Talk:Future of an expanding universe/Archive 1

Question on neutrino gravity and chemistry
This article describes a dark universe in which neutrinos move aimlessly without interaction. I was doing a back of the envelope calculation (purely for purposes of conversation). Based on neutrino, there are three masses of neutrinos and assuming that the lowest is very light, the second should be roughly 0.009 eV. According to escape velocity, the radius in which one neutrino gravitationally captures another should be roughly 2.1^10-42 (m^3/s^2) /(velocity^2). For two such neutrinos to form orbits 1 meter in radius, they should travel around 1.4 ^ 10-21 m/s. This implies a relativistic gamma factor = 1/sqrt (1-((1.4*10^-21)/(3*10^8))^2) = 1+1.1*10^-30, which multiplied by the presumed 0.009 eV rest mass gets a thermal energy of 1*10^-32 eV. Now a hole in this math is that I don't understand how to apply the conversion factor for non-relativistic neutrinos at cosmic neutrino background, but if I ignore it entirely (which makes this take longer) and assume a flat expanding universe, then I want the current 1.9 K temperature (2.45 * 10^-4 eV) to cool down by a factor of 2.48 * 10^-28, i.e. for the universe to be that much bigger and that much older, at 2.5*10^38 years in the future -- times however many meters it will take then to find two adjacent neutrinos, which I can't even start to guess.

Now I'm not a physicist, so I doubt I'm breaking new ground here - has anyone considered what happens when neutrinos get cool enough to stick together? Do you get neutrino "planets"? Should they exhibit some sort of ultra-weak "chemical" (or "nuclear") forces toward one another once they sit next to each other? Wnt (talk) 04:39, 17 July 2008 (UTC)

Edit war continues....
Apparently we're just continuing the edit war here.

I have a number of concerns about this series of edits; an incomplete list of them is below. Essentially all of these concerns were discussed at Talk:heat death of the universe before the timeline was moved into this separate article, and I do not believe the concerns have been satisfactorily addressed. I have marked the edits that I have reverted because I do not believe reasonable people can disagree on; I'll hold off on reverting others.

Note that mentioning a source in the edit summary is not sufficient because it doesn't help readers and is only marginally helpful to other editors; a source needs to be cited for every paragraph and fact in the article.


 * 1) Stelliferous Era time: We have no source (because none exists!) to claim precision to the level of 100.0137 trillion years after the big bang. Note that all the numbers listed here are order of magnitude estimates; when one number is several orders of magnitude larger than another, the smaller one should be neglected (considered equal to zero). (reverted)
 * 2) Star formation ceases: Referenced source says lifetime of a 0.08 solar mass star is slightly more than 1013 years, and that star formation will cease in 1014 years or less, not at least 1014 years. (reverted)
 * 3) "The last stars in the Universe burn out and die": This new section is uncited and contradicted by Adams & Laughlin: it appears to be an alternative view to "Star formation ceases". I think this whole section should be deleted. The sentence "An advanced civilization 200 trillion years in the future would probably be able to manipulate the obits of stars and planets." is very clearly uncited speculation that is not appropriate for Wikipedia.
 * 4) Dynamical relaxation of the galaxy: This section is written so it makes no sense without the header. My feeling is that it's better writing to have the text itself introduce the topic; the header should just be a summary of the text in the section. This section is also unsourced, although I think the material itself is probably fine (if duplicated in other sections).
 * 5) "White dwarfs and Black dwarfs fall or are flung from orbits" and "White dwarfs and Black dwarfs orbits decay by gravitational radiation": These sections split material from "Stellar remnants escape galaxies or fall into black holes", and made the citations unclear. (This division is also symptomatic of a tendency to have many short sections, which I think disturbs the flow of the article.)
 * 6) New Stelliferous Era: section is unsourced and should be deleted. $$10^{10^{10^{10^{10^{1.1}}}}}$$ is so much larger than 100 trillion that adding them makes no sense at the level of precision we have.
 * 7) Black hole table: More rows were added for no particular reason. I still am not convinced that this table is needed at all (we could just, for example, include the equation for Page), but if it is included, I think we only need relatively few items to give the reader a sense of how long black holes of different masses take to decay&mdash;the table as it is now is information overload.
 * 8) Dark Era and Evaporation of black holes: timescale was changed to $$1.7 \times 10^{106}$$ yr, which is a) way too precise and b) not the number used by Adams & Laughlin (10100 yr).
 * 9) A number of other sections were added (using material from Dyson?) without references.
 * 10) The word "universe/Universe", which was consistently lowercase, is now sometimes lowercase and sometimes capitalized. I believe either convention is considered acceptable, but we should stick with one or the other; in such cases, it's normal on Wikipedia to stick with the existing convention unless there's a consensus to switch.
 * 11) "See Also": Many of the links in the new see also section are already included in the article text. I tend to agree with the policy page WP:SEEALSO that this should not be done. Certainly, the current See Also section is not kept in moderation, as it should be.

