I have to admit — and I’m a little embarrassed to say this — I haven’t actually read Slaughterhouse-Five (🙈). I had to look it up (🙈). What! A character who experiences all of time at once, without any real sense of past or future?? Okay, this is going straight to the top of my reading list. Thanks, John!
For a slightly different perspective on experiencing all of time at once, you could look to *Hearts in Atlantis* by Stephen King, where one of the characters, a "breaker" seems to move around between times.
Sometimes I think physics is just here to ruin all our fun — time is an illusion, the universe is on an inevitable path to its heat death, and despite what Han Solo says, it’s not actually possible to travel faster than the speed of light.
Mountain goats and cats seem to routinely defy physics🧐 Do they know something we don't🤔 or are they able to do it because they don't know they shouldn't be able to🧐 Only the Shadow knows. Lol.
Very good points Suzi! The way entropy has historically been presented is as something bad. And for the engineers who discovered it, it was. But it's really just a fact of existence. Without it, we would have a universe of perfect uniformity with no transformation, one without life or information. It's the inhomogeneities, the energy gradients, that make everything we care about possible. Entropy is both the enabler and doom of the universe. It both gives and takes.
Is it not problematic to explain time as a product of the second law, and the second law as a product of how the universe *began*?
But I'm very much on board with entropy helping to explain consciousness, especially considering how it's tied up with information. I think it also dovetails nicely with panpsychist tendencies. Maybe entropy is the "protopsychic" aspect?
Sean Carroll often makes a distinction between time as a dimension and the arrow of time. It's the arrow of time, its one way nature, which is usually thought to emerge from the second law. It seems like the dimension itself has to exist for the second law to play out. Another way to look at it is as related and integrated phenomena.
I'm not sure that resolves it still. We cannot speak of the arrow of time itself "emerging" or "playing out" in a temporal sense, because we cannot attribute a direction to it itself, and if it's not subject to the arrow of time it must itself be reversible, at which point everything under it would be reversible too.
I think it's more likely it's a methodological blind spot for fundamental physics. That makes sense historically because at the inception of modern physics, formal and final causality were intentionally excluded. And I think it makes sense too because it models the smallest scales and simplest scenarios, and time and space seem to "coextend" ie interactions across more space and greater complexity require more time, and the more time we account for the more complicated and extended our models need to be.
If I understand your objection correctly, I don't really take "emerge" here in a temporal sense, but in one where productive models switch as we change scales. (At least for us humans.) Although I'll grant here that even this sense of "emerge" seems awkward. It's more like the statistical tendency in time sequenced relations is to increasingly fragment energy gradients and reduce further transformability due to one direction (the big bang) having lower entropy than the other (heat death, etc).
Hi Mike! Yes, that’s really helpful. I think your point about models shifting with scale gets at the heart of it. Emergence always feels slightly uncomfortable in these contexts, maybe because we’re trying to describe a statistical pattern as if it were a process. But I like the way you frame it: not a mechanism, but a tendency — something that only becomes visible when we’re dealing with systems large enough for entropy gradients to show up.
Hi Joseph — when you say that “the arrow of time must itself be reversible, at which point everything under it would be reversible too,” I wonder if that’s mixing the time-symmetric laws of physics with the time-asymmetric initial conditions. My understanding (inspired by Sean Carroll’s framing) is that the laws themselves are reversible, but the universe’s low-entropy beginning isn’t — and it’s that asymmetry that gives us the arrow of time.
So we don’t need the arrow to “emerge” in a causal sense within time — it’s more like a global feature of the universe’s initial state.
If I’m following, it sounds like you’re suggesting that the arrow of time might itself be the outcome of some deeper directional process — almost like a second-level arrow that generates the first. Is that what you mean?
I think what I'm trying to say is that the explanation of the second law by reference to an "initial state" presupposes a direction of time already. We get the initial state as a given, and then the following states seem to be more or less derived/calculated from it.
If there's no real direction to time, it should be equivalent to take any point in time as our conceptual starting point. But if we do that, the statistical understanding of entropy + the symmetrical laws should mean that the entropy on *either side* of our starting point go up, just because they are more probable. E.g. if we modelled a box of gas particles starting with hot particles one side and cold the other, entropy will increase whether we run the simulation forwards or backwards from the starting point. And that's true however we decide to start the simulation.
The fact that entropy always increases tells us that the past was logically/computationally prior to now. The statistical understanding of entropy increasing due to probability only works if time has a (logical/computational) direction.
To illustrate it, we might suppose that causality did "ripple out" from the big bang in both directions, past and future (from our POV), like the simulation ran in both directions. There's a computational direction of time underlying the entropic direction(s).
Thanks, Joseph — thinking about time is hard work, so I really appreciate your careful unpacking here.
On whether appealing to a low-entropy initial state already assumes a direction of time: from how I understand it (following folks like Sean Carroll and David Albert), the low-entropy past isn’t chosen because it’s in the past — it’s defined as the past because entropy increases away from it. I still find this incredibly hard to think about without imagining time as flowing. But the asymmetry between low and high entropy is what gives us the arrow of time. That’s the heart of the Past Hypothesis — and while it doesn’t explain why the universe began that way, it helps make sense of the directionality we experience.
I went to a talk by Brian Greene yesterday, and he reminded me of some of the bigger questions in physics right now — like whether space and time are actually fundamental, or whether they emerge from something deeper, like information, entanglement, or causal networks. He also made the point that so much of this comes down to how we interpret the findings we observe. The data and the math aren’t usually in dispute — it’s the meaning we layer on top that makes it interesting (and difficult).
But it hasn't yet, so I can move on to a related puzzle you might find entertaining. Suppose the universe were completely deterministic, and one day, the direction of time reversed. What would life be like for the time-reversed you?
My supposition is that you could not tell. At any instant in the time-reversed world, there is a corresponding time in the forward world in which the state of the universe is exactly the same. If, at that time in the forward world, you had certain memories, certain hopes and plans, certain feelings (including all your intuitions about the flow of time), and perhaps were under the illusion that you had free will, then I suppose you would have exactly the same ones (and nothing more) at the corresponding point in the reversed world.
"Time is an illusion. Lunchtime doubly so."--Douglas Adams.
In a low-to-high entropy world — the usual one — I crack an egg into a frying pan. It breaks. I see it happen, signals hit my retina, travel to my cortex, and my brain encodes a memory of the broken egg. Entropy increases.
But in a high-to-low entropy world… the egg splatters are already in the pan. And then — what looks to us like magic — the egg reassembles itself midair and lands perfectly back in my hand.
But everything is reversed — including my brain. So the parts of my brain that held the memory of the broken egg are now being unwritten. Signals are flowing out of my cortex, through my retina, back to the egg.
But I don’t feel like I’m watching an egg unbreak — I feel like I just broke it.
All the signs that tell me which direction time flows are tied to entropy. So if entropy flows the other way — I flow the other way too.
Thanks, Suzi, and yes, that's pretty much the way I see it (but see my final paragraph here.)
There are some important caveats to be made, however. The first is that it is predicated on physicalism - that our minds are the result of physical processes. Dualist and panpsychist hypotheses have not been worked out in sufficient detail to say what would happen if any of them are correct.
The second is that the reasons I have for holding this opinion only work for this particular case, with a fully reversibly-deterministic universe undergoing a complete and instantaneous reversal of all physical processes. I do not think it could be generalized to high-to-low entropy worlds in general.
While writing that paragraph, I realized that I had been careless in my original specification of the scenario. I should have written in the terms I used in the previous paragraph: "suppose the universe's physical laws were completely deterministic and reversible, and one day, every physical process reversed." The question of whether time's arrow reversed at that point seems to be an open one (by the way, I have a vague recollection of seeing that this puzzle had been proposed by Lord Kelvin or one of his contemporaries, possibly in relation to the arrow-of-time question.)
Hi Drew. Suzi said you wrote an interesting comment, and I agree. Since last week I’ve been pondering that physics may have been founded upon the metaphysical premise of entropy because philosophers (or the people who specialize in metaphysics) have failed to give them a better premise. So over there I said it’s not surprising that they spent over a century perplexed by how a magical scenario might decrease entropy. The implication was that the missing entropy should be hiding the magic. It’s a long discussion, though in case your interested, here’s where it begins. https://open.substack.com/pub/suzitravis/p/maxwells-demon?r=5674xw&utm_campaign=comment-list-share-cta&utm_medium=web&comments=true&commentId=101444666
So on to my thoughts about your scenario. And I’ll stick with the revised one from your second comment, which I consider an important clarification. If the universe’s laws were completely deterministic, *and reversible*, then what would happen if they did reverse? In that case I think we’d begin with natural function, though the funky stuff that would occur upon reversal would reflect supernatural function, which is to say, magic. I came to this conclusion in my commentary here in this thread after yours. My solution would be to found physics and all science upon the premise of causality. Thus the magic of reversible laws would technically be forbidden to mainstream science. The arrow of time here would be presumed to only move forward, and at whatever rate effect transpires by means of cause.
Thanks, and your causality-first view appeals to my intuitions more than does a block universe view, though I have to consider the possibility of that just being a sign of my ignorance of the latter.
I agree that the reversal is a magical intervention. I'm not sure that we have to exclude all magic from thought experiments, but we have to be careful that we are not subverting or begging the question by invoking it.
Right, often thought experiments don’t even work without presuming a bit of magic to set them up. But don’t let the magical parts go on to subvert points that are actually being made. From what I can tell Maxwell’s demon itself seems like it should explain any missing entropy. Anyway I’ll put my new position that causality should be considered more fundamental than entropy, into my bag of tricks for future use. It’s nice to feel like I can bitch out physicists in this regard, since I mainly seem to find flaws with the positions of philosophers and soft scientists.
It’s not exactly the block universe itself that concerns me, but rather how the block people sometimes seem to interpret it. If my wife dies, shall I take comfort that she wasn’t erased from the block universe? Nope. Just because we can epistemologically refer to any location in spacetime, shouldn’t mean that they all exist ontologically. Causality should mandate that the past is gone forever.
Yes and no. It's not quite right to say that we would feel that the egg just broke while in reality it didn't.
The arrow of time is relative, it depends on frame of reference. If we are in a simulation running forward, then reversed, and so forth from the beginning of time to some far future, a million billion times, to the simulators we look as if we live many times in both directions. But to us there is only one life and one direction of time.
The arrow of time is that of low to high entropy no matter how you instantiate it. This is why the past hypothesis holds true even in cyclic or backwards scenarios (in some external frame of reference).
I take your point - one that I had overlooked earlier.
There is another issue here which may complicate matters: causality. If we think of physical processes in terms of cause and effect - e.g. it is raining today partly as a consequence of an earlier process in which water evaporated into the air - then after the reversal, the 'actual' causes of current events (those seen by a hypothetical external observer or simulation-runner) lie on the high-entropy side of the present (i.e., in the future, if time's arrow points from low to high entropy.)
I get the impression that block universe hypotheses are seen by some as a resolution of this apparent incongruity, though I cannot say anything more about that.
Thank you. If you accept my view that the arrow of time is always that of low to high entropy, and that experience etc also aligns with the arrow of time, then I think it follows (no meta-pun intended) that macroscopic causation is always in that same direction.
In other words, if an external observer claimed to see rain precede cloud formation, I would correct them and say - that is not rain (the water ascending from the ground). That is not cloud formation. All those concepts are arrow of time-dependent. What do you think? Do you agree?
I am not convinced, but then I might not be grasping your point correctly. Here's a variant of the thought experiment that might throw new light on the question: suppose we have another reversible and fully deterministic universe that, instead of running forwards for a while and then reversing, starts from exactly the same state the first one was in at the instant of reversal, and from then on evolves according to its causal laws of physics. This process will unfold in exactly the same way as did the first universe after its reversal. Would it make sense to say that has reversed causality just because it happened to start from a particular state? What if it started from some intermediate or hybrid state?
My point is basically that rain is, by definition, water falling down to the ground. Therefore, in a frame of reference where rain is reversed, it is not rain. People in that universe do not "live" from old to young. They don't answer questions before the question is heard - because the question isn't heard at all, and it is not a question. The reversal of a question being asked, is air pressure waves coming from all over, including from the "eardrums" of the answerer, coming together and making the "asker's" vocal cords vibrate. The "people" absorb heat, inhale carbon dioxide, and produce oxygen, "eat shit" with our behinds, and puke organised food items . "Plants" and "photosynthesis" uses oxygen and sugar to produce light and carbon dioxide. I wouldn't call any of these things by their ordinary low-to-high entropy names.
A bit messy, but do you see what I'm getting at? I think it is false to say that the answer from one person "causes" another person to ask a question, because there is not anything recognisably person-like about a reverse-person. Therefore I don't think it makes sense to say that causality is reversed. Microscopically, however, I think it makes sense to say that where atom A bumped into B and makes B move faster, the reverse is true. But I'm not sure if I'd call that reversed causality. Isn't that just causality backtracked or retrodicted? Not sure.
I do think that in your copied universe scenario, there is only really one universe, instantiated twice in some frame of reference. And "reversed" is always relational, or relative. So it only makes sense to say that something is reversed when compared to something else. That's my view!
I don't think it makes sense to ask what consciousness would be like without time. My consciousness just moves along with everything else in my life.
I think there are a bunch of mysteries like time and entropy that we still need to figure out. Dark Matter? Free will?
Determinists always say that I can't have free will because physicists have no explanation for it. Well, if we can't figure out the arrow of time it might take a while to figure out free will too. But it's out there somewhere.
I love this — my consciousness just moves along with everything else.
Totally agree. There’s something humbling about realising how little we understand. Who was it that said, 'As our island of knowledge grows, so does the shore of our ignorance'?
The arrow of time is such an interesting expression; I don't know how I haven't heard of it before. We're riding the arrow of time from the Big Bang to the heat death of the universe. It's rather sobering to think about.
I've always pondered the mechanics of the human brain, especially what consciousness is and how it works. This does make me think about how the idea of entropy relates to the human brain. It seems like it spends its entire existence fighting such entropy through the constant firing of neurons and constant flow of energy; but in the end, entropy always wins!
It seems to me that calling the state of the universe at the Big Bang “low entropy”, was merely done for convenience. Let’s imagine it the other way. Here astronomers notice that instead of expanding, our universe actually happens to be shrinking. Would they then decide that the second law of thermodynamics was being violated since apparently entropy was decreasing? No they’d theorize that there was a time when the universe was far bigger and spread out though gravity was pulling it together. That spread out state would now be called “low entropy” instead of the converse. Here time would still continue, eggs would still break rather than the opposite, and hot gasses would still mix with cold gasses when confined in a box. And now physicists would say that the smaller the universe gets, the less entropy there is rather than the converse. Thus it’s an arbitrary or convenient distinction. Metaphysically, in either case I think it would help scientists to presume that systemic causality never fails.
Hey Eric! Really interesting take — it reminds me a bit of the time-reversal thought experiment Drew raised earlier in the thread. Definitely worth checking out if you haven’t seen it!
