Talk:Heat death of the universe

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[edit] Few questions here

[edit] What about electrons?

You cover protons and neutrons, but there's no mention of electrons. What happens to them?

Latrosicarius 16:17, 19 July 2007 (UTC)

I think electrons stay as electrons, since they are elementary and do not decay. The article does mention that leptons remain, and electrons are leptons.Eebster the Great (talk) 17:10, 27 March 2008 (UTC)

[edit] Alternatives to Hawking Radiation?

Hawking radiation is not proven. Can you write a section on the conflicts of this theory if black holes actually don't evaporate? Regardless of your opinions of whether Hawking is right or wrong, this issue should not be snubbed, ignored, or disregarded.

Latrosicarius 16:17, 19 July 2007 (UTC)

If black holes do not decay, the theory would end up with all matter as leptons, bosons, or black holes, rather than simply as leptons or bosons. However, if Hawking radiation is false, the Universe will never truly achieve a heat death since black holes represent maximum entropy and in an accelerating universe not all matter can ever be captured in a black hole. Keep in mind, I'm no physicist, but that's how I understand it. Somebody with a better understanding perhaps should write this section. Keep in mind also, though, that this is just one possible theory, and odds are very, very strongly against protons decaying at all.Eebster the Great (talk) 17:13, 27 March 2008 (UTC)

[edit] Decay into quarks?

In this article protons decay directly into radiation.

Originally, I thought protons would decay via beta decay into 1 free neutron, 1 positron, and 1 neutrino, except this couldn't be the case because it requires energy be input into the equation.

So how, exactly, would they decay? Would just degenerate into free quarks?

On the proton decay page page, it says:

According to some such theories, the proton would have a half-life of 10^36 years, and would decay into a positron and a neutral pion that itself immediately decays into photons in the range of gamma radiation:

Why, exactly do they think that? Why do they say it's a pion and not a full neutron? Where's the neutrino? Can this be explained further?

Latrosicarius 16:17, 19 July 2007 (UTC)

[edit] Alternatives to Singularities?

It is not proven that black holes are ring singularities. The article states that black holes are the only place immune to proton decay. However, if theories are true where there's an actual oblate spheroid of degenerate matter inside a black hole's event horizon, then that matter (which would theoretically be composed of neutrons or quarks) would indeed be under the influence of decay. Again, regardless on your opinions of whether Karl Schwarzschild's solutions to Einstein's Field Equations are correct or incorrect, this is still an important alternative which should not be disregarded.

Latrosicarius 16:17, 19 July 2007 (UTC)

Re your questions:
Electrons. Since no charged particle lighter than the electron is known, and since, assuming that charge is conserved, the decay products of an electron would have to contain at least one charged particle, the electron is presumed to be stable.
Proton decay. A decay channel allowed by some grand unified theories is the reaction (quark, quark) → (antiquark, antilepton). See e.g. Proton decay in terms of an effective baryon-lepton transition, W. Lucha and H. Stremnitzer, Zeitschrift für Physik C 17, #3 (September 1983), pp. 229–242. This immediately gives the reaction p → π0 + e+.
Protons decaying inside a black hole. Whether it happens or not is irrelevant to events outside the black hole as the decay products cannot escape the hole. Spacepotato 01:30, 7 August 2007 (UTC)

[edit] THE NAME

I'm not so sure about despite its name. Heat death to me has always meant the death (nonexistance) of heat, rather than death through overheating. But maybe this is because I don't remember being confused when i first heard the term? Morwen 20:46, 10 Nov 2003 (UTC)

Hmm, I think alot of people will disagree with the idea thatan a universe that contiunes to expand will approach heat death asymptotically.
The first line of disagreement I can see is that although the 19th century scientist who came up with the idea of the heat death of the universe meant it to refer to the maximal entropy state of the universe, he was talking about a steady state model. However heat death conventionally means total thermal equilibrium (which is obviously the same as a maximal entropy state in what we'd normally think of a s a closed system) and I see no reason why an expandingf universe cannot be in thermal equilibrium before it reaches it's maximal entropy state. I'm pretty certain that in general the 'heat death of the universe' is used to describe a state that will occur after a finite period of time (i.e. the usuage I've detailed above) rather than that detailed in the article.
"Secondly even if we do take heat death as equivalent to maximal entropy, does it approach really maximal entropy asymptotically? I can see why it would approach in a declerating infinitely expanding model, but I don't see why it should in one with linear or accelerating expansion. I can't say I'm 100% sure about this but in the latter two models what stops them from having arbitarily high entropies?
"I think these two points do need to be clarified in the finished article.