I must express some frustration: these concerns have been expressed many, many times by multiple editors, and yet the same issues keep getting re-added to the article. I would at least copy-edit the rest of the article (which is now in pretty sorry shape, formatting-wise), but I won't bother because experience tells me that my changes will be reverted as a matter of course. I would appreciate concise replies to the concerns listed here, rather than a continued edit war. —Alex (ASHill &#124; talk &#124; contribs) 06:27, 20 July 2008 (UTC)

Edits A

 * 1) ApJ 531, 22 gives the time until galaxies outside the Local Supercluster are no longer detectable as 2 trillion years.
 * 2) The section following "Star formation ceases" was redundant with the previous section, except for some unsourced speculation.  Also, there's no justification for the 200 trillion year figure.
 * 3) I deleted a paragraph from the Black Hole Era section which was redundant with the previous paragraph and the following section.
 * 4) There is no point in making exactly one subsection for the Black Hole Era which contains all its events.
 * 5) There is no source for the existence of 20 trillion solar mass black holes during the Black Hole Era.
 * 6) Events not conditional on proton decay have been moved to their own section.  Obviously, if protons have all decayed by 1040 years, they can't fuse to iron at 101500 years, and so on.  I rewrote this material, as most of it was uncredited direct quotes from Dyson.  We can't repeat Dyson verbatim without indicating that it's a quote; this is plagiarism.
 * 7) Since the universe is not (might not?) be a black hole in a box with mass according to a certain inflationary model with an inflaton whose mass is 10-6 Planck masses, we can't say that there will be a new Stelliferous Era 10^10^10^... years from now.  In addition, the Poincare recurrence times seem irrelevant to the future of the expanding universe, so I've taken them out.  They are still in 1 E19 s and more.
 * 8) Adams & Laughlin 1997 (section VIB) give 106 years as the starting time of the Stelliferous Era and 10100 years as the ending time of the Black Hole Era and the starting time of the Dark Era.
 * Spacepotato (talk) 20:58, 20 July 2008 (UTC)

Edits B
I undid these two edits.
 * 1) I moved the dates out of the section headings because, per WP:HEAD, headings should be "short—preferably fewer than ten words". I don't think the timeframes in the table of contents are particularly helpful, and the timeframes were in italics immediately following the section headings. This follows the convention established at Timeline of the Big Bang, and is unrelated to whether this timeline is the "full version", as was given as the reasoning in the edit summary.
 * 2) I do agree that the black hole timeline may have some merit on an article like Hawking radiation, but that level of detail just isn't terribly important on a timeline of the whole universe. Mentioning the timeframe at which a solar-mass black hole and a supermassive black hole evaporate seems ample. —Alex (ASHill &#124; talk &#124; contribs) 23:02, 27 July 2008 (UTC)

Explantation for Maldek’s edits once again
Okay well I thought I had already explained my edits many times before but since you keep asking I will try to explain them again.

1. First of all Freeman Dyson in his report “Time without End” clearly states that star formation will end in 10^14 years so this value should be used. In addition to what Dyson says I also have sources I found that give 100 trillion years as the end of star formation by researching. Here they are: http://cedarlounge.wordpress.com/2008/02/27/when-stars-fade-out-a-disturbing-prediction-of-the-future-of-the-universe-but-a-consoling-thought-about-our-present/ http://www.astrosociety.org/pubs/mercury/0001/cosmic.html http://www.physicsbookstore.org/0684865769.html

http://spiff.rit.edu/classes/phys240/lectures/future/future.html

2. Secondly I have already given you reliable sources that claim that the longest-lived red dwarfs have a lifespan of over 100 trillion years. Here they are: http://filer.case.edu/sjr16/stars_lifedeath.html http://filer.case.edu/~sjr16/advanced/stars_avgdeath.html These are reliable sources. Why do you always say that the sources I find are not reliable? Why aren’t these sources reliable?

3. Thirdly, if Star formation ceases in 100 trillion years and the longest-lived red dwarfs have a lifespan of over 100 trilllion years, simple mathematics will prove that all stars will be gone in at least 200 trillion years. In addition to this simple math I also have sources that state this too. Here they are: http://emptv.com/print/334 http://emptv.com/in/science

4. Fourthly, I will mention that I have found many sources that state that in 3 trillion years an observer in our galaxy will not be able to see galaxies beyond our own because all other galaxies would have receded beyond the cosmic horizon. I have many sources that claim a date of 3 trillion years for this but you keep saying that it is 2 trillion years despite all my sources. Here are my sources which claim that in 3 trillion years our galaxy will be the only galaxy visible to an observer on our galaxy: http://www.universetoday.com/2007/05/22/the-universe-will-appear-static-in-3-trillion-years/ http://www.sciencedaily.com/releases/2007/05/070524094126.htm http://www.theallineed.com/astronomy/07060501.htm http://www.newuniverse.co.uk/n-archive_644.html http://www.saao.ac.za/assa/features/cosmology-articles/end.html http://www.universetoday.com/2007/07/25/the-end-of-everything/ What’s wrong with all of these sources? 5. Fifthly, why are you getting rid of the Black Hole Chart. The Black Hole Chart is good and should be kept because it helps people understand when different mass black holes disintrate. 6. Sixthly, The Poincare Recurrence time of the Universe means the time when the Universe will return back to the way that it currently is. That means the Universe will return back to the way it is now. I have found a couple of sources on the Poincare Recurrence time of the Universe at it specifically states that the Poincare Recurrence time of the Universe is 10^10^10^10^10^1.1 years. This information is from “INFORMATION LOSS IN BLACK HOLES AND/OR CONSCIOUS BEINGS? ∗”By Don N. Page:CIAR Cosmology Program, Institute for Theoretical PhysicsDepartment of Physics, University of Alberta Edmonton, Alberta, Canada T6G 2J1. Here are my sources: http://arxiv.org/abs/hep-th/9411193v2 http://www.fpx.de/fp/Fun/Googolplex/GetAGoogol.html

