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328 discussions

the shape of the universe (fwd)
by Boud Roukema 20 Feb '06

20 Feb '06

hi everyone, We have a media question :). i don't want to spam people, so anyone interested, please respond on cosmo-media@ ... rather than cosmo-torun. Below are my proposed "compact" answers. Any corrections before i respond "officially"? Remember the number one rule of the dependent media: "anything you say may and will be misquoted against you". Which is why having this on the cosmo-media archive will at least, in principle, provide some defence... i don't know what time frame the journalist has in mind - but presumably the sooner the better for any answers. IMHO probably a day or two should be OK. pozdr boud > ---------- Forwarded message ---------- > Date: Wed, 15 Feb 2006 23:38:49 +0100 > From: t.rozek at fz-juelich.de > To: boud at astro.uni.torun.pl > Subject: the shape of the universe > > Dear Sir, > > I'm a physicist and scientific writer. Within the new project of Axel Springer publishing house (editor of Newsweek in Poland and Die Welt in Germany) in Poland I would like to invite you to the discussion about the shape of the universe. > > As I know scientific group you are the leader, in 2004 went public with the information that in the microwave background radiation picture there are some indications, that our universe has a shape of dodecahedron. > > Questions I'm asking you are the same like these I have sent to other expert in this field. I will not hide, that his opinion about the shape of the universe is different than your. > > I will be pleased to get from you compact answers to questions which are listed below. Please keep in mind that new Axel Springer daily will be addressed to nonspecialists in physics or astronomy. > > Let me thank you in advance for time you will spend to answer my questions. I'm looking forward to your respond. > > With the best regards > Tomasz Rozek ---------------------------------------------------------------------- > Questions: > 1. Analysis of the microwave background radiation are the only way > - I guess - to collect information about the shape of the > universe. Isn't it risky to draw conclusions resulting from only one > experiment ? Yes, it is risky to draw conclusions from only one experiment. We expect other scientists to read our paper carefully and make their own analyses of microwave background and other data. The most independent test of our work will be testing the prediction that the average, total density parameter of the Universe, including ordinary matter, dark matter and dark energy together, should be about 0.9% to 1.1% higher than the density which would make the Universe perfectly flat ("flat" means that Pythagoras' Theorem is true). This type of test is highly independent of our analysis method. > 2. Why this is commonly believed, that data from WMAP probe, brought > down the concept of flat and infinite universe ? The flat and infinite universe model is still consistent with the WMAP data. It is not the best model, but it is still consistent with the data and most observational cosmologists still take it as the best approximation we have. Please remember, however, that no theoretical cosmologists take the flat and infinite model as a serious model of the entire Universe - it is only treated as a limiting case inside the observable sphere. > 3. There are many ideas concerning the shape of the universe. Maybe > it is like a sphere, cylinder, funnel, but it can also be like bell, > horn or dodecahedron. Why do you claim that space is > dodecahedron-like ? We don't. The first misunderstanding is that "shape" means the shape of *space itself*, not the shape of *space inside of space*. Our intuition is developed to think of objects inside of three-dimensional, Euclidean, infinite space. In order to understand what is meant by the shape of the Universe, you first need to develop a method of thinking about the shape of space itself. A good place to start would be http://pl.wikipedia.org/wiki/Ksztalt_Wszechswiata . One example of a shape of space itself is a space with the name "Poincare dodecahedral space" (PDS). One "ordinary" shape, inside of space, which helps to think about the PDS, is the dodecahedron. The second misunderstanding is that so far our group only claims to have a "hint" of that the shape of space is the PDS. Our analysis follows that by Jean-Pierre Luminet's group. Ralf Aurich's group and Jesper Gundermann have also found similar (though not exactly identical) results. > 4. What are the errors or defects of the idea of horn-like space ? None as far as I am aware of. > 5. Could you in the very easy way explain the expression, that space > has a shape ? Imagine that space only has two dimensions, instead of three. Now we can use our existing intuition about three-dimensional space to imagine many different possible two-dimensional spaces inside of three-dimensional space. In this way, we use one dimension as a purely psychological dimension. It's used by our brain, but has no physical meaning for the two-dimensional space we're thinking about. Of course, real space has three dimensions (we can ignore the time dimension for discussion of "the shape of space"), so if you can now start thinking in four dimensions, then you can use the fourth dimension as a psychological dimension and think of differently shaped spaces, each having three dimensions. > 6. Do efforts to establish a shape of the universe have any > practical meaning or you are doing that just to know ? Both. It is practical to know the shape of a footpath or a tree or a mountain or an atom or a molecule, so it is practical to know the shape of the Universe. But it is also good to knowing the shape of a work of Picasso or a beautiful woman or man, even if this has no practical use. > 7. Did universe have a beginning, and ones will have the end ? The standard hot big bang model is very well established, and this model has a limiting time we can call "time equals zero". If we start today and think backwards towards "time equals zero", then our model of the Universe becomes more and more speculative as we get towards "time equals zero". So it is more realistic to say that we have a standard model which goes *towards* having a beginning rather than saying the Universe actually "had" a beginning. However, theoretical cosmologists have some ideas of universe models extending earlier than "time equals zero". ----------------------------------------------------------------------

