I don’t mean reversing time on the whole universe; that is not really meaningful, for the reasons you specify. What I mean is, since the laws of physics are (nearly) time-symmetric, it seems that it should be possible to have, in our own universe alongside us, some sort of creature that is has a brain that really does remember what we would consider the future, and attempts to anticipate what we would consider the past. How would such a thing arise? Well, presumably by a time-reversed evolution, with mutation and natural selection occuring on a “replicator” that propagates itself backwards in time; that is, after all, what it would have to optimize for (well, given the right environment).
Yes, if you take us out of the picture, you can just negate the t-coordinate and say I’m not proposing anything weird. But the (near) time-reversibility of the laws of physics means that it should possible for us to both occur in the same universe.
Admittedly, if we saw such a thing, we would probably never recognize its “genes” as replicators of any sort—if we saw the pattern at all, they would appear as some sort of anti-replicators. And could we even recognize such creatures as containing decision engines at all?
...OK, having written that out I now can’t help but suspect the problem is in posing the existence of these things in the first place. After all, the anti-replicators that formed their genes, would have to have some causal origin from our point of view, and that seems highly improbable. Anti-replicators become less common, not more common, meaning, but there shouldn’t be any at the start of the universe—or in other words, they should all be extinct by then. What does a time-reversed extinction event look like? Probably not just one thing. But of course, if, for example, we were to hypothetically nuke the whole planet and destroy all life, they’d see the sudden appearance of a whole bunch of anti-replicators, which then slowly annihilate each other over 4 billion years, and have a good causal explanation for the whole thing! If they recognized the pattern at all, that is.
This forces me to wonder if, yes, it really is correct that a time-reversed observer necessarily would have to have such a different point of view that it would be natural to draw the boundaries in a way such that they still saw entropy as increasing.
I don’t actually understand this very well, so I don’t think I’m close to an actual answer, but I think here’s my best attempt: While such things are theoretically possible, if they existed, we could never recognize them (or vice versa), as that would violate the second law of thermodynamics from our (their) point of view? I think? Though that still is not answering the original question.
I don’t mean reversing time on the whole universe; that is not really meaningful, for the reasons you specify. What I mean is, since the laws of physics are (nearly) time-symmetric, it seems that it should be possible to have, in our own universe alongside us, some sort of creature that is has a brain that really does remember what we would consider the future, and attempts to anticipate what we would consider the past. How would such a thing arise? Well, presumably by a time-reversed evolution, with mutation and natural selection occuring on a “replicator” that propagates itself backwards in time; that is, after all, what it would have to optimize for (well, given the right environment).
Yes, if you take us out of the picture, you can just negate the t-coordinate and say I’m not proposing anything weird. But the (near) time-reversibility of the laws of physics means that it should possible for us to both occur in the same universe.
Admittedly, if we saw such a thing, we would probably never recognize its “genes” as replicators of any sort—if we saw the pattern at all, they would appear as some sort of anti-replicators. And could we even recognize such creatures as containing decision engines at all?
...OK, having written that out I now can’t help but suspect the problem is in posing the existence of these things in the first place. After all, the anti-replicators that formed their genes, would have to have some causal origin from our point of view, and that seems highly improbable. Anti-replicators become less common, not more common, meaning, but there shouldn’t be any at the start of the universe—or in other words, they should all be extinct by then. What does a time-reversed extinction event look like? Probably not just one thing. But of course, if, for example, we were to hypothetically nuke the whole planet and destroy all life, they’d see the sudden appearance of a whole bunch of anti-replicators, which then slowly annihilate each other over 4 billion years, and have a good causal explanation for the whole thing! If they recognized the pattern at all, that is.
This forces me to wonder if, yes, it really is correct that a time-reversed observer necessarily would have to have such a different point of view that it would be natural to draw the boundaries in a way such that they still saw entropy as increasing.
I don’t actually understand this very well, so I don’t think I’m close to an actual answer, but I think here’s my best attempt: While such things are theoretically possible, if they existed, we could never recognize them (or vice versa), as that would violate the second law of thermodynamics from our (their) point of view? I think? Though that still is not answering the original question.