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Does the past exist?

  • 23-07-2009 6:48pm
    #1
    Mr.Nice Guy
    Registered Users Posts: 45,535 ✭✭✭✭


    I was watching a documentary on time travel recently and something one of the scientists said interested me. He was talking about the past as if it was something legitimate in the universe and that it exists in some form. I am wondering what science officially makes of this? Does the past exist in the eyes of science? I hope I'm making sense.

    For example, about a half an hour ago I made myself a cup of tea. Is there somewhere in our universe where this is still occurring even though as I write this I'm thirty minutes past that point?

    Important historical figures from centuries ago, loved ones we have lost, obviously they are dead to us at this moment but do they exist out there in some capacity beyond our reach in the past? Are their lives imprinted on time?

    Just curious what the general concensus of the scientific community is on this idea? :cool:

    'It is better to walk alone in the right direction than follow the herd walking in the wrong direction.'



«134

Comments

  • #2
    r3nu4l
    Registered Users Posts: 17,399 ✭✭✭✭r3nu4l


    Great question! I don't have the answer but my very limited and probably wrong!) understanding is that time is a dimension that moves 'forward' and therefore if there is a past then it can never be returned to.

    I'd love to hear a physicists answer to this but I think that the biggest problem the layman has when it comes to time as a dimension is that we grow up with the idea of time travel and parallel universes where every action we take in this universe, spawns a new universe where we took the opposite action and where interfering in events of the past spawns a new reality in the present and future.

    While many of the ideas we see and read in science-fiction must have come from some theoretical piece of physics I'm not sure how much and how far those ideas have been expanded on to make a good story.

    If anyone has any definitive answers then come back to us last week and post about it on the forum :D


  • #3
    nyarlothothep
    Registered Users Posts: 5,176 ✭✭✭nyarlothothep


    I have no idea about it at all but could the universe just be one big zip file which is self extracting?

    Again I am a layman but I think the past must exist for there to be a present. Also if you consider space time geometrically as in minkowski space then it exists relative to the persons position in space time. Isn't it entropy and light cones which determine the arrow of time so that we cannot go back? mehfla.


  • #4
    Mr.Nice Guy
    Registered Users Posts: 45,535 ✭✭✭✭Mr.Nice Guy


    Another thing I can't get my head around is as the poster above says, if the past does not exist any more then how can the present exist? I would have thought the two would be interdependent. In life we go from A to B to C. If A eventually gets swallowed up, then how is B there at all?

    Or is it all an illusion? :)

    'It is better to walk alone in the right direction than follow the herd walking in the wrong direction.'



  • #5
    5uspect
    Moderators, Arts Moderators Posts: 10,515 Mod ✭✭✭✭5uspect


    I read once about a hypothesis that time as we experience is essentially an average of all the collapsing wavefunctions around us in much the same way as heat is the average of phonon vibrations in a mass.

    More here:
    http://www.newscientist.com/article/mg19726391.500-is-time-an-illusion.html?full=true


  • #6
    Trance
    Closed Accounts Posts: 82 ✭✭Trance


    Mr.Nice Guy wrote: »
    He was talking about the past as if it was something legitimate in the universe and that it exists in some form. Does the past exist in the eyes of science? /cup of tea

    When you drop your cup of tea on the kitchen floor (or beam a radiosignal into space), information of that event will travel at a fixed velocity to far-living aliens on the planet Zorg. When they eventually receive that information, that which is their present will have occured in your past — Or more importantly to answer your question; before the event reaches them, that which is their future, will have happened in your past. Events that have happened in your past have yet to happen in other's futures.

    When you see your friend waving at you from across the street, you're looking into his past. From his point of view however, the moment he waves, he knows your future — Time is relative to each individual.

    If you and any other individual had no past, how could anyone else have a future?


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  • #7
    Kesha
    Registered Users Posts: 30 ✭Kesha


    #6 Trance, I believe you are talking about the subjective perception of existence rather than the existence itself. These are two different things.
    If you perceive something id doesn't necessarily mean it exists or ever has.

