Why does time require matter ?

  1. phinds

    phinds 9,155
    Gold Member

    I have read in serveral posts here that the concept of time in a total void is meaningless. That is, many scadzillions of years from now, assuming the expansion continues and black holes evaporate, and all goes REALLY dark (yes, I'm talking about a LONG time), the concept is that time loses its meaning because there's no way to measure it.

    This really is perhaps one of those silly semantic arguments that I usually do not care for but this one is bugging me for some reason.

    I GET completely the fact that you can't MEASURE time without matter but the concept that time just stops passing doesn't make sense to me. It is a somewhat pointless distinction, since even if time goes on, nothing HAPPENS. It's just the concept that "time stops" that bothers me and that SEEMS to be what I'm hearing from some of the threads here.

    I'd appreciate any comments anyone has on this? Do you think time doesn't exist if you can't measure it because there's nothing to make clocks out of (and even no subatomic interactions to measure your ticks by) ?

    Thanks,

    Paul

    By the way, I put this in cosmology since I can't think where ELSE to put it ... if a mod wants to move it, fine by me.
     
  2. jcsd
  3. I dunno, I guess I would also be on the side of those who support the non-existence of an entity if absolutely no way to measure of discern it was even possible. I know this isn't really the same thing but it reminds me of the theological arguments that go like "you can't prove or disprove god" etc. since there's no way anyone would be able to give evidence in the first place. Seems more like a philosophical question to me, but who knows? I'm just here to learn like the rest of us, I would love to see some more thoughts on this as well.
     
  4. I've allways thought of Time as a perception rather than a law of physics

    As far as i am aware Physics cannot explain what time is, all we can do is measure the passing of time from one moment to the next, from the swing of a pendulum to the sun rise.

    So when 'nothing' happens anywhere ever again, Time has lost all meaning and their would be no perceivable way to measure the passing of time or indeed nobody to perceive time pass.

    If time is just a perception that is.
     
  5. Mmm, juicy questions!

    Until three days ago I would have said time doesn't exist. Overnight I started thinking of it as a proper dimension and as of earlier today I began considering the existance of an associated particle. These are the sorts of questions and statements I propose to myself:

    - We use 'time' to measure seperation of events, along with distance.
    - If time doesn't exist why don't events happen all at once.
    - Time dilation is, in effect, the slowing of physical action - the ability of any action to continue occuring at the same rate. Time isn't forced to slow down by high gravity, action is and we, as independent observers, say that time has 'slowed'.
    - The seperation of events tells us what time is, or does time tell us what the seperation of events is?

    To directly respond to your question:

    If time is only an observed measure of events with no 'independent' existance, then in the far future, time ceases to have meaning with nothing to be measured occuring. If on the otherhand, space is expanding, then presumably time is, too, in which case there's just noone there to notice.

    It occurs then, that you may have just asked the cosmological equivalent of the 'do falling trees make no sound if noone is there to hear it' question. Good job!
     
  6. good post salvestrom, I'd press Like if the forum had one.
     
  7. I didnt know matter was required for time to pass. I would think if you were sitting in a 99% materless universe, you could still see your watch tick. I would think time still passes, maybe even faster than now because the more massive an object is, the slower time becomes. So, maybe its opposite in that respect.

    But thats just a guess, I really have no idea...
     
  8. Might I suggest that you take a look at this paper from Alan Guth: http://arxiv.org/pdf/hep-th/0702178v1.pdf

    From the paper, "Although the false vacuum is a metastable state, the decay of the false vacuum is an exponential process, very much like the decay of any radioactive or unstable substance. The probability of finding the inflaton field at the top of the plateau in its potential energy diagram, Fig. 2, does not fall sharply to zero, but instead trails off exponentially with time [26]. However, unlike a normal radioactive substance, the false vacuum exponentially expands at the same time that it decays. In fact, in any successful
    inflationary model the rate of exponential expansion is always much faster than the rate of exponential decay. Therefore, even though the false vacuum is decaying, it never disappears, and in fact the total volume of the false vacuum, once inflation starts, continues to grow exponentially with time, ad infinitum."

    I think he is essentially stating that the vacuum expectation value of free space never reaches zero. As such, quantum fluctuations are not only possible but are expected. And if something can fluctuate, even at a quantum level, there must be space-time to fluctuate in. But these are just my musings and I could be way off base...
     
  9. Time is simply the measure of motion of things. If there are no things, then no motion, therefore no time.
     
  10. phinds

    phinds 9,155
    Gold Member

    But you're missing the point. If you and your watch are there, then that's NOT the circumstance about which my question is posed. I'm talking about when NOTHING is there.
     
  11. phinds

    phinds 9,155
    Gold Member

    Uh ... maybe. What makes you so sure? Cite references.
     
  12. phinds

    phinds 9,155
    Gold Member

    Very interesting. Thanks for that.
     
  13. I believe time is a creation of man. Not a basic physical law of nature as is gravity, for instance. First time was used to measure the rotation of earth and defined the duration of its motion as a DAY. Then the lunar calender used the motion of the moon rotating around the earth as a MONTH (lunar of course). Then to measure the rotation of earth around the sun as the Mayans did defining the YEAR. Hours, minutes and seconds are simply sections of DAY. As you posted with a universe without any matter of any kind there cannot be any motion to measure. Also nobody to measure it, therefor no time.
     
  14. DaveC426913

    DaveC426913 16,374
    Gold Member

    Time got along quite happily while dinosaurs walked the Earth. They ate, they slept, bred, died, generations passed....

    Time got along quite happily before life even appeared on Earth. Mountains grew, weather eroded, volcanoes erupted....

    Time got along quite happily before Earth existed. Stars were born, asteroids collided, galaxies coalesced...

    Time got along quite happily before stars existed...
     
    Last edited: Jan 23, 2012
  15. Of course time has existed since motion of things started. The OP suggested a scenario where nothing exists, empty space, no matter. In this case there will be no motion, therefore nothing to measure time with. Therefore no time.
     
  16. phinds

    phinds 9,155
    Gold Member

    As I said in the original post, I recognize your point of view completly, but it leaves me totally unsatisfied. I recognize that the universe does not CARE whether I am satisfied or not, but again, as I stated originally, "no matter" and "time doesn't exist" do not conflate well for me and the fact that they DO conflate well for you doesn't get me anywhere. Still, I thank you for your input.
     
  17. DaveC426913

    DaveC426913 16,374
    Gold Member

    If
    then
    cannot be true.


    If
    then
    cannot be true.

    Your statements are false regardless of whether there's matter or no matter.
     
  18. Minutes, hours and days are indeed the invention of man. Seconds are a very recent one. But these things and their like are not Time. They are only a measure of Time, as the meter is a measure of distance.

    In fact, to suggest time does not exist in this far future, is to unavoidably accept that distance also does not exist, simply because noone is their to traverse it. To say otherwise is to say that spacetime is not valid. That Einstien was wrong. Now, Einstien was not infalable and we all are aware of how he felt about Quantum Mechanics, but if you're going to argue against spacetime, bring friends. Ones with degrees. Not because you're wrong, but because you can't simply nay say one of the cornerstones of modern physics.
     
  19. phinds

    phinds 9,155
    Gold Member

    I like that.

    I was a bit puzzled by your earlier statemenent

    Did you, in that statement, mean that you believe time would be EXPANDING, or just that time would continue to exist (which would be consitent with the statement above) ?
     
  20. Ah. Um. Prolly best I don't explain that. =D
     
  21. Chalnoth

    Chalnoth 5,491
    Science Advisor

    Looks like this has been a pretty active thread, but I'll just chime in in response to this OP.

    This can be made clear, I think, by marking a distinction between the dimension of time and the arrow of time.

    The dimension of time exists regardless. It is there whether or not you have matter around to experience it. But if there is no matter, radiation, or anything else, then there is no direction to the dimension of time. In other words, there is no arrow of time.

    An arrow of time only appears when you have a universe which is increasing in entropy. But an empty universe is just that: empty. It doesn't change in entropy at all, so it doesn't have an arrow of time. And when a new universe is born, its arrow of time could point either way, depending upon its initial conditions.
     
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