Talk:Observable universe

Misconceptions section: 24 Gpc a diameter or radius?

Recently in this edit Natty4Bumpo suggested there was some ambiguity about whether 24 Gpc is a radius or diameter, writing (and using this article as a reference):

Some have suggested this figure is incorrect; however, Dr. Cornish when answering questions about how the Universe could be 156 billion light years across stemming from the 2004 Space.com article, which first published the figure, through the website's commentary section made no attempt to correct the figure, leaving some ambiguity on the question.

I was pretty sure 24 Gpc was a diameter, for two reasons: 1) multiple other sources say the radius of the observable universe is around 14 Gpc, and it doesn't make sense that looking for repeating patterns in the CMBR would allow you to rule out finite universes significantly larger than the observable universe, and 2) the draft of the Cornish et al. paper on arxiv.org says (as noted in the article) "By extending the search to all possible orientations, we will be able to exclude the possibility that we live in a universe smaller than 24 Gpc in diameter". But just to be sure, I emailed Dr. Cornish to confirm, and he wrote back:

The 24 Gpc is a diameter. Unfortunately our friends in the press read it as a radius, doubled the result, converted to light years and quoted 156 billion light years. I think I was misquoted once, then it got repeated.

I realize a personal communication like this can't be cited in a wikipedia article, but I think the quote from the draft on arxiv.org paper was already pretty definitive, and Natty4Bumpo's argument above seems to violate the WP:No original research rule, specifically the part about coming up with original arguments based on inferences from published sources in WP:No original research#Synthesis of published material that advances a position (the cited source doesn't have Cornish specifically commenting on the 156 billion ly figure, so taking his failure to correct it as evidence that the arxiv.org paper might be wrong seems to go beyond anything explicitly stated by Cornish). So based on the above, hopefully Natty4Bumpo won't object if I revert this edit. Hypnosifl (talk) 19:00, 8 February 2011 (UTC)

Approximate value?

I feel that the '=' should be replaced by '≈' in the following equation. $\frac{5 \times 10^{21}\ \textrm{stars}}{4 \times 10^{30} \ \textrm{ly}^3} = 10^{-9} \ \textrm{stars}/\textrm{ly}^3 = 1\ \textrm{star} \ \textrm{per}\ \textrm{billion}\ \textrm{ly}^3$

While this is technically correct comment for the first equality, I think it is pretty clear and don't see need to change. However I think the level of precision in the section on Matter Content and on Critical Density is rather high in parts and most numbers should be reduced to 1 or at most 2 significant digits. Gierszep (talk) 20:19, 17 April 2011 (UTC)

Distance in KM

9,460,800,000,000 * 93,000,000,000 = 879,854,400,000,000,000,000,000

Eight hundred and seventy-nine Sextillion, eight hundred and fifty-four Quintillion and Four Hundred Quadrillion km to the edge of the visible universe..

Is this right? Neobenedict (talk) —Preceding undated comment added 11:56, 9 May 2011 (UTC).

A light year is exactly 9,460,730,472,580.8 km, so if you want to round it off to five significant figures it should be 9,460,700,000,000 km. And 93 billion light years is the diameter of the observable universe (not the visible universe, see the distinction in the second paragraph of the intro), the distance from us to the edge of the observable universe would only be half that (14.3 billion parsecs works out to 46.6 billion light years). So, 9,460,700,000,000 * 46,600,000,000 = about 4.41 times 10²³ km, or 441,000,000,000,000,000,000,000 km (Four-hundred and forty-one sextillion km). Hypnosifl (talk) 00:10, 19 May 2011 (UTC)

Shrinking Observable Universe???

The statement "in practice an increasing number of galaxies will become extremely redshifted due to ongoing expansion, so much so that they will seem to disappear from view and become invisible." is wrong in spite of the multiple references. This is due to a misinterpretation of the theory. The theory states that we will never be able to see objects that currently exist (but are not yet visible) because the light from them will never get to us - true, but we will always be able to see something at any place in the universe that we can currently observe. It will just appear to be aging much more slowly due to the red shift. We will simply never get to see that part of the universe when it gets to be 13.7 Billion years old as it actually is today. (Which is what the reverences mean.)