I think a physicist might push back on the idea that the early universe is called "low-entropy" just for convenience. I think they might say the reasoning comes from how incredibly smooth the early universe was, especially when you consider gravitational degrees of freedom. A hot, uniform plasma might seem messy from a thermodynamic perspective, but gravitationally, that kind of smoothness is actually very ordered. Gravity tends to clump matter together — and structures like stars, galaxies, and especially black holes carry a huge amount of entropy.
So if the universe were shrinking but entropy were still increasing, I'd imagine that we'd still have the same arrow of time — just in a contracting geometry. Physics is not my area but I think what really matters, isn’t size, but the entropy gradient. That, I believe, is what gives us a sense of direction — the distinction between past and future.
There are some speculative models where the universe might bounce or cycle, and in those cases, both ends of the cycle could be low-entropy. In that kind of scenario, the arrow of time might "flip" at the bounce — but only if the entropy gradient reverses as well. If entropy were actually decreasing in a shrinking universe, then yeah — we’d expect to see some wild reversals, like eggs unbreaking or gases unmixing. That’s the kind of paradox Drew’s puzzle seems to be getting at.
Also, just to clarify: I'm pretty sure that a more clumpy and spread-out universe is actually higher entropy, not lower.
And yes, the idea that the universe began in a low-entropy state is still a hypothesis — but it’s one that’s strongly supported by both observational evidence and theoretical consistency. That assumption (often called the “Past Hypothesis” — Sean Carroll talks about it a lot) is what makes the second law of thermodynamics — and the entire asymmetry of time — make sense.
As for systemic causality — totally hear you. In physics, causality isn’t built into the fundamental laws. It’s something that emerges once you have a time-asymmetric universe with records and memory. That said, I get why the philosophical version of causality feels so intuitive.
[I’ve made a bracketed edit below, which is 14 hours after original publication.]
If it’s true that physicists have good reason to say that the theorized hot plasma that was quickly expanding in the early theorized universe was “low entropy”, then I think I can make an even stronger case than I did last week that physicists invented entropy for metaphysical grounding, though systemic causality ought to provide more effective results.
Notice that the principle reason it’s believed that the universe began with a “bang”, is both given well documented evidence that it’s expanding (starting with the work of Edwin Hubble), and that we can even detect microwave background radiation that seems very much like evidence of this massive bang nearly 14 billion years ago. So maybe the universe is headed for a high entropy heat death given enough time and expansion from that initial bang. But that doesn’t quite settle the matter since perhaps before that time the universe converged together from a cycle where it went from extremely low entropy to extremely high entropy to end with that “bang”? [Edit — looks like I actually got that backwards. In this potential previous scenario it might have began with high entropy and converged to a lower state thus breaking the second law of thermodynamics.] So let’s think a bit more about what could be said if we had strong evidence that our universe was shrinking, and at an accelerating rate as suggested by the causal force of gravity.
Here physicists would know that even though entropy increases in most ways, such as molecules sharing their energies as they interact, and clean rooms getting dirtier rather than cleaner, in a macro sense they’d also know that the universe was becoming more uniform and ordered to create less entropy by means of an overpowering force known as gravity. If their projections held then they might essentially predict how many billions of years it would take for it to become the size of our galaxy, or solar system, or even our planet. Thus while entropy generally increases, in the case of a shrinking universe it would be understood to decrease ultimately.
There’s been lots of talk here about the arrow of time potentially reversing given the presumption that entropy creates this arrow. In such scenarios things seem to function magically, though I think that’s entirely correct — they should be considered magical. In a natural world effects do not create causes, but rather the opposite.
My solution would be to begin with the metaphysical presumption that systemic causality is what exists most fundamentally. Thus our laws would attempt to model causality. Entropy (whether increasing or decreasing) would be yet another idea that we’d use in the attempt to grasp causality. And whether moving fast or slow, time would be understood to only flow one way — like all else it would be understood as a product of cause that leads to effect.
As always, there's so much to love about this post. I start with this sentence: "For reasons we don’t yet fully understand, nearly fourteen billion years ago the universe began as a hot, dense, ordered state." It's hard to move past that sentence! But I'm glad you did.
Consciousness is definitely a function of time. Meaning, time is whatever it is (our puny minds struggle with the concept) but changes, outward-directional or inner-looped, create complexity.
Consciousness, I believe, is a condensation of multiple smaller predictors that predict more and more complex events.
I believe it started with first non-trivial life that learned to predict, for example, that mother-vent at the bottom of the ocean is heating up (move away) or cooling down (move towards). This, I believe, was first decision and first drop of applied consciousness.
I think you’re right: consciousness probably didn’t arrive all at once, but was built out of smaller capacities — prediction, memory, response. And if consciousness has anything to do with modelling change across time, then time isn’t just a backdrop — it’s part of the architecture. I think that's fun to think about.
Is the "a state of simply being, without thoughts or any perception of time" really a state without consciousness? Or, close to it? Interestingly, most of the techniques used to arrive at it seem to be elaborations on the phenomena of sensory adaptation: dark retreats, chanting, candle gazing, watching the breath, visualization of icons, and various one-pointed mind techniques. Maybe the Buddha-mind is sensory adaptation carried to the max where all mental change disappears.
Given the human ability to imagine and even hallucinate, I take any such self-report with a shaker of salt. If one ever truly entered a "timeless" state, how would one ever exit it?
You're talking about the difference between subjective time and objective time. You would exit a "timeless" state by becoming conscious, pretty much what we do when we wake up every morning. The difference between the state of sleep and the state of meditation is that the meditator is awake.
Exactly my point. The sense of “timelessness” in meditation is merely subjective and not actually timeless in any other sense. (For instance, their bodies continue to do what bodies do.)
Hilarious but I just happened to see this in an article on perceived time during exercise.
In 1929, Einstein was claimed to have said: “When you sit with a nice girl for two hours you think it’s only a minute, but when you sit on a hot stove for a minute you think it’s two hours. That’s relativity.”
My sense is that it's something of a category error to say that entropy causes anything. I see it as a *measure* we can make on a (closed) system. To say entropy causes something to me is like saying the odometer numbers in your car cause your car's mileage. It puts the cart before the horse.
Something has to be fundamental and axiomatic, and for me it's time. I don't think it's emergent, I don't think it can go backward (the arrow in inherent), and without it nothing can happen. Anything that can happen implies a "before" and "after". So, I think time must have existed before the Big Bang.
That Einstein quote comes from a letter he wrote to the grieving widow of a good friend of his. Of course, he could not offer the usual platitude about Heaven, so he offered a poetic variation based on his own "religious" views (essentially Spinoza's view of God as the rules of physics). (That quote is often used to support eternalism, but I've long thought that's a misreading.)
So, I think that consciousness and all processes are in fact the *opposite* of entropy. They are the result of energy and physics working to create useful order. Of course, at the expense of an increase in entropy overall, but I view that as the byproduct of that creation of order.
Good point! We talk about entropy causing the arrow of time as shorthand, but really it’s about the statistical behaviour of systems.
I should have probably been clearer in my essay about the difference between time and time’s arrow. It is true that time is a dimension that is included in the fundamental structure of spacetime (e.g., general relativity). But the arrow of time (its one-way character) is not fundamental in the laws of physics.
On thinking time must have existed before the Big Bang -- I think that's a legitimate philosophical position. I think Penrose argues for something like this (if I remember correctly).
I can see why we might want to think that consciousness is the opposite of entropy. But I like to think of it more that consciousness depends on pockets of low entropy.
Yes, it's true that many separate "time's arrow" and time, but I suspect the arrow is inherent. Similar to mass, time always has a positive value. Yes, also, to Penrose. His notion of conformal cyclic cosmology puts time outside our instance of the universe. As do various Big Crunch cosmologies.
