Notices
Results 1 to 23 of 23

Thread: time

  1. #1 time 
    New Member
    Join Date
    Apr 2011
    Location
    earth
    Posts
    1
    It is said one of the unique things about time is that it only goes one way - to the future. It is said as a an example that for instance you can never uncrack an egg.

    First of all 'time' may or may not exist. Its something we make up to make things understandable (like the word 'gene') After all all observation is subjective.

    So does not quantum physic suggest that the whole egg and the cracked egg both exist together, its only our observations that make it seem one follows the other.

    Why?

    Because we need to explain things so that we can understand them, regardless of the REALITY, its how are brains work. We need to put things into patterns

    However thats us. That is not necessarily WHAT IS

    Not only is all relative, but we can only see what we can see, and we can only understand what we can understand. And that is a limit. So therefore all scientific observation is limited to what we can understand, or the stories we make up, to understand

    here is a basic question - why is there something rather than nothing?

    how can we a part of the whole - explain the whole?

    if logic is the pure answer then where is the logic in the following "everything I say is untrue"

    How can we prove TIME exists? ( a clock? the words 'past' and 'future"? )

    If we cannot answer basic questions, no wonder we create scapegoats like time and space to explain our stories


    Reply With Quote  
     

  2.  
     

  3. #2  
    Forum Bachelors Degree x(x-y)'s Avatar
    Join Date
    Jul 2010
    Location
    UK
    Posts
    462
    Time exists because, as far as I know, general relativity proved it to be an extra dimension added onto the 3 dimensions of space (x, y, z)- hence Space-time. The question I must ask the experts on here is: as time is a dimension, does it have an x (length) dimension like space? And, if so, as this spatial dimension can be altered- does this mean the 'length of time' can be altered too (i.e. Time travel)?


    "Nature doesn't care what we call it, she just does it anyway" - R. Feynman
    Reply With Quote  
     

  4. #3  
    . DrRocket's Avatar
    Join Date
    Aug 2008
    Posts
    5,486
    Quote Originally Posted by x(x-y)
    Time exists because, as far as I know, general relativity proved it to be an extra dimension added onto the 3 dimensions of space (x, y, z)- hence Space-time. The question I must ask the experts on here is: as time is a dimension, does it have an x (length) dimension like space? And, if so, as this spatial dimension can be altered- does this mean the 'length of time' can be altered too (i.e. Time travel)?
    Time is not an "added dimension in general relatvity. The spacetime manifold of GR is a 4-dimensional Lorentzian manifold. Both "time" and "space" are local ideas. There is no global definition of either time or space. What clocks measure is "proper time", which is the length of the world line of the clock in terms of the metrc of spacetime. Proper time is associated with each world line, and is not a dimension per se.
    Reply With Quote  
     

  5. #4  
    Forum Bachelors Degree x(x-y)'s Avatar
    Join Date
    Jul 2010
    Location
    UK
    Posts
    462
    Ah, ok. I see, thank you.
    "Nature doesn't care what we call it, she just does it anyway" - R. Feynman
    Reply With Quote  
     

  6. #5  
    Forum Ph.D.
    Join Date
    Dec 2006
    Posts
    959
    Nothing to do with the thread, or physics, but I was just reading a short article about the American writer, William Faulkner, who apparently said about time: "The past is never dead. It's not even past."
    Reply With Quote  
     

  7. #6  
    Forum Freshman
    Join Date
    Apr 2011
    Posts
    16
    and your opinion about that ?
    Reply With Quote  
     

  8. #7  
    Suspended
    Join Date
    Oct 2006
    Posts
    769
    Quote Originally Posted by x(x-y)
    Time exists because, as far as I know, general relativity proved it to be an extra dimension added onto the 3 dimensions of space (x, y, z)- hence Space-time.
    Note quite, it was Minkowski who introduced spacetime in 1908 in Raum und Zeit, which is considered to be a special relativity paper.

    Quote Originally Posted by x(x-y)
    The question I must ask the experts on here is: as time is a dimension, does it have an x (length) dimension like space?
    No. When calculating a spatial distance you use x y and z, but when calculating a spacetime interval you use x y z and -t. The minus sign means time is very different to space. It's a dimension of measure rather than a dimension that offers freedom of motion. In other words you can move through space but you can't move through time. Even if you take a fast round trip such that you suffer time dilation, we meet back up at the same time. You don't end up living in my past.

