In the static block universe we posit a view-from-nowhere perspective.

When taking such a vantage, the thermodynamic arrow of time does not establish a preferred ontological direction of time. There are low entropy and high entropy edges to the block, but just like there is no preferred now, there can be no preferred direction metaphysically.

We humans only experience a single direction, the increasing entropy direction. That is, every time we see a glass of water with ice cubes, we expect to only have experiences of the ice melting.

Yet the view-from-nowhere establishes the thermodynamic reverse is equally real. The direction from glass of ice water toward a solid block of ice (or someone beginning to pour the glass of ice water) is equally real.

We just can't experience such reversals because human experience is so physically limited by its biology. There are other areas of the physical world we think are real but beyond experience, like the universe beyond our horizon, the cosmological multiverse, or other worlds of many worlds, so this shouldn't be so hard to swallow.

Is this a decent summary? Did I add in anything unnecessary, or leave out anything necessary?

[Edit-a restating: In the Growing Block Universe (GBU), "the direction of time points from the past that exists to the future that does not". "It is this process of change at the edge of spacetime, which is continually extending to include more events as time progresses, that determines which is the future direction of time, as opposed to its start". "It arises because the [growing] block universe has a beginning". George Ellis https://euresis.org/wp-content/uploads/2019/06/EJv7id2_Ellis.pdf.

The Static Block Universe (SBU) has no such beginning nor non-extant future, so there can be no ontological direction of time for the SBU. And without a global, ontological direction of time, the arrow of time (the second law of thermodynamics) must also be understood statically--the universe did not begin low entropy, nor will it end high entropy, there are no begins nor ends. The arrow of time (the second law) is within this directionless static block, and does not provide a direction to it. At best the second law describes a pattern of the layout of the block, but it endows no directedness.

So far in this edit there is no reason to suspect only a single direction to conscious experience I would say, yet that is what we perceive. That is, without knowing the nature of consciousness, if we at least know it produces reports of the static block, we have no reason yet to suspect from the nature of the SBU it will only produce reports in one direction. We might say consciousness at least must follow the laws of physics. But that too does not explain the singular directedness to our reports/experiences.

So it must be something about the constitution of consciousness that explains why we experience a single direction. And I do claim we do experience only a single direction, the universe looked lower entropy when I was born than today. And tomorrow will be higher entropy still. And I have never heard another human exclaim the converse.

I can imagine meeting an entity that can record and report sans human consciousness exclaiming the universe looks much more ordered today than their yesterday. Their direction through the block is equally real as mine, but is opposite, and obeys all the same physical laws as me.

So I feel I am forced to declare something about consciousness the moment I accept the the SBU, which seems undesirable.]

  • No. The sort of experience talked about as "conscious experience" is of a much more private sort than publicly observing spontaneous entropy decreases. And they can be and are, in fact, observed because the second law is only statistical. It may be that the directional way we experience the block universe is due to our physical limitations, but non-observability of entropy reversals is not one of them. We are well equipped to observe them, they just do not happen often, and such objective observations are not "conscious experiences" in the relevant sense.
    – Conifold
    Commented Sep 10, 2021 at 20:11
  • 1
    @Conifold The question isn't why we don't observe occasional reversals of entropy - we might rarely observe those and it presents no philosophical challenge. The question is why we don't observe everything in reverse.
    – causative
    Commented Sep 10, 2021 at 20:38
  • @causative I think the question is whether we are prevented from observing that by our constitution, not why it happens (low entropy initial state is the usual explanation). And whether it is related to "conscious experience". And it's a no on both.
    – Conifold
    Commented Sep 10, 2021 at 20:48
  • @Conifold Suppose that the universe is as it is, with low entropy at time 0 and higher entropy at time t>0, but imagine we have a person who goes in reverse: this person has lower entropy at time t and higher entropy at time 0, all their physical processes the inverse of a normal person's. Wouldn't this person experience time in the opposite direction, as all their perceptions and cognitive processes are reversed relative to the normal direction?
    – causative
    Commented Sep 10, 2021 at 20:56
  • @Conifold I'm saying there is a worldline, with no metaphysical now, nor a metaphysical direction. The view-from-nowhere observer could take his/her finger and trace the worldline a to b, or b to a. From a to b, photons fall on a person's eyes and then signals are sent to their brain, then (somehow) forming an experience. From b to a, the physical reverse "occurs". Electrochemical signals leaving the brain does not produce an conscious experience though. (and @causative)
    – J Kusin
    Commented Sep 10, 2021 at 21:09