    OP, I believe that the trend in modern science is that all past, present and future exist and even all possibilities/possible worlds do as well. However, since it is impossible to perceive anything but this one present world, it is the same to us as if they didn't.


  • #8
    dogbert27
    Registered Users Posts: 4,883 ✭✭✭dogbert27


    OP. My thoughts on the matter are as follows: As you said, you are presently standing on point B. To get to point B you chose a future possibility at point A to go to and made your way through space and time to get to point B. At point B (the present) you are faced with future possibilities from 0 to infinity. You then make your decision and go forward you are now at point C, which now becomes your present. The future exists in the form of your possible choices. The present exists in the last chosen possibility becoming reality. The past exists in the chosen possibilites.
    Or picture that you are a presently a point/dot and either side of you is a line stretching to infinity. Behind is a single line, the past. Ahead of you is an infinite amount of lines, possibilities that you choose to create your future.
    So I guess what I’m trying to say is, I think yes the past exists, otherwise there would not be a present.


  • #9
    bonkey
    Registered Users Posts: 15,443 ✭✭✭✭bonkey


    Mr.Nice Guy wrote: »
    Does the past exist in the eyes of science?

    It depends on what you mean by "exist", really...which is more of a philosophical question.
    For example, about a half an hour ago I made myself a cup of tea. Is there somewhere in our universe where this is still occurring even though as I write this I'm thirty minutes past that point?
    If you define the universe in terms of space-time, then yes.


  • #10
    dungeon
    Closed Accounts Posts: 164 ✭✭dungeon


    Now I remember why I dropped Physics and Chemistry!


  • #11
    r3nu4l
    Registered Users Posts: 17,399 ✭✭✭✭r3nu4l


    dungeon wrote: »
    Now I remember why I dropped Physics and Chemistry!

    I dropped them too :) However, I've always had an interest in the more fanciful sides of both subjects. :D


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  • #12
    m83
    Registered Users Posts: 2,021 ✭✭✭m83


    Everything that will ever happen, has already happened.


  • #13
    glaston
    Closed Accounts Posts: 331 ✭✭glaston


    If you could travel faster than the speed of light then you could see the past from a different perspective. But it would be the present from where you are viewing it...
    Kinda...


  • #14
    Rougies
    Registered Users Posts: 2,672 ✭✭✭Rougies


    nyarlothothep wrote: »
    I have no idea about it at all but could the universe just be one big zip file which is self extracting?

    Interesting analogy there!

    As it extracts the files, the past would be "read only" and the future "hidden".
    (would make more sense if the future files were encrypted though).


  • #15
    Gurgle
    Closed Accounts Posts: 5,064 ✭✭✭Gurgle


    dungeon wrote: »
    Now I remember why I dropped Physics and Chemistry!
    This is more philosophy tbh.


  • #16
    Azelfafage
    Closed Accounts Posts: 125 ✭✭Azelfafage


    General Relativity informs us that we live in a "Space-Time Continuum".


    What is on your left side exists.
    What is above you and behind you and below you (3 dimensions) and tomorrow and today and yesterday (4th one.) exist.

    The past exists.

    There is no distinction in physics between space and time.

    .

    .


  • #17
    topper75
    Registered Users Posts: 5,942 ✭✭✭topper75


    Quite amazing to look into the night sky and consider the time it takes for that starlight to reach us. Some of these stars could have ceased to exist long before I was even born.

    Of course, we are not really looking into the past by looking at the stars. It is simply that our becoming aware of a past event is much delayed.


  • #18
    Azelfafage
    Closed Accounts Posts: 125 ✭✭Azelfafage


    "Of course, we are not really looking into the past by looking at the stars."

    We are.
    .


  • #19
    topper75
    Registered Users Posts: 5,942 ✭✭✭topper75


    The light hitting your retina is an event in the present, is it not?


  • #20
    r3nu4l
    Registered Users Posts: 17,399 ✭✭✭✭r3nu4l


    topper75 wrote: »
    The light hitting your retina is an event in the present, is it not?

    It's our present but that light was first emitted in the past, you are arguing semantics. Much of the light we see comes from stars that may no longer exist and are no longer emitting any light so our image of the stars is based on how they were a long time ago and does not relate to how they are now.

