Well said Zephir. Quarkhead, I'll get back to you. What I've got to say is based on this excerpt: When Sean Carroll says "the past is different from the future" and talks about eggs and omelets, the sameness that is entropy, and everything else, he is totally missing the point. The point is this: you can't have negative motion, because motion is motion whichever way it goes. And the arrow of time is derived from counting this motion. It is imaginary, it is an abstraction, it is not real.
No, because as YOU pointed out, there is some geometric difference between time and space. This is exactly what it said in the original post, however.
Farsight, you continue to misunderstand the essence of general relativity. Time is not defined by motion, it is defined in the metric.
Introductory question about time arrow Of course, or the geometrodynamical concept of general relativity -where the time is considered just another dimension of space-time metric - is not valid concept (by my opinion, it's one of most powerfull relativity concepts, instead). So, before we'll start to discuss some particular ideas here, I'd recommend, lets everybody try to answer the above question at first to demonstrate his/her stance towards subject of this topic: "If the time is just one of dimensions of space-time, why the time dimension differs by its arow from space dimensions? By another words, why the time coordinate has a direction, while the space coordinate not?" You can excerp and write down Lumo's/Sean's answers from theirs articles, if you consider them as a relevant opinions, of course.
Since the two bloggers have probably not considered this way of thinking, please disregard what i have said.
OK, because my posts here were deleted by you, I've moved them (1, 2) into AWT topic, so everybody can decide, whether they're relevant to the time arrow understanding, or not.
I will not waste my time by disputing at the places, where my posts can be deleted immediatelly. So, if you're interested about causual consequences of this model, we can discuss them in corresponding thread, living the arrogant trolls alone at the islands of their own formal illusions about physics. Furthemore, I've just obtained the warning from bentheman for my explanation of the time arrow, considered as the OT posting. This is just an example of behavior, how the "scientific" community is working - if some bubble of Aether will start to condense faster, then the rest of environment, it will not be absorbed by the rest of environment, but it will start to reflect the energy instead from the rest of environment due the surface density gradient and it will remain isolated. Of course, such process is acellered by negativistic molecules, which are adsorbing at the surface of the dropplets preferably, thus prohibiting it to exchange the energy and information with the rest of environement. Can anybody here explain the assymetry of time? If not, why just my first (and last explanation of time arrow here) was qualified as the OT post?
This thread seems to be covering old ground, and not as well as previously so I have not posted here before. I content that the equations of physics are reversible (well CPT reversible if technical and P is not too much a problem only CT) This means that there is no "arrow to time." What is taken to be time's arrow has much more to do with the number of distinguishable "micro states" that are collected together and considered, by humans, to have something in common. For more on this see: http://www.sciforums.com/showpost.php?p=1422822&postcount=19 and as it recomends post 17 first at: http://www.sciforums.com/showpost.php?p=1422754&postcount=17 Even though not an alpha thread, that thread had fewer hi-jacking efforts than this one, at least as a percent of all posts. Several other posts both refute and support my POV in it.
I agree with Lubos (and Billy T) in all of this. For me this nails it: My impression of the arrow of time (I posted on this a long time ago) is that the human mind makes this "distinction" as a recognition of the irreversibility of macrostates. Just as we turn photons hitting a rhodopsin molecule into colors, we turn an inherent sense of increasing entropy into "time". For me, the overriding question is, if I can time-reverse a single microstate, why can't I reverse a billion interacting microstates with just as much ease? I think "interacting" is the key word here. I know that QM has been dismissed as a "myth" as the source of the arrow of time, but wouldn't the essential probabilistic nature of QM at the particle level explain why interactions among particles cannot be treated symmetrically?
Well...I don't think so. For example, does an hourglass need a human to watch it? The arrow of time is certainly a feature of classical physics, and not a construct of the human mind. While quantum mechanics is reversible under CPT, classical mechanics is certainly not!
