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Time speed question

  1. Feb 13, 2004 #1
    here is something i've been thinking about a little. keep in mind i've never even taken a single physics class.

    I read that time travels relatively faster the farther away it is from a massive object like the earth. Something to do with the light waze frequency and the gravity if I remember correctly....

    so, lets say there is a pickup truck traveling a very long distance from A to B, and in the back of the truck is an upright 1000 ft pole. Remembering what i've read, but maybe not completely understanding it, I would assume that after a while of the truck traveling from A to B, an observer on the ground would see the 1000ft pole actually leaning toward point B, since time is going faster up there, the top of the pole would reach B before the bottom did.

    My common sense tells me this is not true.

    also, there is a guy at the bottom of a 5000ft cliff and a guy at the top and they are both holding opposite ends of a 5000ft rope. The guy at the bottom tugs the rope.
    Would the guy at the top feel the tug before he saw the bottom guy tug it?
     
  2. jcsd
  3. Feb 13, 2004 #2

    LURCH

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    chalk one up for common sense (a rare victory in dealing with GR!). Although the top of the pole is travelng through time more quickly than the bottom, it is being propelled by the same truck. So when it arrives at point B, the top of the pole will arrive "simultaneously" with the bottom (as seen by an outside observer). But, if you mount clocks on the two ends of the pole, the one at the top will measure more time ellapsed during the trip. So the top of the pole will experience the passage of time to be faster by a very small amount. But to make up for this, it will experience the passing of the road (horizontal movement) as being slower by exactly that same amount. So, if the difference between gravitational potebntials at the two ends is great enough, an observer sitting in the truck would say that the truck was travelling 60kph, and that the clock on top of the pole is running fast. But an observer sitting at the top of the pole will say that he (and the truck) was travelling 50kph, and the dashboard clock in the truck is running slow.

    No, because the "tug" must travel that distance, too. And since it cannot travel faster than light, it cannot arrive before the appearence of the act that initiated it.
     
  4. Feb 13, 2004 #3
    what about a telephone pole thats been standing in the ground for many years. would the top of the pole decay faster than the bottom(exculding any other influences)? since the earth is always rotating, doesnt the top of the pole travel farther in direction of the rotation before the bottom does, but due to the infinate number of "time dilation layers"(my own term) cancelling each others differences out in a perfectly infinate way from an observers point of view at any single layer? My thoughts conclude that the present, past, and future all exist simultaniously, but not at the same "time" or in one single event of "time". An infinate number of futures being created by the relative time difference between the "layers". And the "future layers" dont exist in an observers present untill the time of the "future event" has infinately sincronized itself with the observers present. This would meen that the future of the top of the pole has already been created, but wont manifest itself in any given present untill the futures time has been handed down through the layers of dialation to a point where it seems to an observer at a present to actually be simultaneous.
    The future of the area with weaker gravity is being created and is impossible to see in a present untill that present catched up.
    Past present and future all exist together simultaniously in an exsistance that is organized by the passing of time.
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    Last edited: Feb 13, 2004
  5. Feb 14, 2004 #4

    LURCH

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    Yes, the top of the pole would decay more quickly (by a very tiny amount). The rest of your post I'm still chewing on, gimme a day or two.
     
  6. Feb 16, 2004 #5
    Here's something to think about. Let's say for the guy at the top of the cliff, his watch is ticking off 1.2 seconds for every second that ticks off for the guy at the bottom. So, after 5 seconds have passed for the guy at the bottom, 6 seconds will have passed for the guy at the top. Let's say the guy is tugging the rope at the rate of 1 tug per second. So, after 5 seconds for the guy at the bottom, the guy at the bottom will have tugged 5 times, but the guy at the top will have felt 6 tugs.
     
  7. Feb 16, 2004 #6
    Is that true? (Physics Super-Novice...)

    -Matt
     
  8. Feb 16, 2004 #7
    This is not true. If it were, then (relating to my previous post) I would if fact observe the top of the pole leaning forward relative to the motion of the pole. Like i said earlier, the top's future has arleady been created and is waiting to manifest itself in an arriving present so that it seems simultanious. Likewise,
    oh wait, im on to something here, i'll get back to you on this........
     