    Most people readily understand what you are saying when you say that what we are seeing now is an event from the past...as strange as it sounds :)


  • #21
    topper75
    Registered Users Posts: 5,942 ✭✭✭topper75


    Independent of our human observation though -

    The light has left the star in the past.
    The light reaches our eyes in the present.

    I don't know how this adds up to mean that the past is still happening.

    By it's very definition, the past is not still happening. No semantics required.


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  • #22
    r3nu4l
    Registered Users Posts: 17,399 ✭✭✭✭r3nu4l


    topper75 wrote: »
    Independent of our human observation though -

    The light has left the star in the past.
    The light reaches our eyes in the present.

    I don't know how this adds up to mean that the past is still happening.

    By it's very definition, the past is not still happening. No semantics required.
    No one said the past is still happening...that's what you inferred from what Azelfafage said. There is no issue here at all.


  • #23
    roosh
    Registered Users Posts: 2,552 ✭✭✭roosh


    Mr.Nice Guy wrote: »
    I was watching a documentary on time travel recently and something one of the scientists said interested me. He was talking about the past as if it was something legitimate in the universe and that it exists in some form. I am wondering what science officially makes of this? Does the past exist in the eyes of science? I hope I'm making sense.

    For example, about a half an hour ago I made myself a cup of tea. Is there somewhere in our universe where this is still occurring even though as I write this I'm thirty minutes past that point?

    Important historical figures from centuries ago, loved ones we have lost, obviously they are dead to us at this moment but do they exist out there in some capacity beyond our reach in the past? Are their lives imprinted on time?

    Just curious what the general concensus of the scientific community is on this idea? :cool:

    Reality is the state of things as they actually exist, not as they existed, or as they will exist.

    Therefore, the present moment is all that exists, not in some kind of new age hippy kind of way, but in reality. The past is only a memory which exists in the mind and the future is also only a projection that exists only in the mind.

    Also, mathematics is only an extension of the human mind, it is the manifestation of the human mind's attemtp to rationalise its experiences. Showing mathematically that the past and the future exist simultaneously with the present, is again simlpy imagination, unless of course the past is defined and observed, likewise the future.

    Everything occurs in the present moment, and it is the changing nature of reality that gives rise to the illusion of time, past and future.


  • #24
    roosh
    Registered Users Posts: 2,552 ✭✭✭roosh


    topper75 wrote: »
    Independent of our human observation though -

    The light has left the star in the past.
    The light reaches our eyes in the present.

    I don't know how this adds up to mean that the past is still happening.

    By it's very definition, the past is not still happening. No semantics required.

    indeed you are correct, and it goes back to what an earlier poster said about relative perspective.

    From our perspective it can be claimed that we are seeing a past event, but in reality we are not, we are seeing the current state of reality with respect to the light.

    if we were to consider it from the perspective of the ray of light (or from the perspective of sitting at the front of the ray of light) then it would be completely different. We would have been present when it was first emitted from the star, we would have travelled whatever the distance across space and would only be arriving at earth now.

    The light emitted from the star was done so however many years ago, it then travelled however many light years across the galaxy and what we see is not the actual star but the light waves that were emitted.


  • #25
    topper75
    Registered Users Posts: 5,942 ✭✭✭topper75


    Azelfafage wrote: »
    The past exists.
    r3nu4l wrote: »
    No one said the past is still happening.

    I think Mangeroosh cleared things up. I hope everyone else is happy.:D


  • #26
    roosh
    Registered Users Posts: 2,552 ✭✭✭roosh


    A general question that I think is pertinent to this topic:

    in what way can time can be said to make up the "fabric of reality", does it actually make up the fabric of reality or is the notion that it does, based purely on an assumption, that is inherent in mankind, based on a misperception of reality.

    Also, is it possible that this notion is borne out in the extrememly logical mathematics that have as a starting point, this potentially erroneous "axiom".

    Where:

    reality
    • noun (pl. realities) 1 the state of things as they actually exist, as opposed to an idealistic or notional idea of them. 2 a thing that is actually experienced or seen. 3 the quality of being lifelike. 4 the state or quality of having existence or substance.