The Poincare Recurrence time of the Universe is when the Universe goes back to the way it currently is now. It is when the Univerese will enter its next Stelliferous Era since we are currently in the Stelliferous Era. The Poincare Recurrence time is how long it will take for the Universe to return to the way it currently is, which is in the Stelliferous Era. This is the idea of the Poincare Reccurence time of the Universe. I hope you understand this but if you need more clarification I would be happy to go into greater depths. To reitterate basically The Poincare Reccurece time of the Universe will be the next Stelliferous Era because the Universe goes in Cycles.

If you have any more questions about my edits feel free to ask. Thank you very much for your cooperation.Maldek2 (talk) 05:26, 6 August 2008 (UTC)
 * I have responded to many of these points before.
 * None of the sources you give, including Dyson, discuss when star formation ends. They only say that the last star will cease to shine in around 10^14 years.
 * We don't know where those numbers came from or how they were derived.  As I've mentioned earlier, Laughlin, Bodenheimer, and Adams (Astrophysical Journal 482, pp. 420–432 (June 10, 1997),, ) have modeled low-mass red dwarf stars in detail to obtain their lifetimes.  So, their figure is more reliable.
 * Since your figure for low-mass red dwarf lifetimes is wrong, this figure is also wrong. In addition, these articles in emptv.com were written based on Wikipedia (see Talk:Heat death of the universe), so we can't base our articles on them.
 * Re your sources on the disappearance of galaxies outside the Local Group, the second and third are verbatim copies of a press release  from CWRU.  The first  is a news story, apparently based on the press release.  The fourth  is a verbatim copy of the first.  The fifth and sixth  are mentions in passing.  Rather than rely on the press release, which is a secondhand report on research done by Krauss and others, and the news stories, which are second- or third-hand, it's better to go to the original papers on which these sources are based.  Also, the scientific papers explain the evidence and reasoning leading to the number, which the other sources do not.
 * I'm not convinced the black hole chart is worth the space.
 * The Poincaré recurrence time is for a black hole in a box. We're not in a position to say that it applies to the actual Universe, even if it keeps expanding.
 * Spacepotato (talk) 07:38, 6 August 2008 (UTC)

Some additions to Spacepotato's comments, with which I fully agree:

Maldek, please read WP:reliable sources; the term reliable source has a specific meaning on Wikipedia, essentially that a reliable source should be published. As multiple editors, including me, have explained before, blogs are almost never reliable sources because they are self-published; the space.rit.edu, filer.case.edu, and fpx.de sources are all also self-published sources. For scientific articles, papers in peer-reviewed academic journals are generally best.

1. The sources you cite all talk explicitly about the Adams & Laughlin formulation of the ages of the universe and cite their work! It's best to use the original source, which is published in a peer-reviewed journal, instead of these sources which are based on the original source.

4. Although spacepotato's comment above illustrates the problems with your sources, you didn't actually cite those sources in the revisions you made to the article. Instead, you left in the citation of Krauss & Starkman 2000 (10.1086/308434), which says "In a little less than 2 trillion years, all extrasupercluster objects will have redshifted by a factor of more than 1053. Even for the highest energy gamma rays, a redshift of 1053 stretches their wavelength to greater than the physical diameter of the horizon.... The resolution time for such radiation will exceed the physical age of the universe." [emphasis added] Citing that source to say that 3 trillion years is the appropriate number is false. —Alex (ASHill &#124; talk &#124; contribs) 21:11, 6 August 2008 (UTC)

