Cosmology Definition and 948 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.

View More On Wikipedia.org
Recent contents Top users
  1. astroman707

    What math is used the most in cosmology/astrophysics?

    Considering one is taking all the required math courses for a typical physics degree, what math electives are most crucial to the field of cosmology/theoretical astrophysics? Also, is it true that mathematical modeling courses(discrete and dynamical modeling across physics) are more important to...
  2. F

    I Trying to reproduce curves with angle of CMB anisotropies

    I am looking for a way to get, by a simple numerical computation, the 3 curves on the following figure: For this, I don't know what considering as abcissa (comoving distance ?, i.e ##D_{comoving} = R(t)r## with ##R(t)## scale factor and ##r## the coordinate which appears into FLRW...
  3. F

    I BAO : Relation between redshift, Hubble constant and radial

    From this link https://en.wikipedia.org/wiki/Baryon_acoustic_oscillations#Measured_observables_of_dark_energy , I can't get this relation : ##c\Delta z = H(z)\Delta \chi\quad\quad(1)## with ##z## redshift, ##H(z)## Hubble constant at redshift = ##z## and ##\chi## radial coordinates. One...
  4. S

    A Multiverse theory with impossible universes?

    I found an article written by physicist George Ellis that confused me a little. http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.498.4569&rep=rep1&type=pdf At some part, he says: 3.2 Non-uniqueness: Possibilities There is non-uniqueness at both steps. Stating “all that is possible...
  5. D

    I Troubles understanding slow-roll conditions in Inflation

    I've been reading up on inflation, and have arrived at the so-called slow roll conditions $$\epsilon =-\frac{\dot{H}}{H^{2}}\ll 1\; ,\qquad\eta =-\frac{\ddot{\phi}}{H\dot{\phi}}\ll 1$$ I have to admit, I'm having trouble understanding a couple of points. First, how does ##\epsilon\ll 1##...
  6. shahbaznihal

    A Discuss Open Problems in Gravity & Cosmology | Join the Conversation

    I am making this thread to discuss interesting open questions in Gravity and Cosmology with people working in these or even relevant area. Anyone who is working in these (and relevant) areas, please identify yourself here and we will begin and hopefully people will catch on and contribute.
  7. E

    I Understanding the Ly-α Forest for EnSlavingBlair

    Hi, I'm currently trying to wrap my head around how the Ly-α forest works. This is what I have so far; A distant quasar produces these Ly-α photons, which occur when a hydrogen's electron drops from n=2 to n=1, and has a wavelength of around 121nm (depending on the exact transition). This...
  8. A

    Best Astrophysics Masters Programs in Canada: Recommendations and Opinions

    Hi to whoever reads this, Some back ground info: I am a current undergrad student halfway through their degree, and I'm starting to think about what I'd like to do after I receive my diploma. I know I want to continue studying, and possibly move to a different country to do that. I know I can...
  9. Avi Nandi

    A What are the frontiers of cosmology research?

    I have completed post grad in Physics and in the transition phase between post grad and Ph.D. I am interested in cosmology and also completed a post grad course on Astrophysics and Cosmology. Can anyone enlighten me about what are the current debates and active topics of research going on in...
  10. Urs Schreiber

    A No metastable type IIB de Sitter vacua

    Take note of today's Obied-Ooguri-Spodyneiko-Vafa 18. Curious situation: After it had influenced much the development of the string theory community’s attention and almost all of its public media perception since 2003, after what must be thousands of followup publications, the argument of KKLT...
  11. J

    I Does the Uncertainty Principle imply a linear cosmology?

    If the uncertainty in the age of the Universe is ##\Delta t## then the Uncertainty Principle implies that it has an uncertainty in its energy ##\Delta E## given by $$\Delta E \ \Delta t \sim h.\tag{1}$$ If this energy fluctuation excites the zero-point electromagnetic field of the vacuum then a...
  12. Malek

    B Are Antiparticles the Key to Understanding the Universe?

    There is an assumption in cosmology say that there is another universe Composed of antiparticles? I mean that the atom composed of positron rather than an electron, anti-proton rather than a proton and anti-neutron rather than a neutron.
  13. A

    Quantum Quantum field theory and cosmology

    Hello all, Can you tell me what is the best book to study QFT when you are thinking to follow a PhD in cosmology (Dark energy, scalar fields, extension to GR, string theory).
  14. J

    I Dynamical Casmir Effect in expanding space?

    The Dynamical Casimir Effect is the production of real photons from the vacuum in a system where one has moving mirrors (see https://www.technologyreview.com/s/424111/first-observation-of-the-dynamical-casimir-effect/). The frequency of the photons is related to the ratio of the velocity v of...
  15. platosuniverse

    B Doesn't there have to be more than one observable universe?

    I was just curious because if space can expand faster than light, doesn't that mean there will be a lot of space that we just can't see? Do objects just vanish because we can't see them? For instance, if a hypothetical alien lived in MACS0647-JD galaxy which is 13.3 billion light years away...
  16. Pouya Pourkarim

    I Why is Hawking Radiation Unequal for Matter & Antimatter?

    we say everytime a couple of matter-antimatter particles get born near the edge of a black hole one of them falls into it and the other one escapes. And we everytime mention that the antimatter particle kind of eats a bit of black holes mass out...and by time the black hole gets smaller and...
  17. Maha odeh

    A This is the most active place in the universe

    According to Source: They discover a mega cluster of 14 galaxies that originated only 1400 years after the Big Bang This is the most active place in this universe
  18. G

    B Is quantum physics "retro-deterministic"?

    The question relates to the deterministic views of people like Descartes or Pierre de Laplace, the infamous "an omniscient intelligence who could know precisely the position and momentum of every single particle in the universe would be able to predict the future with total accuracy, past...
  19. M

    Is Quantum-Geometry Dynamics the Key to Solving Modern Physics Conundrums?

    I've always loved physics, since my first science fiction novel in 1971. I won a scholarship to do a Math-Physics double honours program at University of Waterloo in 1977, but was immediately seduced into computer science by the promise of being paid big bucks to play with computers all day...
  20. binbagsss

    GR: conformally flat S-T cosmology

    Homework Statement Homework Equations look up, look down, your pants fell down The Attempt at a Solution [/B] Time-like killing vector is associated with energy. ## \frac{d}{ds} (\frac{\mu^2\dot{t}}{R^2})=0## Let me denote this conserved quantity by the constant...
  21. R

    I Why are non-relativistic particles not redshifted?

    Hey! I was reading some script and when it comes to the cosmological redshift, it says, that only relativistic particles are affected by cosmological redshift. This does feel quite natural, however, I haven't been able to come up with an explanation that shows it with proper physics and...
  22. E

    I Observational evidence against expanding universe in MNRAS

    << Mentor Note -- after a very long Mentor discussion, we acknowledge that this paper, while potentially controversial, has been published in a reputable peer-reviewed journal. We believe that a discussion of this paper can be useful and constructive. Thanks >> This paper of mine was...
  23. Mlesnita Daniel

    B What do I need to become an Astrophysicist?

    Hi! I just started high school and have developed a passion for cosmology and astrophysics. I would like to know if I really need to be very good at physics and mathematics (and if there is more that I need to be good at) and where do i find a job (spaces like N.A.S.A., SpaceX etc). Thanks for help!
  24. V

    Programs Cosmology and quantum mechanics as a joint degree?

    Is it possible for me to do cosmology and quantum mechanics as a joint degree at uni? If so where and does it cost extra? I’ve been wondering for a whole and I’m not sure where to look.
  25. Robert Shaw

    What's the energy-spread of the quantum Universe state?

    If the universe was in an energy eigenstate then d<A>/dt = 0 for any dynamic variable A. Stuff moves which implies that the Universe isn't in an eigenstate. What factors drive the energy spread?
  26. BlackholeGirl

    NASA [NASA] Cosmological projects instead of space exploration

    NASA decided to stop *WFIRST and concentrate on Mars project (send humans to Mars). What do you think about it? In my opinion, since a lot of ventures have begun space developments such as SpaceX and this proves that rockets make money, NASA should tackle WFIRST. Generally, we cannot earn...
  27. T

    Modern Cosmology Dodelson Problem 6.12b (Inflation)

    Homework Statement Show that ##4\pi G(\dot \phi)^2=\epsilon a^2 H^2## Homework Equations Over dots mean derivative with respect to ##\eta##. $$\frac{1}{a}\frac{d}{d\eta}=\frac{d}{dt}$$ $$H=\frac{\dot a}{a^2}$$ $$\epsilon=\frac{-\dot H}{aH^2}$$ $$(\frac{\dot...
  28. T

    Modern Cosmology by Dodelson: Problem 6.12 a

    Homework Statement The general goal of the problem is to derive some useful identities involving the slow-roll parameters during inflation. For part a show that: $$\frac {d} {d\eta} (\frac {1} {aH})= \epsilon - 1$$ Homework Equations $$\epsilon \equiv \frac {d} {dt} (\frac {1} {H})= \frac...
  29. J

    I Should the energy density of the vacuum be zero?

    According to [Dark Energy and the Accelerating Universe](https://ned.ipac.caltech.edu/level5/March08/Frieman/Frieman5.html) quantum field theory says that the energy density of the vacuum, ##\rho_{vac}##, should be given by $$\rho_{vac}=\frac{1}{2}\sum_{\rm...
  30. relatively-uncertain

    I How do CTCs allow a universe to self-create?

    So recently I saw a video with Richard Gott explaining a self-creating universe. There's three quick questions I'm confused about that I did not understand very well from the video: 1. How does a closed time-like curve allow the universe to self-create? Wouldn't the universe just go around the...
  31. W

    Courses Is astrophysics a prerequisite to study cosmology?

    I find it strange that astrophysics is not a pre-requisite to study cosmology in my university, students are only required to have taken general relativity. Is this a trend? How important would you say is astrophysics to learn cosmology?
  32. 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...
  33. 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...
  34. 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...
  35. H

    Other Can Independent Engineers Publish Scientific Papers Without Formal Affiliations?

    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...
  36. 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...
  37. 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...
  38. 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...
  39. 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...
  40. L

    I Is There an Extra Time Dimension in 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...
  41. J

    Relativity Is Gravitation by Misner, Thorne, 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)...
  42. 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...
  43. 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)?
  44. 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?
  45. 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...
  46. 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...
  47. 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...
  48. 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...
  49. 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...
  50. 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...
Back
Top