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Oddity of Time

  1. May 7, 2005 #1
    Time.

    Does time not happen instantaneously?

    For example, is not the past present and future all happenning at the same moment? So, could time be finite?

    No se. Necesito razones!!!
     
  2. jcsd
  3. May 7, 2005 #2
    No offense, but your question has nothing to do with physcis.

    It isn't even philosophy.

    It's just semantics.
     
  4. May 7, 2005 #3
    "No offense", but the theory of relativity - a general theory of PHYSICS - involves profound analysis of time and space. Einstein discussed the possibility of reaching the speed of light, and how you would go back in time if you did; time slows down, because you are traveling much faster, and you eventually go "backwards" in time. Therefore, time must be instantaneous if the past can be reached from the present.

    So, ever heard of THEORETICAL PHYSICS before???
     
  5. May 7, 2005 #4

    pervect

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    You can cut time into as thin a slice as you like, mathematically, but nothing happens in a thin slice of time - there is no cause and effect possible unless one has a region of space and time that allows light to propagate. This requires a structure other than an infintely thin sheet of time.

    The past, present, and future are not all the same moment by definition. An anology illustrates this

    Suppose we have a brick. We say that we can divide the brick into two parts with a mathematical plane, which we can make as thin as we like.

    Of course this is an idealization. But suppose we do it anyway and not worry about the details of cutting atoms.

    Now that we've carefully divided the brick into two parts, it seems very ill-motivated to say that the left hand side of the brick is the same as the right hand side of the brick. The whole point of cutting the brick into two parts in the first place was to distinguish the left side from the right!

    So I have to agree with jdavel - and add a further comment. Not only is infinitetime's thread-starting post mainly philosophical, it's not even particularly good philosophy.
     
  6. May 7, 2005 #5

    JesseM

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    What does the phrase "time happens instantaneously" even mean? Why would the possibility of travelling back in time lead to the conclusion that "time is instantaneous"? Are you just talking about the "block time" concept, discussed in this article by physicist Paul Davies?

    By the way, relativity does not actually allow you to go back in time by accelerating until you pass light speed--it would take an infinite amount of energy to do so. But general relativity does suggest another possible way of going back in time involving "wormholes" (see this thread), although it's an open question whether a theory of quantum gravity will still allow this.
     
  7. May 7, 2005 #6
    Augustinus seemed to have known what time is, sometimes at least:

    What is then time, if nobody asks me I do know, but when asked to explain it, I don't know.
     
  8. May 7, 2005 #7

    robphy

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  9. May 7, 2005 #8
    No.
    No.
    Not a meaningful question.

    re - "relativity" - You're confusing what time is and its properties with its relationship between frames/coordinate systems.

    Einstein concluded that the speed of light cannot be reached.
    That's not quite right. In the first place it is impossible for an object to go back in time (i.e. if all objects can't go faster than the speed of light then there are no closed timelike worldlines). The only meaning given to time dilation is the relationship between the rate at which clocks tick/rate at which time passes. No person at rest in the frame of a clock will ever measure the rate to change. Only the rate of an identical clock which is moving relative to it as measured by an observer at rest with respect to the first clock.
    Yes. But this is not it.

    Note: Please don't yell (spell in all caps). It's poor netiquette. You can bold or italasize text here. That will serve your purpose.

    Andre - Many scholars address the concept of time. Here are a few.
    Whorf was a linguist who, amoung other languages, studied the Hopi language (see An American Indian Model of the Universe - in "The Philosophy of Time").

    There is another excellant point made by a physicist which spoke of basic concepts and that these concepts are the most difficult since they are the most basic. I'm too lazy right now to find it. Will quote later.

    Pete
     
  10. May 8, 2005 #9
    Reply to all of your answers

    :smile: Thanks everyone!

     
  11. May 8, 2005 #10
    It truly is a fascinating subject. There are entire books on the subject. There are also online web pages on this subject. One was created by a relativist friend of mine. See www.wfu.edu/~brehme and click on the time article.

    Pete
     
  12. May 19, 2005 #11
    Wormholes dont allow you to go back in time, they allow you go from point A to point B instantaneously even if they were all the way across the universe.
     
  13. May 19, 2005 #12
    That's not true. A wormhole is a connection between two different points in time just as much as it is a connection between two different points in space.
     
  14. May 19, 2005 #13
    Arguing on hypothetical properties of hypothetical things. Point me the way to such a wormhole and I will go and check.
     
  15. May 19, 2005 #14

    Some questions like those done by infinite are being treated by some physicist, at least simliar ones, see for example:
    http://www.kitada.com/bina/time_VI.pdf

    Julian Barbour has been a promoter of the idea of nonexistence of time, and i really desagree with the point of view that this themes should be regarded as especulations, just for the inconvenients it presents to conscience and perception. Im sure that the questions are made too much wrong, but putting in a good way, are interesting per se. :wink:

    Regards.
     
  16. May 19, 2005 #15

    JesseM

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    According to general relativity, if you move one mouth away from the other mouth and back at relativistic velocities, such that a person travelling along with the mouth that went on the trip would be younger than a person standing next to the mouth that was not accelerated, then travelling through the mouth that went on the trip will spit you out the non-accelerated mouth at the moment it was the same age that the mouth that moved was when you entered it. So if the mouth that went on the trip only experienced 5 years between the time it departed and the time it returned, while the non-accelerated mouth experienced 20 years, then if you travel through the mouth that went on the trip you'll come out the non-accelerated mouth when it had experienced only 5 years since the other mouth departed, taking you 15 years into the past.
     
  17. May 19, 2005 #16

    JesseM

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    Regardless of whether wormholes exist, the question about what the theory of general relativity predicts about how wormholes would behave has a well-defined answer.
     
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