decay of iron stars into neutron stars and black holes
The subsection on decay of iron stars into black holes (in the "Future without Proton Decay" section) seems to suggest it would take longer for them to decay into neutron stars than it would for them to decay into black holes. I would think it would be the other way around, and it was for this reason that I tried to add a different figure citing "The Universe" by Colin Ronan, ISBN 0028655915--Robert Treat (talk) 17:14, 14 September 2008 (UTC) For collapse to a neutron star, N must be large enough so that the collapsing matter forms a stable neutron star. Since the minimum mass for a stable neutron star is estimated to be around 0.1 solar masses (ISBN 3540423400, p. 264), N should be at least 5 × 1055, so 120 N4/3 &ge; 2 × 1076. This will produce a time similar to the 1010 76 year figure given by Dyson. For collapse to a black hole, on the other hand, it's plausible to assume that black holes should exist down to the Planck mass of about 2 × 10−8 kg. This gives an N of about 6 × 1018, so 120 N4/3 ~ 1027, and we get a time similar to the 1010 26 year figure given by Dyson. So, with this assumption the black hole decay time is shorter than the neutron star decay time. Dyson also gives the larger figure of 1010 76 years or so, which comes from the assumption that black holes do not exist below the Chandrasekhar mass.
 * I removed this figure because Ronan gives no derivation or source for it, and it conflicts with the 1010 76 year figure. Curiously, I also found the 101600 year figure in an "Alternate View" column from the October 1985 issue of Analog, which quotes "Time without end", Dyson, RvMP 51, 447 as a reference; this suggests to me that it may originate in a misreading of this paper.
 * Naïvely, you might suppose that it would take longer for a white dwarf to collapse to a neutron star than to a black hole, but according to "Time without End", this is not so. The reason is that these times are based on waiting for a quantum tunnelling effect in which a portion of the matter that formerly made up an iron star suddenly finds itself within a smaller radius, making it collapse to a neutron star or a black hole.  For an amount of matter with total atomic number N, this is estimated to take around e120 N 4/3 seconds (Dyson, (46) and (48)).
 * If a Planck-mass black hole were to form by quantum tunneling in an iron star, it would presumably decay quickly by Hawking radiation into a shower of elementary particles. Many of these would not escape the star but some non-negligible fraction should be neutrinos and antineutrinos, which should escape the star.  The star will therefore lose mass comparable with the Planck mass on a timescale of 1010 26 years, so it will evaporate completely in a time not much longer than this.
 * Spacepotato (talk) 08:25, 15 September 2008 (UTC)

I read the article you cited. I noticed it describes neutron stars forming in 101600 years, and says that these in turn will collapse into black holes in 1010 76 years.

Ronan doesn’t use footnotes, but he does have a bibliography at the end of his book listing other books and websites. The Dyson article isn’t listed, but maybe one of those sources lists it. If Ronan uses Professor Cramer's article, he would appear to have gotten it from a URL other than the University of Washington webpage.

Neutron star formation, in this instance, seems to me an extension of the cold fusion process that produces iron and nickel. These elements go on and fuse into neutronium.

Something I must confess to being a little curious about. 101600 years looks like it would be shortly after 101500 years. It's not, it's a googol times further into the future, but the way it's written suggests it's shortly after. I was thinking, is there any chance this figure could have been left out when they made the online version of Dyson's article?--Robert Treat (talk) 19:04, 15 October 2008 (UTC)
 * No. The 101600 year figure is not in Dyson's paper. Spacepotato (talk) 20:19, 15 October 2008 (UTC)


 * Thanks. You may be interested to know I've since been able to find a direct link to Dyson’s article if you wanted to use it.  While I didn’t quite understand all the technical stuff there, I pretty much understood enough--Robert Treat (talk) 19:10, 17 October 2008 (UTC).

Another question about Dyson's article
What did Dyson mean by the phrase "an unsymmetrical mode of collapse passing over a lower saddle point than the symmetric mode"?--Robert Treat (talk) 05:17, 9 November 2008 (UTC)
 * It's what you would expect&mdash;an unsymmetrical way of collapsing the iron star which is easier than the symmetric way of squashing the star into a denser and denser sphere until it reaches the size of a neutron star. The saddle point in question is in the potential energy surface. Spacepotato (talk) 09:37, 9 November 2008 (UTC)
 * Thanks, I guess. The way it was mentioned in passing in the article suggests to me such a question was asked in one of the original lectures the article was based on--Robert Treat (talk) 17:18, 9 November 2008 (UTC).


 * I found another article that mentions the 101600 year figure. While there appear to be typos, they didn't get it solely from Professor Cramer's article, because Cramer doesn't use the "26" figure for decay to black holes, and Ronan doesn't use either the 26 or 76 figures. This, combined with Professor Cramer's article and Dyson's mention of "an interesting question" lead me to suspect the 101600 figure may have been mentioned in the original lecture or accompanying discussion--Robert Treat (talk) 04:44, 13 November 2008 (UTC).

Maldek
Is obviously vandalising this article. Can someone request a ban, I don't have time.WikiReverter (talk) 04:01, 28 October 2008 (UTC)

Dark Energy?
The article describes the universe as accelerating in its expansion. However, it also describes that the local galaxies such as Milky Way and Andromeda are moving toward each other because of gravitational attraction. If this gravitational acceleration is taking place, could it be influencing our reading of the more distant galaxies by making it appear they are accelerating away from us?--Robert Treat (talk) 06:39, 30 November 2008 (UTC)


 * The acceleration of the Milky Way (relative to the Hubble flow) is too small to matter over the course of human history. The velocity is large enough to matter in some cases, but it's known accurately and always taken into account where it does matter. We don't actually see distant objects accelerating away from us—the effect is far too small for that. What we do is measure such things as the redshift and brightness of standard candles from different eras in the universe's expansion and try to fit that to various models of the expansion. ΛCDM is the simplest model that fits all the data. -- BenRG (talk) 20:30, 30 November 2008 (UTC)

Futures with and without proton decay--could both exist?
We know that free neutrons have a finite lifespan while those bound in nuclei are much more stable. Could it also be that free protons will be more likely to decay over the eons than bound ones? See The Half-Life of Proton Decay and its Relation to the "Heat Death" of the Universe--Robert Treat (talk) 21:43, 17 September 2008 (UTC).

