I share your confusion about the first two, but I believe that the question about the subjective passage of time can be dissolved, unless I am misunderstanding your question.
As you mention, the laws of physics are reversible, but as you mention, entropy gives an arrow of time. That arrow of time causes it to be the case that your brain encodes memories of the past instead of the future. You are not a subjective observer outside of time. You are always experiencing the current moment from the perspective of your brain at that moment. Thus, you always have the experience of being in a brain that remembers the past and remembers the immediately prior moment as the immediate past. So your experience will always be that your current experience has moved forward in time from the past. As a thought experiment, imagine that the 4D block universe existed and that there is some process that evaluates slices at which subjective experience happens. Imagine that instead of that process moving forward in time, it is moving backward in time from the “end” of time to the Big Bang. What would your subjective experience be in that case? It would still be that you are traveling forward in time. Because, as you experienced each moment, you would do so with the memory of the past moment, not of the moment that was experienced sequentially before (which is the temporally future moment). There is therefore no question here except what gives rise to qualia, and perhaps whether the block universe view is correct, or the universe is actually an evolving system for which only some “now” exists for each point in space.
(In reality, I don’t think a block universe makes sense. While I don’t understand what gives rise to qualia, all evidence says that it is tied to the execution of the “thinking” algorithm of my brain. A block universe would have no “execution” and so I think would have no qualia unless qualia exist eternally at all places in the block universe where there is a conscious being.)
The human brain takes time to process sensory signals so that the qualia experienced are slightly delayed from when the sensory input that gave rise to those qualia entered the brain. In that sense, experience happens over time. But at any moment, there is only the qualia that is being experienced. How could it be otherwise? If you say that you then recall that the qualia you had just before that was different. Well, that is a different instant in time in which you are experiencing recall of a memory from your brain.
This brings up an interesting consideration: Imagine two observers existing in the same universe, one being the time reverse of the other. From their internal perspectives, each views its own observations as defining an arrow of time, yet their arrows point in opposite directions. It would seem then, that the arrow of time resides in conscious experience itself, and is not a property of the universe. And yet it would seem to define a “canonical” direction to time, even if the external time parameter were reversed.
So would it even make sense to have an observer that can experience time from the opposite direction? Why can’t I experience my death and then age backwards until my birth? It would seem like the key here is memory itself: that is, memory requires observation, which is inherently a time asymmetric process. But what is experience itself but a brain state, ie. an impression, or memory of the world at large? But then are we saying that qualia themselves have an arrow of time impressed upon them? That a universe that is running backwards nonetheless cannot have conscious beings in the sense that they can experience the same “flow” of time?
Imagine that this time reversed observer were only run partially to completion. That is, their internal states were only run until say the middle of their life instead of to their birth. In what sense do they experience their life? Would it not be the case that their life from birth to the middle of their life was undetermined? But what would it be like to have an internal experience that corresponded to this scenario? It would seem like the way out of this confusion would be the fact that experience only relies on the current state and not on any future or past state. That is, all the information necessary to render a conscious experience is contained in the present moment. This would be similar to a Boltzmann brain scenario where the impressed past is not the “actual” past.
And yet there is still something confusing about this picture, namely which of these moments should be the one being experienced as “now”? Do they all exist in some platonic realm? But then what prevents us from thinking that we are living in a perpetual groundhog day? No, it seems like something is missing from this picture. It definitely seems like time is flowing, that I have not yet experienced this exact moment before, yet it would seem like everything in our physical theories cannot rule out the fact that this could be deja vu, because physical theories are memory-less theories. That is, they can be fully determined from one time slice only and not on any future or past state.
But this cannot fully be the case, because the dynamical equations of motion involve first and second derivatives, which would involve at least two more snapshots of time, at least to get the ball rolling to a calculation of the evolution of the state. But to a first approximation, all the information necessary to determine the state of the universe is contained in only one time slice, and this is the key to the question of the problem of time reversal symmetry. For it would be trivial to break this symmetry if the universe depended not just on the present state, but on future or past states as well, giving them further “existence”.
But then what would the laws look like if they depended not just on the present moment, but on other moments as well? Well for one, there would be no way to just “run the universe backwards” since this would assume you can just use the current state of the world to run the universe backwards, plus two time slices, to get the ball rolling.
But what does this entail? Well, if the physical laws depended on more than one slice of the past, then the time reversed implication would imply that the reversing the universe would require knowing future states that have not yet occurred.
And therefore if we are to believe that we are “extended objects” in time and not just one slice and are forced to trust our senses that we are not living in groundhog day, it would seem as if the future has yet to be “determined”.