    Quote Originally Posted by x(x-y)
    And, if so, as this spatial dimension can be altered- does this mean the 'length of time' can be altered too (i.e. Time travel)?
    The "length" of elapsed time as measured by you can change, but it isn't time travel. Time travel is science fiction.
    Reply With Quote  
     

  9. #8  
    Forum Bachelors Degree x(x-y)'s Avatar
    Join Date
    Jul 2010
    Location
    UK
    Posts
    462
    Thank you Farsight. However, how can you be so sure that time travel is just science fiction? That's hasn't been proven, has it?
    "Nature doesn't care what we call it, she just does it anyway" - R. Feynman
    Reply With Quote  
     

  10. #9  
    . DrRocket's Avatar
    Join Date
    Aug 2008
    Posts
    5,486
    Quote Originally Posted by x(x-y)
    Thank you Farsight. However, how can you be so sure that time travel is just science fiction? That's hasn't been proven, has it?
    The equations of general relativity do not clearly prohibit closed timelike curves. In fact closed timelike curves are known to exist under exotic conditions.

    However Stephen Hawking showed that if the weak energy condition is satisfied then closed timelike curves are prohibited. A more general conjecture of Hawking, the "chronology protection conjecture" states that time travel is impossible at the macroscopic scale in the real universe. It remains an unproved conjecture, but most physicists would be surprised if it were not true.
    Reply With Quote  
     

  11. #10  
    . DrRocket's Avatar
    Join Date
    Aug 2008
    Posts
    5,486
    Quote Originally Posted by Farsight
    Quote Originally Posted by x(x-y)
    The question I must ask the experts on here is: as time is a dimension, does it have an x (length) dimension like space?
    No. When calculating a spatial distance you use x y and z, but when calculating a spacetime interval you use x y z and -t. The minus sign means time is very different to space. It's a dimension of measure rather than a dimension that offers freedom of motion. In other words you can move through space but you can't move through time. Even if you take a fast round trip such that you suffer time dilation, we meet back up at the same time. You don't end up living in my past.
    1. The spacetime interval in Minkowski space is the proper time of the straight line path connecting two points. A clock following that path would record that proper time.

    2. Of course you can travel through time. I just traveled about 90 seconds while typing this. It appears to be impossible NOT to travel through time. Going backwards is a bit more problematic.
    Reply With Quote  
     

  12. #11 Re: time 
    Time Lord
    Join Date
    Mar 2007
    Posts
    8,035
    Quote Originally Posted by ecom131
    It is said one of the unique things about time is that it only goes one way - to the future. It is said as a an example that for instance you can never uncrack an egg.

    First of all 'time' may or may not exist. Its something we make up to make things understandable (like the word 'gene') After all all observation is subjective.

    So does not quantum physic suggest that the whole egg and the cracked egg both exist together, its only our observations that make it seem one follows the other.

    Why?
    Yeah. Our notion of time is tied very closely to our notion of entropy. At the highest level of entropy, like say a really hot gas or plasma, there would be no preferred direction for us to say time is flowing. Backwards and forwards are basically the same.
    Some clocks are only right twice a day, but they are still right when they are right.
    Reply With Quote  
     

  13. #12 Re: time 
    . DrRocket's Avatar
    Join Date
    Aug 2008
    Posts
    5,486
    Quote Originally Posted by kojax
    ... At the highest level of entropy, like say a really hot gas or plasma, there would be no preferred direction for us to say time is flowing. Backwards and forwards are basically the same.
    As per your usual style, this assertion is baseless.

    Did you really pass a physics course somewhere ?
    Reply With Quote  
     

  14. #13  
    Time Lord
    Join Date
    Mar 2007
    Posts
    8,035
    At the extreme of entropy, determinism breaks down. It's an equivalent statement to say that time has no discernible arrow.

    Did you really pass a mathematics/logic/reasoning course somewhere?
    Some clocks are only right twice a day, but they are still right when they are right.
    Reply With Quote  
     

  15. #14  
    . DrRocket's Avatar
    Join Date
    Aug 2008
    Posts
    5,486
    Quote Originally Posted by kojax
    At the extreme of entropy, determinism breaks down. It's an equivalent statement to say that time has no discernible arrow.
    Rubish.