experiments on proton decay
The proton decay section indicates the proton has a half-life of at least 1035 years, and I feel this article should relfect that--Robert Treat (talk) 07:24, 16 January 2009 (UTC).
 * The section Proton decay cites no source for this figure, and if you look at the latest data from the Particle Data Group, you'll see that there's nothing resembling the 1035 year figure there. Spacepotato (talk) 07:40, 16 January 2009 (UTC)
 * I've added a citation needed template to the article. Unfortunately when I tried to visit the site you gave me it froze up our computer, and I had to reboot it--Robert Treat (talk) 08:56, 16 January 2009 (UTC)
 * It's a PDF file; these often cause problems when viewed in a web browser. You might have better luck downloading the PDF file and then reading it with an external reader, such as Adobe Reader. Spacepotato (talk) 10:28, 16 January 2009 (UTC)
 * I had a chance to print out the file at the library. If I’m reading it correctly, physicists feel 90% confident a bound proton has a mean life > 1029 years.  I would figure a bound proton’s lifetime is longer than a free proton’s, since a bound one would have to overcome the nuclear binding energy in order to decay.  Page 4 describes the lifetime limits of dinucleon pairs in an iron nucleus, and the figures seem shorter than the partial mean lifetimes listed earlier.  Aren’t the elements with the strongest binding energy iron and nickel? I’m sure a single proton’s lifetime is longer than the figures listed for the anti-proton; otherwise I probably wouldn’t be writing this message--Robert Treat (talk) 06:11, 20 February 2009 (UTC).

This line
seems pretty dumb: "Once the last star has exhausted its fuel, stars will then cease to shine." i don't know how you guys prefer to edit that stuff but i just wanted to point this out in a helpful fashion instead of vandalizing the page over and over for once —Preceding unsigned comment added by 24.56.7.231 (talk) 01:51, 29 March 2009 (UTC)

This presents another question could the bible be correct when it says that evn the stars will wearout and die funny alos how the old things are gone with great heat anda new universe is created could this mean that at least one proton crashes into anothr at planick scale enrgy causing a new in flating universe ?/ interesting  —Preceding unsigned comment added by 74.229.22.19 (talk) 20:58, 13 May 2009 (UTC)

Gamma rays?
The line "Assuming that dark energy continues to make the universe expand at an accelerating rate, 2×1012 (2 trillion) years from now, all galaxies outside the Local Supercluster will be red-shifted to such an extent that even gamma rays they emit will have wavelengths longer than the size of the observable universe of the time" implies that galactic red-shifting will eventually make them invisible at any wavelength. If they're red-shifted, I thought it would be the radio waves that disappear last, as gamma rays are on the "bluest" end of the spectrum. I didn't edit the article because I don't make edits anymore unless I'm absolutely 100% sure, but wanted to bring it up just in case. Thanks! -jeff (talk) 18:33, 25 June 2009 (UTC)
 * As the shift is from blue to red, it's the radiation at the bluest end of the spectrum that takes the longest to redden to invisibility. So, the gamma rays disappear last. Spacepotato (talk) 18:57, 25 June 2009 (UTC)

Load of bullocks
This article is soo biased, on the side of ignorance, it is unbelievable. It says "planets will drop from their orbits" in 10^15 years, while this, due to gravitational radiation, is on the order 10 magnitudes greater (for Earth at least, if it weren't swallowed by Sun). It says that objects in Galaxies will relax to a Maxwell like distributions (misquoting an obscure Indian journal), which is laconic POV nonsense statement. It tosses speculation along with scientific facts and scientific hypothesis (iron stars, quantum tunneling liquids - what a load of crap). Poor, biased, sensationalism - horrible article. — Preceding unsigned comment added by 109.121.74.189 (talk • contribs) 03:05, 17 March 2011
 * Well, the article is somewhat speculative. However, neither statement is nonsense.  There are two competing processes for the removal of planets: orbital decay by gravitational radiation and ejection by perturbation caused by a passing star.  For the Earth, the Adams/Laughlin reference gives a timescale of 1015.1 years for ejection by perturbation (§IIIF, .)  As for dynamical relaxation, another reference for this is Chapter 7, Binney and Tremaine (Galactic Dynamics, 2e, Princeton, 2008.)  I'm not sure why you're referring to it as POV.  Spacepotato (talk) 04:21, 5 April 2011 (UTC)

"five ages of the Universe" vs. "Physics and Biology in an expanding universe"
This article draws most of its info from Adams and Laughlin's "Five Ages of the Universe", whereas Timeline of the far future draws most of its comparable info from Freeman Dyson's "Physics and Biology in an Open Universe". I am the principle editor of Timeline of the far future; however I did not compose the information drawn from that source. Since the two contradict one another, I was wondering which was more reliable.  Serendi pod ous  06:49, 14 May 2011 (UTC)


