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Universe Has 100x More Entropy Than We Thought
eldavojohn writes "Previous estimates are now thought to skimp on the entropy of the observable universe. The researchers contend that super-massive black holes are the largest contributor of entropy. Since they contribute two orders of magnitude more than previously thought, the total of all the observable universe is correspondingly higher. The paper highlights (in gruesome detail) new issues that arise with these new calculations — like estimating us a little bit closer to heat death (moving entropy totals from 10^102 to 10^104 out of a maximum of 10^122)."
I can finally move forward with the plans for my Entropy Cannon.
Here's a link for anyone curious about the Heat Death of the Universe concept
http://www.mchawking.com/includes/lyrics/entropy_lyrics.php
I propose a Fourth Law of Thermodynamics: There's more entropy than you think there is.
Things are just falling apart all over!
Qxe4
Universe Has 100x More Entropy Than We Thought
Scientists must have discovered my daughters room.
So, it looks like we are closer to the novel than previously thought? And rather than witnessing the "end of the univers" (with dinner and wine) we are observing the cleaning crew (black holes) picking up the ... er ... mess?
L'esperienza de questa dolce vita (The experience of this sweet life) - Dante Alighieri, The Divine Comedy
Because of Neutron decay we've only 10^49 years anyway.
Oh, wait... that's going to happen anyway.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
Everything that comes into a black hole comes back out eventually via Hawking Radiation. It goes in as a star or a chicken or a pistachio and comes out as random energy, which is a pretty clear increase in entropy.
"I zero-index my hamsters" - Willtor (147206)
With the "news" (circa 1998) that the rate of expansion of the universe is increasing, it seems to me that worries about the heat death of the universe should be put on hold. There's something (currently labeled "dark energy") about cosmology that we simply lack sufficient understanding of.
Granted, Evolution isn't the nicest PIM software on the market but impossible? I think that's a bit harsh a verdict.
USE HOT GRITS WITH STATUE OF NATALIE PORTMAN (NAKED AND PETRIFIED)
The universe is still expanding in all directions at the speed of light, then the entropy per unit volume will still stay low enough to be habitable, right? Or is the problem that the rate of increase in volume will not keep pace, since it takes longer and longer for the universe to double in volume at a constant rate of expansion?
So if I connected my server's entropy generator to a black hole I'd never have to type a page full of gibberish to generate my SSH key pair again!
"Order" and "disorder" are human perceptions, not states of matter and energy. Sometimes we perceive more order when there are clear differences in energy states, sometimes we perceive less
To you, which is more ordered: a bowl of cherries next to a glass of water, or a completely smooth blend of all of them? The latter is more entropic. In the case of the room, replace the garbage bin with an incinerator, and the "empty" room (plus the stuff that used to be in it) is now in a more entropic state. The fact that you personally find it tidier isn't relevant. Assuming that you might have actually needed some of the stuff that we just burned, too, you might find it a rather poor solution to the problem of a messy room.
The flaw is that entropy is not exactly synonymous with disorder. Sometimes it is, if a disordered state has a lower energy potential than a higher ordered states. But in many cases, such as falling to the bottom of a gravity well, the "ordered" - actually just more compact - state is the lower energy state. Entropy is just the degree to which a system has moved from a higher energy potential to a lower energy potential. If we had more potential energy after falling into a gravity well than before it, then we'd need rockets to blast ourselves from space back to Earth, rather than the other way around.
If you don't know where you are going, you will wind up somewhere else.
Wow, Vogons posting on slashdot!
Free Martian Whores!
being haughty to AC is like shouting at a tree because a squirrel annoyed you.
I don't see anything wrong with the intent of the question. Maybe he read it and found it too complex. Maybe he didn't understand it at all. Maybe he didn't read it and thought Slashdotters could give the best answer - in any case, no one's forcing you to answer his question.
Three very separate questions
Could this Hawking Radiation be harnessed?
Sure, although there are some minor engineering challenges.
