Re: [time-nuts] Beginner's time reference
In a message dated 13/12/2009 18:52:37 GMT Standard Time, charles_steinm...@lavabit.com writes: Volts and yards, at least, are also not absolute measurements in the same sense that measurements of time are not absolute. Volts express the difference in electrical potential, and yards the physical separation, between two spatial points. But two points in space just define a spatial interval, precisely analogously to two points in time specifying a temporal interval (more below). --- But that is no different than the other three dimensions of spacetime -- measuring intervals is all we have there, too. One kilometer is no different from one second in this regard -- in both cases, it is one unit *between* two places (we usually call places in time events, but it's the same thing). If general relativity (GR) is correct (and we have every reason to believe that it is), time is no different than space, although we perceive it quite differently. For example, in order to move about in the space dimensions we think we need to do something, while we need to do nothing to move about in the usual way in the time dimension (and, indeed, have not figured out how to move differently in time or to stay in one place). But note that we are really hurtling through space at a good clip, without it being apparent to our natural senses -- and in comparison to this, we really haven't much power to move about in space, either. So, we could say that we have an initial velocity through both space and time when we are born, and our initial velocity through time is more apparent to our natural senses than our initial velocity through space -- but in reality, there is no difference between them. -- In my view, these are all questions, not about time, but rather about our perception of time. At the end of the day, we have every reason to believe that GR is correct and, consequently, that spacetime is the fabric of the universe. Space and time are both altered, in complementary ways, by the great forces of the universe (gravity and acceleration -- time will tell whether the nuclear forces do so, as well, and there is some evidence to date that they may), implying that there is a conservation relationship that applies to the four dimensions collectively. But there is no difference in terms of the spatial dimensions being absolute and the temporal dimension not being absolute -- all of our measurements of the four spacetime dimensions are relative and not absolute in the sense you mean (although, as I've pointed out, by refering both back to the origin of this universe, which we have good reason to believe was a mathematical and physical point where this universe began, we could in principle at least have a master datum for all four dimensions, providing a form of absolutism). The puzzle is why we perceive the spatial dimensions so differently from the temporal dimension. It is a fascinating question, but may not be fundamentally a question of the physics of spacetime. --- Hi Charles Many thanks for your reply, but I'm not so sure anymore that spatial and temporal intervals really are quite the same. It deserves more thought. The spatial intervals have the property of persistence until time becomes involved, whereas temporal intervals really have the property of decay regardless. Whether or not we have an initial velocity in any reference frame is not so much the issue as to what was the reference to start with. We are indeed hurtling through space at a good clip but where exactly does that lead us? Mr Flat_Earth mentioned the arrow of time, without any due consideration to the fact that one doesn't need to invoke the second law of thermodynamics, or anything else for that matter, if time is merely an artefact of universal expansion. Should the universe eventually begin to contract it's then we should consider it, time reversal might just be inevitable after all. The puzzle may be one one of perception, but perhaps perception should not always be ignored. I begin to think that we perceive spatial dimensions so differently from the temporal because there might just be a difference. Perhaps not, but at least the mind is open and thinking:-) regards Nigel GM8PZR ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
In a message dated 13/12/2009 05:04:53 GMT Standard Time, charles_steinm...@lavabit.com writes: I think we all agree that intervals are what we measure. The question is whether this has any bearing on whether time is an absolute quantity, and if so, whether time being or not being an absolute quantity is philosophically interesting. A number of us have been trying, without success, to get you to be more precise about what you mean by time being [or not being] an absolute quantity, and how that might be important. As it stands, you have not done so, so we are left to guess what meaning and import this phrase has in your view. The two possibilities I see are that you mean (i) time has no ontological status -- that is, that it doesn't really exist, but is merely an imaginary construct that we impose on the universe; or (ii) even if time does have ontological status, it is not philosophically interesting unless it is absolute (whatever that means). What a number of us have been saying is that the way we measure time is purely conventional (and therefore, I suppose, imaginary), but that accepting this says nothing about either of these two issues -- i.e., whether time really exists or whether it is philosophically interesting. I take no position on the ontological status of time, but not because we measure it only in intervals or because it is not absolute (whatever that means). Rather, for me, it is an issue whether time -- as one dimension of spacetime -- can be a separate ontological entity. In my view, when Einstein, Dirac, Bohr, Lorentz, Schroedinger, and other founding fathers of modern physics spoke or wrote regarding the existence of time, this is the issue they were addressing. However, if we accept that spacetime exists, nothing is really riding on whether time is a separate ontological entity -- it has ontological status as a constituent of spacetime. So, the remaining question is whether the claim that time is not absolute (whatever that means) -- if true -- somehow renders the issue of time a merely semantic matter, or otherwise philosophically uninteresting. I don't see how this could be, but then I cannot imagine what you mean by time not being absolute, other than it can only be measured by intervals, and you have not explained what you mean in any but the most vague and circular terms. If you are able to articulate what it would be for time to be an absolute quantity, and how this would make a difference with respect to its ontological status or philosophical interest, I'll be happy to listen -- but I won't hold my breath. - Whoops, can't even hit the right buttons now, sorry about the earlier empty reply:-) I did agree it becomes a matter of semantics and I obviously wasn't explaining my thoughts at all well but I did start out purely with the intention of suggesting that a previous statement claiming time just exists was perhaps rather simplistic. However, that's perhaps more a reflection on common use of language rather than to imply that time iteslf is merely a matter of semantics or that it's anywhere near philosophically uninteresting. Whether