The Dimension of Time
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From: Inertial on 25 Dec 2009 22:38 "jdawe" <mrjdawe(a)gmail.com> wrote in message news:4aa37bbb-b63e-46dd-82e6-23413e85c791(a)y32g2000prd.googlegroups.com... > On Dec 20, 10:18 am, Ste <ste_ro...(a)hotmail.com> wrote: > >> the question is this: exactly what leads >> us to conclude that we are constantly moving forward in time? > > Well, > > We have time. > > or > > We have distance. > > Which are equally opposing. > > Which means we can: > > Invert time into distance. > > or > > Invert distance into time. > > In other words: > > The greater the distance we travel then the less time we will have. > > or > > The greater the time we have then the less the distance we will > travel. > >> 'constantly moving forward in time' > > Because time is opposed by distance you will never have 100% absolute > time. > > There must always be some distance travelled in time. > > or > > There must always be some time used no matter the amount of distance > we cover. > > So, > > Even at the speed of light time may run very slow but it will never > 'stop' so there is no time. > > The fact that there will always be: > > Some time in distance. > > or > > Some distance in time. > > allows: > > Time to invert back into distance. > > or > > Distance to invert back into time. > Your 'everything is this or that' nonsense is simply that .. nonsense. That you can always categories things into two groups (or three, or four, or however many you want, up to the number of things) does not make that significant.
From: PD on 26 Dec 2009 13:09 On Dec 23, 7:42 pm, Ste <ste_ro...(a)hotmail.com> wrote: > On 23 Dec, 20:14, PD <thedraperfam...(a)gmail.com> wrote: > > > On Dec 23, 2:00 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > > On 22 Dec, 15:23, PD <thedraperfam...(a)gmail.com> wrote: > > > > > > > > I was contemplating the laws of physics, as one does, and in the > > > > > > > course of some basic research on the matter I came across the concept > > > > > > > of the "arrow of time", and the statement that whereas one can move in > > > > > > > both directions in space, currently we can only move forward in time. > > > > > > > > Now I'm not an expert in physics, so perhaps this question may come > > > > > > > across as ridiculously simple. But setting aside for one moment human > > > > > > > perception and common sense, the question is this: exactly what leads > > > > > > > us to conclude that we are constantly moving forward in time? > > > > > > > Because it is an observed fact that certain processes (that can be > > > > > > characterized by certain thermodynamic properties) go in only one > > > > > > direction, and we don't see them go in the other direction. For > > > > > > example, a dropped plate shatters and this is a common observation, > > > > > > but we never see shards reassemble into a smooth plate.' > > > > > > We do see shards reassemble. It happens when the shards become subject > > > > > to the combined forces of human hands and glue. And if we had > > > > > sufficient machinery and expertise, the plate could be put back to the > > > > > exact same state as previous. In that event, how do we distinguish a > > > > > plate reassembled by machinery, to a plate reassembled by the reversal > > > > > of time? Are the plates not truly one-and-the-same in every measurable > > > > > way? > > > > > Note that in this case the shards do not represent a closed system. > > > > There is an external agent involved, or said a different way, the > > > > closed system has to include the machinery involved in reassembling a > > > > part of the system. The second law of thermodynamics is a statement > > > > about processes inside *closed* systems. > > > > Indeed, but what is your point? You gave an example of where entropy > > > increased (the falling plate), and I gave you another (the plate was > > > put back together again). Where you suggested 'we never observe a > > > plate to unsmash', you were clearly wrong. > > > Please don't be argumentative for the sake of being argumentative. > > I gave you an example of a *closed system* where entropy increases. > > You gave an example of a plate being put together by an external > > process. If you consider the plate your system, it's not a closed > > system. If you include the machinery used to reassemble the plate, the > > entropy of that entire system still increases, though the entropy of a > > *part* of it does not. > > > > If you were using this ineptly as a specific example of the general > > > law that entropy is always increasing, then I accept that to be true. > > > The problem is, entropy requires change. Change presupposes the > > > concept of ever-flowing time. > > > Yes, and the law makes note of the fact that nonequilibrium processes > > in closed systems tend to go one way only in time, which imbues time > > with an arrow associated with increasing entropy. > > > Entropy, by