That is, can it be considered as free energy
Not "free energy" because you're converting mass into energy.
as opposed to entropy?
On an entire system wide basis, entropy times temperature equals energy, so "as opposed to" is a weird phrase to use. Lots of energy emitted, at a low enough temperature, means the entropy must be high.
http://en.wikipedia.org/wiki/Entropy
"Science flies us to the moon. Religion flies us into buildings." - Victor Stenger
I want something that does the opposite. When I push a button. Without the billions of years it normally takes.
I'm afraid the BAC analogy really isn't appilcable. You're describing an impurity which builds up to a critical level to "kill" the host, and pointing out that if you could sequester the impurity the sequestered quantity wouldn't matter. Entropy is not an impurity that is slowly building up to eventually cause the universe to break; it's nothing like that at all.
I find it conceptually confusing to think about entropy as a finite/positive quantity. The way it's defined mathematically, of course, it is ... but at a physical level there's just something backwards about it.
Entropy describes the degree to which energy in a system isn't usable. If you consider as a closed system a bit of ice in a glass of hot water: the heat in the water is "useful" in this system. It will melt the ice, and then equalize the temperature of the water from the melted ice to that of the rest of the water. (That may not seem "useful"; I suppose the point is other processes could capture and use the energy for other ends.)
But, as the ice melts and the water temperature equalizes (or as any other process fuels itself by accelerating this process), you don't run out of energy (which is constant) - but you do run out of "usability" of energy. When your system contains only water at a fixed temperature, there is no way to make heat flow, and all of teh energy in the system is useless. (Again, this assumesa closed system.)
So the point with black holes is, they aren't sequestering entropy to keep it from harming the universe in some way (like your BAC example); if anything they sequester energy and keep it from interacting with the rest of the universe, rendering it useless. (Not sure how Hawking radiation fits in that analysis, though.)
If the current age of the universe is finite, then it must have come into being - been created - at some point. There's no real answer to how that might have happened within the real of science. Oh, you can say there's some multiverse which creates universes such as ours, but that just shifts the question: how was the multiverse created?
My personal creation belief is that our universe is itself a supermassive black hole in some much larger universe, and in that universe the riddle of creation has some obvious answer. Perhaps God strides around shaking hands and giving photo-ops. Perhaps you can see the moment of creation with a sufficiently powerful telescope. Perhaps that unvierse does not have afinite current age.
Socialism: a lie told by totalitarians and believed by fools.
As black holes evaporate due to Hawking radiation, does that mean that they defeat the laws of thermodynamics in some way?
No.
Next question. Would quantum mechanics offer any explanation as to why we are less close to heat death than we think we should be?
Um, your question has too many false premises behind it to have a direct answer. We're closer to heat death than we thought we were. If there are people who think we are either closer or further away than we "should be", well, quantum mechanics might offer an explanation, or might not, depending on why the subject in question thinks things aren't the way they should be. You'd have to be more specific.
"Convictions are more dangerous enemies of truth than lies."
Not RTFA.
TFS fails to use them, so I must ask,
What are the units of entropy? Can they be useful at a macroscopic level... like in describing how much entropy your bedroom contains (before it simply must be cleaned)?
The Admin and the Engineer
I'll take this a step further. Science is a useful methodology for the building of models that are extremely useful for making specific predictions. Whenever you forget that its a model, and start BELIEVING it, its no longer science. Most laypeople don't really care about science, or models, so long as "it just works" when you flip the switch. However, they like certitude. It makes them comfortable that when flipping the switch next time, the TV will keep working. Now, Newtonian Mechanics, for instance, works pretty damn well for building bridges. Is it real? Nope. But its a really useful model. It works within a context (things are large enough we can ignore quantum effects, relative velocities are low enough that relativity isn't worth considering, etc...). To say that Newtonian Mechanics is "right" or "wrong" misses not only the mark, but the target. Science is never "right" nor "wrong" in the manner in which you used the terms. It is, however, extremely useful.
Actually, the Hawking radiation doesn't come from inside the black hole.
