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Does G.Relativity Violate Energy Basics?

  1. Aug 1, 2004 #1
    I have two identical clocks. They have batterys carrying exact amounts of energy units. They have identical powerful lasers. They have identical gutters. And a spherical peice of matter. All clocks are measurment tools. The laser shines on the sphere. The sphere moves down the gutter (but takes a very, very logn time) Energy expended equals the amount of displacement the sphere moves down the gutter.

    Just to Clearify: The spheres in each clock displace exactly the same amount of distance per energy from battery.

    I put one clock in a spaceship that will travel the speed of light for say thirty years. The clocks are only 'on' in inertia reference. The spaceship arrives after 30 Earth years, during which it was traveling at c.

    Did each clock expend the same amount of energy after the trip? Did the laws of physics behave the same in each inertial reference? If one clock is slower or faster, what dictated physics to operate at another rate in one clocks frame of reference?
     
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  3. Aug 1, 2004 #2

    russ_watters

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    No. They expended energy at the same rate, but for differnet amounts of time.
    Yes.
    Nothing. Its a common misinterpretation that speed makes clocks slow down. It doesn't. Speed makes time slow down. Big, big difference.
     
  4. Aug 1, 2004 #3
    I wonder what you mean by the speed of light. In relativity, everything moves at the speed of light. Therefore, both clocks move at the speed of light the entire time.

    Or, perhaps you have a Newtonian concept of the speed of light. In this case, you are suggesting that the spaceship will move through space as fast as light moves through space. This is not possible.
     
  5. Aug 2, 2004 #4

    Gza

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    I was just curious, how does one describe a behavior of time in terms of a quantity that requires time itself to describe ( slowing down is a rate of change in time, yet you are describing this happening to time itself.) I'm not asking this to be a smart-aleck, i'm just wondering what it truly is that is "slowing down."
     
  6. Aug 2, 2004 #5
    An amount of time, hmmm. This is a number, which is a symbolic quantity that represents the distance mass moved compared to a standard constant of mass displacement. Here is a possible example, one meter per second is an object that moves a constant velocity exactly over one meter, but only moves the distance of that meter while another object moves over a specific distance at a constant rate. The object moving exactly a meter compared to a simultaneous expression of the constant second is one meter per second. mass(displacement) per mass(displacement), per indicating a simultaneous property

    I see time in general as a mere symbolic expression of mass being displaced quantifyingly compared to another mass displaced and when one mass displacement is compared to a agreed upon constant, it gives us an object's time in symbol expression of speed, acceleration, etc. What do you mean when you represent time, would you express that?

    If I use my known defintion I understand that mass and the position of the mass that makes up the clock and the laws that govern action and reaction determine the expression time. So, the mass will behave the same in both clock frames and give identical expressions of time.

    I've been given the teaching that speed is a property of mass. With my current defintion, it is difficult to understand how speed is a thing that slows something down, when I see it as only a expression that represents the quantity of a constant displacement of a mass.

    Please tell me you definitions, maybe I can get closer to the understanding what you mean.
     
  7. Aug 2, 2004 #6

    Chronos

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    If you rode with the clock in the space ship [just dont go c, or bad things will happen], nothing would appear unusual. The clock would run just like always and the battery would discharge at the same rate as always. Once you landed again, you would be in for quite the shock. Your assistant who stayed behind would be long dead and the other clock would be in a museum.
     
  8. Aug 2, 2004 #7
    In that case (hoping that´s what russ_watters actually meant) one should clearify:
    time = eigentime = time measured by the respective clocks.
    slow down = increase less in respect to coordinate time.

    Note that eigentime usually does not equal coordinate time. In this case, the most sensible choice of coordinates -the one that makes g=diag(1,-1,-1,-1)- would make change in eigentime=change in coordinate time for resting observers and change in eigentime<change in coordinate time for moving ones. One could call that a slow down for moving observers.

    btw: I didn´t really get the "big, big difference". If a clock is a device that shows the (eigen-)time why are the two terms not completely interchangeable?
     
    Last edited: Aug 2, 2004
  9. Aug 2, 2004 #8

    jcsd

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    [itex]\frac{dt}{d\tau}[/itex] perhaps? Well, it's the only I ca think of.
     
    Last edited: Aug 2, 2004
  10. Aug 2, 2004 #9

    russ_watters

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    Most of the post was meaninglss gibberish, but this appears to say that clocks should read the same time in any reference frame. If that's what you mean, its wrong. It contradicts direct observations.
    Time is a dimension, the measurement of which is done by observing periodic physical phenomena. Make a device that counts the occurences of the phenomena and you have a clock.
    That's a meaningless statement. Its like saying golf is a property of rock.
    There are some regular crackpots here who have argued that Relativity's time dilation is a clock rate effect and not a change in the rate of the passage of time. The usual argument is that a pendulum clock changes its rate depending on gravity just like atomic clocks (except by different amounts).
    By "slowing down" I'm talking about the rate of the passage of time - not a spatial speed as in distance over time.
     
  11. Aug 3, 2004 #10
    If they expended the same amount of energy, then the clocks will read the same time. Why, because I have designed it so if the same energy is expent they will read the same time. Energy expediture in this example is the expression of time.