[edit] Heat-death vs Big Freeze

As far as I can understand (and as suggested here), heat death means a flat universe dying from max entropy, and the Big Freeze is an open (constantly expanding) universe dying from expansion causing heat to be spread out - the effects are the same, but the causes different. I've updated the article a little accordingly and linked to that page, but it would be useful if someone could check that this is correct and if so explain it a bit more clearly than I've done :) --Jomel 16:17, 13 Aug 2004 (UTC)

There defintely needs to be more clarification here. As far as I, an amateur, can perceive, the only difference is that "heat death" involves an exhaustion of all entropy whereas "big freeze" involves matter being so spread out that any residual energy is nearly useless. BOTH of these articles need a "compare & contrast" section or else I'd say that an overzealous editor may ask for them to be merged. (Which I don't feel that they should be.) Again, without it being spelled out, it's somewhat difficult to differentiate the two items. JD79 17:47, 1 June 2006 (UTC)

[edit] Helmholtz or Clausius

Does anyone please remember who originated the concept?

Acc to: http://webplaza.pt.lu/fklaess/html/HISTORIA.HTML

it was helmholtz in 1854

interestingly, Clausius is listed LATER with the second law in 1865 ..

Admittedly, there are a few references on the web to this (only a few!) but can anyone actuall give a citation of where Helmholtz actually said this? Cutler 11:41, July 13, 2005 (UTC)
It was neither; William Thomson was the one. I rewrote the history section to show this, with references. --Sadi Carnot 20:26, 28 June 2007 (UTC)

[edit] Third law of Thermodynamics

Doesn't the third law of thermodynamics play a role here, too? As in, assuming an expanding universe, the temperature will decrease to approximately zero - hence the entropy will go to zero, which I guess actually avoids the whole Heat Death at the end, ultimately going towards the Big Freeze. Or is there a way in which the temperature stays at a non-zero value? (I guess this would be possible with a critically flat universe.) Mike Peel 21:56, 15 March 2006 (UTC)

It is my understanding that the temperature will not reach zero because heat is the "basest" form of energy and since energy can neither be created nor destroyed (more or less) then there will always be heat. There will just be a lack of any type of mechanism to change heat into anything else, and everything will be the same temperature. JD79 17:50, 1 June 2006 (UTC)
Though, that temperature would be the limit of e/x, where x is... whatever you want it to be, but something that would give you something like "heat density", as x (essentially the size of the universe) goes to infinity, and e is the 'total' amount of energy that exists. e's exact value doesn't matter, by definition, the limit is 0. So, the average energy is, effectively, 0.... --67.233.205.187 (talk) 03:28, 16 March 2008 (UTC)

[edit] Fate of the Black Holes is wrong

Black holes will only boil away if their temperature is greater than the temperature of the background radiation. Otherwise they will continue to absorb more energy from the background radiation than they give up through Hawking radiation. At the moment (temp = 2.73 K), the tipping point is for a black hole to have approximately the mass of the planet Mercury.

The scenario in the article at the moment appears to be based on the Big Freeze scenario, with the CMB temperature continuing to fall as the universe continues to expand.

But what happens with the Heat Death scenario? Any little black holes presumably boil away. But bigger black holes continue to grow, taking energy from the CMB, which makes it cooler. This may make more of the black holes too small to survive. Eventually, presumably, only the biggest coldest black hole of the lot survives, in thermal equilibrium with the CMB.

At least that's how it would seem to me to have to go. Jheald 13:10, 6 July 2006 (UTC).

