Post by: Alan McDougall on 18/06/2013 16:37:20
What is time?
Some say it is just measure of movement or an aggregation of events. Time is not a constant and I would like you guys to put forward your own ideas on the topic before adding my piece to the story.
Alan
Post by: yor_on on 18/06/2013 17:03:03
locally it is a constant.
It's only when you compare over frames of reference you find it to give you a time dilation. Using gravitational time dilations your body can be defined to belong to different 'time zones' if you like. But from each position (loosely speaking) in SpaceTime its clock has a 'constant rate', definable as locally invariant, just as 'c' will be so for each of those 'frames of reference'. That as a 'gravity' can be translated, according to the equivalence principle, into a uniform constant acceleration. So you can consider all those 'points' of your body as 'differently gravitationally accelerating', although each one of them must present you with 'c' locally, as a 'constant', just as they must with that 'arrow'.
And that is a local definition.
Defining time 'globally', you have to measure over 'frames of reference'. Doing so you compare far away clocks relative your 'local clock', macroscopically defined as being 'at rest' with you (although still subject to microscopic gravitational time dilations). As you in your observatory, measuring, using the clock on the wall as your local reference. Then 'a far away arrow' becomes subject to Lorentz transformation, to fit your local one.
It's a very tricky subject, for example, where is a consciousness situated? Does it have a specific location, or is it a synthesis, undefinable to any single location, over a brain? If it is a synthesis and we assume that it should be able to define a 'frame of reference' as something meaningful in itself (physically). Then choosing Planck scale as the 'smallest common nominator' for both 'c' and that local arrow. Then your brain, and subsequent thoughts, must handle 'time dilations' as well as 'Lorentz contractions', assuming that those two are complementary.
=
corrected a question mark :)
da*n.
=
As I already destroyed the unspoiled beauty of my post, if you're considering presenting a new theory, TNS have a lovely spot for those in 'New Theories'.
And a simple proof for a arrow, as being a local 'constant', is the fact that wherever you go that 'local clock' follows you. And your lifetime, relative that clock, is a set one.
Post by: AndroidNeox on 24/06/2013 22:05:18
I think that a better question than "what is time?" is, "when we measure time, what do we measure?". The first includes the assumption that time is something. Time doesn't seem to be a "something" any more than space does. Neither are conserved quantities. Einstein felt that "space" had no meaning independent of the fields within it.
When we measure time we are counting a sequence of events: heart beats, pendulum swings, quartz vibrations, etc. When we time some process we are comparing counts of two or more sequences.
Post by: Alan McDougall on 25/06/2013 10:03:59
:)
locally it is a constant.
It's only when you compare over frames of reference you find it to give you a time dilation. Using gravitational time dilations your body can be defined to belong to different 'time zones' if you like. But from each position (loosely speaking) in SpaceTime its clock has a 'constant rate', definable as locally invariant, just as 'c' will be so for each of those 'frames of reference'. That as a 'gravity' can be translated, according to the equivalence principle, into a uniform constant acceleration. So you can consider all those 'points' of your body as 'differently gravitationally accelerating', although each one of them must present you with 'c' locally, as a 'constant', just as they must with that 'arrow'.
And that is a local definition.
Defining time 'globally', you have to measure over 'frames of reference'. Doing so you compare far away clocks relative your 'local clock', macroscopically defined as being 'at rest' with you (although still subject to microscopic gravitational time dilations). As you in your observatory, measuring, using the clock on the wall as your local reference. Then 'a far away arrow' becomes subject to Lorentz transformation, to fit your local one.
It's a very tricky subject, for example, where is a consciousness situated? Does it have a specific location, or is it a synthesis, undefinable to any single location, over a brain? If it is a synthesis and we assume that it should be able to define a 'frame of reference' as something meaningful in itself (physically). Then choosing Planck scale as the 'smallest common nominator' for both 'c' and that local arrow. Then your brain, and subsequent thoughts, must handle 'time dilations' as well as 'Lorentz contractions', assuming that those two are complementary.
=
corrected a question mark :)
da*n.
=
As I already destroyed the unspoiled beauty of my post, if you're considering presenting a new theory, TNS have a lovely spot for those in 'New Theories'.
And a simple proof for a arrow, as being a local 'constant', is the fact that wherever you go that 'local clock' follows you. And your lifetime, relative that clock, is a set one.
Even locality is not in absolute terms a constant, simply because the different parts of you physical body move at differently rates, relative to other parts of your body. Thus, your legs might be moving due to walking and your arms held over your head stationary to the rest of your torso. Thus, relative to each other they are moving at different rates and this effects time, albeit so infinitesimally tiny, that on our human macro scale it is meaningless, but, nevertheless real in the quantum world of the minute.
Time is really a mystery?
Alan
Alan
Post by: evan_au on 25/06/2013 10:49:40
Quote
your arms held over your head stationary to the rest of your torsoIf your hands are over your head, then they are further out of Earth's gravitational field.
So time passes more rapidly for your hands than your feet (by an infinitesimal but measurable amount).
Post by: Alan McDougall on 25/06/2013 15:30:30
Quoteyour arms held over your head stationary to the rest of your torsoIf your hands are over your head, then they are further out of Earth's gravitational field.
So time passes more rapidly for your hands than your feet (by an infinitesimal but measurable amount).
What you stated is true, but so is my example!
I, however, disagree that it is possible to measure the difference rates of time, between your hand and feet due to the effect of gravity? The force of gravity is incredibly weak and the effect you are referring to is simply imperceptible to our very best measuring devices, even atomic clocks would not pick up this effect.
Alan
Alan
Post by: yor_on on 25/06/2013 15:38:26
Then there is a third that I'm wondering about, and that is in fact that 'local clock' you either way must use, no matter if you define it macroscopically or microscopically.
It exists, and you can't work around it. And that one, if possible to define, I would define as belonging to Planck scale, as that is where light 'freeze' :), holding at one Planck length in one Planck time. As well as it is there physics stops giving you meaningful answers.
Post by: yor_on on 25/06/2013 15:43:23
Post by: Alan McDougall on 25/06/2013 15:46:21
Yep, you can use gravitational time dilations and their complementary Lorentz contractions to define 'time zones'. But to do that you need a 'local clock' from where to compare it. There are two ways to define one single frame of reference. You can either use being 'at rest', as we macroscopically can be defined being 'at rest' with earth in its relative motion. Or you can refer to some 'inertially defined' object.
Then there is a third that I'm wondering about, and that is in fact that 'local clock' you either way must use, no matter if you define it macroscopically or microscopically.
It exists, and you can't work around it. And that one, if possible to define, I would define as belonging to Planck scale, as that is where light 'freeze' :), holding at one Planck length in one Planck time. As well as it is there physics stops giving you meaningful answers.
I agree at the Plank limits such as Plank time we can't get meaningful answers, however, do we know for sure that the Plank limits on time are really the absolute smallest possible division of time? Has this been proven in any scientific experiment?
Post by: yor_on on 25/06/2013 15:58:49
Post by: yor_on on 25/06/2013 16:12:06
Post by: yor_on on 25/06/2013 16:27:49
Post by: Alan McDougall on 25/06/2013 16:39:34
You can't prove anything, as none can probe that scale Alan, that is as far as I know. What makes me define that way is that it is a limit for what makes sense physically. Under it we meet a new regime. If you use 'c' (locally measured), and split it into even chunks of 'time', to define ones local arrow, then at Planck scale that arrows stops 'move' just as light. What then might be 'under it' must be 'something totally else'. You do not have a arrow (locally defined) under that scale as I expect.
I wonder does time flow like a river or can it be broken down into smaller and smaller discrete moments , something like frames on a movie reel?
Post by: yor_on on 25/06/2013 16:53:36
Post by: lean bean on 25/06/2013 18:30:45
I, however, disagree that it is possible to measure the difference rates of time, between your hand and feet due to the effect of gravity? The force of gravity is incredibly weak and the effect you are referring to is simply imperceptible to our very best measuring devices, even atomic clocks would not pick up this effect.Alan
If the distance between your head and feet is one metre or just under, then these chaps claim to have measured/detected the relative time difference over that distance.
Quote
We can now also detect time dilation due to a change in height near Earth’s surface of less than 1 meter. This technique may be extended to the field of geodesy, with applications in geophysics and hydrology as well as in space-based tests of fundamental physics.From http://adsabs.harvard.edu/abs/2010Sci...329.1630C
Quote
In 2010, Chou et al. performed tests in which both gravitational and velocity effects were measured at velocities and gravitational potentials much smaller than those used in the mountain-valley experiments of the 1970's. It was possible to confirm velocity time dilation at the 10-16 level at speeds below 36 km/h. Also, gravitational time dilation was measured from a difference in elevation between two clocks of only 33 cmfrom http://en.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment#Similar_experiments_with_atomic_clocks (http://en.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment#Similar_experiments_with_atomic_clocks)
Post by: Alan McDougall on 25/06/2013 19:12:11
I, however, disagree that it is possible to measure the difference rates of time, between your hand and feet due to the effect of gravity? The force of gravity is incredibly weak and the effect you are referring to is simply imperceptible to our very best measuring devices, even atomic clocks would not pick up this effect.Alan
If the distance between your head and feet is one metre or just under, then these chaps claim to have measured/detected the relative time difference over that distance.QuoteWe can now also detect time dilation due to a change in height near Earth’s surface of less than 1 meter. This technique may be extended to the field of geodesy, with applications in geophysics and hydrology as well as in space-based tests of fundamental physics.From http://adsabs.harvard.edu/abs/2010Sci...329.1630CQuoteIn 2010, Chou et al. performed tests in which both gravitational and velocity effects were measured at velocities and gravitational potentials much smaller than those used in the mountain-valley experiments of the 1970's. It was possible to confirm velocity time dilation at the 10-16 level at speeds below 36 km/h. Also, gravitational time dilation was measured from a difference in elevation between two clocks of only 33 cmfrom http://en.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment#Similar_experiments_with_atomic_clocks (http://en.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment#Similar_experiments_with_atomic_clocks)
If that is true, it is beyond amazing!
Post by: yor_on on 25/06/2013 23:47:31
In the other we're still here, but your definition of that universe is not mine. I can translate your definition to mine, you can translate mine to yours. If I would take a measurement of a distance in this universe it will be true for me, and my arrow of time, and life span, is directly connected to my measurement of 'c'. But to fit it to your description of a universe, 'time' and a distance we might need Lorentz transformations. We're still 'here' though, but what defines us is 'c', and frames of reference. I was stuck on this one for the longest time, and in a way I still am.
To reconcile those two definitions we use the same constant, 'c'. But looking at it my way simplify some things, your life span for example. And the way we define a repeatable experiment. It becomes two definitions, depending on what view you take of life, the universe, and all, as Douglas Adams would have said :)
It's not as much as one must be truer, it's just that I like to simplify it, as good as I can.
Post by: Alan McDougall on 27/06/2013 13:26:45
You can see the universe we exist in two ways. The one we're most used to is the one in where we share a common universe. In that one we're 'here', all together. I can touch someone, they can touch me. We are 'here'.
In the other we're still here, but your definition of that universe is not mine. I can translate your definition to mine, you can translate mine to yours. If I would take a measurement of a distance in this universe it will be true for me, and my arrow of time, and life span, is directly connected to my measurement of 'c'. But to fit it to your description of a universe, 'time' and a distance we might need Lorentz transformations. We're still 'here' though, but what defines us is 'c', and frames of reference. I was stuck on this one for the longest time, and in a way I still am.
To reconcile those two definitions we use the same constant, 'c'. But looking at it my way simplify some things, your life span for example. And the way we define a repeatable experiment. It becomes two definitions, depending on what view you take of life, the universe, and all, as Douglas Adams would have said :)
It's not as much as one must be truer, it's just that I like to simplify it, as good as I can.
Although off topic, this does relate to your post above. How each person might perceive the same thing differently.
Take colour perception,do you see red exactly as I do RED or
BLUE. So long as our different perception are consistent with each other, how are we ever to know for sure, we are both observing the same thing in the exact same way?
Perception of time might be different from person , to person, under the exact same conditions?
Alan
Post by: Pmb on 27/06/2013 16:27:07
HiI would define time as the phenomena which pertains to different configurations of the world around us.
What is time?
Some say it is just measure of movement or an aggregation of events. Time is not a constant and I would like you guys to put forward your own ideas on the topic before adding my piece to the story.
Alan
What then is time? If no one asks me, I know what it is. If I wish to explain it to him who asks, I do not know. - St. Augustine
Post by: Alan McDougall on 27/06/2013 18:45:58
HiI would define time as the phenomena which pertains to different configurations of the world around us.
What is time?
Some say it is just measure of movement or an aggregation of events. Time is not a constant and I would like you guys to put forward your own ideas on the topic before adding my piece to the story.
Alan
What then is time? If no one asks me, I know what it is. If I wish to explain it to him who asks, I do not know. - St. Augustine
I would like to post a dream about time I had a few years ago, please!, I am not going metaphysical, my odd dream just shows how strange time and movement could be from different perspectives. It is not a reflection of reality
What I am now going to describe is very weird, but it is a lucid dream I have had and for which I simply have no explanation. I seem to go to another dimension or universe, where time and movement were reversed, relative to everything and me, in this alternate dimension, everyone was moving backwards in time and movement.
You might have heard the phrase, "In the land of the blind the one eyed man is king"
In this bizarre alternate reality, I who could move both back and forward appeared to be king as I could easily reveal or hide myself there. Take one example, I saw a man who was walking backward after a workday at 5 pm, to his bedroom when he got up at 9am. As he started to walk backwards from his desk 5pm, from my perceptive, time and movement,I was walking forward. However, in his reality he was moving (walking) back in time to the morning when he left for work at 9am. (moment)
From my viewpoint, I arrived at the moment he began to walk backward from his work desk at 5pm, to the elevator, reversing back to the moment when he got up at 9am in the morning. As I watched him he synchronized exactly with the elevator the moment door of the elevator opened, without looking, he just backed into the elevator. Weird not really! If you play the scenario forward in time and movement, when the elevator reached his floor, it opened and he got out and went to his desk, as if anyone would in our reality.