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You can as they transform in accordance with the REVERSIBLE LAWS OF PHYSICS. This reversibility is usually just "time" or all velocities getting the opposite sign and then the same equations "unwind" the micro state "b" back to microstate "a" but it gets a little more complex if for example the are charged particles and magnetic fields. Even more complex when Parity is involved and perhaps then micostate "b" will not go back to microstate "a" ? - A couple of Chinese Americans got a Nobel for understanding this long after I was a firm (erroneous, I think) believer that if the CPT product was conserved, then "b" would always return to "a." Or, in other words, that if one was watching a movie of some microstate change, it is impossible to tell if a-->b or b-->a is the "backwards version" of the movie.) Where is your quote of Lubos from? As we seem to agree 100% I would like to read more of his/her posts. In my links I use the smoke of an old locomotive and ice cube on warm side walk examples, instead of the more common egg example but the point is the same. Your qoute of me is a general statement of this point. Now to Ben and his "hour glass" example: Certainly no human needs to be watching as the particular initial microstate "a" (one of zillions to the zillionth power = "Z^Z" of the possible arrangements of the sand grains in the "top half," which no human would distintinguish from any other of the (Z^Z-1) possible microstates, and thus calls Macrostate "TF"), tranforms into one particular microstate, "b" (one of approximately Z^Z also, at least for symetric hour glasses) in the "bottom half" of the hour glass and humans recognize as Macrostate "BF." ("TF" is short for "Top Full" and "BF" for "Bottom Full.") The energy of TF state is greater than the energy associated with Macro state BF and thus the temperature associated with BF is no doubt slightly greater (If the glass of the hour glass is included in the definition of "the sustem" energy has been conserved as TF --> BF but the 'quality of this energy has been lowered as now it is only thermal (Taking the gravitational potential of BF to be zero) Thus, entropy of this system has increased. - not much of a surprize. Now for convenience, let me state / define the human POV more precisely: BF = {b} or in words: The macrostate BF is the set of all possible microstates "like b" in which all grains of sand are in the bottom half of the hour glass, in contact with each other, and have a stable configuration (due to mutual friction) against further reduction of their gravitational potential, which is approximately symmetric about the axis of the hour glass. Likewise: TF = {a} and the words might be slightly different. For example, the "axial symmetry MAY be replaced by " the grains of sand with the highest gravitational potential (i.e. the "top ones") approximate a plane surface that need not be exactly horizontal. Note: Reader may desire to (and can without much loss) skip the next paragraph, but it does, I hope, make more clear exactly what the "human role" is in all this.: Thus, most humans would automatically define a "Super Macrostate" TF = {TF}. I.e. the members of set {TF} included in TF are all gravitational stable macrostates, FT, with sand configurations in the top half of the hour glass but each member of {TF} has a "top surface" of sand that humans can distinguish as "having a different shape." For example, to be clear: If the top cover of the hour glass could be removed, and I briefly stuck my finger into the sand near the glass on one side, then the "top surface" would not be either "approximately plane" nor "approximately axially symmetric" but that particular microstate "b" resulting from the "finger poke" is a gravitationally stable member of the set defining Macrostate set {TF} and as such is also a Macrostate configuration included in the Super Macrostate TF. Point of just finished paragraph is that humans without any conscious effort, automatically, aggregate or form Macrostates which included Z^Z different microstates that they do not distinguish from each other. Humans may, often do, also even aggregate Billions to the Billionth power, B^B, of these Macrostates in to Super Macrostate TF. Ben's hour glass at the t = 0 time is an example of a Super Macrostate TF (Ben did not care about the "shape" of the "top surface" of the sand in the hour glass I am assuming here.) Likewise, my "ice cube on the warm side walk" is no doubt a Super Macrostate TF as I did not care about the exact sizes and locations of the tiny air bubbles inside the ice cube or its slight deviations from a true "cube." There is nothing in the laws of physic which makes it absolutely impossible for either a puddle of water on warm sidewalk