# Cosmology

- The origin, evolution, structure and eventual fate of the universe.
 Meta Thread / Thread Starter Last Post Replies Views Views: 5,005 Announcement: Follow us on social media and spread the word about PF! Jan16-12 Pinned: Effort to get us all on the same page (balloon analogy) ( 1 2 3 ... Last) To have an enjoyable cosmo forum we needed a balance between mental freedom on the one hand and a shared knowledge... Aug2-14 07:51 PM marcus 493 167,757 The new A20 tabular calculator lets you look at changing geometry out to about 88 billion years according to the... Jun11-14 11:00 AM Jorrie 65 45,915 How much is it feasible for us to send some probe/s to the event horizon of a black hole? Perhaps Voyager will... Oct19-13 08:10 PM mfb 5 2,337 Hi everyone, Can anyone point me into the right direction on how to compute the deceleration parameter (##q_0##)... Oct19-13 06:11 PM roam 5 884 Now I think there are arguments for the Fine Tuning of the universe. I like Martin Rees' book but I know there are... Oct19-13 05:49 PM MrAnchovy 12 1,089 Hello, We know that according to Hubble's law V=HD that velocity of distant galaxies are proportional to distance... Oct18-13 03:02 PM mfb 3 795 I recently received a private communication that raised this question? I find that I personally cannot imagine the... Oct18-13 09:16 AM us40 31 26,271 Hello, According to Stephen Hawking no boundary condition universe does not have any boundary in space time.If it... Oct17-13 01:21 PM bapowell 5 1,042 I've tried to google the answer but either I'm not reading it clearly or there is no actual answer, but is space... Oct15-13 04:08 PM Tanelorn 30 46,280 If space is expanding like balloon and it disappears wrinkles on surface than after sometimes surface will become... Oct15-13 12:11 PM Adam_Smith 4 925 After the Big Bang the matter of the universe started to condense and we ended up with matter built up of neutrons,... Oct15-13 11:49 AM mfb 1 1,192 Hi all! In Ruth Durrer's book "The Cosmic Microwave Background" there is this picture (Fig. 5.2 page 193) about the... Oct13-13 05:06 PM fairy._.queen 10 2,355 Hi Guys, Just finished watching an episode of Through the Wormhole, where they discuss the Big Bang Theory. I must... Oct12-13 08:01 AM D H 27 19,517 Why is photon gas pressure = photon energy density (per volume) divided by 3? Thank you Oct11-13 08:07 PM andrewkirk 5 3,647 If the universe is a 3 dimensional (plus time) space expanding into something, what is that something? Am I correct... Oct9-13 11:40 PM Genocide 2 1,220 ] arXiv:1310.2072 Intermediate inflation from rainbow gravity John D. Barrow, Joao Magueijo Subjects: Cosmology... Oct9-13 09:17 PM UltrafastPED 1 946 Is dark flow evidence of other universes? Oct9-13 08:37 PM Chronos 2 804 Is it within the realm of physics or cosmology to refer to a dimensionless void that may have preceded the big bang? ... Oct7-13 11:56 AM bapowell 7 7,126 Suppose gravitons do leak into Calabai Yau spaces thereby dragging 3 dimensional space in with them and suppose in the... Oct7-13 04:13 AM ZapperZ 13 2,989 Does a FRW universe with the equation of state: $$p = -\frac{\rho c^2}{3}$$ have a singularity at the Big Bang?... Oct5-13 12:42 AM Chalnoth 2 2,245 I'm confused about the relationship between two seemingly different concepts of flatness of the universe. 1.... Oct4-13 05:27 PM Chalnoth 7 4,480 Why Yab=Xab-kHab+k2HacHcb-... and not Yab=Xab-kHab+(1/2)k2Haccb-...? Y is the curved space-time metric X is the... Oct4-13 04:00 PM maica 6 1,784 When we 'look' at blackholes, we see matter being sucked into it and compressed to an infinitely dense point, a... Oct4-13 12:00 PM mfb 1 1,071 Most people here I think will agree that in order to understand what happened at the big bang we most likely need a... Oct4-13 02:04 AM skydivephil 2 1,585 It makes no mathematical logic to say the universe started with a minute pinhead sized mass that suddenly exploded and... Oct3-13 03:35 PM Khashishi 3 1,656 Hi, I can't visualize how the universe could be infinitely flat according to the big bang theory... The only way... Oct2-13 10:01 PM Chalnoth 10 7,165 So for my physics class, we are trying to find modern applications for different areas of research. I know the HST had... Oct1-13 04:05 AM Bobbywhy 2 1,740 So the observable universe is flat overall but warped (compressed) in locations of gravitational fields. Is it the... Sep30-13 05:13 PM Drakkith 11 2,104 In the far distant future, will all of the stars in a galaxy be pulled into one giant black hole in the center? Are... Sep30-13 10:21 AM Chalnoth 2 2,280 If a small round black hole is traveling normal to the center of the major plane of a larger toroidal black hole, is... Sep28-13 09:32 PM Drakkith 34 11,733 Suppose space is expanding in the universe, then there must be void outside the universe. If this theory is true, what... Sep28-13 02:36 PM D H 7 1,310 Planck CMBR data... Sep27-13 04:00 PM mfb 6 1,406 Are gravitons and gravitational waves analogous to photons and EM radiation? Sep25-13 08:28 PM Drakkith 6 1,863 Not everyone likes the idea of Universe ​​created from a point singularity, so recently grows in popularity the cyclic... Sep24-13 09:12 PM bapowell 3 2,901 I'd just like to preface by saying that I'm not in any way an expert on high-level physics, but I would like to think... Sep24-13 09:21 AM Chalnoth 7 2,348 A short but interesting way of using the CMBR to test the quatization of gravity, what do you think ? Lawrence... Sep23-13 04:29 PM mfb 1 984 This is a phrase I keep seeing dicussed in cosmology papers, can anyone give a summary of what "Galileon cosmology"... Sep23-13 08:59 AM skydivephil 2 937 Dark Energy is said to be present in order to drive the observed acceleration of the expansion of the universe and... Sep22-13 12:50 PM Astronuc 9 2,067 http://arxiv.org/abs/1309.1487 Out of the White Hole: A Holographic Origin for the Big Bang Razieh Pourhasan,... Sep20-13 12:41 PM Chalnoth 8 2,655 Hi, Are Einstein's field equations without the cosmological constant scale invariant? If so does the addition of... Sep20-13 07:17 AM TrickyDicky 10 1,599 One version of the multiverse suggests that our bubble universe came from a progenitor universe and that our universe... Sep20-13 05:05 AM skydivephil 5 1,200 It could be possible for a driven vacuum bubble (like an Alcubierre drive,assuming that it could be possible to... Sep19-13 01:41 PM Chalnoth 1 943