    I defy byou to prove it.

    Quote Originally Posted by kojax
    Did you really pass a mathematics/logic/reasoning course somewhere?
    Several. You either did not or attended a most unusual school -- a school those wishing an education should avoid.

    You have made many positive assertions that without any foundation. Rank unsupported speculation at best, often just plain wrong.
    Reply With Quote  
     

  16. #15  
    Suspended
    Join Date
    Dec 2010
    Posts
    661
    Quote Originally Posted by DrRocket
    Quote Originally Posted by Farsight
    Quote Originally Posted by x(x-y)
    The question I must ask the experts on here is: as time is a dimension, does it have an x (length) dimension like space?
    No. When calculating a spatial distance you use x y and z, but when calculating a spacetime interval you use x y z and -t. The minus sign means time is very different to space. It's a dimension of measure rather than a dimension that offers freedom of motion. In other words you can move through space but you can't move through time. Even if you take a fast round trip such that you suffer time dilation, we meet back up at the same time. You don't end up living in my past.
    1. The spacetime interval in Minkowski space is the proper time of the straight line path connecting two points. A clock following that path would record that proper time.
    This is amusing.

    How will you get a clock to travel a spacelike space-time interval?

    Spacelike paths cannot be physically traveled (as they require moving faster than light).
    http://en.wikipedia.org/wiki/Proper_time
    Reply With Quote  
     

  17. #16  
    . DrRocket's Avatar
    Join Date
    Aug 2008
    Posts
    5,486
    Quote Originally Posted by chinglu
    Quote Originally Posted by DrRocket
    Quote Originally Posted by Farsight
    Quote Originally Posted by x(x-y)
    The question I must ask the experts on here is: as time is a dimension, does it have an x (length) dimension like space?
    No. When calculating a spatial distance you use x y and z, but when calculating a spacetime interval you use x y z and -t. The minus sign means time is very different to space. It's a dimension of measure rather than a dimension that offers freedom of motion. In other words you can move through space but you can't move through time. Even if you take a fast round trip such that you suffer time dilation, we meet back up at the same time. You don't end up living in my past.
    1. The spacetime interval in Minkowski space is the proper time of the straight line path connecting two points. A clock following that path would record that proper time.
    This is amusing.

    How will you get a clock to travel a spacelike space-time interval?

    Spacelike paths cannot be physically traveled (as they require moving faster than light).
    http://en.wikipedia.org/wiki/Proper_time
    You are correct in that the statement applies only to timelike curves. But a worldline if an object is always a timelike curve. So your comment, though technically correct, is basically pointless.
    Reply With Quote  
     

  18. #17  
    The Doctor Quantime's Avatar
    Join Date
    Jun 2007
    Location
    United Kingdom
    Posts
    4,546
    So how does a supermassive black hole cause frame dragging and a relative backwards time travel?
    "If you wish to make an apple pie from scratch, you must first invent the universe". - Carl Sagan
    Reply With Quote  
     

  19. #18  
    Suspended
    Join Date
    Dec 2010
    Posts
    661
    Quote Originally Posted by DrRocket
    Quote Originally Posted by chinglu
    Quote Originally Posted by DrRocket
    Quote Originally Posted by Farsight
    Quote Originally Posted by x(x-y)
    The question I must ask the experts on here is: as time is a dimension, does it have an x (length) dimension like space?
    No. When calculating a spatial distance you use x y and z, but when calculating a spacetime interval you use x y z and -t. The minus sign means time is very different to space. It's a dimension of measure rather than a dimension that offers freedom of motion. In other words you can move through space but you can't move through time. Even if you take a fast round trip such that you suffer time dilation, we meet back up at the same time. You don't end up living in my past.
    1. The spacetime interval in Minkowski space is the proper time of the straight line path connecting two points. A clock following that path would record that proper time.
    This is amusing.

    How will you get a clock to travel a spacelike space-time interval?

    Spacelike paths cannot be physically traveled (as they require moving faster than light).
    http://en.wikipedia.org/wiki/Proper_time
    You are correct in that the statement applies only to timelike curves. But a worldline if an object is always a timelike curve. So your comment, though technically correct, is basically pointless.
    Very good, but you made a general comment about space-time and now you are correcting yourself to only include time-like curves.