Classical physics does seem to work as well with -t as with +t, but quantum physics with wavefunction "collapse" is decidedly one-way. Wavefunction evolution under the Schrödinger equation can be reversed, but the apparent collapse upon measurement cannot.
I'm not sure I follow your last paragraph. How is consciousness depending on low pockets of entropy different from consciousness depending on (a degree of) order?
I think you're right that the collapse issue in quantum mechanics is one place where time asymmetry might be fundamental. This is outside my wheelhouse, but it seems like interpretations such as many-worlds or decoherence try to explain it without introducing a truly one-way process. It feels like it's still very much an open question.
Re: consciousness and entropy — what I was trying to get at is that life is a kind of organised, dynamic system that maintains local low entropy by increasing entropy elsewhere. We consume low-entropy energy in the form of food, and rely on low-entropy input from the sun, etc. So maybe it’s not just order, but the conversion of low entropy into high entropy that makes consciousness possible.
I was trying to get at the idea in Schrödinger's, What Is Life? He famously argued that living organisms maintain their structure and avoid decay by feeding on negative entropy (which today we’d call low-entropy energy).
Yes, you're right about the MWI (which has no WF reduction), and I believe also about decoherence views, though reversing decoherence would be a bit like unbreaking an egg or glass — perhaps not impossible in principle but probably impossible in practice. Distinctly different processes, anyway.
I see what you're saying about entropy conversion. I think it may be two ways of looking at the same thing. Does a car go because it converts low-entropy fuel to motion? Yes. Yes, it does. Does a car go because it has an engine that converts (low-entropy) fuel to combustion products to move pistons? Yes. Yes, it does. Without the fuel, no go. Without the engine, no go.
I've been wanting to read "What is Life?" There's no question that life depends on low-entropy sources. I think it's my sense that entropy itself doesn't "do" anything that biases me more towards the "engine" view than the "fuel conversion" view, but in some sense the latter is more primal and universal. A more general truth.
Yes, I like how you’ve framed this. It depends on whether you're foregrounding the engine (the mechanism) or the flow of entropy (the conditions that make it possible). I agree that entropy doesn’t “do” anything in the causal sense — it’s more a statistical description of what's likely to happen, given the constraints.
This is one of those places where causation gets fuzzy. We say a glass shattered because it fell, or because gravity pulled it, or because its molecular structure couldn't withstand the impact. All true! But none of those explanations quite live in the same layer. Entropy to me feels a bit like that — it explains why some transitions are more likely than others, but not necessarily what makes them happen in a mechanical sense.
I think you'd love What is Life? — it’s a slim one, but boy! it's chewy. I think you'd appreciate how Schrödinger tries to wrestle these big thermodynamic ideas. Reading it feels almost like a philosophy of biology book. Definitely one of those books that has stayed with me.
What you say about "what makes them happen in a mechanical sense" is a big part of why I see entropy as the result of physics+time (and that it is a measure). It's the physical behavior of gas molecules, for example, that explains *why* a gas reaches equilibrium (i.e. a high entropy state).
My library doesn't seem to have "What is Life?" online, nor does Amazon offer it as an ebook. They want almost $100US for a hardback copy. They have it in paperback for 1/5 that, but my desire to read it hasn't quite risen to a $20US level. ... Yet. What you've said about it does raise my interest, though!
In some instances at least, it may not *depend* on pockets of low entropy, but may well reduce it (ie create them). I view thoughts as negentropic, which is why I hate forgetting something I had thought of a moment ago, even if it’s likely the thought was substantively unimportant. Because at least for a moment, disorder was reduced (if only in my mind!)
Exactly why I hate to throw away code fragments I created to do some one-off task. I hate giving up that reduced entropy. And I often reflect on all the wasted low entropy we create during our lives. Low entropy is so… temporary!
The stream not flowing image really struck home. Got me thinking about the stream of consciousness, in the sense of how you note William James described experience.
Remove the arrow of time, the stream stops. Is it a stream?
Remove the arrow of time, the flow of consciousness stops. Is there still experience?
Remove entropy, is there an arrow of time?
Remove entropy, is there experience/consciousness?
And if we can’t find the arrow of time in the maths, then what does the emergent nature of that arrow mean for our understanding experience?
Oh dear, oh my.
Only you could have walked me down this path over a coffee. For that I owe you a coffee or 12.
It is unsettling, isn’t it? The idea that experience itself might depend on something like entropy. That said, it’s worth saying: this essay is meant to be speculative. We're in philosophy-of-science territory here — interpreting what current physics might imply, I don't think we can make settled ontological claims. There’s still so much we don’t understand about time, space, and entropy, let alone consciousness.
There is of course no independent evidence that your awareness (ie you) is the same now as it was a moment ago, or will be in a moment's time (ie 80ms). It's just a self-serving tale we tell ourselves. 4-Space can be viewed as a complete unchanging shape, (whether you want to add in the quantum multiverse or not).
(I've just Googled Billy Pilgrim and the Tralfamadorians in “Slaughterhouse Five” and realise this is more or less what the previous poster said!)
Yes! That’s such a wild and unsettling idea — that there’s no real evidence that the 'you' who began reading this sentence is the same 'you' finishing it. Continuity might just be a story the system tells itself in real time — a useful fiction running on top of an entropic substrate (or a non entropic one).
And I love that you circled back to Billy Pilgrim and the Tralfamadorians — I just started reading Slaughterhouse-Five (on John's recommendation). Clearly Vonnegut was ahead of all of us on this one.
Precognition does happen, and quantum theories also seem to verify that it should be just as possible as "forward-flowing" time consciousness. Our brains are capable of perceiving a wider range of knowledge, even if our bodies are "stuck" in one "spot" in the flow.
I think physics still has a lot of work to do, to catch up with explaining these well-known "anomalies." Precognition is universal and well-attested. Brains somehow experience quantum perception -- now physics has to find out how that works.
Thanks for this — it’s always fascinating to think about how time might work differently than we experience it. I totally agree that physics still has a lot to figure out when it comes to consciousness and perception, especially when we try to connect them to time.
That said, I think it’s worth being cautious about some of the claims here. Precognition is certainly widely reported, but it hasn’t held up under controlled scientific study — at least not in a way that’s reproducible or statistically significant. And while quantum theory does involve time-symmetric equations, that doesn’t imply we can perceive the future. Most physicists interpret those symmetries as mathematical features of the theory, not as gateways to reversed or future-bound perception.
The idea that the brain might somehow tap into quantum effects is definitely out there — Penrose and Hameroff’s theory is one example — but it’s highly speculative and still lacks solid evidence. As far as we know, the brain operates at scales and temperatures where quantum coherence doesn’t stick around long enough to play a meaningful role in cognition.
That doesn’t mean these theories are necessarily wrong — just that we should be careful not to treat speculative possibilities as if they’re established facts.
That’s the best kind of feedback. Thank you!
Well I guess it might be a little like Billy Pilgrim and the Tralfamadorians in “Slaughterhouse Five” by Kurt Vonnegut. Great essay. Many puzzles.
I have to admit — and I’m a little embarrassed to say this — I haven’t actually read Slaughterhouse-Five (🙈). I had to look it up (🙈). What! A character who experiences all of time at once, without any real sense of past or future?? Okay, this is going straight to the top of my reading list. Thanks, John!
For a slightly different perspective on experiencing all of time at once, you could look to *Hearts in Atlantis* by Stephen King, where one of the characters, a "breaker" seems to move around between times.
Thanks Jack!
Time is imaginary. Entropy causes ageing and decay.