 * Bear in mind that there's quite a lot of uncertainty for estimating most of the longer timescales, so it'd be normal for the estimates to disagree. Which specific values were you were concerned about inconsistencies in? --Christopher Thomas (talk) 07:37, 14 May 2011 (UTC)
 * "Five Ages..." lists the beginning of the Black Hole era at 1040 years, whereas Dyson places it at $$10^{10^{26}}$$ years, a difference in scale so vast as to be virtually incomparable.  Serendi pod ous  08:21, 14 May 2011 (UTC)


 * Different assumptions will do that. Dyson's version is the time assuming that proton decay does not occur, which means that stellar remnants have to collapse via quantum tunnelling. This article assumes that proton decay does occur, making stellar remnants vanish much earlier. --Christopher Thomas (talk) 15:55, 14 May 2011 (UTC)
 * I've had a go at reworking Timeline of the far future. Please let me know if the result is better or worse than its predecessor.  Serendi pod ous  17:03, 14 May 2011 (UTC)


 * It's probably worth including both scenarios, rather than assuming protons do decay. While most of our present attempts at a grand unified theory require that they do, nothing in actual experiments has confirmed this (just put larger and larger thresholds on what its lifetime must be). Far-future predictions based on both scenarios have been published, so I'd argue that both are equally notable at this point. --Christopher Thomas (talk) 19:50, 14 May 2011 (UTC)

What happens after this is speculative.
Sorry people, but i must laugh at that sentence. People, the *whole article* is speculative! (that is not necessarily bad, but the speculation does not start after the dark age.) --81.217.14.229 (talk) 06:39, 24 May 2011 (UTC)
 * To illustrate with a supposively true insurrance report (in german): My car hit the guide rail, I somersaulted and blazed a tree. Then I lost control over my car. --Duodecimal2 (talk) 08:24, 24 May 2011 (UTC)

Do we have a time frame for the heat death of the universe?
I think this page should cite roughly when the universe will achieve true heat death.  Serendi pod ous  14:20, 22 June 2011 (UTC)


 * I'm not sure there are agreed-upon predictions for that. In fact, some arguments say that it never will, due to the expansion of the universe increasing the number of possible states with time. It would also be sensitive to assumptions about how the expansion of the universe progresses. That said, if you find predictions in the literature, by all means bring them here for discussion. --Christopher Thomas (talk) 19:08, 22 June 2011 (UTC)

Neutrino nuggets
The statement "Photons, neutrinos, electrons, and positrons will fly from place to place, hardly ever encountering each other." seems to be contradicted by the theory of accelerons and "neutrino nuggets". ,  I started a thread at the Science Refdesk called "neutrino chemistry" about this (can't usefully link to it until it's archived). I don't have the sources or the understanding to add this, but I suspect the future of the universe could be altogether more interesting than this article implies. Wnt (talk) 22:08, 16 September 2011 (UTC)


 * These proposals are based on a highly speculative idea (a new field that causes neutrino mass to vary and other interesting effects). Until it makes a bigger splash than a few arxiv preprints, mentioning it would violate WP:UNDUE. It certainly doesn't reflect how the majority of researchers think neutrinos behave. --Christopher Thomas (talk) 23:30, 16 September 2011 (UTC)

Galaxies will never disappear from the expansion of the universe
The concept that after eventually galaxies would accelerate away from us so fast that they could not be observed is flawed. Basically the premise is that the light leaving them will be more and more red shifted. To eventually even light from the closest galaxy would be too red shifted to be observable. The flaw in this premise, is assuming that light is the only way to detect distant galaxies. Consider, today we can see galaxies in telescopes more than 10 billion light years away formed in the early universe. While it is true that light from these distant galaxies will be more shifted over time, so eventually we could not see light from those galaxies, imagine if a high energy non-zero rest mass particle left at the same time. Unlike light, this massive particle cannot be red shifted into being completely unobservable. However, the massive particle could eventually be accelerated away from us. Lets say for example the non-zero rest mass particle headed at us at nearly 100% of the speed of light. Then the particle would arrive at nearly the same time as the observable light and we would not be able to use it to observe the galaxy in the future. However, say it heads at slightly slower. Then it will arrive with a time delay. Essentially there is some minimum velocity it needs to arrive eventually, anything less will eventually be pulled away from us. Think of this like an escape velocity. A particle that had exactly the right velocity to reach us, would do so in an infinite amount of time. Those with something close to that velocity would arrive in the extremely distant future. Of course if these non-zero rest mass particles decay in route, we might only detect the decay products rather that the original particles themselves. Even more food for thought, consider the implication if light itself has a non-zero rest mass.Bill C. Riemers (talk) 19:57, 24 July 2011 (UTC)


 * You are assuming a universe without dark energy, whereas the paragraph in question does assume dark energy. With the expansion of the universe accelerating, galaxies that are now within the observable universe eventually move outside the observation horizon (the boundary beyond which space is moving away from us faster than light in our coordinate frame). This means there is some finite time beyond which galaxies could not have emitted light that reaches us.


 * The second part of the argument is that the redshift of light that was emitted in the past gets drastically stronger once expansion is dominated by dark energy. Our universe's expansion to date has mostly been dominated by the matter-density within it. As it expands, this stops being the case (matter density drops but dark energy density stays constant). As a result, no, relic radiation does not remain observable.