  • #27
    roosh
    Registered Users Posts: 2,552 ✭✭✭roosh


    mangaroosh wrote: »
    A general question that I think is pertinent to this topic:

    in what way can time can be said to make up the "fabric of reality", does it actually make up the fabric of reality or is the notion that it does, based purely on an assumption, that is inherent in mankind, based on a misperception of reality.

    Also, is it possible that this notion is borne out in the extrememly logical mathematics that have as a starting point, this potentially erroneous "axiom".

    Where:

    reality
    • noun (pl. realities) 1 the state of things as they actually exist, as opposed to an idealistic or notional idea of them. 2 a thing that is actually experienced or seen. 3 the quality of being lifelike. 4 the state or quality of having existence or substance.

    A couple of articles that may be interesting to people. Could be old news but goes some way to putting the above question in more of a scientific context:
    http://qd.typepad.com/17/2005/10/the_problem_of_.html
    http://discovermagazine.com/2007/jun/in-no-time


  • #28
    Azelfafage
    Closed Accounts Posts: 125 ✭✭Azelfafage


    Ok :

    The past does not exist.

    Therefore the future does not exist.

    So Logically.....NOW does not exist either.

    (Seeing as NOW is the dividing line between the past and the future.)

    Eezy Peezy.


  • #29
    Azelfafage
    Closed Accounts Posts: 125 ✭✭Azelfafage


    Joking aside.

    The notion of past and present and future is fundamental to the theory of General Relativity.
    A Black Hole can play havoc with "The River of Time",as seen by an outsider.
    Explained here at this link:

    http://www.cfa.harvard.edu/seuforum/bh_whatare.htm

    Quote from the article:

    "As you get closer to a black hole, the flow of time slows down, compared to flow of time far from the hole. (According to Einstein's theory, any massive body, including the Earth, produces this effect. Earth's gravity is so weak that the slowing of time is not noticeable, but the effect has been confirmed using sensitive instruments. For example, at sea level you age one-billionth of a second less every year than you would if you lived on top of Mt. Everest.) Near a black hole, the slowing of time is extreme. From the viewpoint of an observer outside the black hole, time stops. For example, an object falling into the hole would appear frozen in time at the edge of the hole."

    Eezy Peezy.


  • #30
    Azelfafage
    Closed Accounts Posts: 125 ✭✭Azelfafage


    At the risk of hogging this thread I can point you to the operation of your Sat-Nav. gadget.

    The satellites on which a Sat Nav depend HAVE to take into account Einsten's "Time Dilation".

    GPS technology Explained here:

    http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html

    Quote:

    "To achieve this level of precision, the clock ticks from the GPS satellites must be known to an accuracy of 20-30 nanoseconds. However, because the satellites are constantly moving relative to observers on the Earth, effects predicted by the Special and General theories of Relativity must be taken into account to achieve the desired 20-30 nanosecond accuracy.
    Because an observer on the ground sees the satellites in motion relative to them, Special Relativity predicts that we should see their clocks ticking more slowly (see the Special Relativity lecture). Special Relativity predicts that the on-board atomic clocks on the satellites should fall behind clocks on the ground by about 7 microseconds per day because of the slower ticking rate due to the time dilation effect of their relative motion."

    "Further, the satellites are in orbits high above the Earth, where the curvature of spacetime due to the Earth's mass is less than it is at the Earth's surface. A prediction of General Relativity is that clocks closer to a massive object will seem to tick more slowly than those located further away".

    Won't hog this thread again...I promise
    .


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  • #31
    roosh
    Registered Users Posts: 2,552 ✭✭✭roosh


    Azelfafage wrote: »
    Ok :

    The past does not exist.

    Therefore the future does not exist.

    So Logically.....NOW does not exist either.

    (Seeing as NOW is the dividing line between the past and the future.)

    Eezy Peezy.

    Now is all that exists. The past is merely a mind made construct of "a former now" and the future is merely a projection of what Now will be like.

    Both are man/mind made constructs and are to an extent illusory


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