    Simple negation is not valid support for your claim that my claim contradicts direct observations. What are the reasons that physical expression of time, which is time based upon how matter reacts to matter, how light and matter interact and general energy usuage based on physical constants, would not be identical in each frame after the 30 year period?

    My reasons are clear. Based upon the property of interchange constancy in N III L (equal and opposite reaction), the laws of physics behave the same and create the same amount of displacement for the sphere per amount of energy used from the battery.

    Why should physics act different in one situation, which is required if physical time is expressed different after the 30 year duration?
     
  12. Aug 3, 2004 #11

    Chronos

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    It all works out perfectly, so long as you don't juxtapose reference frames. Each clock and battery is entirely well behaved within its own reference frames. Just ask any cosmic ray particle that consists of a radioactive nuclei. They travel many times their half life yet look like they are fresh out of the oven.
     
  13. Aug 4, 2004 #12
    Since they operate the same in both frames, then humans would age the same. Why do I hear people say that a human will come back younger? If they really would come back younger, how is this explained?
     
  14. Aug 4, 2004 #13

    Tom Mattson

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    It is explained by recognizing that the Galilean view of time is wrong. Specifically, time is not an absolute. If the spaceship changes its state of motion with respect to the Earth, then the worldline of the Earth is a path of greater proper time than that of the spaceship. So if you ask, How much energy did each clock expend?", I have to ask, "When, and in which frame?".

    Do you mean after 30 years on Earth? Or after 30 years on the spaceship?

    This is a direct consequence of there being an ultimate speed limit in the universe. In order for that to be the case, then spatiotemporal intervals between events cannot be absolute.
     
  15. Aug 4, 2004 #14

    russ_watters

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    Who said they expended the same amount of energy? Not I and not Chronos. I said they expended energy at the same rate.
    Fine - two identical, well built clocks should always expend energy at the same rate. That's obvious. I was quite explicit in agreeing with you on this point. The key issue that you are missing is the two clocks do not expend that energy for the same amount of time.
    Fair enough, I'll amend my claim: you have not shown that your claim is consistent with observation. Time for you and your lab to spend some quality time together...
    Because the 30 year period isn't 30 years to both clocks. That fact has been confirmed (is constantly being confirmed by GPS clocks) experimentally.
    Heh: phsyics acts the same in each situation, which requires physical time to be different after the 30 year (from the stationary frame) duration.

    The part before the coma is the 1st postulate of relativity (every version, even Galileo's), and the part after the coma is the implication of that postulate (from Einstein) and the experimental fact that the speed of light is constant. All of this is backed-up by direct observation.
    You're not listening. Chronos said within its own reference frame. As long as you stay with a clock, you will never see any difference regardless of how you and the clock are moving. Consistency between frames isn't now, nor ever has been a requisite of the laws of physics. If it were, every object would have one speed (for exmple). Clearly, the speed of an object depends upon which frame you measure it from.
     
    Last edited: Aug 4, 2004
  16. Aug 5, 2004 #15
    The clocks expend the energy at the same rate.

    Now how does mere difference of speed between two clocks develop a circumstance where less energy is used for one clock?

    It is said to be confirmed by GPS clocks, but confirmation is different than explanation. I can believe it is confirmed, but not believe what the accurate confirmation of the fact implies. It seems to contradict what I think I know, so bear with me.

    A property of interia of each clock tells me each clock has no sense of the other clock's existence (or speed). The circumstance of relative speed of inertia frames imparts no interacting force. To know another clock exists or more imporatantly it's relative speed, some interacting medium of force seems necessary to translate this between them.

    Perhaps one clock's collective matter were to somehow ever so slightly expand in direct proportion to displacement from another clock. Then energy use would be less within it, by mere position of the matter while the rate of energy use would be the same. But in this example, the only expansion between matter is distance between the two clocks. This is an expanse where no energy transfer occurs, therefore there are no forces to act upon interia frames of the clocks.

    Are you guys implying some energy field which relativistically imparts forces upon the clocks based upon an expanding distance between them? If not, then how does mere constant displacement make the difference?
     
  17. Aug 5, 2004 #16
    @Omin:

    Why do you need a "laser shines on sphere that moves down a gutter (whatever that is)"-clock (at least you didn´t let it orbit a black hole in a way that the angluar wavelength equals 42 times the diameter of a tachyon) for such thought experiments? Too scientific to use a Swatch? What else does your clock do except simply measuring the time passed for the observer?

    I´ll assume your laser-powered clocks simply measure time as my alarm clock does. I´ll even assume they do that in a much better way so people using them won´t come late to work every once in a year because battery depleted:
    In that case it´s a bit sad that after putting so much effort into designing the new generation's alarmers (what color is the laser?) you reduced the actually important information down to three sentences:

    >> I put one clock in a spaceship that will travel the speed of light for say thirty years.
    The "bad boy, you cant travel at speed of light ... blah ... infinite energy ... blah ... blah ... forbidden ..."-thing has already been mentioned so I think we can both agree to travel "close to the speed of light". Next to this the more important question is: Will travel close to the speed of light in which coordinate system? Same goes for the 30 years of time your ship is traveling: Measured in with which coordinate system's time-coordinate?
    I hope you understand that/why the question for the coordinate system is so important. Let´s see what your next sentence brings:

    >> The clocks are only 'on' in inertia reference.
    Strictly speaking that´s comletely wrong. If -the inability to describe the whole spacetime with a single coordinate system appearing in GR let aside- an event like "clock is on at certain points" happens in one coordinate system then it happens in all coordinate systems. That´s one reason why closing your eyes won´t help you when you loose control over your car.

    >> The spaceship arrives after 30 Earth years, during which it was traveling at c.
    Nice. What alien species are you going to sell your clock design to? Or in other words: Where does your spaceship arrive? What happened to your 2nd clock, btw? Does the spaceship arrive at clock 2? Did it start there? If "yes" to last two: How did it manage that? Simply flying in a circle or going zig-zag or by more exotic manners like wormholes or taking advantage of the universe -according to super-quantum-brane-graviton-field-theory- being dog-shaped in 92th dimension?

    The main problem with your question (and with almost all other "question about special relativity"-threads) is that you put much useless thoughts in measurement-devices (your´s was still humane, you didn´t even torture uncertainty) but lacked to give the important informations nessecary to answer your question.

    Russ' 1st answer "they expended energy at the same rate but for different ammounts of time" is not a definite answer because your question lacks information to be answered. It´s entirely possible both clocks show the same time after your ominous "30 years" but that entirely depends on where and how both clocks moved in that "time" nad in case they don´t end up in the same point afterwards even on the coordinate system. Russ' answer is simply the standard answer that fit´s to most "I put a clock in a rocket" setups.

    Don´t take this post as an offense. It´s merely meant as a help to you to show where your question needs further thoughts from your side. Also, I´m in a silly mood right now, so don´t mistake it for arrogance (well, I AM arrogant; but not towards people asking questions).
     
    Last edited: Aug 5, 2004
  18. Aug 5, 2004 #17
    Why does it matter where? Why does it matter how? The spaceship will be expending this energy, not the clock in the spaceship. I'm only concerned with two identical clocks and there relative speed through a non-resistive medium of space. Who cares if you razzle dazzle them around like a magician while they tick, put them up your sleeve why don't ya, or wherever, as long as you don't affect there identicalness of how they use energy. Perhaps a huge hand will reach out from the clock on Earth and slow down the clock on the ship differently because it is in one of your "wheres" or it's doing one of your little "hows" through space. Could it be the ghost of Einstien?

    When you say a coordinate systems matter, do you mean fields of force are affecting the circumstance of clocks?

    If a field of force exists, then matter reaching c relative to the field would makes some sense to have hesitation about, but without a field, I'm looking at Newtonian inertia at any speed possible through a non-aether, non-resistive nothingness. Without a field, I don't get the time travel idea. If there is a field, I'll consider that only when it's made fundamental to the explanation of time travel, and then I'll compensate by creating a field identical to the Earth clock inside the spaceship. So far, nobody's said, this-field or that-field theory is necessary to understand why these clocks exapanding distance will create relativisitic proportionate effects upon each other. That I remember. :biggrin:
     
  19. Aug 5, 2004 #18

    russ_watters

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    Simple. The rate of the passage of time differs for the two clocks.
    Relativity is counterintuitive when you first learn it. Everyone has this problem. But you must decide if you wish to hold on to preconceived notions of how the universe should work or accept experimental fact at face value.
    Correct.
    Correct, with the caveat that if the clocks ever come together, one (or both) must accelerate.
    Why? All you have to do is look at it to know it exists and fire a laser at it to know its relative speed.
    Why are you looking for an explanation for a slower rate of energy usage? We are in agreement that identical clocks run at exactly the same rate in their respective frames and thus expend energy at the same rate in their own frames. You are looking for a descrepancy that doesn't exist.
    No. There are no forces involved here (until there is an acceleration) and distance is irrelevant (gps clocks orbit, for example so distance goes up and down, yet the rate difference is constant). Speed itself is what affects the rate of the passage of time.
    Maybe that's part of the problem: what makes you think there is a "medium of space"? Even if it does, it has yet to be detected and as such has no effect whatsoever on our current understanding of physics.
    That's correct: these clocks have no effect on each other. I'm not sure why you think they might or should.
     
  20. Aug 5, 2004 #19

    russ_watters

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    I realize that, but I'm trying not to overcomplicate things (as I'm sure you realize). GPS clocks, for example, don't run slower than their earthbound counterparts as SR would predict - because you also have to take into account GR.
     
  21. Aug 6, 2004 #20
    Ok, I´ll give it a last try. But pls specify the points I critizised, then. It´ll make things easier for all if one can debate using actual formulas and numbers (except you only want attention, of course).

    Because the time measured by an observer is the length of it´s path through spacetime (measured in an indefinite hyperbolic metric, but that´s not the point). So the time the clocks measure is directly dependent on their way through spacetime. And to specify a path you usually need a coordinate system. End of story.

    No, see above :rolleyes: .
     
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