On Sat, Nov 8, 2014 Alberto G. Corona <[email protected]> wrote: > The arrow of time is defined by the increase of entropy >
No, increasing entropy is not sufficient to establish a arrow of time, as I've said it can explain why Entropy will be higher tomorrow but by using the exact same logic Entropy should have been higher yesterday than today too, but clearly that is nonsense. To see how that is true consider all the logically possible microstates of Alberto Corona that would produce the macrostate that both you and I would recognize as Alberto Corona, the vast majority of those microstates must have evolved from high entropy states because they outnumber the low entropy ones by an astronomical (too weak a word but I don't know of a stronger one) number. But nobody thinks that is really true, and yet it is undeniable that you just can not deduce a asymmetry in time from thermodynamics or from any of the known laws of physics; this dichotomy is sometimes called Loschmidt's Paradox or Loschmidt's Objection. > > because that is the only direction in which life can operate. > I don't see why that would be true. If the arrow of time were reversed intelligent beings would just discover different laws of thermodynamics. They would remember that in the distant future, that is to say a long way from your "now", perfume molecules "were" (the most difficult part of of reverse time thought experiments is the grammar) evenly distributed throughout the room, and they would remember that in the more recent future the molecules were only in the lower right part of the room, and they would remember that in the very recent future (very close to your "now") all the molecules were confined inside one small perfume bottle. They would then conclude that entropy always decreases or remains the same. And as to how the bottle got into that room in the first place.... well, you can make educated guesses but essentially the only way to know for sure what the past was like is to wait and see. . But the deepest question isn't why time points in one direction rather than the opposite direction but why it points in any direction at all. After all the fundamental laws of physics are time reversible, if I show you a film of non-macroscopic things you can't tell if the film is running forward or backwards with the electrical charges reversed and the scene photographed in a mirror. Even the laws of logic are reversible; if I gave you line 9 of a valid proof in pure number theory you could deduce both what line 10 must be and what line 8 must have been. So why do we perceive that time has a preferred direction? If the arrow of time doesn't come from physical law it must come from the initial conditions and we need to add a past hypothesis, that is in the distant past for some reason entropy was much lower than it is today. John K Clark -- 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 [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
