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What 'drives' time forward?

  1. Jul 19, 2010 #1
    I'm a student in Physics and I've been doing some thinking on my own (dangerous, I know).

    Something occurred to me about time. It moves in a direction constantly and at different rates. Since time is a dimension like the spatial ones we know love, and it moves through it, what pushes it through that dimension? Right as I typed that I have come to the realization that that question might just be one of those unanswerable absurd questions.

    Anyway, things require some kind of initial force to move them through the spatial dimensions. That fact makes me believe there is something analogous when looking at time. Was there some initial 'force' that pushed it during the Big Bang? Also, time dilation slows the rate of time so is there some opposing force?

    Time being a non-spatial dimension might blow up that theory though.

    Now, I'm hoping this isn't just another "If E = mc^2 is true, shouldn't photons have mass?" type of question. I can't really find any sort of answer to this through any information website or book. Any thoughts?
  2. jcsd
  3. Jul 19, 2010 #2


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    Quite right, and time is not a spatial dimension (it's a time-like dimension!). To illustrate what I mean, refer to the standard minkowski metric:
    Note that the time component has a sign opposite to that of the spatial dimensions! This opposite sign is very important. If time were just another one of the boys, the metric would look like
    [tex]ds^2=dt^2+dx^2+dy^2+dz^2 [/tex]
    Which is just a 4-dimensional flat space (no time!). Fortunately for us, the sign is in fact different and we get to experience a whole world of interesting phenomenon.
  4. Jul 19, 2010 #3
    Time is just a comparison of movement though and movement is again a measurement of space. When a pendulum moves across x amount of space you tick off another mark of time.

    It is no wonder it dilates in different reference frames.

    Therefore there isn't really anything to "drive" forward. Just a persistent illusion.
  5. Jul 19, 2010 #4
    Probability drives it forward. :p
  6. Jul 19, 2010 #5
    Pretty sure Entropy can be thought of as the forward motion of time. Try putting all of the carbon molecules back into the can of pop you just opened. Good luck with that. Also, another idea is try to put an egg back together after it has been shattered on the floor. Not only would you have to get every piece of the shell, the yolk, etc, but you would also have to somehow gather the energy back out of the floor that went into it when the egg collided with it. As you can see, both feats are practically or perhaps theoretically impossible, due to Entropy. You can't undo what has been done.
  7. Jul 20, 2010 #6
    I think of it in a similar way as Fuzzystuff.

    A second is just an arbitrary number of transitions between levels of ground state of cesium. Time, and its units, are simply tools for understanding. I think of entropy as the natural phenomenon we call time. Looked at that way, time isn't driven forward. It's more like it's falling down as our systems tend toward equilibrium.
  8. Jul 20, 2010 #7
    there is no such thing as time. just a figment of our imaginations. Albert Einstein was the smartest man to ever live and he said time is just an illusion.
  9. Jul 20, 2010 #8
    "Right as I typed that I have come to the realization that that question might just be one of those unanswerable absurd questions"

    unanswerable yes, absurd no...
    we are just not smart enough yet....It's like asking what is matter, what is space, what is a particle??

    not really. maybe in another universe...your formula is only a piece of the whole....

    Try here:

    The total energy E of a body is related to the relativistic momentum p by

    E2 = (pc) + (m0c2)2
    where p denotes the magnitude of p. This relativistic energy-momentum relationship holds even for massless particles such as photons; by setting m0 = 0 it follows that

    E = m0c2

    For both massive and massless objects, relativistic momentum is related to the de Broglie wavelength λ by

    E = pc and p = h/lambda

    where h is the Planck constant.

    Those few formulas tie a lot of pieces together...

    There is no theory that either probability nor entropy "drive time forward"....thats speculative..but increasing entropy does point in the same direction as "the arrow of time",,,meaning the evolution of time.

    "It moves in a direction constantly and at different rates."