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120 cell
by Jeff Weeks 06 Feb '06

06 Feb '06

Dear Boud et al., You intuition is correct -- there are some additional in-between layers. The attached images show layers 1 through 5. Layers 6 through 9 are of course symmetrical as you work your way towards the south pole. Note that the cells in layer 5 sit "vertically" with respect to the equatorial hyperplane (i.e. they're orthogonal to the equatorial hyperplane) which is why they appear flat in the attached image (each dark blue hexagon is the 2D shadow of a 3D cell when you project from 4D space to 3D space). Anyhow, here's the accounting: layer 1 1 layer 2 12 layer 3 20 layer 4 12 layer 5 30 layer 6 12 layer 7 20 layer 8 12 layer 9 1 ----------- total 120 Note that all numbers are "dodecahedal numbers", respecting the dodecahedral symmetry of the whole construction. The 120-cell is quite beautiful, isn't it? Best wishes to all of you, Jeff

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MG11 - Topology of the Universe (fwd) (and PDS - how many tiles?)
by Boud Roukema 06 Feb '06

06 Feb '06

hi everyone, The following is self-explanatory - you can reply to Marek directly - here is his email in antispam format (this list is publicly archived so better not write people's email addresses in ways that robots can read them): Marek.Demianski at fuw edu pl > ---------- Forwarded message ---------- > Date: Mon, 6 Feb 2006 15:02:38 +0100 (CET) > From: Marek Demianski > Subject: MG11 - Topology of the Universe > > > Dear Colleague, > > I have been asked to organize a parallel session on "Topology of the > Universe" at the XI Marcel Grossmann Meeting in Berlin, July 23 > - 29, 2006. If you are planing to attend the meeting and would like to > present a contribution at this session please let me know. Please spread this > information among your friends and collaborators. > > More information about the Meeting (and on line registration) you can > find at www.icra.it/MG/mg11. Please register by May 31 > to save 50EURO on the conference fee. > > Sincerely yours, > Marek Demianski BTW: i have a question on PDS (Poincare Dodecahedral Space) intuition which someone might be able to answer. A tiling of S^3 by the PDS has 120 copies of the PDS. If we think of this tiling starting from "here" at the "North Pole" (sorry Marcelo, this is North bias ;) (image 1) and we "stick" a copy (image 2) of the PDS next to itself along a North-Pole-South-Pole axis (e.g. X), and then moving along the X axis, we stick another copy (image 3) next to image 2, and then another and so on, then it seems to me that image 6 covers the "South Pole" and is the "antipode" copy of image 1. In other words, the "distance" between the poles is 5 copies of the FD. This allows an easy order of magnitude check on the total number of copies, since the "radius" of one hemi-hypersphere is 2.5 "copies", so that the total volume is roughly (using flat space arithmetic): 2* (4\pi/3) (2.5)^3 \sim 2* 2^2 * (5/2)^3 = 5^3 = 125 which is a good approximation to 120. (AFAIR, Jeff Weeks showed me how to do this - this is not original.) Now for my question: We have 6 "layers": North pole - 1 FD layer 2 - 12 FD's layer 3 - n FD's layer 4 - n FD's layer 5 - 12 FD's South pole - 1 Clearly layer 3 or 4 has more than 12 copies, there are some spaces that need to be filled. But the value required for the total to be 120, i.e. n= 47, is an odd number. Intuition says that everything should be even and symmetric. Can someone give a nice intuitive explanation for why n is odd and why this 12-symmetry is broken? Maybe a nice diagram? In fact, i have a partial answer: it seems to me there are some in-between layers, which we might call 2.5 and 4.5 and i guess also 3.5. But it's difficult for me to imagine them, and it's still difficult for me to imagine how the 12-symmetry is broken. It would be nice if someone had a nice diagram or intuitive explanation of how the 12-symmetry is broken. Going to a 122 tiling would save the tiling symmetry, but intuition says that 120 is better than 122. On the other hand, 2 * (1 + 12 + 48) = 122 seems simpler in terms of tiling symmetry. In the Nature paper, 120 is quoted: http://arxiv.org/abs/astro-ph/0310253 (After all, we *have* made a few minor mistakes in the past in our subject - e.g. when we said that there were uncountably many negatively curved 3-manifolds, and eventually, at MG IX (?), Jeff explained and showed us that the number was countably infinite - the classification is complicated and unfinished, but the number is countable.) cheers boud