the way, is not dependent on time. It is a state variable, > > which means that you can calculate the entropy of a system without > > regard to whether the time of that state is before or after another > > state. > > > What is true is that spontaneous processes (regardless of time) tend > > to increase entropy. It is secondarily noted that time tends to also > > increase with the increase in entropy. > > I know what you're getting at, but you're still presupposing the flow > of time. Entropy cannot possibly "increase" without a flow of time. Sure it can. I'm comparing two states, A and B, with different values of entropy. State B has a higher numerical entropy than state A. I can do this without any labeling with time at all. Now, what I observe in nature is that in a closed system, and while measuring time, state B happens to be always after state A in that time sequence. There is no obvious reason why this should be. It could have been just as likely that state B occurred before state A. But it DOESN'T. And this observation is where we recognize that there is an arrow of time such that states of higher entropy in closed systems happen after states of lower entropy. > Nothing that involves change can happen without presupposing a flow of > time. The 2nd law of thermodynamics presupposes a flow of time - > begging the very question it is supposed to answer, namely, are our > coordinates in the 4th dimension constantly incrementing. > > While you think about that, think about this: if time is flowing, then > at what rate does it flow? > > > > If you have presupposed ever-flowing > > > time, then your argument puts the cart before the horse (because the > > > idea of ever-flowing time, as a physical rather than a psychological > > > phenomenon, is the very thing in question). > > > > > > > There is therefore an *observational* imbalance. > > > > > > The question is not of what we observe in the world. The question is > > > > > of how to explain it. Nothing I'm saying truly contradicts > > > > > observation, it just contradicts previous explanations of it. > > > > > It turns out this is useless in science. Alternative explanations for > > > > common phenomena do not represent a new kind of understanding. What > > > > happens in science is that if there are two competing explanations, > > > > then the task is to isolate where they make *different* predictions > > > > about what will be seen in nature under certain circumstances, and > > > > then to test which of the predictions better matches experimental > > > > measurement. > > > > Indeed. The point is that the idea of ever-flowing time makes > > > predictions that are logically contradictory (like loops in time), > > > I know of no laws of physics that permit causality loops. There is no > > contradiction there. > > > > or > > > unfalsifiable (like multiple universes). If we start to think of the > > > universe in terms of having no flow of time, then we eliminate those > > > contradictory/unfalsifiable predictions immediately. > > > Multiple universes is not contingent on a one-way flow of time. Nor is > > it obvious that this is unfalsifiable. There is work afoot to > > *experimentally* detect other branes. Do you need some pointers to > > that work? > > Only if the work has produced results. OK, then please note the distinction between "yet to be falsified" and "unfalsifiable". We believe that only 10% of the species of animals on the earth have been identified. Does this lack of completeness mean that the remaining 90% have been proved to not exist? > > > > > > As for the laws of thermodynamics, they can be surmounted if you say > > > > > that energy remains constant across space *and time*, > > > > > Energy conservation IS a statement about being constant in time, not > > > > in space. > > > > Energy conservation says that energy can be neither created nor > > > destroyed, only transformed. On any understanding of that, all energy > > > must be present at all times in some form somewhere within the 4 > > > dimensions. > > > There's a key difference. You're assuming your available space is the > > whole universe. Energy conservation is a statement about the > > invariance of energy with respect to time-slices through that > > universe, and even more importantly, through slices of *subsets* of > > that universe representing closed systems. The closed system does NOT > > have to be a fixed region in space and is often not. > > I'm afraid I have lost you. > > > > > > and indeed on > > > > > that reading the laws of thermodynamics *preclude* any "travelling > > > > > backwards in time", because to turn the whole universe back to a > > > > > previous state would require an input of energy from outside the > > > > > universe (which I use to mean "all time and space" as we know it).. > > > > > I don't follow this. If it's constant, then there's no input of energy > > > > from outside the universe in either temporal direction. Constant