    Time moves according to the observer, not at arbitrarily different rates. My local time ALWAYS moves at the same pace....so does yours; but as you observe my time, it varies according to your relative speed. and vice versa.

    Likewise, in a high gravitational potential, my time still passes the same for me (locally) but you will observe my passage of time from a distant point as slowing relative to yours. I see yours as faster than mine...it's relative as is velocity according to relativity.
    Last edited: Jul 20, 2010
  10. Jul 20, 2010 #9
    Einstein was a genius, but he never said time was an illusion, at least not in the idea you're meaning. Time is real, it's just as real as space. You cannot even describe motion without using both space *and* time. Einstein even made up a new word, space-time, a combination of the 3 dimensions of space and 1 dimension of time, to describe how the universe works.

    This is due to motion and the phenomena that light always travels at c, no matter how fast you are travelling relative to another observer. So that is correct. Light always travels at c, no matter how fast you try to catch up to it, you can't.

    Entropy though, mathematically, suggests that it can move in reverse. Ice cubes can melt in room temperature, and they can also solidify in room temperature, if you only discuss mathematics of Entropy. That is not how it works in reality. Ice cubes do not solidify in room temperature, but they instead melt. It's probable that they could solidify, but the probability of them doing that is practically impossible. So Entropy has this tendency to make ice cubes melt in room temperature, but does not have the tendency to make them solidify in room temperature. It goes against thermodynamics.

    It's speculative that Entropy is the answer to the forward motion of time simply because the forward motion of time cannot be described mathematically. You can always reverse mathematics. There also stands the chance that Entropy could have worked in reverse at some point in the past (or at some point in the future), so this is why it is also speculative.
  11. Jul 20, 2010 #10
    I think you could describe the universe without time. It would just be very tedious as you would need to account for the motion of all objects instead of comparing everything to one objects motion (what we refer to as time).
  12. Jul 20, 2010 #11
    There is a quote somewhere out there of a eulogy Einstein gave for one of his best friends where he said, "time is an illusion; that we who know, know that there is no difference between the past, the present, and the future."

    Now, was Einstein being literal or just saying that his friend will live on forever?

    I've given thought to the question of what "drives" time, and Entropy is indeed a good answer; however, what happens during a true isentropic process? Maybe, at the core of it, time is really just the rate at which information is exchanged. If absolutely zero information is exchanged, how could anyone or anything, regardless of their frame of reference, argue that time has progressed forward? The fact that there is a fundamental limit of how fast information can be exchanged also explains how different observers can divide time up differently.
  13. Jul 20, 2010 #12
    Describing the universe without time would appear to be a snapshot. There would be no movement.
  14. Jul 20, 2010 #13
    Space-time can be thought of, in Einstein's eyes, as a gigantic frozen block of ice. All movement, ever, is inside this block of ice. Does the block of ice exist? Is it completely deterministic?

    And you're right. If there is no information being exchanged or "moving", then there is no time. Try observing a situation like this.
  15. Jul 20, 2010 #14
    Funny how we all have the sense of time. Yet the only thing in the universe that is constant (light) experiences no time.
  16. Jul 20, 2010 #15
    The universe may be deterministic, meaning that the future state of a system is determined by its present or past conditions, but that does not mean the future is predictable. Consider how difficult a system with only 3 bodies is to solve.

    The quote is:

    Interesting point 6Stang7. In an isentropic reaction there is change without an increase or decrease in entropy. My response would be that the entropy of the processes in our brains cause us to perceive the procession of time as moving forward. This has the effect of us describing our observations of the natural world in terms of those perceptions.

    I would argue that for something without consciousness there is no direction for time. There are no perceptions at all.

    If it is possible to describe the universe without time (for more than just a "snapshot"), I'm curious as to how. The only way I can think of would be to know the entirety of the universe from "beginning" to "end" and to describe paths rather than objects. This would require more knowledge than it is foreseeable that we will ever be able to attain.

    And one nit-picky thing: Light does not always move at c. It is quite capable of moving more slowly than this.
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