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Re: Podreczniki
by Boud Roukema 31 Jan '06

31 Jan '06

witam On Tue, 31 Jan 2006, Karolina Wojtkowska wrote: > > Wszystkich pracowników Centrum prosze o przeslanie listy podrecznikow do > wykladów / ćwiczeń przez siebie prowadzonych. Jeśli to znacze, że Biblioteka może kupić kilka kopii książki, że traktuję jak podstawowy dla mój wykładu, wtedy polecam kupić 5-10 kopii Liddle'a po polsku: http://www.proszynski.pl/asp/fiszka.asp?ksiazka_id=1687 Jest nie drogi, więc nie widzę problem kupić kilka. W tej chwili wydaje mi się, jest tylko jeden w CA-UMK - ,,w katalogowaniu", plus jeden w BG: http://lx.bu.uni.torun.pl/cgi-bin/BG/Z2Wumk/z2w_f.pl?kl=23062-1045663056&di… pozdr boud

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sprawozdanie 2005
by Boud Roukema 30 Jan '06

30 Jan '06

czesc sorry, probably by the time you read this, the sprawozdanie meeting will already be over :P Anyway, here it is - only the first few slides are for the 10 minute presentation, of course - the other pages are "extra in-depth material" which you've probably already seen anyway. http://cosmo.torun.pl/~boud/spraw05pp4.pdf The interesting thing is that there are more and more of us IMHO :) we're starting to get near the numbers necessary to making research be more and more motivating, i.e. a real cosmology research group... :) Of course, let's see if we get our projects into good shape and publishable.... pozdr boud

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biblioteka
by Boud Roukema 26 Jan '06

26 Jan '06

Cześć wszystkim, W tej chwili mamy prośbę dać opinii o zakup między ,,standardowymi" książki konferencowych, każdy kosztują coś jak 100-200 euro, dla bibliotece CA-UMK. Ja znakowałem ksziążki, które mi oglądają jak użyteczny dla badania ekstragalaktycznego-kosmologicznego. Ale w ogóle, moglibyśmy prosić do Katarzyny zrobić nowy zakupy książki kosmologiczny, które jeszcze brakują. Chyba ostatnio raz, że zrobiliśmy, było 3 lata temu. Strona www z listę co znalezliśmy (czy kupiliśmy) ostatnio raz jest tu (na starym wiki, tzw. ,,zwiki"): http://adjani.astro.uni.torun.pl:9673/zwicky/BibliotekaCosmo Jeśli ktoś chce to kopiować/edytować do ,,nowym" wiki (twiki), bardzo proszę: http://cosmo.torun.pl/cgi-bin/twiki/view/Cosmo/BibliotekaCosmo Mój pryorytet w tej chwili dla książki byłoby raczej dla teksty podstawowych dla studentów - np kilka Peebles 1993 ,,zbiory" ? W tej chwili mamy dwie ,,czyt" (chyba to znacze, czytać na miejscu?): http://lx.bu.uni.torun.pl/cgi-bin/BG/Z2Wumk/z2w_f.pl?kl=23062-1045663056&di… I UMK w ogóle ma *wiele* Schutz: nowa edycja 2002 - 7 kopii http://lx.bu.uni.torun.pl/cgi-bin/BG/Z2Wumk/z2w_f.pl?kl=5217-1138283783&dis… (Nawet jeden u teologii :P). stara edycja 1995 - 5 kopii http://lx.bu.uni.torun.pl/cgi-bin/BG/Z2Wumk/z2w_f.pl?kl=5217-1138283783&dis… Być może kupimy też 2-3 dla CA-UMK - jeden ,,czytać na miejsce", dwie ,,zbior" ? Nie wiem jak jest doświadczenie ,,czyt" vs ,,zbior" w CA-UMK - chyba bibliotarka i studenci lepiej znają niż mnie... pozdr boud