means > > > > the SAME, no deposits or withdrawals required. Reversing time just > > > > switches deposits and withdrawals, but if there are none in one > > > > direction, then there are none in the other direction. > > > > No. Reversing time would surely consume energy somewhere, and > > > therefore increase entropy somewhere. > > > What? Now you're just making a science fiction babble about a time- > > reversal machine. This doesn't have to do with the physical nature of > > things with respect to time. > > I'm merely voicing the speculative ideas of others. If time is > flowing, then by definition is must be theoretically possible to > navigate the flow in both directions. If it is not possible to > navigate the flow in both directions, then the concept of the past is > a meaningless, and superfluous, concept. Why? Why does symmetric travel have to be present for the past to make sense? In nature, we have causal events separated into future light cones and past light cones. They are not identical, but then again they do not have to be. > > Because once there is no past, events can be described simply in terms > of either being simultaneous (i.e. the events have the same > coordinates in the 4th dimension), or of being separated in time (i.e. > the events are found at different coordinates in the 4th dimension). > Time by that model does not require constant forward flow, nor does > the model even permit a distinction between forward and backward flow. > > > > If energy is consumed in the future in order to send matter back in > > > time, > > > What makes you think this is consistent with the laws of physics? > > Which part? I certainly don't think time travel is consistent with the > laws of physics, because my very position is that I don't accept that > time is flowing at all. I don't know that time travel is consistent with the laws of physics, either. Who says it is? > > > > then the 2nd law precludes time travel, because the infinite > > > iterations of the loop (i.e. infinite journeys through time, and > > > infinite useful energy required to power the time machine at the start > > > of each of those journeys) could not be sustained with the finite > > > useful energy in the universe. > > > > The only way the 2nd law and time travel are compatible is if > > > initiating time travel (i.e. 'revving up the time machine') does not > > > increase entropy. > > > > > > Also note that this interpretation discards the idea of "parallel > > > > > universes". It discards the idea of travel backwards in time, and > > > > > travel to the future can only be achieved by slowing down one's own > > > > > time. It therefore discards loops in time, and the grandfather > > > > > paradox. In fact my theory discards just about every paradox we are > > > > > currently wrestling with, and as yet has none of its own. > > > > > There are no paradoxes in the current theory. There are *teaching > > > > examples*, but no paradoxes. > > > > Everything I've read about time suggests a great number of > > > contrivances or arbitrary assumptions (parallel universes, for > > > example) required to avoid paradoxes. > > > ?? Parallel universes don't have anything to do with resolution of > > paradoxes. > > I think you'll find that they do, because by definition a time > traveller would, from the moment of his arrival, follow a different > "path", and thus he would never reach the point at which he travelled > back in time (because that event then belongs to a parallel universe). ???
From: Ste on 26 Dec 2009 19:12 On 26 Dec, 18:09, PD <thedraperfam...(a)gmail.com> wrote: > > > > > If you were using this ineptly as a specific example of the general > > > > law that entropy is always increasing, then I accept that to be true. > > > > The problem is, entropy requires change. Change presupposes the > > > > concept of ever-flowing time. > > > > Yes, and the law makes note of the fact that nonequilibrium processes > > > in closed systems tend to go one way only in time, which imbues time > > > with an arrow associated with increasing entropy. > > > > Entropy, by the way, is not dependent on time. It is a state variable, > > > which means that you can calculate the entropy of a system without > > > regard to whether the time of that state is before or after another > > > state. > > > > What is true is that spontaneous processes (regardless of time) tend > > > to increase entropy. It is secondarily noted that time tends to also > > > increase with the increase in entropy. > > > I know what you're getting at, but you're still presupposing the flow > > of time. Entropy cannot possibly "increase" without a flow of time. > > Sure it can. I'm comparing two states, A and B, with different values > of entropy. > State B has a higher numerical entropy than state A. I can do this > without any labeling with time at all. Lol. Ok I'll run with this for now. > Now, what I observe in nature is that in a closed system, and