 * With regards to light vs particles, particles become unobservable when they're redshifted enough to be moving substantially slower than light (i.e., when their kinetic energy is comparable to or less than their rest energy). Unlike photons, they cannot lose arbitrary amounts of energy and still propagate at C. Relic particle radiation therefore usually has a much shorter horizon than relic photon radiation. A hard upper bound on both is provided by the Planck energy (the maximum energy that it's meaningful for any particle or photon to have). In practice, the GZK limit provides a far lower boundary.


 * Lastly, the article is supposed to be based on references. Saying "I think this is wrong because X" doesn't satisfy WP:V. If you want to take issue with a statement in the article that's backed up by a reference, you're going to have to provide a reputable reference that says something different.


 * I hope this response is useful to you. --Christopher Thomas (talk) 02:57, 25 July 2011 (UTC)

Christopher Thomas here makes valid points that Bill C Reimers does not respond to. One reference would be Brian Schmidt, the person who viewed the supernova redshifts, who is quoted as saying something like, "in 150 billion years our night sky will be dark except for the light from the Milky Way and Andromeda galaxies, because the light from further will never reach here." This quote is from 2002 Discover Magazine September. Extrapolating, there would be a time, not much later, when light from any star will never reach its planets. Then not much later, energy from within the star would never reach other parts of the star. It seems silly to me to speak of any events after this time. This would cut the timeline on this page far far shorter. P.M. — Preceding unsigned comment added by Healingbrain (talk • contribs) 17:03, 24 October 2011 (UTC)


 * This conclusion only applies to systems that are not gravitationally bound to each other. Galaxies and clusters of galaxies will remain intact under most scenarios (a Big Rip being the exception). I've seen conflicting statements about whether superclusters are gravitationally bound or not. The net effect of an expansion under most conditions is to change the binding energy of such a system, not to render it un-bound (except at the very largest scales). --Christopher Thomas (talk) 23:31, 24 October 2011 (UTC)

Accelerating expansion
The current version of the article states that, assuming accelerating expansion, that galaxies outside the local supercluster (should that be local group?) would vanish. Shouldn't all gravitationally unbound structures eventually disconnect in this way? Doesn't that have implications for what follows?

It sounds to me like it goes something like this: after dynamical relaxation, each remnant is disconnected. These separate universes have somewhat different fates. A disconnected evaporating black hole sends radiation into nothing. The other universes decay differently, depending on proton decay ... blah blah ... Ultimately each stable elementary particle is alone in its own universe, and never runs into anything (so not "hardly ever" but never, and the bit about positronium is flat out wrong). Well except the odd quantum event, but again, unless the result of that is somehow gravitationally bound, the bits just fly off and disconnect. The end.

But I'm an amateur, and this is just my guess, maybe informed by something I read but damned if I remember. Still, I do wonder if maybe some of the stuff in the article is sourced from somewhat older material that didn't really take dark energy into account.

--174.118.1.24 (talk) 04:30, 12 August 2012 (UTC)


 * That's an interesting observation! Good catch.


 * The distant-future parts rely on references written before the accelerating expansion was known. It might be worth adjusting the introduction to those sections to make that clear. If there are references that talk about the impact of accelerating expansion on far-future predictions, that's worth adding a section about, but that would take a fair bit of searching to find (perhaps someone at WT:AST might have heard of something along these lines).


 * If the acceleration behaves the way we'd expect it to if due to a cosmological constant or dark energy, the horizon size remains very large. Depending on assumptions made about expansion rate and about the decay of matter into electrons and positrons, it's not beyond reason that you'd still end up with enough matter to interact with itself before particles exit each others' observation horiozons. This would be especially true in the vicinity of a black hole in the final stages of evaporation (you'd get a burst of radiation in a very compact space). I haven't worked the math, and I'd be very interested in seeing a paper that did. --Christopher Thomas (talk) 06:26, 12 August 2012 (UTC)

Potentially misleading?
We have in the article: "As the black hole's mass decreases, its temperature increases, becoming comparable to the Sun's by the time the black hole mass has decreased to 10^19 kilograms. The hole then provides a temporary source of light during the general darkness of the Black Hole Era."

Well, that's true enough I suppose, but don't get out the Soundgarden albums just yet. I got excited at this, since 10^19 kilos is enough mass to supply the Sun's output for a good long time. But we won't have a sky full of black holes bright as the sun, warming over the long-dead planets for a second lease of life. A black hole of 2x10^19 kg has about the same temperature as the surface of the Sun, but it is far smaller - Schwarzschild radius about 30nm. With so small a radiating surface, it puts out 0.8 microwatts. It would be difficult to warm yourself beside this meagre candle.