Sometimes I think physics is just here to ruin all our fun — time is an illusion, the universe is on an inevitable path to its heat death, and despite what Han Solo says, it’s not actually possible to travel faster than the speed of light.
Boo, physics 👎
Mountain goats and cats seem to routinely defy physics🧐 Do they know something we don't🤔 or are they able to do it because they don't know they shouldn't be able to🧐 Only the Shadow knows. Lol.
🐐🐈
Cats, especially — I’m convinced they treat physics like a suggestion.
Agreed🤣
🐈🐈⬛🐱
Very good points Suzi! The way entropy has historically been presented is as something bad. And for the engineers who discovered it, it was. But it's really just a fact of existence. Without it, we would have a universe of perfect uniformity with no transformation, one without life or information. It's the inhomogeneities, the energy gradients, that make everything we care about possible. Entropy is both the enabler and doom of the universe. It both gives and takes.
Yes — exactly this! I love the way you put it: entropy both gives and takes.
Is it not problematic to explain time as a product of the second law, and the second law as a product of how the universe *began*?
But I'm very much on board with entropy helping to explain consciousness, especially considering how it's tied up with information. I think it also dovetails nicely with panpsychist tendencies. Maybe entropy is the "protopsychic" aspect?
Sean Carroll often makes a distinction between time as a dimension and the arrow of time. It's the arrow of time, its one way nature, which is usually thought to emerge from the second law. It seems like the dimension itself has to exist for the second law to play out. Another way to look at it is as related and integrated phenomena.
I'm not sure that resolves it still. We cannot speak of the arrow of time itself "emerging" or "playing out" in a temporal sense, because we cannot attribute a direction to it itself, and if it's not subject to the arrow of time it must itself be reversible, at which point everything under it would be reversible too.
I think it's more likely it's a methodological blind spot for fundamental physics. That makes sense historically because at the inception of modern physics, formal and final causality were intentionally excluded. And I think it makes sense too because it models the smallest scales and simplest scenarios, and time and space seem to "coextend" ie interactions across more space and greater complexity require more time, and the more time we account for the more complicated and extended our models need to be.
If I understand your objection correctly, I don't really take "emerge" here in a temporal sense, but in one where productive models switch as we change scales. (At least for us humans.) Although I'll grant here that even this sense of "emerge" seems awkward. It's more like the statistical tendency in time sequenced relations is to increasingly fragment energy gradients and reduce further transformability due to one direction (the big bang) having lower entropy than the other (heat death, etc).
Hi Mike! Yes, that’s really helpful. I think your point about models shifting with scale gets at the heart of it. Emergence always feels slightly uncomfortable in these contexts, maybe because we’re trying to describe a statistical pattern as if it were a process. But I like the way you frame it: not a mechanism, but a tendency — something that only becomes visible when we’re dealing with systems large enough for entropy gradients to show up.
Hi Joseph — when you say that “the arrow of time must itself be reversible, at which point everything under it would be reversible too,” I wonder if that’s mixing the time-symmetric laws of physics with the time-asymmetric initial conditions. My understanding (inspired by Sean Carroll’s framing) is that the laws themselves are reversible, but the universe’s low-entropy beginning isn’t — and it’s that asymmetry that gives us the arrow of time.
So we don’t need the arrow to “emerge” in a causal sense within time — it’s more like a global feature of the universe’s initial state.
If I’m following, it sounds like you’re suggesting that the arrow of time might itself be the outcome of some deeper directional process — almost like a second-level arrow that generates the first. Is that what you mean?
I think what I'm trying to say is that the explanation of the second law by reference to an "initial state" presupposes a direction of time already. We get the initial state as a given, and then the following states seem to be more or less derived/calculated from it.
If there's no real direction to time, it should be equivalent to take any point in time as our conceptual starting point. But if we do that, the statistical understanding of entropy + the symmetrical laws should mean that the entropy on *either side* of our starting point go up, just because they are more probable. E.g. if we modelled a box of gas particles starting with hot particles one side and cold the other, entropy will increase whether we run the simulation forwards or backwards from the starting point. And that's true however we decide to start the simulation.
The fact that entropy always increases tells us that the past was logically/computationally prior to now. The statistical understanding of entropy increasing due to probability only works if time has a (logical/computational) direction.
To illustrate it, we might suppose that causality did "ripple out" from the big bang in both directions, past and future (from our POV), like the simulation ran in both directions. There's a computational direction of time underlying the entropic direction(s).
(Hope all that makes sense)
Thanks, Joseph — thinking about time is hard work, so I really appreciate your careful unpacking here.
On whether appealing to a low-entropy initial state already assumes a direction of time: from how I understand it (following folks like Sean Carroll and David Albert), the low-entropy past isn’t chosen because it’s in the past — it’s defined as the past because entropy increases away from it. I still find this incredibly hard to think about without imagining time as flowing. But the asymmetry between low and high entropy is what gives us the arrow of time. That’s the heart of the Past Hypothesis — and while it doesn’t explain why the universe began that way, it helps make sense of the directionality we experience.
I went to a talk by Brian Greene yesterday, and he reminded me of some of the bigger questions in physics right now — like whether space and time are actually fundamental, or whether they emerge from something deeper, like information, entanglement, or causal networks. He also made the point that so much of this comes down to how we interpret the findings we observe. The data and the math aren’t usually in dispute — it’s the meaning we layer on top that makes it interesting (and difficult).
If the flow of time were to stop, then
But it hasn't yet, so I can move on to a related puzzle you might find entertaining. Suppose the universe were completely deterministic, and one day, the direction of time reversed. What would life be like for the time-reversed you?
My supposition is that you could not tell. At any instant in the time-reversed world, there is a corresponding time in the forward world in which the state of the universe is exactly the same. If, at that time in the forward world, you had certain memories, certain hopes and plans, certain feelings (including all your intuitions about the flow of time), and perhaps were under the illusion that you had free will, then I suppose you would have exactly the same ones (and nothing more) at the corresponding point in the reversed world.
"Time is an illusion. Lunchtime doubly so."--Douglas Adams.
Drew! My brain hurts…
Okay, let me try to wrap my head around this.
In a low-to-high entropy world — the usual one — I crack an egg into a frying pan. It breaks. I see it happen, signals hit my retina, travel to my cortex, and my brain encodes a memory of the broken egg. Entropy increases.
But in a high-to-low entropy world… the egg splatters are already in the pan. And then — what looks to us like magic — the egg reassembles itself midair and lands perfectly back in my hand.
But everything is reversed — including my brain. So the parts of my brain that held the memory of the broken egg are now being unwritten. Signals are flowing out of my cortex, through my retina, back to the egg.
But I don’t feel like I’m watching an egg unbreak — I feel like I just broke it.
All the signs that tell me which direction time flows are tied to entropy. So if entropy flows the other way — I flow the other way too.
🤯
Thanks, Suzi, and yes, that's pretty much the way I see it (but see my final paragraph here.)
There are some important caveats to be made, however. The first is that it is predicated on physicalism - that our minds are the result of physical processes. Dualist and panpsychist hypotheses have not been worked out in sufficient detail to say what would happen if any of them are correct.
The second is that the reasons I have for holding this opinion only work for this particular case, with a fully reversibly-deterministic universe undergoing a complete and instantaneous reversal of all physical processes. I do not think it could be generalized to high-to-low entropy worlds in general.
While writing that paragraph, I realized that I had been careless in my original specification of the scenario. I should have written in the terms I used in the previous paragraph: "suppose the universe's physical laws were completely deterministic and reversible, and one day, every physical process reversed." The question of whether time's arrow reversed at that point seems to be an open one (by the way, I have a vague recollection of seeing that this puzzle had been proposed by Lord Kelvin or one of his contemporaries, possibly in relation to the arrow-of-time question.)
