The Technium

There Aint No Heat Death

There’s a famous Woody Allen scene in the movie Annie Hall when the young Woody is brought to the psychiatrist’s office because he is depressed that the universe will keep expanding. Unstated in the scene was the popular notion that this constant expansion meant the universe was running down. And as Woody was wise to notice, that exhaustion should be depressing.

The scientific term for the universe running down is cosmic “heat death.” The idea behind heat death is that all the differences and distinctions we see in the universe today — all objects big and small and all energy (heat) — in the end becomes dilute with expansion until there is no differentiation of any sort between them, only 100% homogenous gray background noise. All life, all potential is gone and dead.

Cosmic heat death stems in part from the second law of thermodynamics which states that differences in heat will equalize over time. In the 1850s Lord Kelvin and others extrapolated this equalization to imagine what it meant for the universe as a whole. Given enough time the universe will eventually be equalized to total stillness. The eventuality of this end state was highly accepted and somewhat the orthodoxy in textbooks. The universe was running down to heat death.

But Freeman Dyson, the legendary physicist, makes a interesting argument about why there isn’t heat death. Writing in the New York Review of Books about James Gleicks’ new book The Information, Dyson mentions almost in passing that “Thanks to the discoveries of astronomers in the twentieth century, we now know that the heat death is a myth. The heat death can never happen, and there is no paradox.” As an explanation Dyson offers his Cooking Rule illustration:

The belief in a heat death was based on an idea that I call the cooking rule. The cooking rule says that a piece of steak gets warmer when we put it on a hot grill. More generally, the rule says that any object gets warmer when it gains energy, and gets cooler when it loses energy. Humans have been cooking steaks for thousands of years, and nobody ever saw a steak get colder while cooking on a fire. The cooking rule is true for objects small enough for us to handle. If the cooking rule is always true, then Lord Kelvin’s argument for the heat death is correct.

We now know that the cooking rule is not true for objects of astronomical size, for which gravitation is the dominant form of energy. The sun is a familiar example. As the sun loses energy by radiation, it becomes hotter and not cooler. Since the sun is made of compressible gas squeezed by its own gravitation, loss of energy causes it to become smaller and denser, and the compression causes it to become hotter. For almost all astronomical objects, gravitation dominates, and they have the same unexpected behavior. Gravitation reverses the usual relation between energy and temperature. In the domain of astronomy, when heat flows from hotter to cooler objects, the hot objects get hotter and the cool objects get cooler. As a result, temperature differences in the astronomical universe tend to increase rather than decrease as time goes on. There is no final state of uniform temperature, and there is no heat death. Gravitation gives us a universe hospitable to life. Information and order can continue to grow for billions of years in the future, as they have evidently grown in the past.


This is a lot to wrap your head around. It was total news to me. Dyson’s explanation is that extremely big objects (astronomical in size) obey a different thermodynamic law that “ordinary” objects, just as extremely small objects (quantum level and smaller) obey different energy laws from the large. The realm of the super large and super small are different from the rest of us. Dyson mentions that the famous Chinese dissident and astronomer Fang Lizhi and his wife had published the best explanation he had seen of this phenomenon in a chapter called “How Order Was Born of Chaos,” in the book Creation of the Universe. (Source of he illustration above.) Fang offers a very technical argument based on the fact that gravity will affect different kinds of energy differently.

The reason why the presence or absence of heat death is important is contained in Fang’s chapter title: the origin of order. It is harder to explain the constant emergence of increased order in the universe over time if the universe is running down to a death state. Heat death can permit temporary order, but it would not have room for unbounded unlimited order. But a universe without heat death would more easily permit what Freeman Dyson calls infinite growth “in infinite directions.” There would be no limits on how much new order could be possible.

Fang believes that gravity changes everything. An oversimplified summary of Fang’s theory is this rough equation: Radiation + Particles + Gravity == Infinite Information and Evolution, as expressed in this chart from his book.


In case you think this tidys up everything with a neat explanation, please note that we have no idea what gravity is, and no idea what causes the universe to inflate. Other than that, all is clear.:-)

The Fang/Dyson idea (for the lack of a better name) says that rather than an inexorable sinking towards heat death, the universe is biased toward a slow and steady march towards increasing differences over time. Gravity will continue to accentuate the uneven clumping of matter, and create ever more uneven energy potential, constantly building up order, even while local areas run down. But over the very long term, the universe as a whole is running up. No need to worry, Woody.