while > measuring time, state B happens to be always after state A in that > time sequence. > There is no obvious reason why this should be. It could have been just > as likely that state B occurred before state A. > But it DOESN'T. But in some cases state A *never* becomes state B. So does that mean time stands still when entropy doesn't change? > And this observation is where we recognize that there > is an arrow of time such that states of higher entropy in closed > systems happen after states of lower entropy. Indeed, but where in the known universe can I find such a "closed system". If anyone can show me where, I'll show you a man with a wild imagination. > > > > or > > > > unfalsifiable (like multiple universes). If we start to think of the > > > > universe in terms of having no flow of time, then we eliminate those > > > > contradictory/unfalsifiable predictions immediately. > > > > Multiple universes is not contingent on a one-way flow of time. Nor is > > > it obvious that this is unfalsifiable. There is work afoot to > > > *experimentally* detect other branes. Do you need some pointers to > > > that work? > > > Only if the work has produced results. > > OK, then please note the distinction between "yet to be falsified" and > "unfalsifiable". Indeed. Reminds me of a joke actually, that there are only two types of scientific theory... > We believe that only 10% of the species of animals on the earth have > been identified. Does this lack of completeness mean that the > remaining 90% have been proved to not exist? Logically, no, although the fundamental proposition, that there is more to be known than we already know, is unfalsifiable. For if I find you enough new species that the total number of known species is still 10 times more than before, it can still be said that there are ten times as many that you have not yet observed? > > > > No. Reversing time would surely consume energy somewhere, and > > > > therefore increase entropy somewhere. > > > > What? Now you're just making a science fiction babble about a time- > > > reversal machine. This doesn't have to do with the physical nature of > > > things with respect to time. > > > I'm merely voicing the speculative ideas of others. If time is > > flowing, then by definition is must be theoretically possible to > > navigate the flow in both directions. If it is not possible to > > navigate the flow in both directions, then the concept of the past is > > a meaningless, and superfluous, concept. > > Why? Why does symmetric travel have to be present for the past to make > sense? > > In nature, we have causal events separated into future light cones and > past light cones. They are not identical, but then again they do not > have to be. I'm afraid you've lost me. > > > > If energy is consumed in the future in order to send matter back in > > > > time, > > > > What makes you think this is consistent with the laws of physics? > > > Which part? I certainly don't think time travel is consistent with the > > laws of physics, because my very position is that I don't accept that > > time is flowing at all. > > I don't know that time travel is consistent with the laws of physics, > either. Who says it is? It is not so much that anyone is saying that time travel is consistent with the laws of physics, only that the current laws of physics themselves seem to suggest such a possibility, for if you can go forward in time, then you must be able to go backward in time - otherwise the concept of backwards and forwards becomes meaningless. Indeed, if we must use backwards and forwards notation, then I would say the astronaut twin has gone "backwards" in time, if only in the sense that when he returns to earth, the homebody is ahead of his brother in age, and the astronaut is astern of his brother in age. Of course most people don't accept this notation. They say only that the astronaut has gone "slower forwards". However, on my reading of relativity, it does not actually require an absolute forward flow of time, relativity merely suggests that events can move either ahead, or astern, of other events. > > > > > > Also note that this interpretation discards the idea of "parallel > > > > > > universes". It discards the idea of travel backwards in time, and > > > > > > travel to the future can only be achieved by slowing down one's own > > > > > > time. It therefore discards loops in time, and the grandfather > > > > > > paradox. In fact my theory discards just about every paradox we are > > > > > > currently wrestling with, and as yet has none of its own. > > > > > > There are no paradoxes in the current theory. There are *teaching > > > > > examples*, but no paradoxes. > > > > > Everything I've read about time suggests a great number of > > > > contrivances or arbitrary assumptions (parallel universes, for > > > > example) required to avoid paradoxes. > > > > ?? Parallel universes don't have anything to do with resolution of > > > paradoxes. > > > I think you'll find that they do, because by definition a time > > traveller would, from the moment of his arrival, follow a different > > "path", and thus he would never reach the point at which he travelled > > back in time (because that event then belongs to a parallel universe). > > ??? I see I've lost you.