When a particle/anti-particle pair tunnels into existence at the edge of a black hole, for some reason, the anti-particle tunnels into existence inside the black hole and is immediately annihilated by an already existing particle in the black hole (thus reducing the mass of the black hole by one particle's worth). The particle that tunneled into existence outside the black hole spins off and is referred to as "Hawking Radiation".
The wikipedia article is excellent.
*sigh* back to work...
No. Even with a finite age, there's absolutely no need for a beginning. Just like the positive reals have no first element (for each positive real, there's a smaller positive real; note that 0 is not a positive real), there need not be an earliest point in time.
The Tao of math: The numbers you can count are not the real numbers.
Everything that comes into a black hole comes back out eventually via Hawking Radiation. It goes in as a star or a chicken or a pistachio and comes out as random energy, which is a pretty clear increase in entropy.
Exactly. Another way to think about it is this: the speed of light is the maximum speed information can travel. Since the escape velocity of a black hole is greater than the speed of light, information cannot escape either.
Because information cannot escape, it means you cannot infer what went into a black hole by looking at what comes out. (Note: information being "destroyed" in a black hole doesn't prevent you from e.g. keeping a record of what you tossed into a black hole. Once it goes inside, it won't somehow destroy your records, as I used to believe was the implication.)
So the Hawking radiation must be completely uncorrelated with what went into the black hole, except that the rate of radiation emission must depend on the temperature of the black hole (which would increase from turning objects into heat). This in turn means that to give the least information possible, Hawking radiation must be the lowest quality (highest entropy) form of energy in the universe.
And, if that doesn't make sense, just keep in mind that destruction of information is thermodynamically irreversible, so a black hole must increase entropy that way.
Information theory is life. The rest is just the KL divergence.
I propose a three level scale: Messy, Messier, and Messiest objects.
Atheist movement? ROFL.
FAIL.
Interestingly, this is wrong, and Stephen Hawking lost a bet over it.
The Second Law is actually very tightly coupled to Shannon-style Information Entropy: if you knew enough information (as a fait accompli) about the current state of a system at equilibrium, you could successfully build a Maxwell's Demon that used that information to separate the system into hot and cold reservoirs, allowing you to cancel out the entropy of the system with your information's "negentropy" (as it's called). Learning the information in the first place causes your information entropy (i.e. correlation with the system, negentropy) to increase, which by physical necessity also causes your thermodynamic entropy to increase in tandem. This is why a Maxwell's Demon doesn't work: the entropy undone in using the information is always less than (or, in a perfect system, equal to) the entropy done while learning it. (If blind faith provided non-tautological and accurate information about the universe with better-than-random chance, then you could build a Maxwell's Demon that broke the Second Law -- and since the Second Law is inviolable, it must be the case that blind faith tells you nothing... except possibly tautologies if your brain uses reversible computing. If you think hard enough about it, it also disproves substance dualism.)
In the specific case of information entropy and black holes, it turns out that the information never crosses the event horizon, and thus never has to break the speed of light limits when leaving it. As modern physics and Stephen Hawking have both discovered, all the entropy of a black hole's formative mass/energy is encoded in two dimensions as ripples in the event horizon of the black hole. Black holes have also been discovered to be maximum-entropy objects in modern physics, containing the largest amount of entropy physically possible for the volume of space enclosed by the event horizon. (This has interesting implications on the nature of reality -- look up the anti-de Sitter/CFT correspondence for all sorts of 2D/3D weirdness, like the universe being equivalent to a 2D hologram.) When a quantum of Hawking Radiation emerges from the event horizon, it carries off precisely the amount of entropy equal to the entropy carried by the change in the surface area of the event horizon when expelling the quantum, thus maintaining the invariant that the black hole is a maximum-entropy object. Because "information entropy" is another way of saying "too random to predict ahead of time" -- that's what information is, by Shannon's definition of it -- the radiation looks quite random indeed. But that doesn't mean it's uncorrelated with the history of the black hole.
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