2 Answers 2


I think that's fair. In a block universe the question is shifted from why time exists, to why the experiences we associate with time exist. And laying down memories is an entropic process, it involves the spreading out not concentrating of information - the 'movement' backwards in time is literally impossible to remember. The time-reversal of antiparticles bolsters this view.

See also: How does biological evolution work in the block universe/b-theory of time?

  • Thanks. This is where my intuition lies and what some physicists/philosophers seem to say, but wasn't/not 100% sure it's correct.
    – J Kusin
    Commented Sep 10, 2021 at 21:10
  • @JKusin: I'm actually a presentist. There the problem's reconciling relativity of simultaneity. Time has to somehow be emergent. Discussed here: 'Any good theories on nature of time in which time is not fundamental?' philosophy.stackexchange.com/questions/53543/… & 'Why is the universe governed by very few laws?' philosophy.stackexchange.com/questions/78748/… It's probably the biggest question in physics
    – CriglCragl
    Commented Sep 10, 2021 at 23:08
  • Thanks. In the link from your answer, I don't understand how changing # of dimensions makes things static vs "alive"/evolving though. Are you saying that means consciousness must be a reduction in dimension?
    – J Kusin
    Commented Sep 10, 2021 at 23:19
  • @CriglCragl You're a presentist? The notion of a "present" is problematic in special relativity; simultaneity in SR depends on relative motion. en.wikipedia.org/wiki/Relativity_of_simultaneity
    – causative
    Commented Sep 11, 2021 at 1:01
  • @causative: I literally included that as the principle issue against presentism in my comment..? I see it bringing the Many Worlds into being real only in-so-far as they are manifest in now, as a major strength. For me the existence of block-past & block-future is as bad as the Many Worlds - where is all the necessary energy coming from? It seems 'wasteful' & inelegant. Also why is the now localised in the way it is in a block universe? I like Loop Quantum Gravity, which admittedly is not quite either, but closer to presentism, imho.
    – CriglCragl
    Commented Sep 12, 2021 at 16:39

We humans only experience a single direction, the increasing entropy direction.

I'm not convinced that that's true or even meaningful.

That is, every time we see a glass of water with ice cubes, we expect to only have experiences of the ice melting.

"Expect" implies that you don't know what will happen, i.e., you don't remember it.

That we remember events from the lower-entropy direction of time and don't remember events from the higher-entropy direction is an objective property of the universe. If you experienced time in the higher-to-lower-entropy direction, you would still expect the ice to melt, not remember it.

I understand the difference between red and green wavelengths of light, but not the difference between perceived red and green. In the same way, I understand the difference between past and future in spacetime, but not the difference between perceived past and future. Perhaps how the past feels to you is how the future feels to somebody else. Given that both of you have learned to use the words "past" and "future" for the same objective time directions, and both remember events in the same direction, would there be any detectable difference between you and the person experiencing time the other way around? I don't know. Maybe not.

That's probably all that can be said about the conscious experience of time in a block universe given our current (total lack of) understanding of the nature of conscious experience.

  • I guess I just want to know about the nature of the arrows. We assume memory and perception emerge from low to high entropy, and we back that up with empirical facts of experience and memory recall. We remember the past and not the future, along an increasing entropy arrow. Are there observers who are forgetting memories likewise (high to low entropy)? At the block universe level, that sequence of physical events is a real arrow. But are we agnostic about that ordering also allowing a consciousness to emerge who experiences constant forgetting, or is experience only valid in our arrow?
    – J Kusin
    Commented Sep 11, 2021 at 17:13

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