I'm sorry, but what are you talking about?? The biggest, coldest black hole? Black holes are billions or trillions of degrees C. Also black holes wouldn't be taking energy from Cosmic Background Radiation... if anything, they'd be disbursing energy into the CBR. And you make it seem like black holes boiling away is somehow another way, besides hawking radiation for them to lose mass. (!) Uh no...
Also, I think you're confused about the Heat Death / Big Freeze issue. The article is talking about Heat Death (as in, the death of heat). It's due to maximum entropy. The Big Freeze is only talking about the universe expanding so much, all the matter is spread way out. There's still matter in the Big Freeze theory. In the Heat Death theory, all matter decomposes into energy.
Latrosicarius 17:15, 19 July 2007 (UTC)
Latrosicarius, you jumped to that conclusion way too fast. Yes, most black holes have enormous temperatures, but over long periods of time absorbing only background radiation they would cool until they reached thermal equilibrium with the background radiation. Black holes WOULD disburse energy via Hawking radiation, and also absorb energy from getting hit by the rays, obviously. The idea is that when the rate of radiation reaches equilibrium with the rate of absorbtion, the black hole would stop "boiling away", and would remain at a constant size and temperature. You also seem to think you know far more on this than he, but you posted several questions already, and, in fact, made mistakes just in that post alone. No, NOT all matter decomposes into energy in heat death, only all baryonic matter--leptons and photons still exist (I assume by energy you mean photons, but leptons are certainly matter by any ordinary definition; other energy might exist as gravitons, Higgs bosons, and virtual particles). Electrons and all 3 neutrinos are stable.Eebster the Great (talk) 18:49, 27 March 2008 (UTC)
I copied the detailed walkthrough of the scenario from an old verion of Timeline of the Universe, which was later merged into Timeline of the Big Bang, to the exclusion of this material. The relevant version, which was the last major one before the merge, is at http://en.wikipedia.org/w/index.php?title=Timeline_of_the_Universe&oldid=28769719
I don't actually have a lot of familiarity with the topic myself. At least, not enough to spot and correct technical errors. If you've got some relevant sources, by all means, go ahead and make the edit. The information here is well over a year old now, and even if it was correct at the time it wouldn't be surprising if this is now outdated. Arturus 03:45, 7 July 2006 (UTC)
I'd prefer to leave any final change to someone who's more of an expert. I just think what's in the article at the moment is not correct, if we're not talking about the Big Freeze. Jheald 17:51, 7 July 2006 (UTC).

[edit] Ultimate fate

"even smallest perturbations make the biggest difference in this era"

I suspect that this is poorly worded and should say something more like ""even small perturbations make a big difference in this era".


I agree with you, and I don't really understand the premise here anyways. Why should microscopic perturbations make a bigger different in the photon era than they do now?Eebster the Great (talk) 01:14, 8 May 2008 (UTC)
I'm a pretty big amateur at this, but it's my understanding that this is a function of approaching maximum entropy. Because the universe is so stable, the smallest events will reverberate across impossibly large scales. Think of it as the difference between throwing a rock into the ocean during a turbulent storm or into a calm pond. In the former, the splash of the rock will almost immediately be destroyed by the crashing waves. In the latter, the ripples will continue much further as there is nothing to get in their way. It still seems like a very difficult concept to comprehend and I would like to see more references and a further fleshing out of the theories. --JD79 (talk) 02:26, 13 May 2008 (UTC)

[edit] Timeline for heat death

I'm no Wikipedia formatting expert, so I'll just pose the question: is there a way to preserve the formatting in the "Timeline for heat death" in the table of contents on the main page? It looks like the black hole age is just 1040 years away, rather than 10^40 years away. Jyoshimi 18:42, 17 October 2006 (UTC)

You could just write 10E40 instead of 1040. I assume most people would understand. (68.98.52.155 01:17, 1 November 2006 (UTC))
I just changed all headers to the 10Exx format instead of the 10xx format, this made the table of content more correct but a bit less pretty. Someone with knowledge might be needed to step in Lyml 15:02, 26 December 2006 (UTC)
I've replaced the 10Exx format with 10¹⁴, etc., using Unicode superscript characters (¹²³⁴⁵⁶⁷⁸⁹⁰) which looks better, but requires better Unicode support.—Ketil Trout 20:55, 7 February 2007 (UTC)
But what if the black hole age is a mere slightly over thousand years away?! Dun dun dun! Not only did I just break countless laws of thermodynamics, but we have less time than we thought to create a utopic society and learn everything we can about life, the universe, and everything! Pass it on through the generations, and mark it on the calendars of the future! There's only 1039 years left now! Shadow Scythe of Strongbadia?! (talk) 07:44, 23 November 2007 (UTC)

Awww...crap.