To try and make him aware my presence, I walked forward in front of him, because from my perspective, he was reversed and walking backward, from his evening at 5pm to his morning at 9pm, when he got up for work. He became very distressed by me, because he saw me, as a being that suddenly appeared in front of him. From his perceptive as he walked forward to his desk, he saw me walking backward in front of him in, no matter how hard tried to get rid of this apparition, that was I, I was always in front of him, reversing by walking backward relative to him. During another moment, I got behind him as he was walking backward and stopped him by placing my hands firmly on his back, thus, in his world he was suddenly stopped by some sort of outside force with a weird sense that there was another entity behind him that he could not identify. I think the hairs on his neck stood up straight. I could really have fun here I was the phantom of the opera in that moment.
In my dream, he was a very real person and I could see he was confused even frightened by the apparition, that was I. To him, I had become an unpleasant ghostly thing from some alternate reality. The interaction between these two alternate reversed time dimensions, were so complex, I think maybe one would need more than an Einstein, to explain what was really going on.
For instance, I noticed that at moments he could see me and tried to rush at me and touch me. When he did that, I simply stood still and slowly receded out of view, from his perceptive. When he to rushed/ran toward me, the time, the time, distance and movement variations between our alternate realities just increased. When he ran faster and faster toward me all that happened was, I moved receded faster and faster backward in distance and time from him.
The harder he tried to touch or reach me, the more I receded. "Weird" very "Weird" From his perspective he was moving forward in time, and I was reversing time and movement. I following him back from 5 pm, the moment he was supposed to knock off work him, until 9 am when he left for work and got out of bed. The dream is hard to explain and confusing and convoluted, but it really gives one a glimpse of how strange time and movement can be from different perspectives and perceptions.
Alan 8D
Post by: RD on 27/06/2013 20:09:17
... it is a lucid dream I have had and for which I simply have no explanation. I seem to go to another dimension or universe, where time and movement were reversed ...
Are you sure it wasn't the "backwards" episode of "Red Dwarf" [:)] ...
Quote from: wikipedia.org/wiki/Backwards_(Red_Dwarf_episode)
Kryten and Rimmer think that the backwards world is wonderful, pointing out that when the second world war comes around again, millions of people will come back to life, and Hitler will retreat across Europe, liberating France and Poland. Lister though looks at the other side of the argument and states that in this universe St. Francis of Assisi is the petty-minded little sadist who maims small animals and that Santa Claus is a big guy who sneaks down chimneys and steals all the kids' favourite toys.http://en.wikipedia.org/wiki/Backwards_%28Red_Dwarf_episode%29#Cultural_references
Post by: Bill S on 28/06/2013 03:07:59
Quote from: Alan
I following him back from 5 pm, the moment he was supposed to knock off work him, until 9 am when he left for work and got out of bed.
I assume you spotted the inconsistency here. At 9am, had he been travelling backwards through time, he would have fallen backwards into bed, his alarm would have gone off and he would have gone to sleep. Time reversal is a complex thing. I'm very pushed for time at the moment, but I hope to have a chance to air a few of my thoughts on the subject.
Post by: evan_au on 28/06/2013 06:40:23
Quote
I, however, disagree that it is possible to measure the difference rates of time, between your hand and feet due to the effect of gravityThe aluminium clock experiment at NIST in 2010 were a significant advance in timekeeping. But I was referring to earlier measurements that were able to detect time dilation effects over altitude differences as small as 30mm (not 30 cm).
The earlier researchers had a coherent beam with a very short wavelength. They aimed it at a target which split the beam in 2 paths, and then recombined it, causing interference fringes.
By rotating the splitter/recombiner, they were able to make the two beams take paths with the same altitude or different altitudes, and they could see changes in the interference patterns. They interpreted the results as showing that when the beam was further from the Earth, time passed more rapidly, so the beam was out of phase when recombined with the lower beam.
This is a very difficult experiment due to the required mechanical tolerances, but was an ingenious way to demonstrate the effect of time dilation on human scales without requiring two calibrated clocks - you just need one stable source.
Post by: syhprum on 28/06/2013 11:01:09
If they have the life time of a mountain 1 Hz would be supersonic but if they have the life time of a fly it would represent an extremely low frequency.
Post by: Alan McDougall on 28/06/2013 14:53:24
Quote from: AlanI following him back from 5 pm, the moment he was supposed to knock off work him, until 9 am when he left for work and got out of bed.
I assume you spotted the inconsistency here. At 9am, had he been travelling backwards through time, he would have fallen backwards into bed, his alarm would have gone off and he would have gone to sleep. Time reversal is a complex thing. I'm very pushed for time at the moment, but I hope to have a chance to air a few of my thoughts on the subject.
Yes it was difficult to write and keep in mind the two opposite arrows of time , within the alternate dimensions. I will look at your comment and correct the error.
Alan
Post by: Alan McDougall on 28/06/2013 15:08:45
... it is a lucid dream I have had and for which I simply have no explanation. I seem to go to another dimension or universe, where time and movement were reversed ...
Are you sure it wasn't the "backwards" episode of "Red Dwarf" [:)] ...Quote from: wikipedia.org/wiki/Backwards_(Red_Dwarf_episode)Kryten and Rimmer think that the backwards world is wonderful, pointing out that when the second world war comes around again, millions of people will come back to life, and Hitler will retreat across Europe, liberating France and Poland. Lister though looks at the other side of the argument and states that in this universe St. Francis of Assisi is the petty-minded little sadist who maims small animals and that Santa Claus is a big guy who sneaks down chimneys and steals all the kids' favourite toys.http://en.wikipedia.org/wiki/Backwards_%28Red_Dwarf_episode%29#Cultural_references
I went to the link, but my dream had nothing to do with that movie, I have dreamed this type of dream a few times, and they are very disturbing, nightmares in fact.
Thinking about the dream again, the two entities in the dream , me and the person in the other backward realm, might only really observe each other in brief 'moments', when they stood still relative each other, (within visual range), or exactly when the exact "moment" the two arrows of times crossed paths in opposite direction.
I , think , however, they do give a sort of an indication how truly strange and complex time can be, if viewed from different relative perspectives :)
Post by: Bill S on 02/07/2013 23:46:14
Professor MacBeath explains, ‘While Jim and Midge are together a face-to-face conversation is hardly likely to get of the ground. To make this clear let us say that they are together from t0 until t10 on Jim’s time-scale, and from T0 until T10 on Midge’s TIME-scale; t0 is then the same temporal instant as T10 and, in general, tn = T10 – n. If Jim at …t2 asks Midge a question, and Midge hears the question at T8, she will answer at T9, and Jim will hear his question answered at t1, before he asked it. What is more, if Jim is inexpert at interpreting backward sounds, and at t4 asks Midge to repeat her answer, Midge will hear this request at T6, BEFORE she has heard the original question; and her puzzled reply at T7 will again be heard by Jim at t3, before he has uttered the request.’
Lucas seems to be on safe ground with his denial of the possibility of communication. MacBeath, however, shows how to refute all of Lucas’s arguments if Midge and Jim are allowed to be clever about how they send messages back and forth. To follow the logic, it will be helpful to look at Fig. 1 (a simplified version of MacBeath's scheme, above) for the time direction for Jim and Midge:
We imagine that Jim and Midge will not actually talk and thus have to decipher backward-spoken language. Rather, they will exchange messages via computer-generated text displayed on monitor screens. We can, in fact, imagine that Jim and Midge are separated by a window that is proof against all penetration but light. Now, at t0 Jim brings a computer to the window. He programs it to wait for four days, until t4, and then to display the following message on the screen: "This message is from Jim, who experiences time in the sense opposite to yours. Please study the following questions and display your answers on a computer screen three days from now."
