Entropy in a casual definition is the tendency of things to progress from order to disorder. There are a variety of specific definitions in different arenas of thought. For example, heat will diffuse from one side of a room to another until the entire room is roughly the same temperature. In thermodynamics then, entropy is the tendency to minimize the variation in heat energy throughout a medium. Other disciplines have their own meaning. In biology entropy might refer to the destruction of complex structures. In cosmology it might be defined to be a part of any process that is irreversible (like matter falling into a black hole). What happens when this natural entropic process is reversed, just slightly?

Unfortunately, the general concept of entropy is not always well defined in a technical sense, but it has captured the imagination of many scientists and natural philosophers.

I am thinking about a region of anti-entropy (or negative-entropy, if you prefer) which is a place where there is a tendency of things to progress from disorder to order. There are many interpretations of what it would mean if we lived in a strongly anti-entropic world, but these interpretations are typically tied to a specific technical concept that ends up being difficult to use in a worldbuilding context.

One classic interpretation of anti-entropy under the order/disorder paradigm would be a shattered vase spontaneously reforming itself, or a spilled mug of coffee spontaneously reforming and up-righting itself. If entropy is the spontaneous creation of disorder, then anti-entropy is the spontaneous creation of order. In the cosmology context we can imagine reversing an irreversible process. If you were to reverse the black hole process, you would see matter, energy, or even complex structures like space ships spontaneously generate and fling themselves away from their origin (AKA a "white hole"). Anti-entropic behavior under the thermodynamic concept would be spontaneous concentration of heat energy. These are neat concepts, but they're such strong strong interpretations that they would disrupt our normal understanding of life.

We never expect a broken vase to spontaneously un-shatter itself, and the inhabitants of this anti-entropic field would not either. Nor would they expect light and matter to spontaneously generate, etc. However, there is a minor tendency towards ordering the world rather than disordering. They might count on the fact that cracks in ceramics slowly fix themselves. Refrigerators are a little more efficient because thermal insulation just works a bit better. Dust might tend to clump together in corners. Kicking a pile of gravel would tend to result in a few odd stacks of pebbles.

  1. What kinds physics would be fudged just a little bit such that our world would look basically the same, but anti-entropic phenomena would occur?
  2. What kinds of phenomena would be intuitive to an inhabitant of a slightly anti-entropic environment?
  3. Would any major physical processes necessary for life be majorly affected?
  4. It might be necessary to say that small-scale local phenomena are allowed to be anti-entropic, but large scale phenomena are required to behave as normal. Could those two things be reconciled?

I'm thinking more qualitatively than hard-science answers, but those are certainly welcome. I'm also not limiting myself to the fields of science I've discussed, those are just the ones I'm more familiar with.

  • 3
    $\begingroup$ I believe the key is defining what sort of order this place tends to. Your examples seem to say that a certain structural ordering is preferred. Maybe the universe "likes" smooth surfaces (like an uncracked vase). The thing is, there are all kinds of different orders but only one disorder. What if all atoms of the same kind tended to clump together? That would be order of a kind but not conducive to life. $\endgroup$ Commented Dec 30, 2016 at 13:09
  • $\begingroup$ If I recall correctly, you can't reverse Black Holes even in theory. $\endgroup$
    – Ayutac
    Commented Dec 30, 2016 at 13:10
  • 1
    $\begingroup$ @HughMeyers The universe can't tend towards order without completely violating physics/maths as we know it - If you break a vase from a single point, there is one configuration where the crack in the vase is perfectly smooth, while the number of configurations where the crack is not smooth numbers billions upon billions upon billions. So, the case where the crack is perfectly smooth is so unlikely to occur that it's essentially impossible. Even an unbroken vase isn't going to be perfectly smooth for the same reason $\endgroup$ Commented Dec 30, 2016 at 14:02
  • 1
    $\begingroup$ @Mithrandir24601 Well, yes, but the question is about what it would be like to have certain anti-entropic behaviors. What I'm saying is that step one is figuring out what that means. OP gives the example of cracks in ceramics slowly fixing themselves. Why? What makes that particular kind of order the favored one? Why not have all objects slowly turn themselves into spheres? Or have all molecules form into crystals? Or all like elements tend to migrate together? I think we need to know that before we can give a good answer. $\endgroup$ Commented Dec 30, 2016 at 14:21
  • $\begingroup$ Points for sidestepping all of the landmines that cluster around trying to reverse entropy, btw! $\endgroup$
    – Cort Ammon
    Commented Dec 30, 2016 at 17:08

7 Answers 7


In a sense the Earth is an anti-entropic environment, if one ignores the big picture. That big picture is that the Earth is not an isolated system. Every day a huge amount of energy arrives in the form of sunlight, and every night almost exactly the same amount of energy is radiated into the cold darkness of interstellar space.

This energy flux causes all sorts of interesting things to happen. Things such as life. Complicated ordered structures growing out of random inorganic collections of atoms.