Yeah, keeping it at 1040 might scare some people. —Preceding unsigned comment added by 68.227.163.40 (talk) 03:14, 8 May 2008 (UTC)

[edit] Question

How does this theroy explain the whole "energy can not be created or destroyed" law. If the universe is going to be nothing but photons, etc, in what form will all of the energy be in? --Cngodles 16:03, 6 March 2007 (UTC)

Energy is defined as the ability to do work. I think that the form of energy for a photon would be related to its wavelength. --Comosabi 17:53, 30 March 2007 (UTC)
Photons do indeed have energy, and this would be where most of the energy of the universe would be at heat death (unless some mechanism converts a lot of mass to neutrinos or what-have-you instead of photons). Entropy doesn't change the amount of energy present; instead, it's a measure of how much energy is "unavailable" (i.e., can't be tapped to do further work). A universe experiencing heat death could be described as being at maximum entropy, but an equally valid description is to say that all of its energy is unavailable (heat, but no heat gradients to tap for power, and so forth). --Christopher Thomas 04:08, 31 March 2007 (UTC)

[edit] Role of Dark Energy and Dark Matter

Keep in mind that ordinary matter accounts for less than 5% of the matter in the universe, while the rest is comprised of Dark Matter, ~20%, and Dark Energy, ~75%. While Dark Matter is not known to contribute to the expansion of the universe, Dark Energy does cause the universe to expand, since Dark Energy repels itself. The understanding of Dark Energy is still in its infancy, but any discussion of the Heat Death theory requires the inclusion of Dark Energy and Dark Matter. Comosabi 17:49, 30 March 2007 (UTC)

I've updated the relevant section to make it clearer, and to remove the flagged weaselling (or at least, to clarify where it comes from). As far as the question of whether the universe is open or closed is concerned, dark matter and normal matter are equivalent (only the total mass density of the universe matters). Dark matter may affect the final form in which matter exists in a universe that experiences heat death (in particular, if it's the most stable form of matter, normal matter may be converted to it by some mechanism). However, the best guess is that all normal matter decays into photons (via being absorbed into black holes that later evaporate), and that dark matter is either processed in the same manner (if it has enough self-scattering to diffuse into one or enough time to tunnel into one), or stays dark matter (decaying to the most stable dark matter particle, if it isn't already in that state).
Dark energy, on the other hand, causes the universe to expand in an accelerating manner. Dark energy that behaves in a manner similar to the cosmological constant, which is the simplest assumption, just perturbs the final state of the universe a bit (it's still a Big Freeze, but the universe doesn't quite reach heat death). Dark energy with the properties needed to produce a Big Rip scenario gives you a very different situation, but I'm not sure how entropy is affected under those conditions. My impression is that you end up with an arbitrarily large amount of usable energy, and so low entropy, but I could easily be wrong about that. One of the lurking physics-types may be able to give a better answer. --Christopher Thomas 04:42, 31 March 2007 (UTC)

[edit] Tweaks to "current status"

I've partly rewritten the "current status" section to avoid weaselling. To the best of my knowledge, it reflects the current beliefs about the probable fate of the universe, and for completeness it touches on noteworthy past conjectures (while making clear which ones are current). Two things are needed: The crew from Wikipedia:WikiProject Physics or a similar crowd needs to check it for accuracy, and all of the statements marked with "citation needed" templates need to get properly referenced. These references certainly exist; I just don't know them off the top of my head (whereas physics and cosmology types might). --Christopher Thomas 04:52, 31 March 2007 (UTC)

[edit] Compared to Big Rip or Big Freeze, is this theory considered to be the most likely to occur?

^Topic 64.236.245.243 14:57, 14 June 2007 (UTC)

That is an interesting question, though I do not see it as something of great importance in this article, which is about how a heat death would occur. But to be honest, scientists cannot really be sure. However, one problem for the heat death scenario is that the universe is an open system due to its expansion. This might pose a problem for entropy ever approaching maximum. Another possible scenario is that the universe runs out of hydrogen and all stars die. As for what happens next, that is outside my knowledge. Overall, there is so much we do not know about the universe, so many varying factors, and so many possibilities that there is no scientific consensus (as far as I know) on the final fate of the universe. 68.175.106.168 05:06, 13 October 2007 (UTC)

Heat death of this type is considered unlikely, as no experiments have ever discovered the decay of a single proton, and the theory which requires proton decay suffers from numerous other problems. I can't calculate odds or anything, but this appears to be much less likely than the big freeze or big rip, but probably more likely than the big crunch, which would require a massive, inexplicable, and not usually theoretically accepted cosmic collapse, also against experimental data. However, if protons are stable, a big freeze-esque scenario can still be considered a heat death, since all matter as protons, electrons, neutrinos, and photons would have the highest entropy. Hopefully the Large Hadron Collider will give further insight into this area.Eebster the Great (talk) 19:00, 27 March 2008 (UTC)

[edit] Eh?

