Question about linearity from a non-mathematician

Discussion in 'Physics & Math' started by GeoffP, Jun 29, 2010.

  1. James R Just this guy, you know? Staff Member

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    noodler:

    I can't teach you general relativity here, noodler. You'll have to take a course for that, or read a book.

    You used the term. I thought you'd know what it meant. My mistake.

    Maybe electrons have more mass than what? Or, are you claiming that electron masses change at different altitudes? If so, what's your theoretical reason for that?

    How would a viscous coefficient affect time at different altitudes? Please explain.

    Do you have any experimental references to time slowing down and speeding up as something approaches and departs from a gravitational centre of mass? Please provide links.

    I don't see any reference to time in that notation. I don't see how it can be used to calculate anything. Please explain how I would calculate the difference in time at two heights using your notation. Thanks.

    Please provide a diagram of your interferometer setup and explain how to calculate the phase difference from that. Thanks.

    I asked you specifically about your claim that time relates to a phase difference. Why didn't you answer my question?

    So you don't really know why you think that. Ok. That clears that up.

    Now, can you answer my other questions above?
     
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  3. noodler Banned Banned

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    JamesR: you don't seem to have got this at all. I have answered your questions, at least as well as you did, about why or if it matters that measurement is possible, in relativity.

    Although, you seem to have missed the obvious connection there, between measurement, which I do mention, and time. I already stated that these are the same thing, they are indistinguishable, remember? Or do you know of a way to determine time that isn't a measurement? Please elaborate, if so.
     
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  5. James R Just this guy, you know? Staff Member

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    Time and measurement aren't the same thing; that's a silly statement. You can measure all kinds of things other than time.

    And asking "How do you determine time without measuring it?" is an equally inane question. If you want to know the time, you look at your watch or whatever - obviously.

    Previously, I asked you whether you'd ever considered the difference between a bad clock and a good clock. You had no answer.

    I think I've wasted enough time on you. You seem good at throwing around jargon, but there's no depth to anything you say. I think you know a few buzzwords and that's about it.
     
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  7. James R Just this guy, you know? Staff Member

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    Where are the answers to these questions

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    * Or, are you claiming that electron masses change at different altitudes? If so, what's your theoretical reason for that?

    * How would a viscous coefficient affect time at different altitudes? Please explain.

    * Do you have any experimental references to time slowing down and speeding up as something approaches and departs from a gravitational centre of mass? Please provide links.

    * Please explain how I would calculate the difference in time at two heights using your notation. Thanks.

    * Please provide a diagram of your interferometer setup and explain how to calculate the phase difference from that. Thanks.
     
  8. noodler Banned Banned

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    JamesR: please explain why you want me to explain interferometry, to you I presume. Why is the speed of light assumed to be constant in any isotropic medium?
    Why don't you seem to know what Dirac notation is? It doesn't need to describe a complex number, or anything.

    You asked me to explain what I mean by time being a phase-difference, that is measured. I have explained it, and written a general state vector for something that would qualify as such a thing. Suppose a and b are the paths for a beam of cohererent light, after meeting a half-silvered mirror, that reflects 1/2 of the photons on average, and transmits the remaining 1/2.

    I can't be arsed with this. I'll let you decide how to decide what time is if, as you claim, it doesn't matter about measurement being possible.

    Oh, about all those other things you say you can measure, is time a part of the measurement process, or do these things somehow communicate without it, that is: 'timelessly'?

    No, you didn't ask me this. But I would have answered: you tell by how accurately it measures time. You use a timebase (atomic time, which is kept at its natural frequency 'artificially') to compare it. Again, compare/measure, are the same thing.
     
    Last edited: Jul 2, 2010
  9. noodler Banned Banned

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    751
    The answer might be 42:

    Q1: Why do atomic clocks run more slowly on the earth's surface, than they do above it?

    A1: According to general relativity, massive objects like planets curve spacetime around them. The particular geometry can be modelled, to a first approximation, by the Schwarzschild metric. Being stationary in a gravitational field means that the observer is in a non-inertial reference frame.

    When we say "higher clocks run more slowly", we must be careful. This is a relative thing. We're comparing the rates of two clocks at different heights. There is no absolute measure of the rate at which time runs.