Fig. 1
earlier Jim (normal time) later
t0 t1 t2 t3 t4
T4 T3 T2 T1 T0 LATER MIDGE (reversed time) EARLIER
Jim’s message ends with a list of questions. Since this will appear at t4, Midge sees it at what we will now call T0. As requested, she brings her computer to the window, enters the answers to Jim’s questions, and programs the machine to display them (after a three-day delay) on its screen. Thus, at T3, which is Jim’s t1, Jim sees Midge’s computer screen light up with: "Hi, Jim. This is Midge. The answers to your questions are at the end of this message. Now, I’ve got some questions for you. Please display the answers two days from now." Midge’s message ends with Jim’s answers and her list of questions. Jim sees Midge’s message at t1, enters the answers to her questions and sets the machine to answer after a two-day delay, at t3, which is Midge’s T1 – and by now you see how the process goes. It’s cumbersome, but, according to MacBeath, it does work.
I have very grave doubts about this and would be glad to hear what others think before going further.
Not least among my doubts is the length of time which they would have together. This links us to Alan's moment in time.
Post by: yor_on on 03/07/2013 09:26:39
To really have two arrows going in the opposite direction, relative each other, becomes to me a contradiction in terms. Just consider the implied entropy for it to happen, sharing a 'same' coordinate system, as it here is assumed.
Post by: yor_on on 03/07/2013 09:43:44
Post by: yor_on on 03/07/2013 23:43:04
Post by: AndroidNeox on 04/07/2013 01:22:43
Yep, you can use gravitational time dilations and their complementary Lorentz contractions to define 'time zones'. But to do that you need a 'local clock' from where to compare it. There are two ways to define one single frame of reference. You can either use being 'at rest', as we macroscopically can be defined being 'at rest' with earth in its relative motion. Or you can refer to some 'inertially defined' object.
Then there is a third that I'm wondering about, and that is in fact that 'local clock' you either way must use, no matter if you define it macroscopically or microscopically.
Right.
Example:
A simple clock suitable for relativistic thought experiments might be a resonant chamber of known length with mirrors reflecting a pulse of light back and forth. Usually the reference clock is not under any acceleration (occupying an inertial frame). Since the speed of light is guaranteed to always be the same for all observers in all reference frames, a resonant chamber of known length would register one reflection of the light pulse every t seconds, (2 x Distance btwn. mirrors)/c.
Post by: yor_on on 04/07/2013 09:55:50
==
This one is me using ideas from a 'globally same, common' universe, just as we normally find it to be. 'Locally defined' the universe becomes something different. And discussing a 'arrow of time' as something 'unitary', sweeping through the universe taking us with it, becomes a lot more tricky if we introduce 'locality' as the base from where we observe. But it also has to do with our definitions of dimensions, distances, etc.
=
To me it's all about comparisons, done relative ones own (local) clock. And joining your reference frame to what you measured, all clocks tick the same. That makes a local definition of a clock possible, equivalent to 'c'. Relative such a 'perfect' local(ized) clock, your life has a unchanging constant duration, your life span the same everywhere.
One can imagine it as a SpaceTime of perfect clock quanta, all set to a 'same rhythm' at some 'origin' (as proven by joining 'frames of reference' into one singular). Then introduce relative motion, accelerations/decelerations and mass/'energy', and comparisons between frames of reference..
Post by: yor_on on 04/07/2013 10:11:48
But it's also about what a 'frame of reference' represent. Take for instance being 'at rest' with something. Using gravitational time dilations nothing is perfectly 'at rest' with anything, as a guess. Not if I define a clock to a 'quanta', defining that as a smallest meaningful origin of a 'frame of reference'. But I think it is that way, anyway :)
Post by: yor_on on 04/07/2013 10:53:28
Don't mix this with QM and the idea of you changing a variable (outcome), through changing the measurement though. That one can be thought of a having a 'set pattern', but it also assume 'free will', meaning you changing your mind under that measurement.
The other way to see it is to assume causality not to be needed, in which case a arrow isn't there anymore, although you still presume a logic to exist to even define this idea. What would that logic be based on? Can't use statistics, that belongs to histories aka a arrow existing. What will you use?
=
Using scales we find QM, and new definitions, but scale related. Whatever allows you to grow old macroscopically, and see others doing the same, will be a arrow to me. That arrow is what defines causality. Without it 'energy' is for free, nothing is forbidden, limits won't exist, and wild magic runs free :). QM has rules just as relativity so there must be limits set there too, and causality, as everything you measure first must become a outcome to exist for us. Defining a unlimited energy to something over a too short period of time to be able to exist tells you the same, limits exist as well as causality. We are governed by this, outcomes define our universe and they follow a logic becoming our arrow, and causality.
Post by: Thibeinn on 24/07/2013 19:27:35
As the velocity of the Human with a clock increases, the inertia of every atom in the Human's body and every atom in the clock increases. This results in more and more energy being needed to move those atoms in such a way as for the Human's bodily functions and the clock's functions to continue with the result that both the Human's biological functions, and the clocks functions, slow down. Another result is that the Human's rate of aging slows down.
Likewise, as the gravity increases, the weight of the atoms increases and require more and more energy to move them.
As the velocity of the Human with a clock decreases, the inertia of every atom in the Human's body and every atom in the clock decreases. This results in less and less energy being needed to move those atoms in such a way as for the Human's bodily functions and the clock's functions to continue with the result that both the Human's biological functions, and the clocks functions, speed up. Another result is that the Human's aging speeds up.
Likewise, as the gravity decreases, the weight of the atoms decreases and require less and less energy to move them.
Time is simply the measurement of this speeding up or slowing down due to increased or decreased inertia and/or weight brought about by increased or decreased velocity and/or gravitational force.
Post by: AndroidNeox on 23/09/2013 21:03:26
When we observe, or measure, time, we observe a sequence (ticks, pendulum swings,...). To observe a sequence, information about prior states has to be retained. The longer the sequence, the more state info is required. For a system like our universe in which time seems to be proceeding without end, the entropy accumulation would be unbounded.
Post by: Pmb on 24/09/2013 03:05:36
HiTime is merely what we associate and use to specify the way things in the world around us change. E.g. how long has it been since my last cup of coffee or how long has my coffee be cooling off.
What is time?
Some say it is just measure of movement or an aggregation of events. Time is not a constant and I would like you guys to put forward your own ideas on the topic before adding my piece to the story.
Alan
A good discussion has been given by my friend at http://users.wfu.edu/brehme/time.htm
Post by: Yojimbo on 18/07/2014 13:38:29
Post by: Bill S on 18/07/2014 16:03:11
Like St Augustine, we all know what time is, if no one asks. The problem is that people will ask. This leads to countless personal animadversions and interminable discussions which tend to progress in circles towards the inevitable non-conclusion.
Does time exist? Discounting diversionary responses like “define existence”, the answer must be “yes”. Time exists, but does it exist as something independent, or is it only something that exists in our minds? Compare questions such as: “Does truth exist?”. Again the answer must be yes. It exists as a concept that is relevant to human communication. Without rational beings it has no significance. We know what it means, but philosophers can argue interminably about it. Time is very similar. It is essential to our reasoning, our understanding of the Universe and every aspect of our lives. It is essential to every measurement we make, but without something to measure, it has no significance. Why do we need to ask more of it?