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Accuracy of Planck vs. WMAP re universe age (fwd)
by Andrzej Marecki 24 Jan '06

24 Jan '06

There is a discussion thread on Planck mission on sci.astro.research. The 1st posting in this thread is attached. -- a. Newsgroups: sci.astro.research Subject: Accuracy of Planck vs. WMAP re universe age Date: Mon, 23 Jan 06 11:49:03 GMT Organization: http://groups.google.com Lines: 8 Approved: sci.astro.research-request(a)slimy.greenend.org.uk (mjh) Message-ID: <mt2.0-22784-1138016943(a)hercules.herts.ac.uk> Hi - does anybody have a rough idea of the increase in accuracy which the upcoming ESA Planck CMB Probe will give us regarding the age of the universe? The combined results of WMAP, BABAR et al gave us an age of ~13.7 (+/- .2) *10^9 years. Ie: How much will Planck improve on this value and its error bars? thanks, Gene -- end of forwarded message --

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[astro-ph/0510760] Constraints on changes in fundamental constants from a cosmologically distant OH absorber/emitter
by Andrzej Marecki 04 Jan '06

04 Jan '06

Better late than never... Only now I have spotted this: http://de.arxiv.org/abs/astro-ph/0510760 See also NRAO Press Release: http://www.nrao.edu/pr/2005/constants/ -- a.

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H_0 stuff - christmas/new year meeting...
by Boud Roukema 22 Dec '05

22 Dec '05

hi everyone, Bartek L should be around for the next few days or so, also Krzyszek K - we'll try to meet up to talk about H_0/jet stuff. If anyone else is interested in meeting, try to find us by email, sms, gabber/gadu-gadu or whatever. So far we don't know when/where we'll meet up... Weso³y ¶wi±t itd itd :) pozdr boud

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Nature's News Feature: Science in the Web age
by Andrzej Marecki 15 Dec '05

15 Dec '05

----- Forwarded message from NatureAlert <NatureAlert(a)info.nature.com> ----- [...] ---------------------- NEWS FEATURES ---------------------- Science in the web age: The expanding electronic universe Sarah Tomlin http://info.nature.com/cgi-bin24/DM/y/eV4x0BfWLH0Ch0qVj0ES Science in the web age: Joint efforts At its best, academia is a marketplace of ideas. But many scientists are reluctant to embrace the latest web tools that would allow them to communicate their ideas in new ways, says Declan Butler. http://info.nature.com/cgi-bin24/DM/y/eV4x0BfWLH0Ch0qVV0E7 Science in the web age: The real death of print Despite clashes with publishers over copyright, Google's plan to make millions of books available online is turning the tide for efforts to digitize the world's literature. Andreas von Bubnoff tracks the demise of the printed page. http://info.nature.com/cgi-bin24/DM/y/eV4x0BfWLH0Ch0qVk0ET Science in the web age: Start your engines Google has launched another challenge to commercial search services - this time aimed at scientists. But is the new engine running as smoothly as its fans hope? Jim Giles investigates. http://info.nature.com/cgi-bin24/DM/y/eV4x0BfWLH0Ch0qVW0E8 [...] ----- End forwarded message ----- P.S. The access to these articles is free. a.m.

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