    So, what's really happening here is that we're comparing clocks in two different reference frames, both of which are non-inertial. Just as relative motion in special relativity affects the relative rates of clocks, so does the difference in reference frames near the Earth.
    ...

    (Q1a: but how does this curvature, and relative motion, explain the slowing down, of atomic clocks?? what is the mechanism that slows time?)

    Q2:
    Do you have any experimental references to time slowing down and speeding up as something approaches and departs from a gravitational centre of mass? Please provide links.

    A2: Do you have any references to time remaining constant for a clock which approaches and then departs from a gravitational centre of mass (that is, the clock is lowered into, then raised from, a field potential)? Please provide links.

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  10. James R Just this guy, you know? Staff Member

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    noodler:

    You threw around comments on phase differences and stuff. I don't actually think you know anything about interferometers, other than the name.

    Because experimental tests support that conclusion. Why else?

    I know what Dirac notation is. You said that a state vector was a phase, or something, which suggests strongly to me that you don't know what Dirac notation is.

    You gave no expression for a phase difference. You have explained nothing. I don't think you're capable.

    Fine. Then we won't see you making uninformed comments on such topics in future. If you are going to comment on stuff, I suggest that you start by being "arsed" in future, ok? Like, try finding out about what you're talking about before you open your mouth.

    I'll give you an example. I can jump on my bathroom scale and it will tell me my weight. All I have to do is stand there, doing nothing. I don't need a clock for that.

    Looking at a clock in the "wrong" reference frame. Like I said. Read the paragraph I've quoted here from my previous post. If you don't understand, you can ask questions.

    I also asked you what your alternate explanation is. Can you answer that?

    You failed to answer the question. I asked first. You answer mine, then I'll answer yours. That's how these things work, noodler. Quid pro quo. It's the art of polite conversation and debate. Do I have to teach you that, too?
     
  11. noodler Banned Banned

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    Ok, smart guy. Sorry, I'm not happy with your repsonses (or your dismissive attitude, so here

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    1. The speed of light, and presumably the time it takes to measure its speed, remain constant "Because experimental tests support that conclusion. Why else?"

    Which seriously suggests that time is linear, with regard to measuring the speed of light, because you always get the same 'straight' answer.

    2. your example of not requiring time to measure your weight, requires time after all:
    Ok, you don't need to know how long it takes for the scales to settle and "show" your weight. But you do need to wait for this to "happen", and, you can't jump on or off these scales in zero time.

    Then you suggest that this:
    explains why time appears to slow down. It doesn't. I don't understand it.

    Please explain the mechanism that is responsible for atomic clocks running more slowly at the earth's surface, than they do above it. How is "looking at a clock in the wrong reference frame" an answer??
     
  12. James R Just this guy, you know? Staff Member

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    noodler:

    I have no idea what you mean by this. Want to try again?

    When you ask somebody their weight, do you also ask them what time of day they measured it, how long they were on the scales for, etc.? I don't think you do.

    You've contradicted yourself here. If you don't understand it, then you're in no position to make pronouncements on whether it does or does not explain it. Agree?

    So which is it? You don't understand it, or you think you do understand it and you think it doesn't explain time dilation?

    Ok. Let's start at the start.

    Have you studied special relativity formally, or at least informally?
    Have you studied general relativity formally, or at least informally?
    Do you understand special relativistic time dilation?

    After you've answered those questions, we'll move on.
     
  13. noodler Banned Banned

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    Why do you "need" to ask more questions?

    ... time is linear, with regard to measuring the speed of light, because you always get the same 'straight' answer.

    When you measure the speed of light, do you get different results depending on the time you measure it? Does the time it takes to do the calculation have any effect?

    Please explain why time slows down for an atomic clock, when it is closer to the earth's surface, and speeds up when it is far away from the surface. Why does the explanation "require" that whoever reads it has studied Einstein?

    Do you realise that the close/far away clock scenario is the same as a coordinate system that approaches then leaves a center of mass?

    oops, one more:
    Not usually. You don't record the time it took either but you assume there was some.
     
    Last edited: Jul 3, 2010
  14. James R Just this guy, you know? Staff Member

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    The term "linear" is derived from the word "line". Where's the line you're talking about when you talk about the constancy of the speed of light? Are you referring to a "time line"? What would a non-linear time look like?

