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GR and SR and the speed of change

  1. Apr 29, 2004 #1
    Hi guys,

    Just wanted to know how GR or Sr can determine the answer to this question?

    How fast does the universe change?
     
  2. jcsd
  3. Apr 30, 2004 #2

    HallsofIvy

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    Define "universe", define "change" and, especially important for general relativity, define "fast"!
     
  4. Apr 30, 2004 #3
    Universe meaning the universe entirely
    Change means change through time ( time in continuum)
    speed meaning relative to "c"

    There is a reason for this convoluted approach. It is really about how the attributes of light are applied to time in continuum.

    The point in time that is neither past or future. And the speed at which this point in time changes ( hmmm...moves in a linea fashion through time)
    This is very difficult to explain conceptually.......
     
  5. Apr 30, 2004 #4
    this point in time I would call an event horizon or teeter point. In the middle between past and future. Other wise referred to as the Now.

    How fast does this point change?
    How does relativity deal with this question?
    BTW I am not trying to be smart or entrap. I am genuinely interested in an answer if possible.
     
  6. May 1, 2004 #5

    jcsd

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    I think yoummean how fast can information travel, the answer is c.
     
  7. May 1, 2004 #6
    no, although information is important, it is the actual change of the object without including the time to "Inform" so to speak that I am interested in. AS all frames of reference are subject to change in continuum I wonder how relativity helps us understand this.

    The information speed of delivery is "c' and Iwould go on to suggest that the rate of change is also 'c'.
     
  8. May 1, 2004 #7
    One way to view the universe is to consider every frame, point, object, whatever, as moving at the velocity of light - either temporally or spatially. When the motion consists of both space and time, the square of the composite spatial and temporal increments will always total (ct)^2. This is essentially why the interval in SR is always invarient during transformation.
     
    Last edited: May 1, 2004
  9. May 1, 2004 #8
    Yogi, I think what you say explains it in a nutshell....and I thank you for that...below is a link to a single web page that shows this basic question.

    If I could get confirmation that I am thinking right on this point I would appreciate it.

    speed of change link
     
  10. May 2, 2004 #9

    Nereid

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    When I clicked on the link, I could see only a nice coloured (bent) rectangle, with a couple of axes labelled in seconds. Several object on the page did not display.

    I'm afraid I still don't understand your question. If you make a model of the universe - of which there are several, in cosmology - you will incorporate GR. This model will have many parameters, some of which will change with 'time' (suitably defined). Is it some subset of these 'time derivatives' that you are interested in?
     
  11. May 2, 2004 #10
    Neried, Thanks for your interest. I have checked the link and it appears fine to me, maybe try it again.

    The question is about how fast the future becomes the past. And how relativity can answer this.
    From what I understand to answer this question we have to take an unchanging ( timeless) frame of reference, as if we are outside the universe looking in.
     
    Last edited: May 2, 2004
  12. May 3, 2004 #11

    russ_watters

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  13. May 3, 2004 #12
    Thanks Russ, yes at first glance it certainly seems to be within the realms of my question.
     
  14. May 4, 2004 #13
    Russ,
    I have given it some thought and I want to thank you for the link. Yes it appears that it does answer my question. And I found it very interesting historically as to why absolute time was finally dropped.

    Again thanks for working out what the dickens I was trying to say..... :wink:
     
  15. May 4, 2004 #14
    Just as a matter of interest I thought I'd show you a three dimensional gravity (space time) cones I developed about 4 years ago.
    I had no idea it was already partially in use.

    The center of the cones is the centre of time.

    http://www.paygency.com/Corecones.htm
     
  16. May 7, 2004 #15
    When we view the observable world, that is everything that we can theorectically see, such as electron motion in the center of the earth, and we couple this with the ever rnearing closeness to the observor as his attention is rawn from the extrema of observation to closeness, such as the immediate surroundings, indeed the concept of on the " . . .outside the universe looking in." makes sense, more than sense. Somehow considering the 'questioner' in you' cannot be defined by the 'observable' of you, to wit your physical and observable reailty. All the participation of brain activity is only that, and we recognize that we are considering 'ourselves', or 'us' as other than mere chemical activity.

    The language we use in this consideration is "our body", "my mind" etc. There is an implied coordination of something other than the observables. Like a previous posting in this thread of what is after the past and the future?, the here and now.

    Forgive the psychological stroll here, but I think we may make some progress. We, I at least, have a sense that the here and now is not an instantaneous event that flickers away with each tick of the clock. But yesterday at this same time of day is clearly the past. Likewise, the futrure, while only a "figment " of one's imagination, the future is as real and important as the past, Plans, hope, fears etc and of course dynamically moving systems, events and the whole shebang. In other words, we contemplate the future as including the familiar items of the past. The sun rising, positions of the stars, repeatability of excpeimentalally verifiable events.

    We know of the limitation on processes, at least those we've measured, though the 'how fast they change' is still a bit ambiguous: as fast to me may mean average speed to you who thinks in terms of cascading mountanins of photons churning along at the speed of light.