Post by: chiralSPO on 18/07/2014 19:42:48
I wonder if it has been considered when we seek to communicate with aliens that they may have vastly different life times than us and that their conception of time may be very different from ours.
If they have the life time of a mountain 1 Hz would be supersonic but if they have the life time of a fly it would represent an extremely low frequency.
I don't know how well lifetime correlates with perceived time (especially across species or across galaxies). But I agree with the premise that communication (or even recognition of intelligence or life) is limited by our perception of time. We are beings built of complex chemical compounds, and governed by chemical physics and chemical kinetics. I wonder if there could be life composed of complex nuclear states and governed by nuclear physics and kinetics (given that there is demonstration of catalysis in nuclear chemistry [see CNO cycle], I maintain that there could be life based on such processes. Their lifetimes would be very small, and the related energies and frequencies very large, so presumably they would have very short attention spans as well...
As far as beings (particles are a different matter) interacting with beings of opposite time flow, this is very tricky to think about, but I suspect that it would be impossible. There is no such thing as entropy for a system containing one immutable particle, but as there are more particles involved in a system, entropy begins to have meaning, defining a time arrow for that collection. If we consider transferring information from one system of interacting particles to another, then we have to consider the system containing both systems--in which direction does the whole system move? Whose rules are followed and whose are broken? The only way that the three systems behave with no contradictions is if there is no interaction. With photons, which do not experience time, there may appear to be a loophole, but for any photon that is exchanged, there would be a disagreement between the two systems, each believing it was the one that emitted the photon before the other absorbed it (or both thinking they had absorbed it after the other one emitted it). Conservation of energy is maintained, and no information was transferred.
I'm not really sure what the current theory is on how close particles need to be in space and time to interact--taking account of uncertainty, we have to put error bars on the spatial and temporal coordinates so there is essentially some 4-D spacetime sphere in which the particles need to be to interact. It might be possible for beings to communicate with each other for a brief instant when they are at the "same" time, but as they each move to substantially different times, they won't be able to interact anymore.
On the other hand, if one can think of a positron as an electron that is traveling backward in time, clearly it interacts with electrons moving forward in time (the electrons think the backwards moving positron is an electron and the positron thinks the "backward" moving electrons are positrons).
Post by: Bill S on 18/07/2014 21:11:40
One might say: “It must be possible to travel backwards in time, because Feynman said that an antiparticle is just a particle travelling backwards in time.” In fact, Feynman did not say that. What he said was that the mathematics governing the evolution of a particle as time moves forwards is the same as the mathematics governing the evolution of an antiparticle as time moves backwards. This is true, but it certainly does not mean that any physical object is travelling backwards in time. Consider the electron and the positron. We call the electron a particle and the positron an antiparticle; but that is simply convention. We could equally well call the positron a particle and the electron an antiparticle. Which of these would then travel backwards in time?
Post by: PmbPhy on 19/07/2014 09:03:42
The idea that an antiparticle is a particle travelling backwards in time is, perhaps, one of those unfortunate things that has arisen from a misapprehension. One might say: “It must be possible to travel backwards in time, because Feynman said that an antiparticle is just a particle travelling backwards in time.” In fact, Feynman did not say that. What he said was that the mathematics governing the evolution of a particle as time moves forwards is the same as the mathematics governing the evolution of an antiparticle as time moves backwards.Actually the idea was Wheeler's, not Feynman's. Feynman just popularized it who himself attributed it to Wheeler who was his advisor. It's suspected that he meant it as a cocktail party joke. Not something to be taken seriously.
All of this is found in Introduction to Elementary Particles by David Griffiths, page 65-66. Griffith warns the reader not to take it too seriously.
Post by: petm1 on 19/07/2014 20:24:36
Mass is the past relative to us all, space is the present moment we all share as observers, and the force of gravity is us dilating into the future.
Post by: PmbPhy on 19/07/2014 21:45:44
Quote from: petm1
Space and time, opposites yet the same.Woa! Where did you get that notion from? It's certainly not true. While in some respects space and time are treated on the same footing in relativity mathematical, it's certainly not true that their anything alike physically, that's for sure. Space is what you measure with a rod. Time is what you measure with a clock. You can go back in space but you can't go back in time. You can rotate one spatial axis (i.e. a rod) into another spatial axis but you can't rotate a rod into a clock.
Let me quote something Einstein said about this. From A Brief Outline of the Development of the Theory of Relativity by Albert Einstein, Nature, Feb. 17, 1921. page 783
Quote
From this it follows that, in respect to it's role in the equations of physics, though not with regard to its physical significance, time is equal to space coordinates (apart from the relations of reality).
Quote from: petm1
Photon is unchanging in time..That too is also untrue. A photon moves through space and its phase changes with time. You're thinking about transforming into a photons frame of reference and making measurements there with a clock and comparing it to the photon's frequency, etc. However since it's impossible to do that you can't even speak of it. Therefore the only time that you can speak of regarding a photon is coordinate time. Just because you can't speak of a photons proper time it doesn't mean that it's unchanging. You'd never be able to step into a photons frame of reference to verify it and that's not science.
Post by: Bill S on 19/07/2014 22:49:26
Quote from: Pete
Actually the idea was Wheeler's, not Feynman's. Feynman just popularized it who himself attributed it to Wheeler who was his advisor. It's suspected that he meant it as a cocktail party joke. Not something to be taken seriously.
My apologies to Wheeler. Of course, this is part of the pop-sci misapprehension. Outside scientific circles, many people think Feynman was the originator and that he meant it to be taken seriously. One can interpret this by saying that many people who read pop-sci books lack the discernment to realise the truth, and should educate themselves more thoroughly in scientific matters before reading pop-sci books; or one could say that scientists who supplement their income by writing books for non-scientists should run their explanations past (thinking) non-scientists to see if their readers are likely to hear what the authors intend saying.
Post by: PmbPhy on 19/07/2014 22:58:40
You'd be surprised, my friend. Even some intelligent physicists think the same thing. I almost believed it myself in fact. When I heard it seemed dumb to me but I held off making a definite decision until I came to learn particle physics in much more depth. That's when I spoke to Griffiths and he told it to me. Griffiths and I communicate quite often in e-mail so I have a good source of information in many areas. He's a wonderful person and he's a great author.Quote from: PeteActually the idea was Wheeler's, not Feynman's. Feynman just popularized it who himself attributed it to Wheeler who was his advisor. It's suspected that he meant it as a cocktail party joke. Not something to be taken seriously.
My apologies to Wheeler. Of course, this is part of the pop-sci misapprehension. Outside scientific circles, many people think Feynman was the originator and that he meant it to be taken seriously. One can interpret this by saying that many people who read pop-sci books lack the discernment to realise the truth, and should educate themselves more thoroughly in scientific matters before reading pop-sci books; or one could say that scientists who supplement their income by writing books for non-scientists should run their explanations past (thinking) non-scientists to see if their readers are likely to hear what the authors intend saying.
Post by: Ethos_ on 20/07/2014 20:00:10
I quite agree AndroidNeox. As you have said, Einstein determined that space has no meaning without the presence of the electromagnetic field. And likewise, in my estimation, time has no meaning unless we understand the significance of the words: Past, Present, and Future.