Hi Drew. Suzi said you wrote an interesting comment, and I agree. Since last week I’ve been pondering that physics may have been founded upon the metaphysical premise of entropy because philosophers (or the people who specialize in metaphysics) have failed to give them a better premise. So over there I said it’s not surprising that they spent over a century perplexed by how a magical scenario might decrease entropy. The implication was that the missing entropy should be hiding the magic. It’s a long discussion, though in case your interested, here’s where it begins. https://open.substack.com/pub/suzitravis/p/maxwells-demon?r=5674xw&utm_campaign=comment-list-share-cta&utm_medium=web&comments=true&commentId=101444666
So on to my thoughts about your scenario. And I’ll stick with the revised one from your second comment, which I consider an important clarification. If the universe’s laws were completely deterministic, *and reversible*, then what would happen if they did reverse? In that case I think we’d begin with natural function, though the funky stuff that would occur upon reversal would reflect supernatural function, which is to say, magic. I came to this conclusion in my commentary here in this thread after yours. My solution would be to found physics and all science upon the premise of causality. Thus the magic of reversible laws would technically be forbidden to mainstream science. The arrow of time here would be presumed to only move forward, and at whatever rate effect transpires by means of cause.
Thanks, and your causality-first view appeals to my intuitions more than does a block universe view, though I have to consider the possibility of that just being a sign of my ignorance of the latter.
I agree that the reversal is a magical intervention. I'm not sure that we have to exclude all magic from thought experiments, but we have to be careful that we are not subverting or begging the question by invoking it.
Right, often thought experiments don’t even work without presuming a bit of magic to set them up. But don’t let the magical parts go on to subvert points that are actually being made. From what I can tell Maxwell’s demon itself seems like it should explain any missing entropy. Anyway I’ll put my new position that causality should be considered more fundamental than entropy, into my bag of tricks for future use. It’s nice to feel like I can bitch out physicists in this regard, since I mainly seem to find flaws with the positions of philosophers and soft scientists.
It’s not exactly the block universe itself that concerns me, but rather how the block people sometimes seem to interpret it. If my wife dies, shall I take comfort that she wasn’t erased from the block universe? Nope. Just because we can epistemologically refer to any location in spacetime, shouldn’t mean that they all exist ontologically. Causality should mandate that the past is gone forever.
Yes and no. It's not quite right to say that we would feel that the egg just broke while in reality it didn't.
The arrow of time is relative, it depends on frame of reference. If we are in a simulation running forward, then reversed, and so forth from the beginning of time to some far future, a million billion times, to the simulators we look as if we live many times in both directions. But to us there is only one life and one direction of time.
The arrow of time is that of low to high entropy no matter how you instantiate it. This is why the past hypothesis holds true even in cyclic or backwards scenarios (in some external frame of reference).
That's my view, anyway.
I take your point - one that I had overlooked earlier.
There is another issue here which may complicate matters: causality. If we think of physical processes in terms of cause and effect - e.g. it is raining today partly as a consequence of an earlier process in which water evaporated into the air - then after the reversal, the 'actual' causes of current events (those seen by a hypothetical external observer or simulation-runner) lie on the high-entropy side of the present (i.e., in the future, if time's arrow points from low to high entropy.)
I get the impression that block universe hypotheses are seen by some as a resolution of this apparent incongruity, though I cannot say anything more about that.
Thank you. If you accept my view that the arrow of time is always that of low to high entropy, and that experience etc also aligns with the arrow of time, then I think it follows (no meta-pun intended) that macroscopic causation is always in that same direction.
In other words, if an external observer claimed to see rain precede cloud formation, I would correct them and say - that is not rain (the water ascending from the ground). That is not cloud formation. All those concepts are arrow of time-dependent. What do you think? Do you agree?
I am not convinced, but then I might not be grasping your point correctly. Here's a variant of the thought experiment that might throw new light on the question: suppose we have another reversible and fully deterministic universe that, instead of running forwards for a while and then reversing, starts from exactly the same state the first one was in at the instant of reversal, and from then on evolves according to its causal laws of physics. This process will unfold in exactly the same way as did the first universe after its reversal. Would it make sense to say that has reversed causality just because it happened to start from a particular state? What if it started from some intermediate or hybrid state?
My point is basically that rain is, by definition, water falling down to the ground. Therefore, in a frame of reference where rain is reversed, it is not rain. People in that universe do not "live" from old to young. They don't answer questions before the question is heard - because the question isn't heard at all, and it is not a question. The reversal of a question being asked, is air pressure waves coming from all over, including from the "eardrums" of the answerer, coming together and making the "asker's" vocal cords vibrate. The "people" absorb heat, inhale carbon dioxide, and produce oxygen, "eat shit" with our behinds, and puke organised food items . "Plants" and "photosynthesis" uses oxygen and sugar to produce light and carbon dioxide. I wouldn't call any of these things by their ordinary low-to-high entropy names.
A bit messy, but do you see what I'm getting at? I think it is false to say that the answer from one person "causes" another person to ask a question, because there is not anything recognisably person-like about a reverse-person. Therefore I don't think it makes sense to say that causality is reversed. Microscopically, however, I think it makes sense to say that where atom A bumped into B and makes B move faster, the reverse is true. But I'm not sure if I'd call that reversed causality. Isn't that just causality backtracked or retrodicted? Not sure.
I do think that in your copied universe scenario, there is only really one universe, instantiated twice in some frame of reference. And "reversed" is always relational, or relative. So it only makes sense to say that something is reversed when compared to something else. That's my view!
Great post!
I don't think it makes sense to ask what consciousness would be like without time. My consciousness just moves along with everything else in my life.
I think there are a bunch of mysteries like time and entropy that we still need to figure out. Dark Matter? Free will?
Determinists always say that I can't have free will because physicists have no explanation for it. Well, if we can't figure out the arrow of time it might take a while to figure out free will too. But it's out there somewhere.
I love this — my consciousness just moves along with everything else.
Totally agree. There’s something humbling about realising how little we understand. Who was it that said, 'As our island of knowledge grows, so does the shore of our ignorance'?
The arrow of time is such an interesting expression; I don't know how I haven't heard of it before. We're riding the arrow of time from the Big Bang to the heat death of the universe. It's rather sobering to think about.
I've always pondered the mechanics of the human brain, especially what consciousness is and how it works. This does make me think about how the idea of entropy relates to the human brain. It seems like it spends its entire existence fighting such entropy through the constant firing of neurons and constant flow of energy; but in the end, entropy always wins!
Looking forward next week's article!
Yep, here we are — sipping our coffee, checking our email, and hurtling inevitably toward the heat death of the universe.
Thanks, physics. Happy Wednesday.
Let's all enjoy the journey together!
Happy Wednesday my dudes!
It seems to me that calling the state of the universe at the Big Bang “low entropy”, was merely done for convenience. Let’s imagine it the other way. Here astronomers notice that instead of expanding, our universe actually happens to be shrinking. Would they then decide that the second law of thermodynamics was being violated since apparently entropy was decreasing? No they’d theorize that there was a time when the universe was far bigger and spread out though gravity was pulling it together. That spread out state would now be called “low entropy” instead of the converse. Here time would still continue, eggs would still break rather than the opposite, and hot gasses would still mix with cold gasses when confined in a box. And now physicists would say that the smaller the universe gets, the less entropy there is rather than the converse. Thus it’s an arbitrary or convenient distinction. Metaphysically, in either case I think it would help scientists to presume that systemic causality never fails.
Hey Eric! Really interesting take — it reminds me a bit of the time-reversal thought experiment Drew raised earlier in the thread. Definitely worth checking out if you haven’t seen it!