    So, how fast does the future change to the past? The vast majority of the observed universe we move about in is invariant. The sun rising, positions of the stars etc. Futures to australian bushmen aren't of interest to what your future is, save those parameters that are commn : total earth calamity, or righteous outpouring of peace on earth. In one sense the speed of future to past that is measured, or sensed , by the observer looking in, an be emasured by the time spna of your here and now. Depending on what you are specifically engaged in the here and now can vary, though we like to beleieve thagt our scientifically arrived at realities can effectibvley provide some accurate and meaningful average for events transitioning through the here and now.

    AS electrons don't ask question like yours, we can safely say that the question os [pecuiliar to rational entioties able to forulate mental images of past, future and change. Lions in Africa knw when it is time to prepare foe he nightime, but do they contemplate the rising of he sun, probably not.

    IN any event, I wols say thagt the speed of future to past changes is a personal rate involving awareness of events distinbguished by awaeness f the events occuring here and now. Contenplating a future action or a future natural event while technically 'here and now' is concepetually distinguishable by the relative lack of personal awareness of yourself as the observer.

    After we've contemlated heobsercer and what is obsevable we ae left with some insanswered qiestion, like what is everyting else? That is, as some have said unobservable reality. We infer its coordinaion with the observable world and often after the fact of local/nonlocal force exchanges, but the defining process has carefully excluded the pinpointing of personal essence, which while nonlocal is ever present in awareness of that fact.

    i suppose I will just take the easy way out and say that definitions of past and present may be sufficient to define the here and now from the lefovers of all the implications of the definitions of past and future. Using any physical theory, that I know of, probably wont fill your bill, except for those matters we take as granted without concern for their 'real physical description' such as the sun rising. Our only concern is that the expected events occur.
     
  17. May 7, 2004 #16
    speed of future to past transitions

    When we view the observable world, that is everything that we can theorectically see, such as electron motion in the center of the earth, and we couple this with the ever rnearing closeness to the observor as his attention is rawn from the extrema of observation to closeness, such as the immediate surroundings, indeed the concept of on the " . . .outside the universe looking in." makes sense, more than sense. Somehow considering the 'questioner' in you' cannot be defined by the 'observable' of you, to wit your physical and observable reailty. All the participation of brain activity is only that, and we recognize that we are considering 'ourselves', or 'us' as other than mere chemical activity.

    The language we use in this consideration is "our body", "my mind" etc. There is an implied coordination of something other than the observables. Like a previous posting in this thread of what is after the past and the future?, the here and now.

    Forgive the psychological stroll here, but I think we may make some progress. We, I at least, have a sense that the here and now is not an instantaneous event that flickers away with each tick of the clock. But yesterday at this same time of day is clearly the past. Likewise, the futrure, while only a "figment " of one's imagination, the future is as real and important as the past, Plans, hope, fears etc and of course dynamically moving systems, events and the whole shebang. In other words, we contemplate the future as including the familiar items of the past. The sun rising, positions of the stars, repeatability of excpeimentalally verifiable events.

    We know of the limitation on processes, at least those we've measured, though the 'how fast they change' is still a bit ambiguous: as fast to me may mean average speed to you who thinks in terms of cascading mountanins of photons churning along at the speed of light.

    So, how fast does the future change to the past? The vast majority of the observed universe we move about in is invariant. The sun rising, positions of the stars etc. Futures to australian bushmen aren't of interest to what your future is, save those parameters that are commn : total earth calamity, or righteous outpouring of peace on earth. In one sense the speed of future to past that is measured, or sensed , by the observer looking in, an be emasured by the time spna of your here and now. Depending on what you are specifically engaged in the here and now can vary, though we like to beleieve thagt our scientifically arrived at realities can effectibvley provide some accurate and meaningful average for events transitioning through the here and now.

    AS electrons don't ask question like yours, we can safely say that the question os [pecuiliar to rational entioties able to forulate mental images of past, future and change. Lions in Africa knw when it is time to prepare foe he nightime, but do they contemplate the rising of he sun, probably not.

    IN any event, I wols say thagt the speed of future to past changes is a personal rate involving awareness of events distinbguished by awaeness f the events occuring here and now. Contenplating a future action or a future natural event while technically 'here and now' is concepetually distinguishable by the relative lack of personal awareness of yourself as the observer.

    After we've contemlated heobsercer and what is obsevable we ae left with some insanswered qiestion, like what is everyting else? That is, as some have said unobservable reality. We infer its coordinaion with the observable world and often after the fact of local/nonlocal force exchanges, but the defining process has carefully excluded the pinpointing of personal essence, which while nonlocal is ever present in awareness of that fact.

    i suppose I will just take the easy way out and say that definitions of past and present may be sufficient to define the here and now from the lefovers of all the implications of the definitions of past and future. Using any physical theory, that I know of, probably wont fill your bill, except for those matters we take as granted without concern for their 'real physical description' such as the sun rising. Our only concern is that the expected events occur.
     
  18. May 8, 2004 #17
    that we a rather interesting diversion from the cool clinical world of physics and where physics and perception merge of course is all important.

    Afterall is not physics ultimately the servant of our raging intellects?
    ( by the way if this continues to be soooo philosophical this thread may end up being moved....)
     
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