I think that a better question than "what is time?" is, "when we measure time, what do we measure?".
And as well, the term Past has no meaning without the memory of it which occurs in the Present. And likewise, the Future has no meaning without the cognizance of the Present in which the Future is anticipated.
The Present is the only true reality and it vanishes before us at the Planck scale. So how are we to measure it? Can we trust our memory? What is evident is that we all feel this passage of ours from the Present into the Future with varying degrees of trepidation and wonder.
John S. Mill's quote: "The more things change, the more they remain the same."
The passage of time is merely a measure of the change we record in our memory. Again I ask; "Can we trust our memory?"
Post by: Alan McDougall on 03/08/2014 19:34:21
I quite agree AndroidNeox. As you have said, Einstein determined that space has no meaning without the presence of the electromagnetic field. And likewise, in my estimation, time has no meaning unless we understand the significance of the words: Past, Present, and Future.
I think that a better question than "what is time?" is, "when we measure time, what do we measure?".
And as well, the term Past has no meaning without the memory of it which occurs in the Present. And likewise, the Future has no meaning without the cognizance of the Present in which the Future is anticipated.
The Present is the only true reality and it vanishes before us at the Planck scale. So how are we to measure it? Can we trust our memory? What is evident is that we all feel this passage of ours from the Present into the Future with varying degrees of trepidation and wonder.
John S. Mill's quote: "The more things change, the more they remain the same."
The passage of time is merely a measure of the change we record in our memory. Again I ask; "Can we trust our memory?"
Your response was more philosophical than scientific, but I agree that time is a mystery. Einstein once humorously said "time is something we invented to prevent everything from happening at once" What you presented in your post is the philosophical concept of "presentalism" look it up?
Post by: PmbPhy on 03/08/2014 20:28:30
Quote from: Ethos_
And as well, the term Past has no meaning without the memory of it which occurs in the Present.I disagree. To a small extent the past can be deduced from causality as well as memory.
Post by: Bill S on 03/08/2014 21:11:03
Quote from: AndroidNeox
I think that a better question than "what is time?" is, "when we measure time, what do we measure?"
What do we mean when we talk of measuring time? Surely, time is the "thing" with which we do the measuring.
Post by: Ethos_ on 15/08/2014 15:41:02
You make a fair point here Pete, causality is the foundation for the deterministic world view. But in the quantum realm, physicists discard that view in favor of the probabilistic one. I must ask: If we are to trust causality, how deep into the Planck realm does it reach? And even more importantly, how far reaching does the probabilistic effect the information we collect about the past? I'm not sure we can establish exact limits on either case at this point. When taken in total, how probabilistic are world events, and how does that influence how much we trust causality and the connection between the past and the present?Quote from: Ethos_And as well, the term Past has no meaning without the memory of it which occurs in the Present.I disagree. To a small extent the past can be deduced from causality as well as memory.
Post by: jeffreyH on 15/08/2014 22:12:10
Post by: Bill S on 15/08/2014 22:47:02
Transfer this thinking to objects moving through time. If time is quantized, motion through time takes place in a succession of jumps. The only thing that appears to move smoothly through time is EM radiation. Everything else moves more slowly, so it pauses between jumps, and these pauses become longer as things move more slowly. Even with very slow moving objects, these pauses would be too short for us to observe them.
Post by: jeffreyH on 15/08/2014 22:57:25
Post by: jeffreyH on 16/08/2014 11:54:24
. Now any other particle that is not a photon or hypothetically a graviton cannot attain this speed. So how do we proceed? We can say that our electron, if we have quantization, cannot reach 
easily as this is half light speed. So it should be a speed defined by 
where we don't know what n is. The only other possibility is applying a factor to the Planck length as well as the Planck time. In which case we no longer have a definitive boundary to quantization. If quantization is to be maintained this seems to indicate a separation between space and time. I am wondering about the massless photon, its kinetic energy and angular momentum as to whether or not it should impart enough energy to an electron to move it far at all.
Post by: jeffreyH on 16/08/2014 12:24:54
Post by: jeffreyH on 16/08/2014 12:28:38
Post by: Ethos_ on 16/08/2014 14:33:12
Another conundrum lies in the interaction between light and either the medium it is traveling through or a gravitational field acting on the photon. The photon now no longer travels 1 Planck length in 1 Planck time.From my understanding, the photon always travels at 1 Planck length in 1 Planck time. The reason it appears to slow down is, when in any medium other than the vacuum, the photon will be absorbed and then subsequently re-emitted. This interruption in the photon's path has the appearance of slowing it down. But in truth, the speed of the photon from one absorption to the next is still c. Between each interruption the photon still travels at light speed, 1 Planck length in 1 Planck time.
Post by: jeffreyH on 16/08/2014 17:27:53
Another conundrum lies in the interaction between light and either the medium it is traveling through or a gravitational field acting on the photon. The photon now no longer travels 1 Planck length in 1 Planck time.From my understanding, the photon always travels at 1 Planck length in 1 Planck time. The reason it appears to slow down is, when in any medium other than the vacuum, the photon will be absorbed and then subsequently readmitted. This interruption in the photon's path has the appearance of slowing it down. But in truth, the speed of the photon from one absorption to the next is still c. Between each interruption the photon still travels at light speed, 1 Planck length in 1 Planck time.
I'm still thinking about this one.
Post by: jeffreyH on 16/08/2014 21:46:27
Post by: Ethos_ on 17/08/2014 04:39:12
Quote from Albert Einstein: "The distinction between the past, present, and future is only a stubbornly persistent illusion."
Post by: jeffreyH on 17/08/2014 11:18:31
So,..........what is time according to Einstein?
Quote from Albert Einstein: "The distinction between the past, present, and future is only a stubbornly persistent illusion."
He is right with respect to time being a human invention used to explain change. The state may change but the contents don't. You could look at time as the current state of all the waveforms in the universe regardless of how long it has taken them to get to that state.
Post by: jeffreyH on 17/08/2014 11:58:50
Post by: jeffreyH on 17/08/2014 12:05:38
Post by: jeffreyH on 17/08/2014 12:25:24
Post by: jeffreyH on 17/08/2014 12:47:07
Post by: petm1 on 17/08/2014 22:52:15
Quote from: petm1Space and time, opposites yet the same.Woa! Where did you get that notion from? It's certainly not true. While in some respects space and time are treated on the same footing in relativity mathematical, it's certainly not true that their anything alike physically, that's for sure. Space is what you measure with a rod. Time is what you measure with a clock. You can go back in space but you can't go back in time. You can rotate one spatial axis (i.e. a rod) into another spatial axis but you can't rotate a rod into a clock.
Let me quote something Einstein said about this. From A Brief Outline of the Development of the Theory of Relativity by Albert Einstein, Nature, Feb. 17, 1921. page 783QuoteFrom this it follows that, in respect to it's role in the equations of physics, though not with regard to its physical significance, time is equal to space coordinates (apart from the relations of reality).Quote from: petm1Photon is unchanging in time..That too is also untrue. A photon moves through space and its phase changes with time. You're thinking about transforming into a photons frame of reference and making measurements there with a clock and comparing it to the photon's frequency, etc. However since it's impossible to do that you can't even speak of it. Therefore the only time that you can speak of regarding a photon is coordinate time. Just because you can't speak of a photons proper time it doesn't mean that it's unchanging. You'd never be able to step into a photons frame of reference to verify it and that's not science.