The background radiation is redshifted about 1098 times. That means that what we currently see only appears to be aging about 1 day in every three of our years. We will always be able to observe this background radiation. No mater how much the universe expands or how much faster the expansion rate gets, the background radiation will fill every part of the universe. We will always be seeing some part of the universe just transitioning into a neutral gas where the background radiation appears and it will always be 300 Million years old as timed from the Big Bang. But it will be even more redshifted and it will appear to us to be aging even more slowly than what we now see. Even if inflation stopped today, in order to see the part of the universe that we currently see as background radiation age to 13.7 Billion year would take 15 Trillion more years. Since inflation is not stopping today, we will never see that part of the universe at age 13.7 Billion year. (That is what the theory means.)

Allyn — Preceding unsigned comment added by 97.65.82.66 (talk) 15:20, 5 July 2011 (UTC)

It's not wrong, because the statement is not saying the light from these galaxies will stop arriving, just that it'll be too redshifted to observe in practice by equipment resembling what we use today (there are plenty of possible wavelengths that are much too large for equipment available today, or in the forseeable future, to detect). Perhaps the statement does need to be clarified to explain more what is meant by "in practice", though. I found this thread discussing the issue in which "caveman1917" posted a number of useful references, like this paper which says on p. 2: "Finally, their apparent brightness declines exponentially, so that the distance of the objects inferred by an observer increases exponentially. While it strictly takes an infinite amount of time for the observer to completely lose causal contact with these receding objects, distant stars, galaxies, and all radiation backgrounds from the big bang will e†ffectively "blink" out of existence in a finite time; as their signals redshift, the timescale for detecting these signals becomes comparable to the age of the universe, as we describe below." Hypnosifl (talk) 16:30, 30 July 2011 (UTC)

Units for star quantity

In section 4, Matter Content, the number of stars in the observable universe is estimated at about 3 to 100 × 10²² stars (30 sextillion to a septillion stars). Given that the SI unit for quantity is the mole and that the range of numbers reported here is on the same scale as a mole, would it be useful to also report this quantity in units of moles? It would come out to .05 to 1.666... moles of stars. 74.134.129.136 (talk) 02:23, 27 August 2011 (UTC)

The unit "mole" is a chemistry-specific term meant to count the number of "elementary entities" (usually molecules, but sometimes also other basic chemical units like atoms or electrons) in a substance...see section 2.1.1.6 on p. 22 here. I've never heard it used for large numbers of other entities that aren't basic elements in chemistry, like stars or cells or grains of sand. Hypnosifl (talk) 20:05, 5 September 2011 (UTC)

4% atoms, 22% cold dark matter, & 74% dark energy

Latest measurments: 4% atoms, 22% cold dark matter, & 74% dark energy. http://hubblesite.org/hubble_discoveries/dark_energy/de-what_is_dark_energy.php http://www.sciencemeetsreligion.org/physics/big-bang.php - Brad Watson, Miami 71.196.11.183 (talk) 04:49, 21 December 2011 (UTC)

Danwitty Neutrino Reuptake Correction.

The article fails to mention or even to accommodate Danwitty's Neutrino Reuptake Correction, insofar as conformal topological mappings of Govenwile eruptics have led to revisions of the arc secant functors of temporal cohomotophy, as for instance as has been observed in nolinear compact neighborhoods of gravitational masses near the Dimwitty Limit. Be that as it may, however, and noting how quark wake turbulence is now expressly supposed to NOT perturb alpha-pneumatic deBrollie strains (and this without qualification of the clitsine hydrogen spectra as depicted by Samuelson and Drovebit), it seems likely that Devonshire-Radish velocities in excess of 1.0x10^54 megaparsecs/nanosecond would need to be explained, or perhaps drafted as a regular semi-calonic cacaphore. And perhaps an even more egregious lapse is the failure to mention Largassey's unbounded tensor products and their implication at distances beyond Bloombers's Castle Rail Shore-Jamb plethorae. These are the most serious flaws, ignoring for the sake of argument the author's inability to form non-psychotic Chomsky aural-olfactory chemical emissions. I would strongly recommend that Edith's Head of the Great Dome in plenstissimal or exhubearential tonal sacs be deviated by malagamathy shirks. — Preceding unsigned comment added by Iwanturkitty (talk • contribs) 13:14, 26 December 2011 (UTC)