From: PD on 28 Dec 2009 18:48 On Dec 26, 6:12 pm, Ste <ste_ro...(a)hotmail.com> wrote: > On 26 Dec, 18:09, PD <thedraperfam...(a)gmail.com> wrote: > > > > > > > > > > If you were using this ineptly as a specific example of the general > > > > > law that entropy is always increasing, then I accept that to be true. > > > > > The problem is, entropy requires change. Change presupposes the > > > > > concept of ever-flowing time. > > > > > Yes, and the law makes note of the fact that nonequilibrium processes > > > > in closed systems tend to go one way only in time, which imbues time > > > > with an arrow associated with increasing entropy. > > > > > Entropy, by the way, is not dependent on time. It is a state variable, > > > > which means that you can calculate the entropy of a system without > > > > regard to whether the time of that state is before or after another > > > > state. > > > > > What is true is that spontaneous processes (regardless of time) tend > > > > to increase entropy. It is secondarily noted that time tends to also > > > > increase with the increase in entropy. > > > > I know what you're getting at, but you're still presupposing the flow > > > of time. Entropy cannot possibly "increase" without a flow of time. > > > Sure it can. I'm comparing two states, A and B, with different values > > of entropy. > > State B has a higher numerical entropy than state A. I can do this > > without any labeling with time at all. > > Lol. Ok I'll run with this for now. > > > Now, what I observe in nature is that in a closed system, and while > > measuring time, state B happens to be always after state A in that > > time sequence. > > There is no obvious reason why this should be. It could have been just > > as likely that state B occurred before state A. > > But it DOESN'T. > > But in some cases state A *never* becomes state B. So does that mean > time stands still when entropy doesn't change? Not at all. Why would you say that? The question is about whether there is any preferential order in time from the point of view of physical processes. If it there were no preferred order or arrow of time, then all physical processes would be observed to be symmetric in time -- running just as often from state A at earlier time to state B at later time, compared to state B at earlier time to state A at later time. But there's an asymmetry OBSERVED. > > > And this observation is where we recognize that there > > is an arrow of time such that states of higher entropy in closed > > systems happen after states of lower entropy. > > Indeed, but where in the known universe can I find such a "closed > system". If anyone can show me where, I'll show you a man with a wild > imagination. Closed systems are like inertial frames. They are closed if the transactions across the boundary are smaller than the resolution of the experimental detection. This can be achieved pretty straightforwardly. This idealization of systems is essential to physics. > > > > > > or > > > > > unfalsifiable (like multiple universes). If we start to think of the > > > > > universe in terms of having no flow of time, then we eliminate those > > > > > contradictory/unfalsifiable predictions immediately. > > > > > Multiple universes is not contingent on a one-way flow of time. Nor is > > > > it obvious that this is unfalsifiable. There is work afoot to > > > > *experimentally* detect other branes. Do you need some pointers to > > > > that work? > > > > Only if the work has produced results. > > > OK, then please note the distinction between "yet to be falsified" and > > "unfalsifiable". > > Indeed. Reminds me of a joke actually, that there are only two types > of scientific theory... And so your problem with this is what? > > > We believe that only 10% of the species of animals on the earth have > > been identified. Does this lack of completeness mean that the > > remaining 90% have been proved to not exist? > > Logically, no, although the fundamental proposition, that there is > more to be known than we already know, is unfalsifiable. > For if I find > you enough new species that the total number of known species is still > 10 times more than before, it can still be said that there are ten > times as many that you have not yet observed? No and nor would that be claimed. > > > > > > > > No. Reversing time would surely consume energy somewhere, and > > > > > therefore increase entropy somewhere. > > > > > What? Now you're just making a science fiction babble about a time- > > > > reversal machine. This doesn't have to do with the physical nature of > > > > things with respect to time. > > > > I'm merely voicing