    No and no.

    Because the best explanation for time dilation is Einstein's theory of relativity.

    Or are you asking me to explain Einstein's theory in a hand-waving way without the maths, so that you can start getting a grip on it? I notice that you avoided my questions about your training in the theory.

    No. I'm not clear how it is the same. Please explain.
     
  15. noodler Banned Banned

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    This thread is a good example of how off-the-wall this site is.

    But, at least something has been agreed about (the process of) measurement; that time is a measurement should be obvious. That everything else that can possibly be measured involves the measurement of time, should be obvious too.

    Even if you don't record the time that another measurement (temperature, say) is taken, or the time it takes to measure it, both things really do exist, if the measurement exists.

    Time on a clock corresponds to the angular difference between the hands (another name for this difference is a phase angle).


    Lowering or raising a clock against a gravitational potential is the same as moving towards or away from a centre of mass.


    But let's dispute all the above, just to keep going. Maybe those cleaners aren't coming after all.
     
  16. QuarkHead Remedial Math Student Valued Senior Member

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    No such agreement has been reached, as far as I can see. And even it had, I would not agree; time can be measured, for sure, let's say by clocks (whatever these might be), but there are measurements that require NO clocks, so your assertion seems to be false.
    Well, it's not obvious to me, or to JamesR, seemingly. If I were to state that I am 190 cm tall, because I measured myself yesterday, Why (assuming I have reached adult-hood - always in doubt!), should not be true independent of time?

    "Angular difference"? Don't you just mean angle? Or is there some trig class I missed? Anyway, the last time I looked at my analogue watch, the angle between the hands at 12:05 was identical to their angle at 1:10, likewise at 2:15 etc
    Oh no it's not. In fact have you any clue what is meant by "phase angle"? I tremble to ask, but maybe you could explain how YOU use this phrase.

    noodler you really are priceless.

    Look, over the years, I have made more than one wrong assertion here, for which I was mildly embarrassed, but not terminally so - we all make mistakes. The trick is to take on board other's corrections, apologize for one's folly if need be, and move on.

    I believe it goes by the name of "intellectual honesty". Try it, it cleanses the soul.....
     
  17. noodler Banned Banned

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    That may be true, but there aren't any measurements I know about that require no time...
    In all intellectual honesty, I can't equate time with a clock. This is because time isn't a clock. A clock is something that 'measures'. Is it possible to use, say, a weighing balance and some known weights, as a clock? Could you mark the passage of time by weighing yourself?

    Can you list examples of measurement that don't require ANY TIME (that's zero seconds) to determine?
    But the phase-difference isn't the angle between the hands, it's the distance between one hand and the other. At 12:05 the two hands are pointing in different directions than at 1:10. "The hands" have an angular difference, and the time corresponds to this difference. You also have to take note of the positions or directions the hands are pointing (I thought that was obvious). In other words, for a clock with hands, time corresponds to the angle between the two hands and the difference between their 'absolute' positions, or directions they point in.

    Note: if the clock face isn't marked, and the clock face is also rotating, you will only have the phase-difference and no points of reference.

    Another note: the angle between the hands, at the different 'absolute' locations: 12:05, 1:10, and 2:15 is identical.

    The question is then: is the interval of time identical? If so, then identical intervals of time correspond to identical angular differences on the clock face. Because the face is oriented in space (normally 12:00 corresponds to the direction "straight up"), the positions of the hands are also oriented.

    Therefore identical intervals of time, swept out by the two hands, are oriented by the external markings (you only need one external mark, in fact. In fact a wristwatch is oriented by the straps on it; it makes no difference in that case if the wearer has it oriented "upside down", does it?). Nope, don't think so...
     
    Last edited: Jul 4, 2010
  18. James R Just this guy, you know? Staff Member

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    It's a good example of how you duck and weave and avoid questions when you're pushed a little. You know a few buzzwords, like I said, but you have no real knowledge of physics as far as I can tell.

    Profound. Raising or lowering against a potential, eh?
     
