5 ms·

When you do not look at the coin result that gets recorded, your knowledge of the state of the recorder (the record inside) is not "exactly the same as before".

by effie 4y ago

When you do not look at the coin result that gets recorded, your knowledge of the state of the recorder (the record inside) is not "exactly the same as before". You lack information on the state of the recorder that you would have if you looked. Yes, knowledge of details of how the recorder works is indeed largely irrelevant, but that was obvious. The point was that being successful with predictions or retrodictions of some system is correlated with having enough information on its state and the laws it obeys. This difference of success for predicting playback vs predicting result of a future experiment sensitive to unknown conditions is due to sufficient information vs insufficient information. I don't see anything in your responses that shows some universal asymmetry between past and future that would explain why your original argument does not work for past macrostates, but does work for future ones.

lisper 4y ago
> You lack information on the state of the recorder that you would have if you looked. No, I lack information about the state of the coin. All of my observations and knowledge of the operation of the recorder are exactly the same as before. I can still see the camera, see that it is pointing at the location of the coin (even though the coin itself is hidden from me). Nothing has changed in that regard. > I don't see anything in your responses that shows some universal asymmetry between past and future Maybe it would be clearer if I change the scenario slightly: instead of one camera, I'll use N>>1 cameras, all pointing at the same coin. I flip the coin in view of all the N cameras, but hidden from my view, and then I put the coin in my pocket without ever looking at it. At this point I can make no reliable predictions. But if I wach the playback on one of the N cameras, I can then reliably predict the outcome of viewing the playback on any and all of the other cameras. But under no circumstances can I ever accurately predict the outcome of flipping the coin again. Why? Because there is a fundamental asymmetry between the past and future. It is possible to make reliable records of the past, and if you make multiple records of the same event, all of those records will agree on what the outcome was (that's what "reliable record" means). By way of very stark contrast, it is not possible to make reliable records of the future.
- effie 4y ago
  > No, I lack information about the state of the coin. And that implies you lack information on the record, which is decisive for predicting successfully its playback. > But under no circumstances can I ever accurately predict the outcome of flipping the coin again. Because you lack the necessary information, because you assume those experiments are that way. If you set them up so that you don't look at the coin flip result, but in the next coin flip you measure the initial conditions and the flipping process accurately enough, the conclusion would be the opposite - you would accurately predict the new coin flip, and would not be able to predict the playback. > Why? Because there is a fundamental asymmetry between the past and future. Not at all. The asymmetry is due to how you defined constraints on the experiments. > It is possible to make reliable records of the past, ... it is not possible to make reliable records of the future. Record is, by definition, a pattern that has been created in the past, and this is likely to correlate more with the past states than with the future states. This is a property of the concept, not of some universal asymmetry between past and future. We may introduce analogous concept of a future record, which will be created in the future, and which will correlate with the future states. We can talk instead about prediction and retrodiction. And then this is more of an easy/hard thing, not possible/impossible thing, and the distribution of success on this axis depends on details. Predicting Moon's position on sky 2 years into future is easier than retrodicting it 20 000 years into past. None of this explains why your original argument does not apply to past macrostates.
  - lisper 4y ago
    > None of this explains why your original argument does not apply to past macrostates. Yeah, that's gonna be a long row to hoe if I can't even get you to acknowledge that there's a difference between the past and the future independent of the second law itself. Maybe I should just ask: do you think there is any difference between the past and future (independent of the 2nd law)? If so, what is it? But in the meantime: > that implies you lack information on the record This turns on what it means to have information "about" something. All of the data I have first hand access to comes to me through my senses, mainly my eyesight. When I say a coin is heads-up it's because I can see the coin, i.e. there are photons emitted from the coin (presumably) that end up on my retina and create electrical impulses that go to my brain and leave me with the subjective sensation of seeing a heads-up coin. There are all kinds of background assumptions about how light works, how coins work, how my retina works, and how my brain works, but for the most part one chooses to sweep those under the rug and accept as a working hypothesis that the reason I have the subjective sensation of seeing a heads-up coin is that there is in point of actual fact a coin "out there" and that it is, again in point of actual fact, heads-up. But the camera is a very different story. I get direct input from the camera in the same way that I get direct input from the coin. I can see the camera just as I can see the coin. But unlike the coin, the camera's state with respect to what it has recorded is not directly apparent to me. That state is part of the internal state of the camera. It is hidden from me. I cannot directly observe it simply by looking passively at the camera the way I can with the coin while my visual cortex of my brain does the heavy lifting. I cannot even tell that there is hidden internal state based on anything that I can see about the camera while it is recording. Making a prediction about what will happen during "playback" (indeed, even predicting that there will be something interesting to observe at all!) requires a much more complicated model of the world and chain of inference than it took for me to conclude that the coin was heads-up. I introduced multiple cameras so that the structure of the example eliminated all that complexity and everything was symmetric. All the cameras are the same, and my knowledge of them is all the same -- until I start looking at the playback, at which point things start to diverge. When I look at the playback on one camera, I now have direct information about the (previously hidden) state of that camera, but not of any of the others. So here again the question is: why should (direct) information about the state of one camera tell me anything about the state of any of the other cameras? It is because of a very complex chain of inference, part of which includes the hypothesis that there are, in point of actual fact, events which have occurred in the past (and which now cannot be changed) and that there are things in the present (like cameras) whose states correspond to those past events, and for that reason correlate with each other in the present. I've lived a long time and I've engaged in a lot of philosophical discussions, but you are the first person with whom I've ever had to go into that level of detail on such a foundational matter. Not that there's anything wrong with that, you're keeping me on my toes. But my point is just that if you're going to insist that I be excruciatingly precise about something this elementary, it's going to be a very long time before we can come back to talking about thermodynamics.

by effie 4y ago

lisper 4y ago

> You lack information on the state of the recorder that you would have if you looked. No, I lack information about the state of the coin. All of my observations and knowledge of the operation of the recorder are exactly the same as before. I can still see the camera, see that it is pointing at the location of the coin (even though the coin itself is hidden from me). Nothing has changed in that regard. > I don't see anything in your responses that shows some universal asymmetry between past and future Maybe it would be clearer if I change the scenario slightly: instead of one camera, I'll use N>>1 cameras, all pointing at the same coin. I flip the coin in view of all the N cameras, but hidden from my view, and then I put the coin in my pocket without ever looking at it. At this point I can make no reliable predictions. But if I wach the playback on one of the N cameras, I can then reliably predict the outcome of viewing the playback on any and all of the other cameras. But under no circumstances can I ever accurately predict the outcome of flipping the coin again. Why? Because there is a fundamental asymmetry between the past and future. It is possible to make reliable records of the past, and if you make multiple records of the same event, all of those records will agree on what the outcome was (that's what "reliable record" means). By way of very stark contrast, it is not possible to make reliable records of the future.

effie 4y ago
> No, I lack information about the state of the coin. And that implies you lack information on the record, which is decisive for predicting successfully its playback. > But under no circumstances can I ever accurately predict the outcome of flipping the coin again. Because you lack the necessary information, because you assume those experiments are that way. If you set them up so that you don't look at the coin flip result, but in the next coin flip you measure the initial conditions and the flipping process accurately enough, the conclusion would be the opposite - you would accurately predict the new coin flip, and would not be able to predict the playback. > Why? Because there is a fundamental asymmetry between the past and future. Not at all. The asymmetry is due to how you defined constraints on the experiments. > It is possible to make reliable records of the past, ... it is not possible to make reliable records of the future. Record is, by definition, a pattern that has been created in the past, and this is likely to correlate more with the past states than with the future states. This is a property of the concept, not of some universal asymmetry between past and future. We may introduce analogous concept of a future record, which will be created in the future, and which will correlate with the future states. We can talk instead about prediction and retrodiction. And then this is more of an easy/hard thing, not possible/impossible thing, and the distribution of success on this axis depends on details. Predicting Moon's position on sky 2 years into future is easier than retrodicting it 20 000 years into past. None of this explains why your original argument does not apply to past macrostates.
- lisper 4y ago
  > None of this explains why your original argument does not apply to past macrostates. Yeah, that's gonna be a long row to hoe if I can't even get you to acknowledge that there's a difference between the past and the future independent of the second law itself. Maybe I should just ask: do you think there is any difference between the past and future (independent of the 2nd law)? If so, what is it? But in the meantime: > that implies you lack information on the record This turns on what it means to have information "about" something. All of the data I have first hand access to comes to me through my senses, mainly my eyesight. When I say a coin is heads-up it's because I can see the coin, i.e. there are photons emitted from the coin (presumably) that end up on my retina and create electrical impulses that go to my brain and leave me with the subjective sensation of seeing a heads-up coin. There are all kinds of background assumptions about how light works, how coins work, how my retina works, and how my brain works, but for the most part one chooses to sweep those under the rug and accept as a working hypothesis that the reason I have the subjective sensation of seeing a heads-up coin is that there is in point of actual fact a coin "out there" and that it is, again in point of actual fact, heads-up. But the camera is a very different story. I get direct input from the camera in the same way that I get direct input from the coin. I can see the camera just as I can see the coin. But unlike the coin, the camera's state with respect to what it has recorded is not directly apparent to me. That state is part of the internal state of the camera. It is hidden from me. I cannot directly observe it simply by looking passively at the camera the way I can with the coin while my visual cortex of my brain does the heavy lifting. I cannot even tell that there is hidden internal state based on anything that I can see about the camera while it is recording. Making a prediction about what will happen during "playback" (indeed, even predicting that there will be something interesting to observe at all!) requires a much more complicated model of the world and chain of inference than it took for me to conclude that the coin was heads-up. I introduced multiple cameras so that the structure of the example eliminated all that complexity and everything was symmetric. All the cameras are the same, and my knowledge of them is all the same -- until I start looking at the playback, at which point things start to diverge. When I look at the playback on one camera, I now have direct information about the (previously hidden) state of that camera, but not of any of the others. So here again the question is: why should (direct) information about the state of one camera tell me anything about the state of any of the other cameras? It is because of a very complex chain of inference, part of which includes the hypothesis that there are, in point of actual fact, events which have occurred in the past (and which now cannot be changed) and that there are things in the present (like cameras) whose states correspond to those past events, and for that reason correlate with each other in the present. I've lived a long time and I've engaged in a lot of philosophical discussions, but you are the first person with whom I've ever had to go into that level of detail on such a foundational matter. Not that there's anything wrong with that, you're keeping me on my toes. But my point is just that if you're going to insist that I be excruciatingly precise about something this elementary, it's going to be a very long time before we can come back to talking about thermodynamics.