the speculative ideas of others. If time is > > > flowing, then by definition is must be theoretically possible to > > > navigate the flow in both directions. If it is not possible to > > > navigate the flow in both directions, then the concept of the past is > > > a meaningless, and superfluous, concept. > > > Why? Why does symmetric travel have to be present for the past to make > > sense? > > > In nature, we have causal events separated into future light cones and > > past light cones. They are not identical, but then again they do not > > have to be. > > I'm afraid you've lost me. Where? Do you know what a light cone is? > > > > > > If energy is consumed in the future in order to send matter back in > > > > > time, > > > > > What makes you think this is consistent with the laws of physics? > > > > Which part? I certainly don't think time travel is consistent with the > > > laws of physics, because my very position is that I don't accept that > > > time is flowing at all. > > > I don't know that time travel is consistent with the laws of physics, > > either. Who says it is? > > It is not so much that anyone is saying that time travel is consistent > with the laws of physics, only that the current laws of physics > themselves seem to suggest such a possibility, for if you can go > forward in time, then you must be able to go backward in time - > otherwise the concept of backwards and forwards becomes meaningless. That's nonsense. The forward is accessible to us in a causal manner, the backwards is not. This doesn't render one of them meaningless. Nor does having meaning associated with both imply that we would be able to causally influence the past. > > Indeed, if we must use backwards and forwards notation, then I would > say the astronaut twin has gone "backwards" in time, if only in the > sense that when he returns to earth, the homebody is ahead of his > brother in age, and the astronaut is astern of his brother in age. But he HASN'T gone backwards in time. He's aged -- that's FORWARD in time. It's just that his Earth buddy has gone forward in time faster. If you have two cars that only have forward gears, and one of them travels forward faster than the other, this doesn't mean that the slower one has suddenly acquired a reverse gear! Are you thinking straight? > > Of course most people don't accept this notation. They say only that > the astronaut has gone "slower forwards". > > However, on my reading of relativity, it does not actually require an > absolute forward flow of time, relativity merely suggests that events > can move either ahead, or astern, of other events. No, relativity says nothing of the kind. Perhaps you need some guidance on your reading of relativity. > > > > > > > > > > Also note that this interpretation discards the idea of "parallel > > > > > > > universes". It discards the idea of travel backwards in time, and > > > > > > > travel to the future can only be achieved by slowing down one's own > > > > > > > time. It therefore discards loops in time, and the grandfather > > > > > > > paradox. In fact my theory discards just about every paradox we are > > > > > > > currently wrestling with, and as yet has none of its own. > > > > > > > There are no paradoxes in the current theory. There are *teaching > > > > > > examples*, but no paradoxes. > > > > > > Everything I've read about time suggests a great number of > > > > > contrivances or arbitrary assumptions (parallel universes, for > > > > > example) required to avoid paradoxes. > > > > > ?? Parallel universes don't have anything to do with resolution of > > > > paradoxes. > > > > I think you'll find that they do, because by definition a time > > > traveller would, from the moment of his arrival, follow a different > > > "path", and thus he would never reach the point at which he travelled > > > back in time (because that event then belongs to a parallel universe).. > > > ??? > > I see I've lost you.
From: Ste on 29 Dec 2009 01:21
On 28 Dec, 23:48, PD <thedraperfam...(a)gmail.com> wrote: > > > > Sure it can. I'm comparing two states, A and B, with different values > > > of entropy. > > > State B has a higher numerical entropy than state A. I can do this > > > without any labeling with time at all. > > > Lol. Ok I'll run with this for now. > > > > Now, what I observe in nature is that in a closed system, and while > > > measuring time, state B happens to be always after state A in that > > > time sequence. > > > There is no obvious reason why this should be. It could have been just > > > as likely that state B occurred before state A. > > > But it DOESN'T. > > > But in some cases state A *never* becomes state B. So does that mean > > time stands still when entropy doesn't change? > > Not at all. Why would you say that? > The question is about whether there is any preferential order in time > from the point of view of physical processes. If it there were no > preferred order or arrow of time, then all