cosmology. I don't have ready access to a particle accelerator or anything like that so I would assume that it would have to be theoretical. I am sorry to ask such a broad question, but I don't...
  15. H

    I Gravitational time dilation in Weinberg's "Cosmology"

    I have a question about the gravitational time dilation explained in Appendix B of the book "Cosmology" written by S. Weinberg. Why can the author say "In the negative gravitational potential at the surface of a star clocks therefore tick more slowly than in interstellar space, or in the much...
  16. C

    A Press Schechter function -- the variance on mass scale

    In obtaining the Press Schechter function, the variance on mass scale is differentiated with respect to mass. The variance on a mass scale is a function of wavenumber k through the Power spectrum and transfer function. To eliminate k dependence, some value of k must be inserted into the...
  17. A

    Learn What You Need to Know for Cosmology Research

    Hello, I don't know if this is the right place to post this topic, I could not figure out the right one. I have recently finished my Masters in Condensed Matter. Now I want to follow a PhD where I can work/research on the dynamics of the Universe especially on dark energy, modified gravity...
  18. S

    How Does a Career Change to Astronomy Begin?

    Hi everyone, My name is Zack and I'm new to the forum. I recently changed careers from audio engineering to astronomy and am queuing up to attend the University of Oregon in about a year. I'm a big fan of all the historic great astronomers, scientists and others who have contributed to the...
  19. K

    I Implications of validating loop quantum cosmology

    suppose, for example, Pre-inflationary universe in loop quantum cosmology Tao Zhu, Anzhong Wang, Gerald Cleaver, Klaus Kirsten, Qin Sheng (Submitted on 22 May 2017 (v1), last revised 4 Jun 2017 (this version, v2)) The evolutions of the flat FLRW universe and its linear perturbations are studied...
  20. O

    B Age of the universe: observable or entire universe?

    I was wondering if we are only aware of the observable universe, and the actual universe could be infinite, what do we mean when we say the age of the universe is 14 billion years? Are we talking about the age of only the observable universe or the whole universe?
  21. J

    A Hawking and Unruh effects -- Differences and interpretations

    Hello, I am a bit confused on the relation between the Hawking effect(radiation) and the Unruh effect. What I understood with my little knowledge is that the Hawking temperature is the temperature that is emitted at the event horizon of a black hole as measured by an observer at infinite spatial...
  22. X

    Cosmology Modern Graduate Level Cosmology Textbook.

    I've been reading a lot of "Modern" Cosmology by Scott Dodelson and Introduction to Particle Cosmology by A. D. Dolgov and Cosimo Bambi. I like how rigorous and through Dodelson is but in 2017 it is quite dated. I love how modern and up to date Introduction to Particle Cosmology is but I wish it...
  23. X

    Courses Should I Take Graduate Level Cosmology?

    I'm a physics Ph.D student who just complete his first year of classes. I struggled a lot and found this year to be academically the hardest of my life. However in the end I did get excellent grades in all of my core classes. I would really like to take it easy next semester and only take 1...
  24. Riotto

    I Why do galaxy and galaxy clusters look so colorful?

    Why do galaxy and galaxy clusters look so colorful?
  25. D

    B How can anyone explain the universal equilibrium density problem

    With NASA defining this equilibrium density at 9.9 x 10<30 gm/cm3, how can an increasingly expanding universe maintain a steady density as it expands?
  26. S

    I Experimental bound on the scalar spectral index

    Based on the paper by Visinelli (https://arxiv.org/abs/1605.06449), He stated in page 6 that the scalar spectral index as given by the Planck 2013 data (https://arxiv.org/abs/1303.5076) is, ##n_s = 0.9655 \pm 0.0062~~## (##68\%## C.L.) but when I looked into the Planck 2013 paper, I did not...
  27. A

    B Wave-particle-duality and the evolution of the universe

    If I've understood correct, every particle in the universe exists in a waveform, which I've understood to mean propability where the particle does exist? Then which I've understood is, that the wave transforms into a particle only when observed, is this correct? Then if it is correct, how...
  28. L

    Filmmaker/Artist/Quantum Physics/Physics/Cosmology/Parent

    Hello folks. This thread is open for discussion among those who want to explore the similarities between the experiential principles found in art and physics.
  29. Beans56

    I Life permitting ranges for fine tuning constants

    Does anyone know What the life permitting ranges for the constants usually mentioned in the Fine Tuning argument are? i.e. h, G, e, rate of expansion, amount of dark matter ect... My thinking is that if they are just kind of randomly placed inside their respective ranges then that would indicate...
  30. L

    Other Quantum Information and General Relativity

    Last year I've finished the undergraduate course in Mathematical-Physics and Mathematics and this year I've started on graduate school on Physics in order to obtain a master's degree. What I'm really interested are two main topics: general relativity and quantum field theory. I also like...
  31. S

    A Calculating the power spectra of scalar perturbation

    I'd like to numerically calculate the power spectra of the scalar perturbation at the Hubble crossing in warm inflation, my problem is that I don't know how to do it. As I know, the Hubble crossing happens at the onset of warm inflation where the different modes become larger than the Hubble...
  32. J

    I Comoving mass density leads to linear cosmology?

    The Friedmann equation expressed in natural units (##\hbar=c=1##) is given by $$\left(\frac{\dot a}{a}\right)^2 = \frac{l_P^2}{3}\rho - \frac{k}{R^2}$$ where ##t## is the proper time measured by a comoving observer, ##a(t)## is the dimensionless scale factor, ##l_P=\sqrt{8\pi G\hbar/c^3}## is...
  33. fresh_42

    B Who is Lisa Randall and What Can We Learn from Her Interview?