I share your confusion about the first two, but I believe that the question about the subjective passage of time can be dissolved, unless I am misunderstanding your question.
As you mention, the laws of physics are reversible, but as you mention, entropy gives an arrow of time. That arrow of time causes it to be the case that your brain encodes memories of the past instead of the future. You are not a subjective observer outside of time. You are always experiencing the current moment from the perspective of your brain at that moment. Thus, you always have the experience of being in a brain that remembers the past and remembers the immediately prior moment as the immediate past. So your experience will always be that your current experience has moved forward in time from the past. As a thought experiment, imagine that the 4D block universe existed and that there is some process that evaluates slices at which subjective experience happens. Imagine that instead of that process moving forward in time, it is moving backward in time from the “end” of time to the Big Bang. What would your subjective experience be in that case? It would still be that you are traveling forward in time. Because, as you experienced each moment, you would do so with the memory of the past moment, not of the moment that was experienced sequentially before (which is the temporally future moment). There is therefore no question here except what gives rise to qualia, and perhaps whether the block universe view is correct, or the universe is actually an evolving system for which only some “now” exists for each point in space.
(In reality, I don’t think a block universe makes sense. While I don’t understand what gives rise to qualia, all evidence says that it is tied to the execution of the “thinking” algorithm of my brain. A block universe would have no “execution” and so I think would have no qualia unless qualia exist eternally at all places in the block universe where there is a conscious being.)
But experience itself isn’t instantaneous, it’s something that happens over time.
I don’t understand what you mean.
The human brain takes time to process sensory signals so that the qualia experienced are slightly delayed from when the sensory input that gave rise to those qualia entered the brain. In that sense, experience happens over time. But at any moment, there is only the qualia that is being experienced. How could it be otherwise? If you say that you then recall that the qualia you had just before that was different. Well, that is a different instant in time in which you are experiencing recall of a memory from your brain.
This brings up an interesting consideration: Imagine two observers existing in the same universe, one being the time reverse of the other. From their internal perspectives, each views its own observations as defining an arrow of time, yet their arrows point in opposite directions. It would seem then, that the arrow of time resides in conscious experience itself, and is not a property of the universe. And yet it would seem to define a “canonical” direction to time, even if the external time parameter were reversed.
So would it even make sense to have an observer that can experience time from the opposite direction? Why can’t I experience my death and then age backwards until my birth? It would seem like the key here is memory itself: that is, memory requires observation, which is inherently a time asymmetric process. But what is experience itself but a brain state, ie. an impression, or memory of the world at large? But then are we saying that qualia themselves have an arrow of time impressed upon them? That a universe that is running backwards nonetheless cannot have conscious beings in the sense that they can experience the same “flow” of time?
Imagine that this time reversed observer were only run partially to completion. That is, their internal states were only run until say the middle of their life instead of to their birth. In what sense do they experience their life? Would it not be the case that their life from birth to the middle of their life was undetermined? But what would it be like to have an internal experience that corresponded to this scenario? It would seem like the way out of this confusion would be the fact that experience only relies on the current state and not on any future or past state. That is, all the information necessary to render a conscious experience is contained in the present moment. This would be similar to a Boltzmann brain scenario where the impressed past is not the “actual” past.
And yet there is still something confusing about this picture, namely which of these moments should be the one being experienced as “now”? Do they all exist in some platonic realm? But then what prevents us from thinking that we are living in a perpetual groundhog day? No, it seems like something is missing from this picture. It definitely seems like time is flowing, that I have not yet experienced this exact moment before, yet it would seem like everything in our physical theories cannot rule out the fact that this could be deja vu, because physical theories are memory-less theories. That is, they can be fully determined from one time slice only and not on any future or past state.
But this cannot fully be the case, because the dynamical equations of motion involve first and second derivatives, which would involve at least two more snapshots of time, at least to get the ball rolling to a calculation of the evolution of the state. But to a first approximation, all the information necessary to determine the state of the universe is contained in only one time slice, and this is the key to the question of the problem of time reversal symmetry. For it would be trivial to break this symmetry if the universe depended not just on the present state, but on future or past states as well, giving them further “existence”.
But then what would the laws look like if they depended not just on the present moment, but on other moments as well? Well for one, there would be no way to just “run the universe backwards” since this would assume you can just use the current state of the world to run the universe backwards, plus two time slices, to get the ball rolling.
But what does this entail? Well, if the physical laws depended on more than one slice of the past, then the time reversed implication would imply that the reversing the universe would require knowing future states that have not yet occurred.
And therefore if we are to believe that we are “extended objects” in time and not just one slice and are forced to trust our senses that we are not living in groundhog day, it would seem as if the future has yet to be “determined”.