physical processes would be > observed to be symmetric in time -- running just as often from state A > at earlier time to state B at later time, compared to state B at > earlier time to state A at later time. > But there's an asymmetry OBSERVED. I get your point. What I'm saying is that the theoretical model we have to explain our observations needs to be questioned. People once saw the Sun move over the sky, and assumed that the Sun orbited the Earth. And the credibility of that model, and the credulity of the very best and brightest, remained long after a better and more simpler model had been conceived - that of the Earth orbiting the Sun. Indeed the problem is that humans are apparently very poor at developing perspective. Physical processes may well be symmetric in time - in that every transformation of energy can ultimately be reversed by the fundamental forces of nature. And indeed I think that is true, and it is a snug fit with other laws like energy conservation. And yet, we cling to the model of time flowing ever- forwards, of entropy ever-increasing - and clinging to this model means that every new discovery puts a new epicycle into contemporary theoretical physics, in the same way that in the middle ages every new star discovered, every new telescope developed, put another epicycle into the contemporary astronomer's model of the sky. That is why I don't place any value on the existing maths in theoretical physics, because a model begins life in its most mathematically refined state, to which only epicycles can then be added. And if you commit yourself to fitting your theories around the existing hoard of counter-intuitive epicycles, you'll spend a life's work at the rump of your subject. Indeed if there is one thing I know from my broad knowledge in many subjects, it is that those who talk of asymmetry, of complexity, of change, of difference, actually don't have perspective on their subject, and those who can talk *convincingly* of symmetry, of simplicity, of constancy, of similarity, do have perspective. And I think at the moment theoretical physics is stuck in terms of talking about asymmetry, because today physicists again find themselves unable to question the very foundations of their conceptual models. > > > And this observation is where we recognize that there > > > is an arrow of time such that states of higher entropy in closed > > > systems happen after states of lower entropy. > > > Indeed, but where in the known universe can I find such a "closed > > system". If anyone can show me where, I'll show you a man with a wild > > imagination. > > Closed systems are like inertial frames. They are closed if the > transactions across the boundary are smaller than the resolution of > the experimental detection. This can be achieved pretty > straightforwardly. Indeed. > This idealization of systems is essential to physics. Not at all. Science is supposed to be about idealising the model in the first place, and then making allowances for it's practical implementation. Thermodynamics was once at the cutting edge - industrialists knew ash didn't combust into coal, furnaces never became spontaneously hot, ores didn't spontaneously form into finished metals. Of course, they knew *in practice* it was difficult to keep any system truly closed, but the conceptual model, in its idealised form, rested on the foundation that they could *theoretically* keep a system thermodynamically closed. Science now having moved on however, we know that you *cannot* keep a system closed in the thermodynamic sense, *even theoretically* - the only possible closed system is the universe itself. At the very least, there is no known mechanism for excluding the force of gravity from a system. Why, then, people are referring back to thermodynamics as a theoretical proof of any modern concept is beyond me. Thermodynamics is to chemistry what classical mechanics is to physics - a relatively simple rule of thumb for everyday purposes, but its theoretical underpinnings are long since superseded. > > > > > > or > > > > > > unfalsifiable (like multiple universes). If we start to think of the > > > > > > universe in terms of having no flow of time, then we eliminate those > > > > > > contradictory/unfalsifiable predictions immediately. > > > > > > Multiple universes is not contingent on a one-way flow of time. Nor is > > > > > it obvious that this is unfalsifiable. There is work afoot to > > > > > *experimentally* detect other branes. Do you need some pointers to > > > > > that work? > > > > > Only if the work has produced results. > > > > OK, then please note the distinction between "yet to be falsified" and > > > "unfalsifiable". > > > Indeed. Reminds me of a joke actually, that there are only two types > > of scientific theory... > > And so your problem with this is what? I don't have a problem. I was just acknowledging that I know the difference between "unfalsifiable" and "not yet falsified", and