I think a physicist might push back on the idea that the early universe is called "low-entropy" just for convenience. I think they might say the reasoning comes from how incredibly smooth the early universe was, especially when you consider gravitational degrees of freedom. A hot, uniform plasma might seem messy from a thermodynamic perspective, but gravitationally, that kind of smoothness is actually very ordered. Gravity tends to clump matter together — and structures like stars, galaxies, and especially black holes carry a huge amount of entropy.
So if the universe were shrinking but entropy were still increasing, I'd imagine that we'd still have the same arrow of time — just in a contracting geometry. Physics is not my area but I think what really matters, isn’t size, but the entropy gradient. That, I believe, is what gives us a sense of direction — the distinction between past and future.
There are some speculative models where the universe might bounce or cycle, and in those cases, both ends of the cycle could be low-entropy. In that kind of scenario, the arrow of time might "flip" at the bounce — but only if the entropy gradient reverses as well. If entropy were actually decreasing in a shrinking universe, then yeah — we’d expect to see some wild reversals, like eggs unbreaking or gases unmixing. That’s the kind of paradox Drew’s puzzle seems to be getting at.
Also, just to clarify: I'm pretty sure that a more clumpy and spread-out universe is actually higher entropy, not lower.
And yes, the idea that the universe began in a low-entropy state is still a hypothesis — but it’s one that’s strongly supported by both observational evidence and theoretical consistency. That assumption (often called the “Past Hypothesis” — Sean Carroll talks about it a lot) is what makes the second law of thermodynamics — and the entire asymmetry of time — make sense.
As for systemic causality — totally hear you. In physics, causality isn’t built into the fundamental laws. It’s something that emerges once you have a time-asymmetric universe with records and memory. That said, I get why the philosophical version of causality feels so intuitive.
[I’ve made a bracketed edit below, which is 14 hours after original publication.]
If it’s true that physicists have good reason to say that the theorized hot plasma that was quickly expanding in the early theorized universe was “low entropy”, then I think I can make an even stronger case than I did last week that physicists invented entropy for metaphysical grounding, though systemic causality ought to provide more effective results.
Notice that the principle reason it’s believed that the universe began with a “bang”, is both given well documented evidence that it’s expanding (starting with the work of Edwin Hubble), and that we can even detect microwave background radiation that seems very much like evidence of this massive bang nearly 14 billion years ago. So maybe the universe is headed for a high entropy heat death given enough time and expansion from that initial bang. But that doesn’t quite settle the matter since perhaps before that time the universe converged together from a cycle where it went from extremely low entropy to extremely high entropy to end with that “bang”? [Edit — looks like I actually got that backwards. In this potential previous scenario it might have began with high entropy and converged to a lower state thus breaking the second law of thermodynamics.] So let’s think a bit more about what could be said if we had strong evidence that our universe was shrinking, and at an accelerating rate as suggested by the causal force of gravity.
Here physicists would know that even though entropy increases in most ways, such as molecules sharing their energies as they interact, and clean rooms getting dirtier rather than cleaner, in a macro sense they’d also know that the universe was becoming more uniform and ordered to create less entropy by means of an overpowering force known as gravity. If their projections held then they might essentially predict how many billions of years it would take for it to become the size of our galaxy, or solar system, or even our planet. Thus while entropy generally increases, in the case of a shrinking universe it would be understood to decrease ultimately.
There’s been lots of talk here about the arrow of time potentially reversing given the presumption that entropy creates this arrow. In such scenarios things seem to function magically, though I think that’s entirely correct — they should be considered magical. In a natural world effects do not create causes, but rather the opposite.
My solution would be to begin with the metaphysical presumption that systemic causality is what exists most fundamentally. Thus our laws would attempt to model causality. Entropy (whether increasing or decreasing) would be yet another idea that we’d use in the attempt to grasp causality. And whether moving fast or slow, time would be understood to only flow one way — like all else it would be understood as a product of cause that leads to effect.
As always, there's so much to love about this post. I start with this sentence: "For reasons we don’t yet fully understand, nearly fourteen billion years ago the universe began as a hot, dense, ordered state." It's hard to move past that sentence! But I'm glad you did.
Haha, thanks Jack! Yep, that idea carries such weight, doesn’t it?
Consciousness is definitely a function of time. Meaning, time is whatever it is (our puny minds struggle with the concept) but changes, outward-directional or inner-looped, create complexity.
Consciousness, I believe, is a condensation of multiple smaller predictors that predict more and more complex events.
I believe it started with first non-trivial life that learned to predict, for example, that mother-vent at the bottom of the ocean is heating up (move away) or cooling down (move towards). This, I believe, was first decision and first drop of applied consciousness.
I think you’re right: consciousness probably didn’t arrive all at once, but was built out of smaller capacities — prediction, memory, response. And if consciousness has anything to do with modelling change across time, then time isn’t just a backdrop — it’s part of the architecture. I think that's fun to think about.
Yes, we’re on the same page.
Time causes changes in higher entropy spot (vent activity).
Activity emits signals (chemical, temperature).
Life learns by having its RNA react to predictive stimuli by carrying signals (move to keep eating but not get scalded).
Life eventually manages to preserve this conditioning in progeny, stapling our very first consciousness quanta on the whiteboard.
Is the "a state of simply being, without thoughts or any perception of time" really a state without consciousness? Or, close to it? Interestingly, most of the techniques used to arrive at it seem to be elaborations on the phenomena of sensory adaptation: dark retreats, chanting, candle gazing, watching the breath, visualization of icons, and various one-pointed mind techniques. Maybe the Buddha-mind is sensory adaptation carried to the max where all mental change disappears.
Given the human ability to imagine and even hallucinate, I take any such self-report with a shaker of salt. If one ever truly entered a "timeless" state, how would one ever exit it?
You're talking about the difference between subjective time and objective time. You would exit a "timeless" state by becoming conscious, pretty much what we do when we wake up every morning. The difference between the state of sleep and the state of meditation is that the meditator is awake.
Exactly my point. The sense of “timelessness” in meditation is merely subjective and not actually timeless in any other sense. (For instance, their bodies continue to do what bodies do.)
Do you have a sense of “time" that is not subjective?
Everything we experience is subjective. That's why I use a clock!
Hilarious but I just happened to see this in an article on perceived time during exercise.
In 1929, Einstein was claimed to have said: “When you sit with a nice girl for two hours you think it’s only a minute, but when you sit on a hot stove for a minute you think it’s two hours. That’s relativity.”
My sense is that it's something of a category error to say that entropy causes anything. I see it as a *measure* we can make on a (closed) system. To say entropy causes something to me is like saying the odometer numbers in your car cause your car's mileage. It puts the cart before the horse.
Something has to be fundamental and axiomatic, and for me it's time. I don't think it's emergent, I don't think it can go backward (the arrow in inherent), and without it nothing can happen. Anything that can happen implies a "before" and "after". So, I think time must have existed before the Big Bang.
That Einstein quote comes from a letter he wrote to the grieving widow of a good friend of his. Of course, he could not offer the usual platitude about Heaven, so he offered a poetic variation based on his own "religious" views (essentially Spinoza's view of God as the rules of physics). (That quote is often used to support eternalism, but I've long thought that's a misreading.)
So, I think that consciousness and all processes are in fact the *opposite* of entropy. They are the result of energy and physics working to create useful order. Of course, at the expense of an increase in entropy overall, but I view that as the byproduct of that creation of order.
Good point! We talk about entropy causing the arrow of time as shorthand, but really it’s about the statistical behaviour of systems.
