Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

What is Time?

  1. Jun 21, 2006 #1
    What is Time???

    I dont know if this is the right section to post this. What is time exactly. We all know time is a kind of measurment but what is its defention what is it in reality. The every concept of time is in everything in nearly all the formulas that we humans have derived time exist. I have been thinking in this direction and came to a few conclusions here are they:
    1) Either time is an inherent propert of space or it is something that is further depended on something else which is inherent.
    2) If time doesnt exist nothing can be described or even studied by humans.
    3) But time could be something that is depended on our frame of reference
    can anyone guide me?

  2. jcsd
  3. Jun 21, 2006 #2
    I know that you are probably expecting some deep answer to this, but there are a few questions that I don't ponder for very long. There are other people who will gladly provide the deep answers. Personally, I use this:

    Time is what my wristwatch says.
  4. Jun 21, 2006 #3
    It will take till the end of time before we know what time is.
  5. Jun 21, 2006 #4
    Time, in SizarieldoR's humble opinion, is the dimension in which changes take place
  6. Jun 21, 2006 #5
    Time is the continuum in which periods exist. Time changes at the rate that periods change. A period is a block of time. Every defined unit of time is a period. Dilation of time means dilation of periods. Periods of specific events depend on the location within the space-time continuum. Time may be dialated in some places more than others. Mass dilates periods, for mass causes time dilation. Speed causes objects to dilate its periods. Energy dilates periods, therefore energy dilates time. Movie speeds are measured in frames per second. Speed in meters per second. Light in wavelengths per second. The second itself is a period, which itself is subject to dilation. This dilation varies throughout the universe, therefore, so does the second.

    Time exists in the way that a continuum exists. Continuums are not objects and so they do not exist as objects, but as something lacking real bounds.
  7. Jun 21, 2006 #6


    User Avatar
    Gold Member

    Some might say time is very much like the other physical dimensions, except that we have no direct control over our movement through it. We're doomed to move at a constant pace thorugh this 4th dimension.

    (We do, however, have *indirect* control over our movement through it, by dramatically increasing our movement through the 3 we can move in).
  8. Jun 22, 2006 #7
    I just posted a message about this yesterday to the "Time Travel...Yeah I know! maybe some parallel universe talk too!" thread, which was moved to this category.

    It needs to be recognized, that time is a semantical concept we use to describe motion. For motion to exist, time dimension doesn't need to, and time is a derivation of observation of motion. (=Time is never observed in a metaphysical sense)

    It would be very problematic philosophically, to think that time actually metaphysically exists as an actual dimension, like we visualize it in spacetime graphs.

    But just for the sake of argument, let's say time dimension does exist fundamentally, in the way implied by Minkowski (world is a 4D-spacetime);

    Nothing moves in 4D spacetime. But if nothing moves, what causes our (conscious) experience of time flowing forwards? Surely it must be something in physical existence, some fundamental, which is not present in this interpretation of relativity.

    But if instead it is motion that exists fundamentally, there is real, metaphysical motion in our brain processes, and this would give us real sense of what we call "flow of time".

    Another idea is to include a concept of fundamental 3D-slices to each matter particle, that metaphysically moves through the 4D-spacetime making motion real to us. But for anything to move through the time dimension, there would need to be another notion of time to describe the motion of this metaphysical 3D-slice through time. This leads to obvious infinite regress and is just far too naive worldview to be considered true.

    It has been said that time is an illusion and any slicing of 4D-spacetime is completely arbitrary, but it should be plain to see to anyone dabbling in philosophy, that our conscious experience is the only thing we know for sure to exist, and our experience of time flowing forwards cannot be denied just because on spacetime diagrams nothing moves. Indeed, it would need a special mind to deny one's own experience to be real, just to make the mathematical equation of reality look simpler on paper.

    Another related question is, does time have to be a dimension for relativity to work? Well, no. At first it might seem that relativity of simultaneity could not exist if time is not a dimension, but actually the idea about relativity of simultaneity is also just one interpretation of the math. It is probably impossible to make any clear ontological interpretation of relativity anyway.

    For example, can we suppose that planes of simultaneity really describe the state of the world around us, and therefore clocks around us actually move at different paces or even backwards just because we change directions? I don't know of a single interpretation that would not be problematic one way or another, which is not to say the math couldn't be right. (we should expect reality to be very very elusive to our semantical minds anyway)

    And btw, another related question is, what is "space"? Does space exist, metaphysically? What do we even mean with space? When there is no matter, is there still this invisible backdrop that exists, or does there only exist matter? Well, metaphysically, the concept of space doesn't make much sense, only the concept of "distance" does (which, like "time", is a matter of taking one physical thing, and simply comparing it to another physical thing. Even if there are no metaphysical distances, there still are comparisons between things and the differences are real metaphysically)

    Think about an atom, for example. Where does the atom end and space begin? We know there is actually no "boundary" to an atom in any real sense of the word. If we scaled our size down, we would not find a "wall" of an atom. The location where one atom collides another atom is just the distance where their electromagnetic forces stabilize and keep them from collapsing together. This is just a physical function of the stable system we call an atom, so can we really say atom is a "particle" in "space"? No, we can't. It is a particle in space only in the specific mental model that we use to classify reality, but metaphysically atom is extended and if it has any size, the size is its whole area of influence, which is potentially the whole size of the universe. We are swimming inside extended atoms all the time.