    You have proven yourself to be a good pupil, but you did not prove me wrong based on your statements.

    You talked about general Minkowski spacetime with your example, and I corrected you because you were wrong. You included space-like intervals.
    Reply With Quote  
     

  20. #19  
    Forum Radioactive Isotope MagiMaster's Avatar
    Join Date
    Jul 2006
    Posts
    3,440
    Having read DrRocket's comments, he made no mention of space-like curves, only spacetime (which is all of everything, includeing space-like, time-like and light-like curves).
    Reply With Quote  
     

  21. #20  
    Suspended
    Join Date
    Oct 2006
    Posts
    769
    Quote Originally Posted by x(x-y)
    Thank you Farsight. However, how can you be so sure that time travel is just science fiction?
    I'm sure because I understand time. There's an interesting book called A World Without Time: the Forgotten Leagcy of Godel and Einstein that's fairly interesting. It's heavy going at times, but there's some good history in there. It describes how Godel and Einstein worked out what time was all about in 1949. The blurb says time does not exist, but actually it ought to be time isn't what people often say it is. It isn't something that flows, and it isn't something you can travel through. To understand this, think about a stasis box. Thatís science fiction too, kind of like fighting fire with fire, but it's a good one. No motion occurs inside the box, so when I put you inside one, electromagnetic phenomena donít propagate, nor do nerve impulses, nothing moves, nothing happens at all. So you canít see, you canít hear, your heart doesn't beat, and you canít even think. Hence when I open the door 5 years later, to you itís like I opened the door just as soon as I closed it. You ďtravelledĒ to the future by not moving at all. Instead everything else did.

    If you don't like this stasis box just think in terms of a refrigerator. We can freeze human embryos now. A child is born maybe five years after it was conceived, but it didn't "travel through time".

    Quote Originally Posted by x(x-y)
    That's hasn't been proven, has it?
    No. Nor has the non-existence of fairies.
    Reply With Quote  
     

  22. #21  
    Suspended
    Join Date
    Dec 2010
    Posts
    661
    Quote Originally Posted by MagiMaster
    Having read DrRocket's comments, he made no mention of space-like curves, only spacetime (which is all of everything, includeing space-like, time-like and light-like curves).
    Excellent.

    Then he also said that a clock could follow such path.

    To be scientific, you must include all information.

    Are you scientific?
    But, a clock cannot follow a space-like path.

    Now do you understand?
    Reply With Quote  
     

  23. #22  
    . DrRocket's Avatar
    Join Date
    Aug 2008
    Posts
    5,486
    Quote Originally Posted by Farsight
    I'm sure because I understand time. .
    We have been through this before in some detail.

    You don't understand time, general relativity or much else.

    You have proved yourself to be a menace on the board and a well-recognized crank across many boards on the internet.

    You are a positive danger to neophytes on the board who are trying to learn real science.

    The notion that time halts in a "stasis chamber" is pure science fiction, which you present as real science. CRANK
    Reply With Quote  
     

  24. #23  
    Time Lord
    Join Date
    Mar 2007
    Posts
    8,035
    Quote Originally Posted by Farsight

    If you don't like this stasis box just think in terms of a refrigerator. We can freeze human embryos now. A child is born maybe five years after it was conceived, but it didn't "travel through time".
    Maybe that kind of time travel is the best we can hope for. If reverse time travel were possible, it probably would have to consist in a similar process, except instead of bringing all the chemical processes to a halt, it makes them work backwards. A time travel machine that just teleports you to the time you want to visit would be like trying to make that embryo pop out of existence and suddenly reappear 5 years later instead of being present in a frozen form for all that time.

    Of course that's a really big "if", but such is the nature of the topic.

    It's all about causality. If you can create a situation where the last event (from our perspective) triggers the first event (from our perspective), then you've defined an object that travels backward through time (from our perspective). Naturally that object would perceive us to be the ones going backward in time, not itself. I don't have any good ideas about how to do that. I'm just saying that is the definition of backwards time travel.


    Quote Originally Posted by x(x-y)
    That's hasn't been proven, has it?
    No. Nor has the non-existence of fairies.

    This experiment at least appears to have sent information back in time.

    http://en.wikipedia.org/wiki/Delayed...quantum_eraser
    Some clocks are only right twice a day, but they are still right when they are right.
    Reply With Quote  
     

Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •