What is Cosmology: Definition and 918 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. marcus

    Henderson video: spinfoam approach to cosmology

    Henderson gives a good talk. He's been working with Abhay Ashtekar on reformulating loop cosmology as a spinfoam-like path integral---also using GFT (group field theory) where a parameter shows up that may have physical interest (possible connection with the cosmological constant). He got...
  2. J

    Is evolution part of cosmology?

    Is evolution (Darwinian) considered part of the science of cosmology? or would that be another subject entirely?
  3. L

    Questions on Relativity & Cosmology Regarding Galaxies

    I'm confused a little bit by this and have a few questions. I wasn't sure where to put this because it's kind of a relativity question (time dilation) and a cosmology question combined. From what I understand, all galaxies are moving away from us. But isn't the Andromeda galaxy eventually...
  4. E

    String theory cosmology on inflation, CMB, gravitional waves?

    cosmology strings vs loops How well does string cosmology account for inflation, CMB, gravitational waves, evolution classically using FRW metric? does string cosmology offer either qualitative or quantitative predictions? This paper addresses these in the loop framework...
  5. D

    Curvatue Cosmology for a static stable universe

    Curvature Cosmology is a cosmology based on two hypotheses. The first, curvature redshift, is an interaction between photons and curved spacetime and produces the observed Hubble redshift. It can also explain the anomalous Pioneer 10 acceleration. The second, curvature pressure, is a...
  6. X

    Cosmology or Theoretical Physics for job?

    ¿Cosmology or Theoretical Physics? I have a dilemma. I have an offer for Cosmology and I have an offer for Theoretical Physics. I'm ofcourse aware of both fields, but I would like to know from you what their main differences are. Thank you!
  7. P

    Special Relativity / Cosmology

    2 galaxies are "moving" away from each other due to the expansion of space, if each is moving away at 3/4 the speed of light relative to the other would they not be moving faster than light relative to each other? Is the expansion of space limited to 1/2 light speed ? Does the law of non...
  8. C

    How Does Energy Density Change with Scale Factor in Cosmology?

    Homework Statement The fluid equation in cosmology is given as: \dot{\epsilon} + 3*(\dot{a}/a)*(\epsilon+P) = 0 Where \epsilon is the energy density and a(t) is a scale factor. Using the equation of state, P = w*\epsilon, show how \epsilon change with a(t). Homework Equations...
  9. planethunter

    God & Cosmology: Perceptions & Opinions

    A pretty loaded title for the thread (I know). I would like to know what are everyone's perceptions/opinions regarding the beginning of the universe (of time) as it relates to the notion of a god or God?
  10. O

    Entropic gravity and cosmology

    Entropic gravity and cosmology The considerable impact of Verlinde’s recent paper in which he suggests that gravity is nothing but an entropic force has familiarised many with this type of force. Verlinde wrote: The examples he mentions involve constituents in thermal equilibrium with...
  11. F

    Theoretical Physics vs Theoretical Cosmology

    What exactly is the difference? The latter does not seem so popular to me? On average how much does the latter earn?
  12. A

    Good Cosmology Books: Recommendations

    Hey! Can you please recommend me some good and up to date cosmology books? Thanks!
  13. Physics Monkey

    Loop Quantum Cosmology: Exploring Physics

    Hi everybody, I would like to chat about the physics of loop quantum cosmology. Let me list a few broad topics I'm interested in understanding better: 1. What simplifications/approximations make loop quantum cosmology a solvable simplification of full loop quantum gravity? 2. How is...
  14. S

    Astronomy, Astrophysics, Cosmology, Planetary Science

    What exactly are the differences between Astronomy, Astrophysics, Cosmology, Planetary Science?
  15. G

    Programs Best Physics PhD Programs in Cosmology?

    What are the best "2nd tier" physics PhD programs known for cosmology? Thanks
  16. Ivan Seeking

    Astronomy or Cosmology Christmas gift ideas

    I have a friend asking for ideas for an A or C oriented gift, including things that might be a bit of a scam, like having a star named after you. I know that you can buy land on the moon but that is expensive. Any ideas?
  17. R

    Cosmology: Horizon of the universe

    Homework Statement This is what the question says exactly: Assume the universe today is flat with both matter and a cosmological constant but no radiation. Compute the horizon of the Universe as a function of \OmegaM and sketch it. (You will need a computer or calculator to do this).Homework...
  18. C

    Cosmology Time of Decoupling

    Homework Statement At the time of decoupling the universe was 1/1000 of its present size. How for could light have traveled in the time up to decoupling? (assume that the universe was dominated by radiation until then) Homework Equations The Attempt at a Solution I'm a little...
  19. A

    How Much Does Your University Reputation Matter for PhD Applications in Cosmology?