    Lisa Randall (Harvard): https://www.physics.harvard.edu/people/facpages/randall Video: http://www.3sat.de/mediathek/?obj=62357 (41 minutes long, English, click the picture)
  34. T

    I Einstein Field Equations: PDEs or ODEs? - Thomas

    This past semester, I just took an introductory course on G.R., which translates to a lot of differential geometry and then concluding with Schwarzschild's solution. We really didn't do any cosmology. However, one of the themes that kept creeping up again and again is that in 4-dimensions...
  35. Gjmdp

    Studying What is better, Astrophysics or Cosmology?

    Even though Cosmology and astrophysics are pretty much the same thing, still there are some differences. Cosmology is like more mathematical, more theoretical. If you are a cosmologist you can apply ideas from String Theory or so. But if Astrophysics is more "experimental". I mean, obviously...
  36. D

    Schools How good is the cosmology program at OSU? (Ohio State University)

    I might be accepted to the OSU physics PhD program and I have mainly an interest in cosmology / early universe stuff. How is OSU's program in cosmology? I hear their astronomy program is very good, but how is their cosmology especially?
  37. R

    How can thermal fluctuations decrease entropy?

    https://en.wikipedia.org/wiki/Future_of_an_expanding_universe "Over an infinite time there could be a spontaneous entropy decrease, by a Poincaré recurrence or through thermal fluctuations (see also fluctuation theorem)"
  38. F

    A End of Inflation: Definition, Meaning & Models

    From cosmology, the end of inflation is usually defined as when the Hubble slow roll parameter is equal to one, ##\epsilon_{H} = -\frac{\dot H}{H^2} = -\frac{d\ln H}{dN} = 1## Is this really the definition of the end of inflation? Or is it for the standard cold inflation only? How about the...
  39. CassiopeiaA

    I Curvature and the size of the Universe

    I always have trouble understanding this concept. Please correct me if I am wrong somewhere in my line of thought. Is the universe finite or infinite? Using the famous balloon analogy, we can think of it as a finite expanding universe. But in that analogy the balloon has a curvature. Does the...
  40. phyzguy

    A Is Dark Energy an Illusion? A Closer Look at Concordance Cosmology

    What do people think of this paper? If I understand correctly, they are saying that the need for Λ disappears if we do N-body simulations that properly take account of GR. I think they are saying that past simulations have used Newtonian approximations that don't properly account for density...
  41. R

    Other A module choice between Cosmology and Fluid Mechanics....

    Hi all, I study Mathematics and Theoretical Physics at university. Next year, I'll have a choice between three modules; Thermodynamics and Statistical Physics Cosmology Fluid Mechanics My main interest is Condensed Matter Physics; therefore, thermodynamics and statistical physics is a given...
  42. J

    Cosmology - determining if a model universe would recollapse

    Homework Statement Show mathematically that a model with: Ω_M0 = 3 Ω_Λ0 = 0.01 Ω_R0 = 0 Ω_T0 = 3.01 is a model that re-collapses in the future. Be certain to indicate at what value of the scale factor 'a' the expansion reverses and becomes contraction. Homework Equations It's hinted pretty...
  43. binbagsss

    Schwarzschild spacetime proper time to fall radially inward

    Homework Statement Question attached My method was going to be: set ##r=R## and solve for ##n(R)## set ##r=2GM## and solve for ##n(2GM)## I was then going to integrate proper time ##s## over these values of ##r##: ##\int\limits^{n=cos^{-1}(\frac{4GM}{R}-1)}_{n=cos^{-1}(1)=0} s(n) dn ###...
  44. durant35

    I Many worlds and cosmological evolution

    Hello guys, I have a question that came up to my mind while thinking about the evolution of our universe and quantum mechanics. It involves cosmology so maybe that was the right spot to post it, and of course the moderators can do it if they feel it's more adequate for the thread, but my...
  45. R

    I Big Freeze and Law of convervation of energy

    (Kurzgesagt- In a Nutshell) says that in the Big Freeze scenario all the matter will decay in the end, how is this possible without breaking the law of convervation of energy?
  46. R

    I How does nucleation work in cosmology?

    In this article https://en.wikipedia.org/wiki/False_vacuum#Bubble_nucleation it says that "In the theoretical physics of the false vacuum, the system moves to a lower energy state – either the true vacuum, or another, lower energy vacuum – through a process known as bubble nucleation." What is...
  47. R

    How does Nucleation work? Relationship with vacuums?

    What is nucleation and how it works? In cosmology, which is the relationship that nucleation have with quantum tunneling, vacuums and Big Bang?
  48. L

    I Exploring Evidence and Data Pre-CMB in the Early Universe

    I have been looking online and in other resources for some answers to no avail. Thought I would sign up on astrophysics forums to find the answer.What is the evidence and data for the period before the cosmic microwave background (CMB) in the early universe? In other words, is the idea of energy...
  49. arnazkh

    How Can I Plot Multiple Alpha Values in Cosmology Using Python?

    Hello! I've been working on a code that solves the Friedmann equation with quintessence using a scalar field potential of the form x^(-alpha) where alpha is a free parameter. I would like to plot different values of alpha in the same plot with annotations for each. For now, my code has initial...
  50. Andy_K

    Cosmology Review of Hidden In Plain Sight Series

    Has anyone read the 7-book series http://amzn.to/2lwgn66 by Andrew Thomas? Just wondering what you think of his conjectures / speculations at the final sections of each book, i.e. on the link between relativity and quantum mechanics, equation of the universe, etc... I like that he...
Back
Top