I'd say that mild anti-entropy might look a lot like what we are used to, but absent that huge ball of hot gas we call the sun. If total entropy is decreasing, an energy flux from a hot sun to a cold rest of universe would not be needed to "make things happen".


What you describe actually is reality. It is exactly what life does.

What kinds physics would be fudged just a little bit such that our world would look basically the same, but anti-entropic phenomena would occur?

Don't mess with this one. This would necessitate an increase in energy of the system. Doing so globally would violate the conservation of energy. By Nother's Theorem, conservation of energy is directly entwined with the time symmetry of the laws of physics. To have global anti-entropic phenomena, one would literally have to have laws of physics which change over time!

Instead, you would probably do best by modeling an "external" energy source. When we look at our planet, the sun acts as an external energy source for all intents and purposes. We have virtually no control over what it does, and it's emitting energy for a long enough period that everyone except astronomers and cosmologists can get away with pretend it will never die. This can create a local anti-entropic region which appears to be global simply by choosing to ignore the parts which are increasing in entropy (inside the sun)!

What kinds of phenomena would be intuitive to an inhabitant of a slightly anti-entropic environment?

Anything life-like would be intuitive. In fact, one of the characteristics of life that science recognizes is something called negentropy, which is the term given to how creatures use metabolism to decrease the entropy of their selves (by expelling more entropy than they consume). It's the more generalized version of what a refrigeration cycle does.

One key phenomena that would be of interest is a pattern in what order does appear. For example, life on Earth has a tendency to form self-reflective patterns. Our children generally look like us. From a genetic perspective, they look very much like us! If there is some global concept of order increasing, there is some metric describing what is more ordered than other things. It would be very interesting for scientists in such an area to explore these phenomena.

Would any major physical processes necessary for life be majorly affected?

Hopefully by now it's clear the answer is nothing at all needs to be affected, because this is what life does.

It might be necessary to say that small-scale local phenomena are allowed to be anti-entropic, but large scale phenomena are required to behave as normal. Could those two things be reconciled?

As stated, this is exactly what life does. It allows the body to oppose entropy by decreasing the entropy of that around them. Not only can these two extremes be reconciled, they are, in fact, what occurs!


Entropy can be a very abstract idea, so my answer will involve more abstraction than hard-science, forewarning.

You're asking about anti-entropy, or reverse entropy, which is a huge conceptual issue because entropy itself states that things in high-energy states will naturally degrade into lower energy states, and you want the opposite. (if only very slightly) Essentially we're asking entropy to stop being entropy anymore.

Entropy is broad. Technically, heavy radioactive particles decaying into lighter, more stable elements is entropy, and so is erosion. It applies to heat transfer and electrical systems. It's well defined as the freakin' Second Law of Thermodynamics. You're asking to break physics, and you know that the scientists never appreciate it very much when you do that.

Without it, we're saying that instead of a rock breaking down into lower energy states, it could spontaneously assemble itself into higher energy forms.

But we have examples of things that flow against entropy, don't we?

This is a question I've debated with friends many times, and I always land on "Yes, life itself seems to organize energy," although I haven't been able to convince most of my friends of that yet. In fact, I would go as far as to say that Entropy is the natural selection that Evolution is fighting against, or, er working with.

I'll even go out on a limb with the most radical example I can think of, take Virtual Reality theory. Everyone is still toying out the details, but I believe the one thing we can all agree on is a larger reality would be of the same fundamentals this derived reality contains. Namely: evolution, and entropy.

The theory is, with unlimited time and too broad of possibilities, evolution might become stale, and the rate it could reduce its entropy would slow. So create a variety of VR's, all with slightly different (much more strict) laws of physics and all with a time limit, so that evolution might explore the specifics of reducing its entropy in certain areas.

Doesn't matter if that's too far off the deep end for you, the point is: Entropy may be so fundamental it may span dimensions / realities.

And to try to actually answer your question in the most elegant way I can think of:

What is anti-entropy? = evolution.

Er, or Life itself.

Or let's just create a VR with the parameters you specified and run the simulation. :)


The second law is rather special. There are many formulations, one is "Particles don't care" (which is handsomely brief, if short on technical detail). In a world in which the second law is broken, even slightly, is a world that posits that particles have desires.

To break the second law would mean that the Universe is fundamentally non-rule based. It would mean that the building blocks of nature can act in a way that can act out of volition. A universe without the second law is a universe without science. To quote Eddington:

The law that entropy always increases holds, I think, the supreme position among the laws of Nature. If someone points out to you that your pet theory of the universe is in disagreement with Maxwell's equations — then so much the worse for Maxwell's equations. If it is found to be contradicted by observation — well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation.

A world in which the second law is broken is a world based on magic. A world in which a jar can mend itself is a world in which the quarks and electrons that make up a jar have a desire to see it made whole, and enough intelligence to understand and act on that desire.

I can think of one existing example of a book which posits intelligent particles, and that is Phillip Pullman's Dark Materials trilogy. In that world dust is a particle of consciousness, which allows humans to be conscious, and allows for angels made of pure dust to form.