then I went on to reflect comically on the fact that the only scientific theories that will not eventually be falsified are those that are unfalsifiable. > > > > > > No. Reversing time would surely consume energy somewhere, and > > > > > > therefore increase entropy somewhere. > > > > > > What? Now you're just making a science fiction babble about a time- > > > > > reversal machine. This doesn't have to do with the physical nature of > > > > > things with respect to time. > > > > > I'm merely voicing the speculative ideas of others. If time is > > > > flowing, then by definition is must be theoretically possible to > > > > navigate the flow in both directions. If it is not possible to > > > > navigate the flow in both directions, then the concept of the past is > > > > a meaningless, and superfluous, concept. > > > > Why? Why does symmetric travel have to be present for the past to make > > > sense? > > > > In nature, we have causal events separated into future light cones and > > > past light cones. They are not identical, but then again they do not > > > have to be. > > > I'm afraid you've lost me. > > Where? Do you know what a light cone is? No, and with respect I don't think I want to know, because something that includes the "past and future" model of time is bound to confound me. > > > > > > If energy is consumed in the future in order to send matter back in > > > > > > time, > > > > > > What makes you think this is consistent with the laws of physics? > > > > > Which part? I certainly don't think time travel is consistent with the > > > > laws of physics, because my very position is that I don't accept that > > > > time is flowing at all. > > > > I don't know that time travel is consistent with the laws of physics, > > > either. Who says it is? > > > It is not so much that anyone is saying that time travel is consistent > > with the laws of physics, only that the current laws of physics > > themselves seem to suggest such a possibility, for if you can go > > forward in time, then you must be able to go backward in time - > > otherwise the concept of backwards and forwards becomes meaningless. > > That's nonsense. The forward is accessible to us in a causal manner, > the backwards is not. This doesn't render one of them meaningless. Nor > does having meaning associated with both imply that we would be able > to causally influence the past. My point is that "cause and effect" are an arbitrary classification to describe something of meaning to humans. The reason the "past" can never be "affected" in a "causal" manner is because, by its very definition, cause always precedes effect in the forward-flowing model of time. Another, symmetric, model of time would say that every process has an equal an opposite process so that all forms of energy, including momentum, are ultimately conserved. "Cause and effect" can only exist in the ever-forward flowing model of time. Process and counter-process know no concept of flowing time (because one never happens absolutely "before" or "after" the other, the two having occurred, and continuing to occur, for all eternity in a reciprocal, symmetrical, motion). > > Indeed, if we must use backwards and forwards notation, then I would > > say the astronaut twin has gone "backwards" in time, if only in the > > sense that when he returns to earth, the homebody is ahead of his > > brother in age, and the astronaut is astern of his brother in age. > > But he HASN'T gone backwards in time. He's aged -- that's FORWARD in > time. It's just that his Earth buddy has gone forward in time faster. But that's because "going backwards in time", to you, means someone's age reducing in *absolute* terms. To me, the fact that one twin is younger than the other is evidence that one has gone back in time *relatively*. Remember, the absolutism of classical mechanics doesn't stop that theory having use-value even today. But I look forward to people talking of "classical time" - so we can say that the astronaut has aged 2 years less in classical time, whereas he has aged -2 years in relative time. > If you have two cars that only have forward gears, and one of them > travels forward faster than the other, this doesn't mean that the > slower one has suddenly acquired a reverse gear! Are you thinking > straight? No, I'm thinking *relative*. Are you? > > Of course most people don't accept this notation. They say only that > > the astronaut has gone "slower forwards". > > > However, on my reading of relativity, it does not actually require an > > absolute forward flow of time, relativity merely suggests that events > > can move either ahead, or astern, of other events. > > No, relativity says nothing of the kind. Perhaps you need some > guidance on your reading of relativity. I think perhaps others need reminding about the implications of relativity. People just about seem happy with relative positions in space. They seem less happy with relative positions in time. |