If emission only happens in the present then as an observer and being a receiver means that which ever direction I look I am seeing the past. The longer the photons travel time the longer the distance the further back in time you are seeing. This kaleidoscope from the past I see as my present is described using a signature of either +++- or ---+ opposites to describe the same thing.
Does E=hf change during a photon's lifetime other than as a measure for the expanding space in which it travels? Or in the case of a gravity well, where we do not think of space expanding, do you think it may be time that is changing the red shift of our rulers?
Post by: mxplxxx on 27/10/2014 07:44:09
By the way, relativity states that the speed of light is a constant and uses this fact to postulate that time passes at different rates depending on the speed an object is moving. The theory seems to fail to account for the fact that light does not have momentum, never stops, never accelerates, and whose quantum nature is poorly understood. Put another way bosons (light e.g.) are quite different objects from fermions and relating the two via by time may just not work.
Post by: phyti39 on 29/10/2014 18:42:49
From 'The Meaning of Relativity', Albert Einstein, 1956:
page 1.
"The experiences of an individual appear to us arranged in a series of events; in this series the single events which we remember appear to be ordered according to the criteria of "earlier" and "later", which cannot be analysed further. There exists, therefore, for the individual, an I-time, or subjective time."
page 31.
"The non-divisibility of the four-dimensional continuum of events does not at all, however, involve the equivalence of the space coordinates with the time coordinate."
page 32.
"Finally, with Minkowski, we introduce in place of the real time co-ordinate l=ct, the imaginary time co-ordinate..."
From "On the Electrodynamics of Moving Bodies", A. Einstein, June 30 1905:
par 1.
``The pointing of the small hand of my watch to 7 and the arrival of the train are simultaneous events."
The author of SR didn't believe or promote the idea of an objective time. In contrast, he developed the idea of clock time or time measurement as being motion dependent! It was Minkowski who expressed the time variable as a mathematical 'dimension', but solely for mathematical purposes, as noted above.
Subjective time requires memory as mentioned in the first quote, which allows a comparison of a current state to a previous state for any changes, which lends itself to an interpretation of time flowing. Patients with brain damage to specific areas involved in maintaining a personal chronology, lose their ability to estimate elapsed time, short or long term. Consider the fact that people waking from a comatose state, have no memory of how much elapsed time, whether hrs, days, or even years.
Consider one of the greatest misnomers ever used, 'motion pictures' or 'movies', where a person observes a sequence of still photos and the mind melds them to produce moving objects where there is no motion.
The simplest argument against the arrow of time, time is a scalar, a magnitude with no direction.
The operational definition of assigning a time to an event as mentioned by A.E. in the 1905 paper is essentially what it is, and how it's been done since humans appeared.
It is a correspondence convention, i.e., assigning events of interest to standard clock events, a measure and ordering of activity, with 'time' always increasing/accumulating.
It is an accounting scheme developed out of practical necessity, for human activities like agriculture, business, travel, science, etc. The unit of measure for time initially referred to relative positions of astronomical objects, stars, sun, and moon, which implies earth rotations and earth orbits. The year equates to the periodic motion of the earth relative to the sun, the month, the moon relative to the earth, and the day, the earth rotation relative to the stars. All units of time are by definition, involving spatial motion or distance. The clock further divides the day into smaller units of measure. The reference in the 1905 paper of the watch hand to a position on the watch face involves nothing more than counting hand cycles (hand motion of specific distances representing subdivisions of a day). Finally, with the present day light clock, with internal light oscillations between an emitter and a mirror spaced a distance d, the time t represents a quantity of light motion equal to 2kdc, i.e. a distance labeled as 'time'.
In the world of quantum physics, suppose a particle can have three states, a, b, and c. Suppose the first three observations record abc, and the second three record cba. Did time 'flow' backward? No, and we have proof, since the 'time' of each observation was recorded. It was just a reversed sequence.
Flipping a coin is governed by the rules of physics, yet the results are independent of time. The probability of H or T is always 1/2.
If an object is dropped from a height, next to a vertical measuring stick, and recorded on video, analysis of the video allows a mathematical relation to be formulated between the time stamp of each frame and the height of the object, like (h = h0 -.5gt2). Notice that verification of the experiment requires a clock, since measurement is the modus operandi of science. More importantly notice, gravity, not time, causes the object to fall, and the clock is just a means of ordering and relating the events.
To bury the idea of time (as we know and use it) as a causal factor, note that the time of an event is assigned after perception of the event.
Nothing like an objective 'time' has yet been discovered, but that doesn't imply it doesn't or couldn't exist. Consider all the 'fundamental' particles that were discovered, once the appropriate experiment was designed.
Post by: JohnDuffield on 30/10/2014 13:24:01
..."The non-divisibility of the four-dimensional continuum of events does not at all, however, involve the equivalence of the space coordinates with the time coordinate"...Good stuff phyti.
The author of SR didn't believe or promote the idea of an objective time. In contrast, he developed the idea of clock time or time measurement as being motion dependent...
Post by: David Cooper on 30/10/2014 19:11:45
This is the "arrow" of time business, but it's more than a mere arrow, for it sets out an order in which arrangements of stuff exist. Even if you imagine that the past arrangements continue to exist such that past, present and future are all eternally stored in a kind of block, the past parts of it must have been laid down before the present and future ones because if the later ones were not created later than the earlier ones, there cannot be any causation from the earlier ones to dictate the form of the later ones - the apparent causation becomes nothing more than coincidence, and it would be a coincidence of such magnitude that the word "astronomical" is almost completely useless even as a component of the description of the unlikelihood of the apparent causation existing in the block.
If there is real generation of the future from the past so that causation can be real, then there is a kind of time that flows; not a mere arrow.
[An edited-in addition follows:-]
It would be perfectly possible to imagine that the universe exists as an eternal block in which we can move forwards or backwards in time to experience it from different viewpoints, and in doing this we would be exploring an eternal block universe in which past, present and future all exist in a timeless way, but when you try to account for the existence of that block universe, you hit the problem that there would have to be an earlier phase in which it was generated starting with the far past and ending with the far future, all the construction done under the governance of some kind of flowing time which would allow events to be rolled out in order of causation. The alternative is to believe that there is no causation written through it at all and that all the patterns of apparent causation are down to nothing more than chance because there was no opportunity for causation to generate future arrangements of the content of the block from past ones. That would be to believe in something so unlikely that the word "ridiculous" is likewise incapable of expressing more than the tiniest hint of the scale of it.
Post by: yor_on on 02/11/2014 11:28:13
=
Actually I find it best to think of a local arrow as a property. With magnifying, aka QM, you can find other properties existing, as spin. And you can see yourself two ways, as consisting of those 'point properties', or as consisting of particles interacting. Neither seems wrong to me :) but depending on how you then go past that one you might want to define 'time' as something 'interacting' (particles), or not, or both. Meaning that you possibly could split the property (arrow) from what we define as 'time' when interacting/comparing.
