On 5 January 2014 17:10, Jason Resch <jasonre...@gmail.com> wrote: > On Jan 4, 2014, at 9:56 PM, LizR <lizj...@gmail.com> wrote: > > On 5 January 2014 16:29, Jason Resch < <jasonre...@gmail.com> > jasonre...@gmail.com> wrote: > >> On Jan 4, 2014, at 9:16 PM, meekerdb < <meeke...@verizon.net> >> meeke...@verizon.net> wrote: >> >> You don't really have to say it's an illusion. It's a description of the >> world and the fact that you put different t-labels on events at the same (x >> y z) doesn't undo the fact that there are different events at those >> different t-values. Memory provides an arrow of psychological time - but it >> doesn't always follow the arrow of physics (entropy increase). >> >> Doesn't the von neumann-landauer limit imply information can only be >> stored in the direction of time in which entropy increases? >> >> Surely information being erased is the same as it being stored in > reversed time? > > To store information is to overwrite some information that was already > there. Think about writing a bit to a hard drive. If you write a 1 to > position X you can no longer say if position X was formerly a 0 or a 1. So > setting a bit (storing information) is equivalent to irreversible erasure. >
I believe with most hard drives overwriting is imperfect so you can say what was there before if you inspect it carefully enough. But the point is taken. Certainly in the future, when computers really do operate at or near the Landauer limit, it's possible that erasing a bit will completely replace whatever used to be there. However, I still feel a teensy bit of scepticism here, because if I believe QM, no information can be lost from the universe. > > Erasing information requires an entropy increase, which only happens in > one direction of time. > > The thing is, I always thought entropy was an emergent phenomenon. In practice it happens in one time direction, but in principle - and at a fine-enough grained level of description - it doesn't exist, all the interactions involved being reversible. However this is taking us away from the topic under discussion, and giving Edgar an excuse not to reply to our questions (again)... -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to email@example.com. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/groups/opt_out.