Wait rather longer and a black hole will reach the _luminosity_ of the Sun, putting out enough power to illuminate a whole solar system. At a temperature north of 10^20 kelvin, you'd better be an enthusiast for gamma rays. If you're not so keen, just take cover. It'll only last another 70 nanoseconds.

http://xaonon.dyndns.org/hawking/

149.241.212.44 (talk) 20:13, 1 October 2012 (UTC)

Move discussion in progress
There is a move discussion in progress on Talk:Age of the universe which affects this page. Please participate on that page and not in this talk page section. Thank you. —RMCD bot 04:00, 3 October 2013 (UTC)

Capitalization of universe
There is currently a discussion about the capitalization of Universe at . Please feel free to comment there. —sroc &#x1F4AC; 13:15, 19 January 2015 (UTC)

Lol. I thought you were talking about a universe filled with intelligent life and capital goods - a different universe from the lifeless, mindless one described in the article. Doubledork (talk) 19:05, 1 April 2015 (UTC)

This article is too hard to believe
"It will then be impossible for events in the local group to affect other galaxies" - Because no one anywhere in the universe, over 1,000,000,000,000 years, can figure out how to build an Alcubierre drive or manipulate the metric tensor / expansion of space in any way. Doubledork (talk) 19:18, 1 April 2015 (UTC)
 * Perhaps because those things may be impossible? Certainly as far as I know, according to mainstream General Relativity, they aren't possible without some kind of exotic things like negative energy density, which haven't been shown to exist yet. Banedon (talk) 01:25, 2 April 2015 (UTC)
 * Intelligent life isn't magic, they can't violate the laws of physics no matter how much time you give them AkariAkaori (talk) 15:12, 7 April 2015 (UTC)

Eternal Expansion
http://apod.nasa.gov/apod/ap151206.html

70.189.251.205 (talk) 11:50, 10 December 2015 (UTC)

Encyclopedic Tone
Should this article really be using flowery language such as calling the photon "lovely", or text like "... but even these giants are not immortal.", even in image captions? At the risk of possibly being the killjoy, I propose to change this prose. 96.237.166.57 (talk) 17:21, 20 July 2016 (UTC)

Redlink for "Dynamical Relaxation"
Under Stellar remnants escape galaxies or fall into black holes, there's a redlink to dynamical relaxation. Looking around, it appears that this should be dynamic relaxation, which does have an article associated with it. Is this correct? Laefk (talk) 17:24, 20 July 2016 (UTC)

Is the timeframe for new Big Bang incorrect?
In the section 3.5 Beyond, it is stated that the timeframe for a possible new Big Bang is 1010 56 years.

However, in the cited paper by Carroll and Chen the probability is stated as P ∼ 10-10 10 56  which is the inverse of 1010 10 56  , that is 1/(1010 10 56   )

Would not the matching timeframe to realize the probability be 1010 10 56  ? Tensegrity (talk • contribs) 20:51, 11 October 2016 (UTC)

Black Holes
Why won't there be anymore nucleons in the universe? Evaporating black holes create protons in the last stage of evaporating. 32ieww (talk) 18:57, 26 February 2017 (UTC)
 * See proton decay, which is linked in the article.--Jasper Deng (talk) 02:20, 1 March 2017 (UTC)

Speed of Andromeda/Milky Way movement towards each other does not match with other sites on Wikipedia
Example: The article about "Andromeda–Milky Way collision" does state another speed of movement of the 2 galaxies coming closer. Please check that. E.g. if you take the time 4*10^9 years and the distance 2,5*10^6 light years as given, then you can compute the velocity. Would of course be very dubious if you computed this way.

— Preceding unsigned comment added by 88.78.31.168 (talk • contribs) 00:43, 8 October 2014 (UTC)

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Universe should be nearly pure vacuum in Dark Era (assuming proton decay)
The convergence of the Hubble Parameter to a future value of 55.4 km/s/Mpc implies the universe will double in size every ~12.2 billion years. After 10100 years, the universe will have expanded by a factor of more than $${10^{10^{89}}}$$ (and by 10200 years, by $${10^{10^{189}}}$$). An estimate of the average particle density (~$$1/{10^{10^{89}}}$$) after such immense expansion suggests the universe will be nearly pure vacuum. Given that estimates of the future size of the cosmological event horizon converge to ~16 Gly, and also the estimate of a total of 1097 subatomic particles in the universe, it would seem that almost all such particles would be forever removed from the possibility of interaction with other particles, and the chance of particle collision would be beyond unlikely and continuing to decline exponentially with the continued expansion of the universe. Even if there were 10100,000 subatomic particles, most such regions of ~(16 Gly)3 would be absent any particles of all. (It really doesn't matter what the exponent is of the subatomic particle estimate is, if expressed directly in decimal form - the result doesn't appreciably change. Similarly even if you increased the radius of the event horizon to $${10^{10^{88}}}$$ Gly, most such regions are still unlikely to contain any particles).

Rsbaker0 (talk) 14:34, 25 March 2019 (UTC)

Expansion of Dark Era section
The text added several hours ago seems to be a paraphrased version of narration in the YouTube video “TIMELAPSE OF THE FUTURE” by melodysheep https://m.youtube.com/watch?v=uD4izuDMUQA

I’m unsure if a YouTube video is generally an acceptable reference for Wikipedia. If it is, the video is linked above and takes you to YouTube.

Savie Kumara (meow) 02:33, 24 June 2020 (UTC)
 * Hi there. I found it. I feel like it is a bad reference (you cite Timelapse of the Future, all melodysheep does is comppilating--whaa?) and that it should be replaced with a different style of writing. I'll try edit it.  Gerald WL  14:08, 29 July 2020 (UTC)