"The probability of all things approaches a maximum of 1 in this age. (i.e. a school bus randomly appears out of the nothingness) All comprehensible laws of reality cease to exist. A surrealist universe begins."

What?

I was about to comment on that same passage. I'm far from having even an average understanding of physics, but doesn't "maximum enthropy" mean that there is not usable energy left in the universe? And if all matter has decayed, down to even the proton itself, there's nothing to hold information about what a "school bus" is or looks like, right? So one couldn't possibly "randomly appear out of the nothingness". And certainly life couldn't appear in such a universe, so the probability of "all things" would certainly not be "1".190.73.98.191 15:00, 5 July 2007 (UTC)
I removed it; it's not only wholly illogical on its face (from nothing, nothing comes) but also vandalism wrapped up in pretty words. 75.66.172.38

[edit] Possible Flaws Section

I've deleted the section until someone busts out some sources, or said section makes some degree of logical sense. 75.66.172.38

[edit] Contents

Did anyone notice that the powers in the content box aren't displayed correctly and look like they're part of their bases (eg. 1014 years)? —The preceding unsigned comment was added by 213.222.167.61 (talk) 23:35, August 22, 2007 (UTC)

[edit] Image captions

We don't need poetic captions in an encyclopedia. -- 195.195.166.31 (talk) 14:21, 1 March 2008 (UTC)

+1 User:Krator (t c) 21:38, 17 March 2008 (UTC)

[edit] Neutrinos

Neutrinos do not decay, nor interact with photons, therefore they will be remaining after all other matter has been lost. —Preceding unsigned comment added by 144.173.6.75 (talk) 16:04, 13 March 2008 (UTC)

And as such, the article mentions that leptons will persist for a very long time if not until the end of the universe. The only reason they perhaps would not exist to the very end would be if all the leptons in the universe were swallowed by black holes before those black holes faded away. I don't see there being an adequate reason all leptons would be thus swallowed, though, so I imagine some neutrinos and electrons would indeed exist at the end of the universe. Eebster the Great (talk) 01:08, 8 May 2008 (UTC)

[edit] Planets fall or are flung from orbits: 10^15 years, stars by 10^16 years

Is there a source for this? Serendipodous 10:42, 2 April 2008 (UTC)

[edit] This entire article assumes proton decay

I think something has to be done about the fact that this entire article assumes proton decay to be true, despite a complete lack of evidence that proton decay even exists. Most of the article assumes proton decay as automatically true. That makes most of this article speculative. Seems to be a problem for a Wikipedia article, based on what I know. Any thoughts? SkepticBanner (talk) 02:28, 19 April 2008 (UTC)

I noticed that too. "If estimates of the half-life of protons are correct," then the article makes sense, but it has to clear up the fact that there isn't any evidence that protons decay. Besides, the article seems to assume the lower bound for proton half-life (if it were shorter we would have observed proton decay), without providing a good reason for doing so. Eebster the Great (talk) 01:02, 8 May 2008 (UTC)
Mostly unrelated, but in the same paragraph, is the statement "Effectively, all matter would be contained within black holes, which are immune to proton decay, and leptons". Why are black holes immune to proton decay? I can't find anything in the black hole article either --JD79 (talk) 02:23, 13 May 2008 (UTC)

[edit] What if it's final?

What if the heat death is final, and nothing wlll ever change after that? JIP | Talk 19:40, 20 May 2008 (UTC)

Heat Death is supposed to be final. That's what death means. But particles will still exist on the Quantum level if it makes you feel any better. So there may always be some Quarks and Leptons to form into something. They'll have an infinite amount of time after all. That could be how this Universe was created in the first place.76.31.64.54 (talk) 14:43, 29 May 2008 (UTC)