Your irrationality with regards to The Observable Universe page

Concerning a reason recently for re-adding the "Big Bang" comment at the beginning of this article: it is logically fallacious claim "reverted to standard scientific context" to use as a justification for re-adding "the big bang" at the beginning. That is NOT a justification. Your statement no more explains why "study on bananas" should be added to the beginning anymore than "The Big Bang". The comment is "unhinged" as one troll here would say as it is NOT LINKED TO ANY EXPLANATION AS TO WHY IT IS THERE, not even in the beginning AND THERE IS NO STANDARD SCIENTIFIC CONTEXT MENTION. It is obvious propaganda from biased weasels like yourself. Get a life and stop trolling Mr. Irrational. Who, non-genius, needs to believe in your magical unseen big explosion from billions and billions of Carly Sagan years ago to see anything? NO ONE NON-GENIUS. Stop being a troll. The Big Fairy Fart is a recent comment and the builders of Stone Henge, and the Pyramids, and all the other megaliths we can't build all over the world from ancient times, which does not support evolutionary fairy theory, nor the Catholic Galileo and Christian Copernicus did not need it to see stars anymore then I do. On top of all that: Who in THEE Hell says that everything on Wikipedia needs to be put in a "standard scientific context"? So the JPOP page must have "in the Big Bang Universe Japanese people were created from the Big Bang via evolution which lead to JPOP"?! Insane much? Deluded much? "DAMN THOSE CHRISTIANS FOR SAYING THAT THE UNIVERSE WAS MADE IN 6,500 YEARS! HOW STUPID!? HOW CAN THEY KNOW WHAT HAPPENED SO LONG AGO! WHY THAT'S IMPOSSIBLE SCREW ALL THERE ARCHEOLOGICAL BLEE BLAH AND HISTORICAL RECORD STUFF BLEAAAH ME IS TROLL BRAIN why they need to believe the obvious that the universe was created by a big massive bang BILLIONS AND BILLIONS OF YEARS AGO! WE HAVE PROOF! LOOK THE UHHH, THE BACKGROUND RADIATION THING! LOOK! SEE HOW OBVIOUS IT IS? SEE? WELL DO YOU SEE!? UH, JUST BELIEVE THAT IT'S PROOF OF THE BIG BANG AND THERE'S NO OTHER POSSIBLY EXPLANATION CUZZZZ UHHHH, CUZZZ WE SAY WE'RE THE STANDARD SCIENTIFIC PEOPLES, AND MAJORITY MAKES RIGHT, MAJORITY DECIDES THE TRUTH! TRUTH IS BY CONSENSUS! Oh wait I forgot, 'Wikipedia ISN'T ABOUT TRUTH ANYWAYS' Duuuuuuuuuur. Bye liars who don't care about truth, just what the "mainstream" says Mrs Appeals to Authority.

"P.S.. peoples, just ignore all that evidence the Christians (oops I mean "cretinists") says goes against the Big Bang Theory, forget that they keep citing mainstream scientific articles which say so, duuuuuuuur me is troll."

Yes, you are trolling in God's universe which does not belong to you. FAIL, FAIL, FAIL. NOWEASELWORDS (talk)

I have restored the reference to Big Bang cosmology, because this article is based on the Big Bang cosmological model, as opposed to an alternate or obsolete cosmological model. Cheers, Dawn Bard (talk) 18:06, 16 January 2012 (UTC)

Talk pages are not a forum. See WP:NOTAFORUM. They are not your personal soapbox. You can post specific suggestions for improving this article. Citations must come from third party reliable sources. See WP:RELIABLE. --Harizotoh9 (talk) 18:21, 16 January 2012 (UTC)