  19. noodler Banned Banned

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    Hmm. Perhaps using the word "against" is a good indication of how little physics I know. Possibly, you being the expert, can suggest a better terminology for motion in a gravitational potential. Since, as far as I can figure, if you want to get away from the earth's surface, you have to move against a downward force of acceleration.

    And I notice you haven't yet managed to suggest anything at all about the mechanism that "makes" a clock slow down, or speed up at different distances from the earth's surface. Apart from a vague suggestion that it has something to do with Einstein's theories. What does it have to do with them? Why, as you suggest, does your answer require whoever reads it, to have studied Einsteins' theories for a few years? That has to be the lamest excuse I've seen for quite a while.

    But by all means, keep up the good work patting yourself on the back despite a clear lack of explanations, won't you?

    BTW, your and Quarkhead's totally lame objection to "needing a clock" to measure anything falls a little flat, when you go back and notice I actually said you need time to measure anything. Time isn't a clock, Ok? Did that detail escape your superior notice? Tsk tsk.

    And you are the one ducking questions. You've done this by asking other (more or less irrelevant) questions, in order to divert from your obvious lack of an answer to the question I have repeatedly asked. Why can't you just admit you have no idea why gravity affects time, or if you do have an idea, you can't explain it to anyone?

    Please note: I have zero concerns about your estimation of my knowledge, of anything at all. One of the things I'm sure about is that you do a lot of talking, little of which makes any impression. How's that for a potshot, dude?

    I haven't contradicted myself. I don't understand why you think it answers the question. It doesn't answer it, it's much too vague.
    That's what I don't understand, you see, I don't understand why you think it's an answer.
    Get it?
     
    Last edited: Jul 5, 2010
  20. James R Just this guy, you know? Staff Member

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    noodler:

    Do you think force is the same as potential? If not, what do you think the difference is?

    On the contrary, I explained exactly the "mechanism" that makes lower clocks run slower. Granted, I explained it in layman's terms, since that's about the level I think you're equipped to deal with. I also explicitly asked you whether you had more education in relativity, special and/or general, but you avoided that question. Which suggests to me that I assumed right the first time.

    Do you know what an inertial reference frame is? Do you understand why being stationary in a gravitational "potential" is not an inertial frame of reference according to Einstein's general theory? Do you understand that two stationary clocks at different heights are in different non-inertial reference frames? Do you want a deeper explanation with mathematics?

    Please let me know your educational level, and I will endeavour to tailor future responses to suit it.

    By all means, keep up the good work posting meaningless buzzwords. Chances are you'll fool some of the people some of the time, won't you?

    Great. Then we agree.
     
  21. James R Just this guy, you know? Staff Member

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    Lame comeback, and a couple of days late, I'm afraid. You would have been better just letting it rest.
     
  22. noodler Banned Banned

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    Goodbye James. It's been fun trying to get an explanation out of you.

    I'm quite glad I failed. Although your explanation is technically correct I imagine not many people have any real idea what a Schwarzschild metric is. Good job holding on to that oh so privileged information you think you have.

    The explanation for time slowing down might be that particles have more or less energy, as the field varies? Or that because gravity bends space, getting "the time" is harder because there are more field lines to cross, for the particles that are "carrying time information"? Or as I conjectured, because the operator is more entangled with the measurement?

    Or. who really cares why? I know you probably don't and I know it's something that doesn't have me losing sleep. Speaking of which, this thread is starting to make me yawn...
     
  23. James R Just this guy, you know? Staff Member

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    Are you leaving? Ok then.

    You're right. The question is: do you know what a Schwarzschild metric is? Because you throw the buzzwords around as if you know, but then you use the language of physics in ways that nobody actually trained in physics would use them, so you give away your real lack of depth of knowledge.

    I'm always happy to answer questions, but like I said before, I can't teach you general relativity from scratch in a thread on sciforums. Well, I could, but I have neither the time nor the inclination, and I somehow doubt you'd be a good student anyway.

    I haven't referred to anything classified. There are many many websites where you can start to educate yourself about relativity. Maybe you should start with wikipedia and work your way up from there.

    How could a particle's energy affect how time flows, exactly?

    I'm not sure what you mean by this.

    Which operator? Which measurement?

    Ah yes. Feign boredom when you don't have any answers.

    Cya.
     

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