=
Let us assume that we can translate our four dimensions into a plane (one dimension, ok, I know :) two dimensions) mathematically, finding a equivalence there. Then you will be 'point properties' there, or a line. No different from the way causality needs Lorentz transformations in relativity, to prove our seamless universe 'co-existing' mathematically.
Post by: phyti39 on 03/11/2014 17:07:20
Depends on definitions phyti. Time is locally unchanging for each observer in my thoughts, you do not gain more life by sitting on a event horizon for example, observing a universe die. That's why we all live and die, doesn't matter where or how fast. The other comparisons is between frames of reference, and there NIST has proven time dilations to exist at centimeters. If you now want to expand on that line of wondering you might ask yourself where it all ends? Is there a discrete 'point' representing a equivalent local arrow, as a 'property' more or less.All human knowledge depends on definitions, since that is all we have. We observe the world indirectly via light. Since we don't know what the patterns represent, we invent abstract concepts in their place, using our wonderful graphics oriented brain. In the process, we must remember to distinguish the concepts from what's out there, and not rely excessively on using known concepts to model new ones. Bricks are not made of smaller bricks.
=
Local time is constant due to effects of length contraction and time dilation.
Expressions like, "a 2 days ride", a 3 hr drive, "a half day march". are common practice throughout history to express distance and time interchangeably. The history of time keeping shows its dependence on the motion of something, with the light clock being the simplest device to directly demonstrate this.
Consider two identical clocks synchronized to the standard second. Adjust clock2 to run at half the rate of clock1. After an 8 hr workday, clock2 reads 4 hr. Was clock2 measuring time? No, and neither was clock1. The faster clock allows more precision but does not provide more "time". If the emitter-mirror distance in the light clock is halved, the frequency is doubled, and the precision improves.
Like the metronome, the clock provides the periodic "clock event" that humans use to assign to an event of interest. The historical record of events serves many purposes. The metronome provides a beat that helps musicians play music as written. The (passive) ruler which doesn't measure distance, and the clock are tools that enable a person to make measurements.
t = x/v = meter/meters/sec = sec
Time is a scalar, and has no direction, so there is no arrow of time.
Clocks just keep accumulating ticks. If we used the Chinese or Jewish calendars, we are at about 6000 yrs worth.
Post by: PmbPhy on 03/11/2014 23:30:11
Quote from: phyti39
Time is a scalar, and has no direction, so there is no arrow of time.I recommend that if you wish to delve into the physics of special relativity that you learn the mathematical terms correctly. This won't be possible unless you pick up a good textbook on special relativity that explains it using tensors. Tensor analysis is the language of relativity, and hence the math that you should learn. May I inquire as to the level of math that you're familiar with?
The term scalar as you used it comes from elementary school math and science textbooks. It that sense it means a number, real or complex. In tensor analysis it means something else, i.e. A scalar is a tensor of rank zero. This means that it's a number which remains unchanged upon a valid change of coordinates. For example; if you were working in special relativity and using Cartesian coordinates for your spatial coordinates then the coordinate transformation from one inertial frame to another, which is in standard configuration with the original one, is referred to as a Lorentz Transformation. So a Lorentz scalar is a number which remains invariant (i.e. unchanged) upon a Lorentz transformation.
I mention it so that you learn this early on. If you continue to discuss relativity with learned physicists then you'll have to learn the jargon.
Post by: JohnDuffield on 04/11/2014 08:33:32
The guy is right. And if you'd like to prove him wrong by pointing to the future, be my guest.Quote from: phyti39Time is a scalar, and has no direction, so there is no arrow of time.I recommend that if you wish to delve into the physics of special relativity that you learn the mathematical terms correctly. This won't be possible unless you pick up a good textbook on special relativity...
Post by: evan_au on 04/11/2014 09:25:52
Quote from: JeffreyH
Reflection and refraction follow definite paths.... This is the concept I have a problem with. Application of the uncertainty principle should mean that this path deviates and yet it doesn't.
The design of optical telescopes takes into account of the fact that a photon which has reflected from a mirror (or been refracted by a lens) can be detected in a range of locations, making images of stars blurry.
You can constrain the amount of deviation by making the mirror larger (or the lens larger, for a refracting telescope). When building telescopes, Bigger is Better!
Deviation of photons from the "classical" laws of reflection and refraction is a fundamental part of quantum theory.
Post by: phyti39 on 04/11/2014 20:05:19
Time as a derived number, distance/speed, is a variable. The Lorentz tranformation of t results in a different value for t', for relative motion.Quote from: phyti39Time is a scalar, and has no direction, so there is no arrow of time.I recommend that if you wish to delve into the physics of special relativity that you learn the mathematical terms correctly. This won't be possible unless you pick up a good textbook on special relativity that explains it using tensors. Tensor analysis is the language of relativity, and hence the math that you should learn. May I inquire as to the level of math that you're familiar with?
The term scalar as you used it comes from elementary school math and science textbooks. It that sense it means a number, real or complex. In tensor analysis it means something else, i.e. A scalar is a tensor of rank zero. This means that it's a number which remains unchanged upon a valid change of coordinates. For example; if you were working in special relativity and using Cartesian coordinates for your spatial coordinates then the coordinate transformation from one inertial frame to another, which is in standard configuration with the original one, is referred to as a Lorentz Transformation. So a Lorentz scalar is a number which remains invariant (i.e. unchanged) upon a Lorentz transformation.
I mention it so that you learn this early on. If you continue to discuss relativity with learned physicists then you'll have to learn the jargon.
You can do SR using algebra!
I'm not here to impress anyone, so my level of math is irrelevant.
I don't expect to discuss relativity with learned physicists on a public forum.
Post by: yor_on on 04/11/2014 20:09:41
Post by: yor_on on 04/11/2014 20:19:34
Post by: yor_on on 04/11/2014 20:32:25
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And that goes especially for you moderating.
Keep on doing the work you do.
And now I will define 'c' as something similar to a turtle, I'm positive you will agree?
Post by: PmbPhy on 04/11/2014 22:26:51
Quote from: phyti39
Time as a derived number, distance/speed, is a variable.What do you mean by a "derived number"?
Quote from: phyti39
The Lorentz tranformation of t results in a different value for t', for relative motion.Yep. I'm well aware of that. There are two measures of time in relativity. One is called proper time and the other is called coordinate time (or simple "time"). Proper time is the time as measured on a clock which passes through the two events of concern while moving on a geodesic. The coordinate time isn't. The proper time between two events is a Lorentz invariant whereas the coordinate time between the same two events isn't.
Quote from: phyti39
You can do SR using algebra!Yep. I'm well aware of that.
Quote from: phyti39
I'm not here to impress anyone, so my level of math is irrelevant.I never assumed that you were. I was merely pointing out a small point on the definition of what the term "scalar" means in SR. That's all. :)
Post by: phyti39 on 05/11/2014 19:38:49
All in all. TNS is probably the best place i know, although I've seen some very close to it. But, we still have that glimmer of humility hiding behind our convictions, and that is in my mind, what science is about, not bullying, talking.
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And that goes especially for you moderating.
Keep on doing the work you do.
And now I will define 'c' as something similar to a turtle, I'm positive you will agree?
I would like to believe that the original intent of science forums was similar to that of "Scientific American", to present complex ideas in terms understandable to the common person with limited technical knowledge. Some have drifted away from that purpose. Those in their specialized fields have their own resources for staying current.
I trust your recommendation is true.