  9. Feb 17, 2004 #8
    the TOP of a mountain is traveling towards the direction of the rotation of everything (B) in spacetime much like the BOTTOM of this same mountain is. These two locations on the mountain are at two different worldlines because of the relative time difference between them due to G-time dilation. we look up into the future from the bottom and see the top of the mountain leaning towards (B). the same goes for an observer at the top. he looks (down) into the past, he sees the bottom of the mountain dragging behind. does this make any sense?
     
    Last edited: Feb 21, 2004
  10. Feb 18, 2004 #9

    russ_watters

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    Everything is fine until the last sentence. It doesn't follow from the rest of the post. The guy at the top feels 6 seconds have past, but feels the same 5 tugs. You said in the first sentence, 1.2 seconds for the top guy for every second that passes for the bottom guy. 1.2*5=6. And since 1.2 seconds for the top guy = 1 second for the bottom guy, he feels a tug every 1.2 seconds - for a total of 5.
     
  11. Feb 18, 2004 #10
    Let's say the guy at the top has a defective watch that runs fast and ticks off 6 seconds for every 5 seconds that tick off of the watch of the bottom guy. Time is passing at the same rate for both of them. Then, for the guy at the top, after 6 seconds he will have felt 5 tugs. So, what you have described is a situation where the guy at the top has a defective watch but is not experiencing time dilation.

    If time is passing faster for the guy at the top then not only is his watch going to tick faster but everything else will keep in synch.
     
    Last edited: Feb 18, 2004
  12. Feb 21, 2004 #11
    the TOP of a mountain is traveling towards the direction of the rotation of the earth (B) in spacetime much like the BOTTOM of this same mountain is. These two locations on the mountain are at two different worldlines because of the relative time difference between them due to G-time dilation. we look up into the future from the bottom and see the top of the mountain leaning towards (B). the same goes for an observer at the top. he looks (down) into the past, he sees the bottom of the mountain dragging behind. does this make any sense?
     
  13. Feb 21, 2004 #12
    Where ever you look, you are looking into the “past”, since it takes time for the light to reach your eyes.

    Regarding the mountain, an atomic clock speeds up such a slight amount on top of a mountain, this can’t really be considered as a “time” speed up, in terms of nearly all human experiences. In fact, if you cool chemicals on top of a mountain, the chemical reactions will take place at a slower rate, as an atomic clock “ticks” more rapidly on top of a mountain. In fact, biological functions on top of a mountain will generally be slower, not faster, because of the lower temperature. This is thermodynamic time.
     
  14. Feb 21, 2004 #13
    If there were only 5 tugs, the guy at the top will feel only 5 tugs, whether he is wearing a watch or looking at a clock or not.

    All the guys have to do is look at the sun, and they’ve got the same “clock” that moves or “ticks” at exactly the same rate for both of them, no matter what watches or atomic clocks do at the top of or the base of the mountain.
     
  15. Mar 2, 2004 #14
    So then is this tug scenario true or false?

    -Matt
     
  16. Mar 2, 2004 #15
    although interesting to think about, My opinion is that it is false. If 2 guys were at the top, and they punched each other once every 1.2 of the bottom guys seconds, then the guy at the bottom with binoculars would see 5 punches after 6 of his seconds.
    In this case, the light takes .2 seconds to travel from the top to the bottom. The light info from the punches takes .2 seconds to reach the bottom guy.

    The action of the rope tugging can travel only as fast as the speed of light and the action doesnt go that fast. The guy at the top OR the bottom would see the action of the tugging through binoculars BEFORE they would feel it. They would NOT FEEL the tugging before they saw it happen, otherwise the action would be traveling faster than the speed of light. BTW, I think that the action of the tugging travels through the rope at the speed of sound and the elasticity of the rope would damper the action's travel time verses distance traveled.
     
  17. Mar 2, 2004 #16
    That makes sense...

    -Matt
     
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