  • Mike4748


    cells form, reproduce, and die within complex organisms that are born,
    reproduce, and die, within species and civilizations that eventually
    segue into new species and civilizations or simply carry on until they
    become extinct. All because stars are born, age, die, and are replaced,
    some former and current stars facilitating habitable planets and life.”

    quick version is simple and seems irrefutable. “We are star stuff.”
    Star stuff comes from dead stars. The death of stars contributes to the
    theoretical heat death of the universe expected to run its course
    trillions upon trillions of years from now. Wouldn’t it be fair then to
    say that the existence of Earth,life, and you and I are aspects of the
    heat death in progress? Yet I have never found this pointed out.

    it relates to disorder in certain respects, people often become
    confused about “entropy,” the second law of thermodynamics, as disorder.
    So, it is being redefined in many introductory textbooks for physics
    and chemistry as energy dispersal thanks to retired chemistry professor,
    Frank L. Lambert. “Energetically, the second law of thermodynamics
    favors the formation of the majority of all known complex and ordered
    chemical compounds from the simpler elements. Thus, contrary to popular
    opinion, the second law does not dictate the decrease of ordered
    structure in its predictions, it only demands a “spreading out” of
    energy in all processes.”–Frank L. Lambert, from the website:

    This all comes as a confirmation of something I
    have wrestled with for some time as a non-scientist, although science
    does run in my family. Doing a lot of reading that sometimes left me
    scratching my head in regard to the traditional definition of the second
    law, (Such as work by Stephen Hawking.), I discerned many processes
    that would be defined as entropy that also happen to be necessary for
    evolution and life.

    All of these issues are addressed in the
    title essay in this short book which was rated 5 stars on Goodreads.
    There are also several poems pondering aspects of science and/or
    spirituality, often from a Panentheist perspective, one of which
    appeared in Philosophy Now Magazine.

    Celebrated physicist and
    author, Louis Del Monte. “Excellent question. Yes, life is an aspect of
    the “heat death” in progress.” via Twitter.

    “…Latranz is a burgeoning Albuquerque author with obvious skill at his craft.”~Local i.Q. newspaper.

  • Febreze

    Disorder isn’t increasing. Symmetry order is increasing, and grouping order is diminishing. That can explain why we get ordered things like life and galaxies. What looks like increasing disorder is only the passage from one order to the other. The bing bang atom was the top of grouping order. The Universe is now going to absolute zero and perfect symmetry (balance).

  • Febreze

    It states that usable energy is decreasing. That’s what entropy is. Science links that to disorder, because hey, we know the Universe “started” at the Bing Bang, and what could be more ordered than the Bing Bang pre-atom? but imo its all wrong. Its more about going from one order to another, about imbalance going towards balance.

    • AnthonyC

      Well, dig down a level. More precisely, the second law of thermal dynamics is the observation that given some amount of energy or matter and some types of ways of arranging it, those macrostates (defined by properties like temperature, density, pressure, etc.) that can be made in more ways (microstates, where you assign each unit of matter and energy its quantum state) are more likely to arise spontaneously. That’s it. It’s the counting principle. Divide the number of microstates corresponding to a particular macrostate by all possible microstates, and you have the probability of the system being at that macrostate when you observe it. And the logarithm of the number of microstates (times Boltzmann’s constant) is the entropy.

      Of course, for anything for of the entire universe, some outside entity could intervene to adjust its state. Boltzmann’s constant is the experimental result, showing how much work it takes to influence the state of a system, lowering its entropy.

      What you are calling symmetry, or balance, is a maximum entropy state, precisely because many arrangements or interchanges of matter and energy have no effect on the overall system. It has no gradients of matter and energy that will result in spontaneous, internally-driven change.

      The issue with this particular one of Dyson’s speculations is that he ignores most of the system’s entropy. He looks at “a star” getting hotter and some other object getting colder and sees a spontaneously forming gradient. So what? The expanding cloud of gas and light they give off carries enormous and growing entropy no matter what a shrinking core does, and while the core can only shrink until it disappears the cloud can expanding indefinitely. Entropy still goes up.

  • xuinkrbin

    Kevin Kelly, I am about 3 1/2 years in Your future but have a great big across-time-and-space kiss for this article. Thank You so very much!!!!!!!

  • Quentin

    My doubt about heat death is how can you apply the laws of thermodynamics to the universe which is not a closed system ( it is continuously expanding with accelerating rates) ??

  • abrogard

    In Dyson’s scenario the sun is losing energy all the time. That’s the point isn’t it? That lost energy is out in the universe representing increased entropy.

    there is no mechanism to translate that energy back into matter is there?

    matter has been ‘destroyed’, converted to energy. can’t be converted back. so with no matter to act on gravity does nothing. the universe sits there, a vast energetic gravitational field and nothing more.

    that would be what it is now, in fact, only at this stage imperfect, wouldn’t it?