Pullman wasn't going to let the science get in the way of a good plot. The trouble with an intelligent particle is that it becomes a deus ex machina that needs to be handled as carefully as any other use of magic.


The second law of thermodynamics states that global entropy of an isolated system always increases or remains constant

This tells us a couple of things that are relevant here:

  • If the system is not interacting with anything, entropy cannot decrease. I.e. the entropy of the universe will never decrease without violating the laws of physics as they are currently known
  • If you have a sub-system of the above isolated system, the entropy of the sub-system can decrease. However, this causes entropy somewhere else to increase so that the total change is either positive or $0$

A simple example of a decrease in entropy of a sub-system is taking some water vapour and cooling it down to become liquid - you've taken heat out of a system. This heat has gone somewhere else and increased entropy there, but the entropy of the water vapour has decreased. A fridge is a good example of a physical object that can cause this to happen.

A white hole is different, as it (I think) decreases the entropy of the universe, so invalidates the second law of thermodynamics and so are assumed to not exist because:

“The law that entropy always increases, holds, I think, the supreme position among the laws of Nature. If someone points out to you that your pet theory of the universe is in disagreement with Maxwell's equations—then so much the worse for Maxwell's equations. If it is found to be contradicted by observation—well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics, I can give you no hope; there is nothing for it but to collapse in deepest humiliation.” Sir Arthur Eddington (The Nature of the Physical World, 1915)

In other words, anything that increases order in any way gives a decrease of entropy of whatever is becoming increasingly ordered, but at the cost of increasing the entropy somewhere else.

So to answer all your other questions: We already live a world where entropy of small regions can decrease!

Interesting aside: It is possible for a "broken vase to spontaneously un-shatter itself", it's just that the probability of such an event occurring is so small that you would have to wait longer than the age of the universe for it to have any reasonable probability of occurring

Edit: I've re-read the question and feel that I should add the below: Things like kicking a pile of gravel and the result being smaller piles of pebbles is 'impossible' due to probability, not entropy. That is, as per 'interesting aside', it's perfectly possible for such a thing to happen, it's just that the probability of it happening is tiny when compared with the probability of it not happening. Saying that an isolated system tends towards maximum entropy is essentially the same as saying that the system tends towards the most likely outcome, because they are the same thing. The above quote from Eddington is true, not because of physics, but because a system increasing in entropy is a system tending towards the most likely outcomes, which is unavoidable by definition. So, if you want to decrease the entropy of something, you can do it easily (e.g. pour boiling water into a mug, then put it in the fridge). If you want an area where this happens by itself, then you need to either travel backwards in time, a white hole or something similar, which is all assumed to be impossible (to current knowledge) because they violate the second law of thermodynamics. Quantum physics does however do weird things with probabilities (see e.g. the Wigner function), so who knows what's actually possible on the tiniest of scales? Using quantum physics to decrease entropy of a subsystem is entirely possible - http://www.nature.com/nature/journal/v474/n7349/full/nature10123.html - but again, the 2nd law of thermodynamics isn't broken.

To sum up, entropy is probabilistic by definition, so things like vases fixing themselves doesn't happen, not because of physics, but because of probability. However, decreasing entropy of a subsystem (at the expense of increasing entropy somewhere else) is an everyday occurrence.


Pocket of space where time is going in reverse

The simplest thing I can think of that would meet your goal would be to take an area of space and in that space time is flowing backwards. If you are outside of the area and were capable of observing in, things would appear as you described. Note that since everything is flowing in reverse light and other things you would observe would also be flowing in reverse, so trying to observe what is on the other side of the barrier should look really weird if not totally impossible.

Getting into such an area would and should be a challenge. An area of space flowing temporally backwards would create all kinds of issues at the edge where it touches normal space. I would put it on the same difficulty level of trying to fly through a black hole. Faster Than Light (FTL) travel typically is hand waved in that it does not result in time travel. In your case I would theorize that a ship in FTL bends space and time and so it could bend reality just enough to cross the barrier separating the two. Note though once you are on the other side time would appear to be flowing correctly inside while everything outside of the space would be traveling in reverse. Needless to say this would be a form of time travel with all the fun paradoxes that come with it.


Interesting notion, IMHO the key is in the "mildly" part of your question: What constrains/limits the non-thermodynamic behavior, so the world still mostly works as we expect (and are well adapted to survive in), except when magic adds something useful to the tale.

I had related thoughts that magic (or the 'power'driving fictive magical happenings) might be explained by something (probably localized in time and space) distorting thermodynamic behavior, something like eddies or vorticity in entropy. Think 'magical ball lightning.'

For better world building, think about practical in-story aspects and how they could help you.

  • Where and how much 'magical power" is available?
  • Available to whom?
  • Under what conditions can it be unleashed?
  • What happens if a spell using negative entropy goes wrong?
  • Is it a finite resource? (How) can you get more?

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .