In the criticisim of Boltzman, entropy sounds like a radio dial that someone is tweaking rather than a property of some space. I may be misunderstanding something.
Basically, if some tiny part of some enormous universe happened to condense into a very low-entropy state, that does not mean that it could spontaneously jump to a high-entropy state. It would, with extremely high probability, slowly return to a high-entropy state. It thus seems like we could see what we actually see and not be at risk of spontaneously turning into static. Our current observable universe has a certain amount of entropy and had a certain amount before the current time. If we were in some different bubble, the universe would presumably look quite different, and probably only certain bubbles could generate conscious observers, and those bubbles would not be at risk of spontaneously maximizing entropy.
The argument as applied to consciousness makes perfect sense, but at the very least I seem to be missing something about the universe argument.
It thus seems like we could see what we actually see and not be at risk of spontaneously turning into static. Our current observable universe has a certain amount of entropy and had a certain amount before the current time.
If the low-entropy area of the universe was originally a spontaneous fluctuation in a bigger max-entropy universe, than that is vastly improbable.
Such a fluctuation is exponentially more likely for (linearly) smaller volumes of the universe. So the parsimonious explanation for what we see, on this theory, is that the part of the universe that has low entropy is the smallest which is still enough to generate our actual experience.
How small is “smallest”? Well, to begin with, it’s not large enough to include stars outside the Solar System; it’s vastly more likely that the light en route from those stars to Earth was spontaneously created, than that the stars themselves and all the empty space between (very low entropy!) were created millions of years earlier. So the parsimonious explanation is that any moment now, that light created en route is going to run out and we’ll start seeing static (or at least darkness) in the night sky.
Similarly: we have a long historical record in geology, archaeology, even written history. Did it all really happen? The parsimonious explanation says that it’s vastly more likely that an Earth with fossils was spontaneously created, than that an Earth with dinosaurs was created, who then became fossils. This is because the past light cone of, say, a billion-year-old Earth is much bigger than the past light cone of a 6000 year old earth. And so requires the spontaneous creation of a vastly bigger section of universe.
Finally, it’s vastly more likely that you were spontaneously created a second ago complete with all your memories, than that you really lived through what you remember. And it’s vastly more likely that the whole spontaneous creation was only a few light-seconds across, and not as big as it seems. In which case it’ll stop existing any moment now.
I agree. The idea that low-entropy pockets that form are totally immune to a simplicity prior seems unjustified to me. The universe may be in a high-entropy state, but it’s still got physical laws to follow! It’s not just doing things totally at random; that’s merely a convenient approximation. Maybe I am ignorant here, but it seems like the probability of a particular low-entropy bubble will be based on more than just its size.
In the criticisim of Boltzman, entropy sounds like a radio dial that someone is tweaking rather than a property of some space. I may be misunderstanding something.
Basically, if some tiny part of some enormous universe happened to condense into a very low-entropy state, that does not mean that it could spontaneously jump to a high-entropy state. It would, with extremely high probability, slowly return to a high-entropy state. It thus seems like we could see what we actually see and not be at risk of spontaneously turning into static. Our current observable universe has a certain amount of entropy and had a certain amount before the current time. If we were in some different bubble, the universe would presumably look quite different, and probably only certain bubbles could generate conscious observers, and those bubbles would not be at risk of spontaneously maximizing entropy.
The argument as applied to consciousness makes perfect sense, but at the very least I seem to be missing something about the universe argument.
If the low-entropy area of the universe was originally a spontaneous fluctuation in a bigger max-entropy universe, than that is vastly improbable.
Such a fluctuation is exponentially more likely for (linearly) smaller volumes of the universe. So the parsimonious explanation for what we see, on this theory, is that the part of the universe that has low entropy is the smallest which is still enough to generate our actual experience.
How small is “smallest”? Well, to begin with, it’s not large enough to include stars outside the Solar System; it’s vastly more likely that the light en route from those stars to Earth was spontaneously created, than that the stars themselves and all the empty space between (very low entropy!) were created millions of years earlier. So the parsimonious explanation is that any moment now, that light created en route is going to run out and we’ll start seeing static (or at least darkness) in the night sky.
Similarly: we have a long historical record in geology, archaeology, even written history. Did it all really happen? The parsimonious explanation says that it’s vastly more likely that an Earth with fossils was spontaneously created, than that an Earth with dinosaurs was created, who then became fossils. This is because the past light cone of, say, a billion-year-old Earth is much bigger than the past light cone of a 6000 year old earth. And so requires the spontaneous creation of a vastly bigger section of universe.
Finally, it’s vastly more likely that you were spontaneously created a second ago complete with all your memories, than that you really lived through what you remember. And it’s vastly more likely that the whole spontaneous creation was only a few light-seconds across, and not as big as it seems. In which case it’ll stop existing any moment now.
That’s the experience of a Boltzmann Brain.
I agree. The idea that low-entropy pockets that form are totally immune to a simplicity prior seems unjustified to me. The universe may be in a high-entropy state, but it’s still got physical laws to follow! It’s not just doing things totally at random; that’s merely a convenient approximation. Maybe I am ignorant here, but it seems like the probability of a particular low-entropy bubble will be based on more than just its size.