to transform back into the ice cube OR for the particular state "b" of the Macrostate BF to transform back to at least some microstate "a" member of the MacroStates TF in Ben's hour glass example. This would be a violation of the system entropy must always increase "law" but that law is not a "rigid" law of physics. It is only a very useful guide that has thus far never been violated when one is dealing with Macrostates defined by humans that include Z^Z different microstates as members of the Macrostate set. To see that this is true, without waiting more than B^B time the age of the universe, consider a closed box with easy to open lid (perhaps a cigar box) with four red and four black marbles in it. Also assume that there is a slight elevated ridge glued across the box floor which forces the marbles to be on one side or the other. Now shake the closed box and then set it on the table and look where the marbles are. I will designate the color by R & B (or r & b) and if in one half of the floor by a capital letter and by a lower case level if in the other side of the dividing ridge. Then some of the micro state included in the Macrostate "NR" (NR = "Normal Result) are: RRBBB + rrb = rrb + RRBBB* RRBB + rrbb etc. for many more; but there is only one member of the entropy law violating Macrostate "SR" (SR = Strange Result). It is: RRRR + bbbb. With a cigar box and only these 8 marbles, I bet you could demonstrate this violation of the second law of thermodynamics in less than a day, certainly in less than a year if testing results 8 hours each day. ONLY ONE VIOLATION PROOVES IT IS NOT A TRUE LAW OF PHYSICS. Put 400 red marbles and 400 black marbles in the box, a try to get perfect separation by shaking it while lid is closed, and I doubt you will in your life time, if doing nothing else 8 hours every day get "perfect separation" - perhaps you will be able to still demonstrate the violation of the second law, but that will depend upon how you have defined your Macrostate SR. For example if 95% (38 marbles) of one color and two marbles of the other color on one side are microstates included in SR then in a life time of trying, perhaps you can demonstrate entropy decreased. If some not equal numbers on each side (for example 37 of one color and two of the other for 39 total) are allowed in the definition of macrostate SR, then I bet a life time might be sufficient (given a sutably "lax" definition of the microstates "b" included in the macrostate SR) Thus it is just "law of large numbers" or the probabilities associated with MacroStates that include Z^Z possible microstate in their defining sets than gives time it "arrow" not any law of physics. TIME HAS NO "ARROW," but appears to if dealing with large sets of microstates aggregated into one Macrostate. -------------- *I have here assumed I cannot distinguish the two sides of the barrier. For example, the box floor is a uniform pink and I am out of the room before it is opened and some else always rotates the box before I return to open it.
I agree. I suppose my statement was more of an aside, attempting to explain why we percieve a "flow" of time. It can safely be ignored. Please Register or Log in to view the hidden image!
post 24 -relativity measures spatial intervals using a clock! post 32 -you're assuming the reversed order implies reversed time. If a particle transitions abc, and later transitions cba, it's just a reversed sequence, and the observer who recorded it never saw it leave his 'present' state. Particles don't have memory, their transitions are random, so where's the time? A coin tossed HHT is not moving back in time when tossed THH. post 34 -It doesn't need a human to watch it, but it only has meaning to a human.
I don't know about an arrow... It is certainly not a trianglePlease Register or Log in to view the hidden image! but it is most definitely a circular "aspect".
Ben, if you're looking for a straight "vote" without discussing personal theories, my vote is for Carroll. I saw many comments by Motl that made me say "wha??". For example, Motl kept bringing up friction as a phenomenon that stands outside of the 2nd law of thermodynamics and therefore implies an arrow of time that is also divorced from entropy. But what is friction? It's the force resisting relative motion of surfaces from sliding against each other...but the concept of surfaces is itself a low-entropy concept. If his theory that friction was divorced from entropy were true then friction would exist in a high-entropy environment like diffused gas particles, where, unfortunately for Motl, friction (i.e. heat energy) is just as likely to speed things up as it is to slow them down. I could explain my belief of why we experience the arrow of time but I don't want to violate the terms of the OP...
