Arrow of Time
in [Physics]
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From: Sam on 19 Jun 2010 23:14 On Jun 19, 1:58 pm, bert <herbertglazie...(a)msn.com> wrote: > > Sam Time has 5 arrows TreBert 3.1 The thermodynamic arrow of time 3.2 The cosmological arrow of time 3.3 The radiative arrow of time 3.4 The causal arrow of time 3.5 The particle physics (weak) arrow of time 3.6 The quantum arrow of time 3.7 The psychological/perceptual arrow of time
From: Sam on 19 Jun 2010 23:23 On Jun 19, 5:36 pm, bert <herbertglazie...(a)msn.com> wrote: > Interesting how Einstein merged time with space (Spacetime) Did you mean Minkowski?
From: Mathal on 20 Jun 2010 01:45 On Jun 19, 8:58 am, "Robert L. Oldershaw" <rlolders...(a)amherst.edu> wrote: > An interesting discussion has started at sci.physics.research > concerning the nature of the "arrow of time" > > Below are the original post and a follow-up. Check it out and > contribute! > -------------------------------------------------------- > > I would like to explore an idea one more time. > > Could we not define the arrow of time as the arrow of causality? > > Consider a typical Rube Goldberg device. Event 1 triggers event 2, > which triggers event 3, and so on. There is no way that the sequence > could go backwards, or that the ordering of events could be changed. > > In any part of the cosmos that we can fully investigate, causality > appears to be always obeyed and always moves in one direction from > cause to effect. > > Is there any reliable, fully tested empirical knowledge that prevents > us from simply saying: > > ARROW OF TIME = ARROW OF CAUSALITY ? > > Thinking of the Rube Goldberg device again, we say the diagram > represents a temporal or causal sequence. > > Perhaps the concept of time is a simple way to describe the ordering > of causal sequences, and a simple way to define magnitude relations > between the rate at which two sequences proceed? > > RLOwww.amherst.edu/~rloldershaw > ---------------------------------------------------- > > On Jun 19, 3:58 am, hel...(a)astro.multiCLOTHESvax.de (Phillip Helbig---undress to reply) wrote: > > > There are several arrows of time: thermodynamic, cosmological, causal > > etc. Everyone agrees they exist. By "defining" one as "the" arrow of > > time, we gain nothing. In other words, WHY can we define a causal arrow > > of time? Microscopically, the laws of physics are time-reversible, but > > on larger scales, we observe various arrows of time. Why? That is the > > question. > > -------------------------------------------------- > > (1) We are not absolutely required to accept unconditionally the > statement that "Microscopically, the laws of physics are time- > reversible,..." > > In fact, I reject this Platonic over-idealization categorically. Can > you prove me wrong empirically? The "laws" *you* subscribe to may be > reversible, but mine are definitely not. Mine are always causal, > deterministic [in the nonlinear dynamical systems sense] and > irreversible [although limited periodic behavior is permited]. > > (2) There may be many "arrows of time", but there is always ONE and > the same Arrow of Causality. A subtle, but important distinction, I > admit. > > RLOwww.amherst.edu/~rloldershaw In this group you will find little dispute with the idea that time moves forward. From a 'human' perspective that is inevitable. I doubt if anyone would propose that time moves backwards to the perspective that we see it 'moving'. From a purely QM perspective time doesn't move- it's another dimension and all phenomena can be seen as just as 'true' with time moving in either direction. From (John) Wheeler's perspective and implied in Feynman's perspective time isn't 'really' on either side of any 'reaction'. My opinion is that is inevitable that the human mind thinks it is rational and that it is in control of what it thinks. I am not suggesting that' god' or 'spirits' are in control, we just live our lives, thinking we are making sense. The photon your eye captures when you look out at the sky that came from who knows how many light years away in time and distance may have been 'destined' to be captured by you,but you have as much right to say nonsense, I just looked up at that moment. I personally believe both are true. Mathal
From: oen on 20 Jun 2010 03:59 On Jun 19, 5:58 pm, "Robert L. Oldershaw" <rlolders...(a)amherst.edu> wrote: > An interesting discussion has started at sci.physics.research > concerning the nature of the "arrow of time" > > Below are the original post and a follow-up. Check it out and > contribute! > -------------------------------------------------------- > > I would like to explore an idea one more time. > > Could we not define the arrow of time as the arrow of causality? > > Consider a typical Rube Goldberg device. Event 1 triggers event 2, > which triggers event 3, and so on. There is no way that the sequence > could go backwards, or that the ordering of events could be changed. > > In any part of the cosmos that we can fully investigate, causality > appears to be always obeyed and always moves in one direction from > cause to effect. > > Is there any reliable, fully tested empirical knowledge that prevents > us from simply saying: > > ARROW OF TIME = ARROW OF CAUSALITY ? causality do not need an arrow, it is just that, causal, without which you get chaos, which we dont like > > Thinking of the Rube Goldberg device again, we say the diagram > represents a temporal or causal sequence. > > Perhaps the concept of time is a simple way to describe the ordering > of causal sequences, and a simple way to define magnitude relations > between the rate at which two sequences proceed? > > RLOwww.amherst.edu/~rloldershaw > ---------------------------------------------------- > > On Jun 19, 3:58 am, hel...(a)astro.multiCLOTHESvax.de (Phillip Helbig---undress to reply) wrote: > > > There are several arrows of time: thermodynamic, cosmological, causal wrong, all of them are causal > > etc. Everyone agrees they exist. By "defining" one as "the" arrow of > > time, we gain nothing. In other words, WHY can we define a causal arrow > > of time? Microscopically, the laws of physics are time-reversible, but > > on larger scales, we observe various arrows of time. Why? That is the > > question. yes, i just said that, you are contradicting yourself > > -------------------------------------------------- > > (1) We are not absolutely required to accept unconditionally the > statement that "Microscopically, the laws of physics are time- > reversible,..." no, it is a matter of limitation of detection the causality still exist at quantum level !!! > > In fact, I reject this Platonic over-idealization categorically. Can > you prove me wrong empirically? The "laws" *you* subscribe to may be > reversible, but mine are definitely not. Mine are always causal, > deterministic [in the nonlinear dynamical systems sense] and > irreversible [although limited periodic behavior is permited]. i just said that > > (2) There may be many "arrows of time", but there is always ONE and > the same Arrow of Causality. A subtle, but important distinction, I > admit. agreed > > RLOwww.amherst.edu/~rloldershaw good bye, learn physics from a book
From: Thomas on 20 Jun 2010 05:02
On 19 June, 15:58, "Robert L. Oldershaw" <rlolders...(a)amherst.edu> wrote: > An interesting discussion has started at sci.physics.research > concerning the nature of the "arrow of time" > > Below are the original post and a follow-up. Check it out and > contribute! > -------------------------------------------------------- > > I would like to explore an idea one more time. > > Could we not define the arrow of time as the arrow of causality? > > Consider a typical Rube Goldberg device. Event 1 triggers event 2, > which triggers event 3, and so on. There is no way that the sequence > could go backwards, or that the ordering of events could be changed. > > In any part of the cosmos that we can fully investigate, causality > appears to be always obeyed and always moves in one direction from > cause to effect. > > Is there any reliable, fully tested empirical knowledge that prevents > us from simply saying: > > ARROW OF TIME = ARROW OF CAUSALITY ? 'Time' is defined by 'change', and change as such does not constitute an arrow, i.e. it is an absolute notion. This is why time can only go forwards (after all, if you watch a film running backwards, you obviously won't grow any younger by doing this). Thomas |