Cosmology Definition and 952 Threads

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...

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...

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...

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...

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...

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...

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...

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...

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

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).

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...

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...

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...

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...

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:

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...

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

What is the difference between Astronomy and 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...

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...

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...

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...

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...

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...

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.

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...

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...

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?

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...

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...

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...

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...

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...

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...

arXiv:0901.1956 [ps, pdf, other] Title: A Critique of the relativistic cosmology Authors: R. K. Thakur Comments: 8 pages, Comments welcome Subjects: General Physics (physics.gen-ph)

Homework Statement a) Using the Robertson-Walker metric, write down an expression for the proper distance in terms of the coordinate r. For objects moving with the expansion of the universe, show that the proper distance increases with time in the manner described by the Hubble Law. b) Use...

SDSS is perhaps the most ambitious astronomical survey ever undertaken, and it has provided a wealth of new data. Unfortunately for cosmologists (or fortunately, if cosmologists are willing to re-group), some of the findings are quite inconsistent with their expectations. Scroll down to Nov 2...

http://arxiv.org/abs/0812.2720 Chandra Cluster Cosmology Project III: Cosmological Parameter Constraints A.Vikhlinin, A.V.Kravtsov, R.A.Burenin, H.Ebeling, W.R.Forman, A.Hornstrup, C.Jones, S.S.Murray, D.Nagai, H.Quintana, A.Voevodkin ApJ, in press: Feb 10, 2009 issue (Submitted on 15 Dec...

People find their own ways of making sense of modern cosmology. Unless they are utterly unable to get comfortable and reject it whole hog (as some do quite vehemently :biggrin:). If you have a way of making your peace with cosmology, feel free to describe how you do it. Or try this recipe and...

First i need someone to help break it down what's the difference. Instead of just saying the origins of space is cosmos. Ima tell you what I am interested in and let me know which one i will do better in. I am interested in learning about space and how it was created, not only I am interested in...

[37] arXiv:0811.4684 [ps, pdf, other] Title: Six Puzzles for LCDM Cosmology Authors: L. Perivolaropoulos Comments: 9 pages, 3 figures. Invited article to the TSPU anniversary volume "The Problems of Modern Cosmology" on the occasion of the 50th birthday of Prof. S. D. Odintsov Subjects...

I have to write a 4000 word paper for my Astronomy 302 (Foundations of Cosmology) class and I really do not know what to do. I was thinking about doing it on the effects black holes on the furture of the universe but I can not find any scholarly peer-reviewed journal articles on it to write a...

Homework Statement For K=0 of matter dominated universe, i.e at z>>1, find the energy density of starlight if f portion of matter condensed in solar type stars and the stars are uniformly distributed in space. Homework Equations Friedman eqn: \rho_m = \frac{3H^2}{8 \pi G} The...

Learned Gentlemen, My Doctorate is in Medicine, so my questions and comments might be below you. Where can I ask questions and make comments about an issue in cosmology? Thanks, tfb

Quantum Wave Cosmology is a niche in cosmology that consists of a group of “not easily refuted” protoscience ideas about a universe composed of nothing but energy. A few QWC ideas include: The universe is composed of one commodity, energy. Energy cannot be created or destroyed and so...

arXiv:0810.1285 [ps, pdf, other] Title: iCosmo: an Interactive Cosmology Package Authors: Alexandre Refregier (1), Adam Amara (2), Thomas Kitching (3), Anais Rassat (1) ((1) CEA Saclay, (2) ETH Zurich, (3) Univ. Oxford) Comments: 5 Latex pages including 2 tables and 4 figures. Submitted to...

arXiv:0809.1084 [pdf] Title: Practical cosmology and cosmological physics Authors: Yu. Baryshev (1), I. Taganov (2), P. Teerikorpi (3) ((1)Astron. Inst. St.-Petersburg Univ., (2)Russ. Geograph. Soc., (3)Tuorla Obs. Turku Univ.) Comments: 16 pages, summary of the conference "Problems...

First question: According to Hubble's Law, the redshift observed by distant galaxies are proportional to their distance. This is what I already know: It says on wikipedia that Hubble observed cepheid variable stars in a spiral nebulae to calculate their distance, cepheid variable stars are...

I would appreciate some guidance. I don't get very far in reading peer-reviewed papers before I'm really confused --- they're way beyond my level. Even some posts on this forum are a little beyond me. And "popular" books can be misleading or just plain wrong ---and there are LOTS of...

Nice picture of quasar accretion disk---pat on back for standard cosmology in Nature The 24 July issue of Nature reports some beautiful observational work, using a polarized light filter. Actually able to SEE the hot blue accretion disk whirling around a supermassive black hole at the center of...