    So, I'm interested in the big questions. I guess that leads me towards cosmology - though, quantum or particle physics, or string theory are also tied to the stuff that I want to find out. I'm doing my BS in physics right now and I'm trying to figure out where I want to go for the PhD. I...
  20. B

    Cosmology inequality that I'm struggling to make sense of

    My lecturer has written the following:Given \frac{4 \pi \rho a^3 c^2 }{3} and V = \frac{4 \pi a^3}{3} , then substituting \frac{dE}{dt} = -p\frac{dV}{dt} we have: \frac{d(\rho a^3)}{da} = -\frac{3pa^2}{c^2} \leq 0 (1) Ok that part is fine - substitute and use the chain rule: So, if we...
  21. B

    Cosmology Raw Data: Access Unanalyzed Experiments

    I was reading Roger Penrose's book and he mentions that there are huge amounts of raw data from experiments that haven't yet been fully analysed. Is there a way I can get my hands on this raw data, for cosmology experiments or any other experiments with large amounts of raw data? I know that...
  22. M

    How Do Observers Measure the Universe's Age and Size in Cosmology?

    Forgive me if these questions are asked here a lot, but I couldn't find any posts answering them in the first few pages... I'm just starting to learn a bit about cosmology...because I'm currently learning general relativity. I'm just curious, what does it mean to say that the universe has a...
  23. E

    What is most influential candidate quantum cosmology today?

    What is the most influential candidate quantum cosmology today? By influential it (a) reproduces known observation, (b) offers speculative ideas in the Planck epoch, (c) professionally researched and published in peer-reviewed journals. I suppose the time line should be 2007-2009 The two I am...
  24. N

    M branes in Cosmology, PhD inquiry

    I'm considering a PhD in cosmology, but the university I'm interested in focuses particularly on models based on branes. I'm finding it difficult to get information on the specifics of this topic, but for the moment i'd just like to know whether it is entirely based in string theory. In...
  25. M

    What is the boundary of the observable universe in the Milne universe?

    What is the difference of cosmological horizon and particle horizon in cosmology?
  26. P

    Astronomy vs Cosmology: Understanding the Differences Explained

    Hi all, This question may seem innocent, but I can't see a clear boundary between the two. Who could explain it please. (as short as possible).
  27. S

    Future in Cosmology: College Requirements & Pay

    Alrite I am sure this question has been asked many times. What do i need to take in college for a future in cosmology? i don't want to waste too much time in school but if i have to I am willing to do it, and i was wondering if a job in cosmology paid well? if so or not how much?? I've also...
  28. MathematicalPhysicist

    Programs A phd in pure maths and postdocs in theoretical physics (cosmology).

    Is this unheard or a lot of people do such a thing? I mean if someone like me would like to do research in both areas, but knowing that doing 2 phds is too much (although I have read of a few who have done two phds one in CS and one in maths), I think my compromise would be to do first in pure...
  29. putongren

    Quantum Cosmology - Imaginary Time

    I have trouble understanding the concept of imaginary time. As I understand it (by reading other online sources), imaginary time was developed by Stephen Hawking and Hartle in their theory of quantum cosmology. Quantum cosmology is applying quantum mechanical principles to cosmology as a...
  30. O

    Multiverse Cosmology: Exploring Physicists' Views

    I really know nothing whatsoever about cosmology although I find it very interesting. It seems that a lot of physicists nowadays reckon there's a multiverse. I don't particularly want there to be a multiverse. WHAT DO YOU FOLKS THINK. Also, if there was a multiverse, would the laws of physics be...
  31. J

    How Can Beginners Learn Physics and Cosmology Effectively?

    Hi everyone, I'm a new member. Just joined tonight, actually. I'm new to physics & cosmology. I'm here to learn as much as I can because it all feels natural to me. Hopefully some of you can better help me understand the basics and help me learn all I need to know. :blushing:
  32. marcus

    Exploring the Language of Cosmology Basics: Introducing Terminology to Newcomers

    In this PF Cosmo forum context we have to be sensitive/practical about language. How to state cosmo basics, especially to newcomers who may not have assimilated technical terms like "scalefactor" yet. This does not mean we dumb everything to the max! Introductory terms should lay a basis of...
  33. E

    Recommend a textbook of cosmology

    I am a graduate student. I want to study the cosmology, now. Can someone recommend a textbook of cosmology?
  34. S

    Difference between Astronomy and Cosmology is?

    What is the difference between Astronomy and Cosmology?
  35. T

    Exploring the Limits of the Balloon Analogy for Cosmology

    The analogy always used is to draw two points on the surface of a balloon and then blow air in the balloon. The points move away as the balloon expands. The issue I have with this is: now draw a "meter stick" on the surface of the balloon. It expands too, at the same rate, so that the number...
  36. marcus

    What causes the research interest in cosmology?

    I just happened to notice a way to gauge the degree of research interest in cosmology---which I think has something to do with its importance in uncovering new physics. What this does is search Stanford's Spires HEP database for the overall most highly cited physics papers that have appeared...
  37. T

    Electromagnetic in cosmology

    Homework Statement Title should be: ELectromagnetic signals in cosmology. \int\frac{d\rho}{\sqrt{1-k\rho^2}}>=-\int\frac{dt'}{a(t')} The integrals being from r1 to r and t1 to t respectively. I can't understand the need for the prime here. Could someone explain to me the significance of...
  38. P

    Theoretical Cosmology: PhD Programs & Math for UK Students

    Hey people. I hold an Astrophysics Msci (undergraduate masters) at 2:1 in the UK, and I'm currently preparing to apply to PhD programmes in 6-7 months time. I have a few questions. I'm interested in theoretical cosmology, and theories of galactic evolution - I'm looking for good universities...
  39. J

    Recommendations for Cosmology DVD for Kindergarteners

    Can someone please recommend a cosmology dvd? In Amazon, I see very good review for Carl Sagan's cosmos dvd set. But I'm wondering since it was made in 80's, the the graphics would be inferior. Has anyone watched it? I would like to show it to my daughter (kindergarten), hoping she would develop...
  40. C

    Programs Cosmology PhD in oxbridge - what are my chances?

    Hello everybody! I'm about to make an important decision concerning my PhD, and I'm totally lost. Here is my situation: I'm about to finish my MSc in physics (cosmology) in my home country (which is neither in the USA nor in Europe). I suppose my university is quite good by international...
  41. nicksauce

    Cosmology Book Suggestions: Upper Undergrad/Grad Level

    I'm looking for a comprehensive introduction to cosmology at the upper undergrad or grad level. Any suggestions? I took out Narlikar's (An introduction to cosmology) book from the library, and it looks alright, but I would like some suggestions on other books as well.
  42. Q

    Cosmology Question: Finite Universe with Overdensity & Cosmological Constant

    Hi All Let's assume the Universe's topology is a standard hypersphere (i.e. it's finite) and it's only a bit over-dense (Ωo = 1.02 - 1.01.) Say it has a mass-energy break-down like our own, 27% matter and 73% cosmological constant. In that case how do we work out its current radius? Can it...
  43. T

    Connecting with Fellow Cosmology Enthusiasts in Brisbane

    Hi! I'm a law and business student in Brisbane, Australia and have recently developed a keen interest in cosmology, physics and all the rest of it! I am sorry to not pose an intellectual question of the calibre of the other "newbie" :) but I am feeling somewhat disconnected from my peers at...
  44. E

    Can information be transmitted faster than c in inflationary cosmology?

    can information be transmitted faster than c in inflationary cosmology where with a large positive cosmological constant, space is itself expanding in an exponential faster than c manner?
  45. marcus

    Path Integral formulation of Loop Cosmology (a first)

    Today (17 March) we got our first news of a Path Integral formulation of LQC. Adam Henderson is a PhD student in Ashtekar's group at Penn State. He gave an internationally distributed seminar talk on his research. http://relativity.phys.lsu.edu/ilqgs/henderson031709.pdf...
  46. I

    Exploring Cosmology with Balloons and Foam: A New Perspective

    Hi, to pick up on marcus' https://www.physicsforums.com/showpost.php?p=2015482&postcount=67" in the sticky thread: Recently, I tried to see where this analogy could bring us if evaluated properly, and I was surprised to find that it is actually far better than what marcus pessimistically...
  47. marcus

    Tests of LQG in cosmology (proposals, prospects etc)

    In the last couple of years there'v been several papers on this, often by people I hadn't heard of before. The question came up in another thread "can you summarize in a single post" the various ideas being discussed? Personally I couldn't but I can dig up some links. Toss them out for you to...
  48. Dadface

    Does cosmology have the answers?

    Armed with a mass of observations and mathematical equations cosmologists tell us that the universe started with a big bang and that its ultimate fate is,as yet,unknown.Fair enough but now the ordinary person in the street is starting to believe the big bang theory and that we will soon have a...
  49. Fredrik

    Definitions (continued from the cosmology forum)

    This is a reply to a comment made in the cosmology forum. That's not correct. Do you really believe that physicists are that dumb? The real story goes something like this: The speed of light is a constant in the real world. Therefore, we define a mathematical model in which the speed of...
  50. wolram

    Cosmology: Futility of Exploring Beyond Our Solar System

    Since the speed of light has been proven to be an absolute limit on the speed of travel, it is obvious humans will never reach beyond our solar system, humans may do some fantastic parallax measurements, but beyond them we will never have any thing other than a rubber ruler to measure with...
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