    All the observations of quantum realm are strongly indicative that the above paradigm would be in fact more useful way to understand the reality than standard model where particles exist like little billiard balls. (No, matter is not made of matter, btw :)

    Oh well, my $0.02
  9. Jun 22, 2006 #8


    User Avatar

    Staff: Mentor

    Have you checked a dictionary?
    It is a property of events (or objects).
    All the measurement of all dimensions depends on your frame of reference.
    Last edited: Jun 23, 2006
  10. Jun 22, 2006 #9
    Time is the word for the transformation that maps one state (viewed as a set) of the universe onto the next, i.e. the (mathematical) transformation that connects the states of the universe.
    Last edited: Jun 22, 2006
  11. Jun 23, 2006 #10
    Time is simply a property of the universe which allows the existence of sentient beings like ourselves. If the universe did not have this particular property, we would not be here to ask the question, would we?

    Thus, time is a necessary property for sentient existence.

    Best Regards
  12. Jun 28, 2006 #11


    User Avatar
    Gold Member

    Hawking spoke of three arrows of time in 'Brief History of Time' (forgive me for the reference if you tire of pop-science as I do). It is mostly regarded as a phenomena still, but can be talked about because of the things it affects:

    One arrow I remember is simply from our point of view as the observers; that we remember the past but not the future.

    The second is entropy. That the order of the universe is always increasing.

    I forget the third arrow, but commonly time can be thought of as a measurement between events. It is relative and not absolute, we can only move forward through it (I've always contemplated that we are actually always time traveling into the future and we can't help it, but as a previous post says, we can slow it down by making our displacement through the other three dimensions larger, as in traveling near the speed of light. The real trick would be to stop time traveling!!!)
  13. Jun 28, 2006 #12
    Time is nothing at all quite literally., and can only be measured with markers. Only the present is possible, where the past and future can only be represented by old markers or potential markers stored in your brain for present use.
  14. Jun 28, 2006 #13
    http://ccat.sas.upenn.edu/jod/latinconf/11.html [Broken]

    What is then time? when nobody asks me, I do know, but when asked to explain it, I don't know.

    Augustine of Hippo
    Last edited by a moderator: May 2, 2017
  15. Jun 28, 2006 #14
    According to the definitions Russ Watters have posted;

    At some 'point' there was no 'time' dimension, then it was. However, we can see that as 'the time when there was no time' and then 'the time when there was a time' if we consider the starting of time as an event.

    This can lead to ask about the 'bigger time' continuum that the time we know has happened inside it and started as an 'event'

    If I am not wrong, since infinity in one dimension does not exist, and so negative infinity; all the 'times' must have a beginning at one point, and regardless how much we take a 'zoom out' and see a bigger time continuum we will end up at 'the biggest' continuum.

    In this sense, i can see time as a 'relation' between objects and its rates of changes, that in itself contains of some objects already exist in realisty.

    [roughly speaking, as a conpet of a family that bound a group of people, they can exist and not exist without the 'family' relation, but that family relations in oreder to exist bust have some persons and family will be the realtions between them]
  16. Jul 8, 2006 #15
    Time is given to us in insuffeicient quantity.
  17. Jul 8, 2006 #16


    User Avatar
    Gold Member

    That's an excellent comparison for psychological time, but there is also a sort of mechanical time. It's not absolute by itself (it's my understanding that spacetime is actually absolute, while time and space are relative if held independent of one another...) but it still goes on while you sleep:

    For instance, the night/day cycle, the clock ticking, seasons, all continue on regardless of your state of consciousness. I think one of the more 'stable' mechanical clocks is (ironically) the radioactive decay of atoms.

    This is all mostly conjecture though, I've only just begun my 3rd year in physics.
    Last edited by a moderator: Jul 10, 2006
  18. Jul 8, 2006 #17
    Aristotle: Physics, Bx VI: Ch. 6: ...that which is intermediate between moments is time...
  19. Jul 11, 2006 #18
    A thought. If, following Aristotle on time, we consider that "that which is intermediate between existents is space", then perhaps "that which is intermediate between moments of existents is space-time" ?
  20. Jul 11, 2006 #19
    And if 'is intermediate between existents' is taken to mean 'on a closed interval', time never ends, thus, space-time never ends.
  21. Jul 14, 2006 #20


    User Avatar
    Science Advisor

    A 2D drawing of a box in an isometric perspective might look 3D even though its constituents are laid on a plane. It might be that, in the same manner that we might interpret the drawing of the box to be 3D, we may be interpreting the universe as being 4D, when possibly it isn't.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook