What proof do we have that TIME exists?

  1. When we "measure" time, we are obeserving movement, really. Or aren't we? Is there a physics theory where time existence is questionned? why do we need time? & what would be the alternative? What woudl be a universe without time?
     
  2. jcsd
  3. If you and a friend agree to move your bodies to the same place, meet each other, and then move your bodies back to your respective homes is it enough to agree on the place of the meeting?
     
  4. Time is the measure of existence as viewed by an observer.
     
  5. 'Time' is the name for an observed property of the universe. 'Time' wasn't proposed as a theory that could be falsified, its a pure observation---around which extensive theoretical work has been formed.

    Time is a fourth dimension of change/freedom ('movement' as you accurately put it), that behaves fundamentally different from the standard 3D people think of. Why time is different is quite a question in theoretical physics that---to my knowledge---people are only really starting to look at, for instance Sean Carroll at CalTech is very interested in the nature of time.

    All I know is from popular articles which suggest that in some/many string theories time needn't have been so different, or have exhibited the characteristics it does.
     
  6. Chalnoth

    Chalnoth 5,085
    Science Advisor

    Time is a model which has proven very useful in understanding how our universe behaves.
     
  7. Time is what keeps everything from happening at once. And space is what keeps it all from happening to me. - John Wheeler
     
  8. "Time" is not a "thing", like a planet, or dog, or grain of sand, or atom, are "things". "Time", like an "inch", "yard", "meter", "fathom", etc., etc., etc., is a measurement. "Time" is what we call this measurement. (We could have called it anything, and we do in different languages). Like an "inch", "yard", etc., etc., etc., "time" it is a man-made construct rooted in reality devised to measure change, i.e., season to season, day to day, minute to minute, heartbeat to hearbeat, etc., etc., etc.

    The notion of "time" is valid and rooted in reality, e.g., the earth's full revolution around the sun is both observable and predictable; we call this full revolution a "year"-our measurement of how long this takes, a man-made construct firmly rooted in reality. Whether we call it a "year" or not, is irrelevant to these celestial observations. Just like "time", all other valid measurements must be rooted in reality.
     
  9. The Earth is about 5 billion years old, My dog died at 13 years, that grain of sand has a duration, as do all things. Time is a mosaic however I view it, with each four dimensional object adding but its own part to this dilating image I see as my present. :wink:
     
  10. Thanks all for the diverse and superb answers. I am humbled by the level of this forum.
     
  11. throw a drinking glass on the ground. it breaks. that's forward time. it will never self assemble, dive up from the ground and put itself back into your hand.
     
  12. What do you think the probability would be of the glass forming itself without the help of the co-moving frame of consciousness in humans?
     
  13. Chalnoth

    Chalnoth 5,085
    Science Advisor

    Consciousness has zero effect on the behavior of reality (except the obvious bits like building houses, computers, etc.).
     
  14. I'm not convinced you can actually measure time (or space). I suspect we are only able to measure the finite things that exist within spacetime. asking what a universe would be like without time is like asking what a universe would be like without space. it's nonsensical to us (finite beings). time plays a real part, albeit the most elusive one, imo. this is also what makes it the most interesting (imo)
     
    Last edited: Mar 19, 2012
  15. i think we need both space and time to provide reference points. the alternative would be something that we could not really put into words b/c we wouldn't be able to make any sense out of it. unless the alternative (no time) was what we were used to, then we could discuss it. does that make sense :wink:
     
  16. and if you REALLY think about it, time and space might actually BE the same "thing" (for lack of a better word). stick that into your equation!

    actually, has anyone?
     
    Last edited: Mar 19, 2012
  17. Consciousness is required for us to see the behavior of reality, and the co-moving frame of my consciousness is the one second part of time that I am always within, what do you think makes up our present.
     
  18. alt

    alt 322
    Gold Member

    I've always thought that when thinking about what time is, or whether it exists, one has to look at the immediate, first hand experience of it - the present.

    And when trying to work out what the present is, I get even more perplexed. Is it a certain amount of time ? It must be, for if it was a point instant, it would be static, and no movement would be possible.

    But how long IS your experienced present ? A second ? Half that ? Douple that ? One hundredth that ? In any case, it would still have (unless it was a point instant), a component of past, and possibly future in it. Weird !
     
  19. Super weird indeed. Moreover, if time exists, & it passes linearly, it should have an infinite speed, since it passes continuously..Time is weirder than existence itself
     
  20. Chalnoth

    Chalnoth 5,085
    Science Advisor

    Why would you think this?

    And anyway, time "passing" is just a colloquial description that doesn't have any relation to reality, as near as I can tell.
     
  21. I think there is unanimous agreement that as humans, we all experience something which can be called "time" in English, which describes a one-directional increase in entropy of the universe at a constant rate. In this sense it is perfectly reasonable to assume that it exists. The real challenge is trying to abstract beyond the individual's perspective and learn about the nature of time itself.

    We know that time does not actually move at a constant rate, and that an individual will never notice a difference despite the relative rate of time compared to that of those moving more slowly, or in places with less gravity. My own speculative opinion is that time appears to us the way it does because of the makeup of our bodies. All that we feel, say and do is a result of physical and chemical interactions and therefore the same rules of entropy that govern forms of matter in the universe determine our experience of life and "time". If there exists a somewhat biological being in a macro-verse that contains our universe, they may be able to see our universe as a static entity with 4 "spatial" dimensions.
     
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