I should have probably been clearer in my essay about the difference between time and time’s arrow. It is true that time is a dimension that is included in the fundamental structure of spacetime (e.g., general relativity). But the arrow of time (its one-way character) is not fundamental in the laws of physics.
On thinking time must have existed before the Big Bang -- I think that's a legitimate philosophical position. I think Penrose argues for something like this (if I remember correctly).
I can see why we might want to think that consciousness is the opposite of entropy. But I like to think of it more that consciousness depends on pockets of low entropy.
Yes, it's true that many separate "time's arrow" and time, but I suspect the arrow is inherent. Similar to mass, time always has a positive value. Yes, also, to Penrose. His notion of conformal cyclic cosmology puts time outside our instance of the universe. As do various Big Crunch cosmologies.
Classical physics does seem to work as well with -t as with +t, but quantum physics with wavefunction "collapse" is decidedly one-way. Wavefunction evolution under the Schrödinger equation can be reversed, but the apparent collapse upon measurement cannot.
I'm not sure I follow your last paragraph. How is consciousness depending on low pockets of entropy different from consciousness depending on (a degree of) order?
I think you're right that the collapse issue in quantum mechanics is one place where time asymmetry might be fundamental. This is outside my wheelhouse, but it seems like interpretations such as many-worlds or decoherence try to explain it without introducing a truly one-way process. It feels like it's still very much an open question.
Re: consciousness and entropy — what I was trying to get at is that life is a kind of organised, dynamic system that maintains local low entropy by increasing entropy elsewhere. We consume low-entropy energy in the form of food, and rely on low-entropy input from the sun, etc. So maybe it’s not just order, but the conversion of low entropy into high entropy that makes consciousness possible.
I was trying to get at the idea in Schrödinger's, What Is Life? He famously argued that living organisms maintain their structure and avoid decay by feeding on negative entropy (which today we’d call low-entropy energy).
Yes, you're right about the MWI (which has no WF reduction), and I believe also about decoherence views, though reversing decoherence would be a bit like unbreaking an egg or glass — perhaps not impossible in principle but probably impossible in practice. Distinctly different processes, anyway.
I see what you're saying about entropy conversion. I think it may be two ways of looking at the same thing. Does a car go because it converts low-entropy fuel to motion? Yes. Yes, it does. Does a car go because it has an engine that converts (low-entropy) fuel to combustion products to move pistons? Yes. Yes, it does. Without the fuel, no go. Without the engine, no go.
I've been wanting to read "What is Life?" There's no question that life depends on low-entropy sources. I think it's my sense that entropy itself doesn't "do" anything that biases me more towards the "engine" view than the "fuel conversion" view, but in some sense the latter is more primal and universal. A more general truth.
Yes, I like how you’ve framed this. It depends on whether you're foregrounding the engine (the mechanism) or the flow of entropy (the conditions that make it possible). I agree that entropy doesn’t “do” anything in the causal sense — it’s more a statistical description of what's likely to happen, given the constraints.
This is one of those places where causation gets fuzzy. We say a glass shattered because it fell, or because gravity pulled it, or because its molecular structure couldn't withstand the impact. All true! But none of those explanations quite live in the same layer. Entropy to me feels a bit like that — it explains why some transitions are more likely than others, but not necessarily what makes them happen in a mechanical sense.
I think you'd love What is Life? — it’s a slim one, but boy! it's chewy. I think you'd appreciate how Schrödinger tries to wrestle these big thermodynamic ideas. Reading it feels almost like a philosophy of biology book. Definitely one of those books that has stayed with me.
What you say about "what makes them happen in a mechanical sense" is a big part of why I see entropy as the result of physics+time (and that it is a measure). It's the physical behavior of gas molecules, for example, that explains *why* a gas reaches equilibrium (i.e. a high entropy state).
My library doesn't seem to have "What is Life?" online, nor does Amazon offer it as an ebook. They want almost $100US for a hardback copy. They have it in paperback for 1/5 that, but my desire to read it hasn't quite risen to a $20US level. ... Yet. What you've said about it does raise my interest, though!
In some instances at least, it may not *depend* on pockets of low entropy, but may well reduce it (ie create them). I view thoughts as negentropic, which is why I hate forgetting something I had thought of a moment ago, even if it’s likely the thought was substantively unimportant. Because at least for a moment, disorder was reduced (if only in my mind!)
Exactly why I hate to throw away code fragments I created to do some one-off task. I hate giving up that reduced entropy. And I often reflect on all the wasted low entropy we create during our lives. Low entropy is so… temporary!
The stream not flowing image really struck home. Got me thinking about the stream of consciousness, in the sense of how you note William James described experience.
Remove the arrow of time, the stream stops. Is it a stream?
Remove the arrow of time, the flow of consciousness stops. Is there still experience?
Remove entropy, is there an arrow of time?
Remove entropy, is there experience/consciousness?
And if we can’t find the arrow of time in the maths, then what does the emergent nature of that arrow mean for our understanding experience?
Oh dear, oh my.
Only you could have walked me down this path over a coffee. For that I owe you a coffee or 12.
It is unsettling, isn’t it? The idea that experience itself might depend on something like entropy. That said, it’s worth saying: this essay is meant to be speculative. We're in philosophy-of-science territory here — interpreting what current physics might imply, I don't think we can make settled ontological claims. There’s still so much we don’t understand about time, space, and entropy, let alone consciousness.
There is of course no independent evidence that your awareness (ie you) is the same now as it was a moment ago, or will be in a moment's time (ie 80ms). It's just a self-serving tale we tell ourselves. 4-Space can be viewed as a complete unchanging shape, (whether you want to add in the quantum multiverse or not).
(I've just Googled Billy Pilgrim and the Tralfamadorians in “Slaughterhouse Five” and realise this is more or less what the previous poster said!)
Yes! That’s such a wild and unsettling idea — that there’s no real evidence that the 'you' who began reading this sentence is the same 'you' finishing it. Continuity might just be a story the system tells itself in real time — a useful fiction running on top of an entropic substrate (or a non entropic one).
And I love that you circled back to Billy Pilgrim and the Tralfamadorians — I just started reading Slaughterhouse-Five (on John's recommendation). Clearly Vonnegut was ahead of all of us on this one.
I thought I'd read Slaughterhouse 5 many years ago (until this exchange), but the plot I remember was completely different.
Precognition does happen, and quantum theories also seem to verify that it should be just as possible as "forward-flowing" time consciousness. Our brains are capable of perceiving a wider range of knowledge, even if our bodies are "stuck" in one "spot" in the flow.
I think physics still has a lot of work to do, to catch up with explaining these well-known "anomalies." Precognition is universal and well-attested. Brains somehow experience quantum perception -- now physics has to find out how that works.
Thanks for this — it’s always fascinating to think about how time might work differently than we experience it. I totally agree that physics still has a lot to figure out when it comes to consciousness and perception, especially when we try to connect them to time.
That said, I think it’s worth being cautious about some of the claims here. Precognition is certainly widely reported, but it hasn’t held up under controlled scientific study — at least not in a way that’s reproducible or statistically significant. And while quantum theory does involve time-symmetric equations, that doesn’t imply we can perceive the future. Most physicists interpret those symmetries as mathematical features of the theory, not as gateways to reversed or future-bound perception.
The idea that the brain might somehow tap into quantum effects is definitely out there — Penrose and Hameroff’s theory is one example — but it’s highly speculative and still lacks solid evidence. As far as we know, the brain operates at scales and temperatures where quantum coherence doesn’t stick around long enough to play a meaningful role in cognition.
That doesn’t mean these theories are necessarily wrong — just that we should be careful not to treat speculative possibilities as if they’re established facts.