or not time is, or more correctly can be expressed in terms of, an absolute quantity is certainly of philosophical interest to me. Outside of that though I wouldn't be so pretentious as to make claims of it actually having any importance:-) I use absolute in the sense that is commonly implied in the term absolute quantity, where an absolute quantity is the measure of the absolute occurence of a variable, as in so many volts, yards, kilos, etc. I probably should have explained it better but I think Didier hit it on the head when he commented.. There is at least one thing that you cannot do with time, which you can do with pretty much everything else: you cannot go back and recheck your measurement. ... I know one could argue that since time has moved on one can't actually measure the same voltage or whatever but let's ignore that for now. At one point in this discussion it was questioned what units I measured in but the actual units we use are totally irrelevant other than for day to day convenience, it's the existence and measurability of the quantity that's the issue. Perhaps measurability will now be called into task as another undefined term but hopefully that one's more obvious. If we accept for now that nothing, including time itself, existed before the Big-Bang, and yes I know there's suggestions that this might not be the case, then it becomes of interest to also consider the implications of that, which of course is hardly anything new. Whether or not one accepts that everything in the universe was initially collapsed into a singularity, even if we still haven't observed large parts of that everything, it would seem that everything physical in that universe,
Re: [time-nuts] Beginner's time reference
This discussion started off interestingly enough, but has deteriorated to a point where it reminds me of a tale told to me by one of my mentors well over 40 years ago. At the time, I was very interested in existential philosophy myself and studied it and thought about it ad infinitum. It goes something like this: A young physicist/philosopher becomes shipwrecked on some island. He is the only survivor. Besides food items, he is able to retrieve from the ship cases of paper and lots of pencils. At the time he does not know what to do with them, but saves them regardless. Of course he expects to be saved any time soon. Well, days become weeks and then months and so on, and, no rescue. He is becoming bored and does not know what to do. He decides he is going to attempt to figure out the meaning of life and document it. So, he starts thinking and writing and as years go by his document grows and after about 10 or so years he has the meaning of life figured out and documented. Now what to do? Well, he decides to go over the document and expand/clarify various sections and after about 10 more years he has one he is satisfied with and is now about a foot thick. Still, no rescue. Rather disappointed that he has it all figured out and cannot share it, he contemplates some more as to how to occupy himself. He decides to condense the manuscript making sure he does not lose the significant premise. Again, years go by and after about 40 years total, he is rescued. He is weak, dehydrated, can barely talk. He keeps on pointing to his pocket for the rescuers to see. Finally, one rescuer reaches into his pocket and pulls out a piece of paper with the single word on it bullshit. Regards - Mike Mike B. Feher, N4FS 89 Arnold Blvd. Howell, NJ 07731 732-886-5960 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
Nigel wrote: I use absolute in the sense that is commonly implied in the term absolute quantity, where an absolute quantity is the measure of the absolute occurence of a variable, as in so many volts, yards, kilos, etc. Volts and yards, at least, are also not absolute measurements in the same sense that measurements of time are not absolute. Volts express the difference in electrical potential, and yards the physical separation, between two spatial points. But two points in space just define a spatial interval, precisely analogously to two points in time specifying a temporal interval (more below). Whether or not one accepts that everything in the universe was initially collapsed into a singularity, even if we still haven't observed large parts of that everything, it would seem that everything physical in that universe, including space, fits my definition of absolute. No matter how large or small, in one way or another, and in theory at least, it can be measured and quantified. The properties of what we call time, however, are unique and lie outside of that categorisation. Time as such, unlike everything else, is not a physical entity that would have been collapsed into that singularity but can only have come about as a consequence of the ongoing expansion of material out of it that followed the Big-Bang. I know I've laboured to death the point about measuring time intervals but that's because it's really all we have. But that is no different than the other three dimensions of spacetime -- measuring intervals is all we have there, too. One kilometer is no different from one second in this regard -- in both cases, it is one unit *between* two places (we usually call places in time events, but it's the same thing). If general relativity (GR) is correct (and we have every reason to believe that it is), time is no different than space, although we perceive it quite differently. For example, in order to move about in the space dimensions we think we need to do something, while we need to do nothing to move about in the usual way in the time dimension (and, indeed, have not figured out how to move differently in time or to stay in one place). But note that we are really hurtling through space at a good clip, without it being apparent to our natural senses -- and in comparison to this, we really haven't much power to move about in space, either. So, we could say that we have an initial velocity through both space and time when we are born, and our initial velocity through time is more apparent to our natural senses than our initial velocity through space -- but in reality, there is no difference between them. When considering whether or not time exists, perhaps we should first ask exactly what we mean when we refer to time, do events occur within time, for example, or is time merely a consequence of events occuring? If the latter then does time have any real existence other than as a convenience to describe sequentiality, is spacetime really an entity or just a mathematical convenience, etc etc? In my view, these are all questions, not about time, but rather about our perception of time. At the end of the day, we have every reason to believe that GR is correct and, consequently, that spacetime is the fabric of the universe. Space and time are both altered, in complementary ways, by the great forces of the universe (gravity and acceleration -- time will tell whether the nuclear forces do so, as well, and there is some evidence to date that they may), implying that there is a conservation relationship that applies to the four dimensions collectively. But there is no difference in terms of the spatial dimensions being absolute and the temporal dimension not being absolute -- all of our measurements of the four spacetime dimensions are relative and not absolute in the sense you mean (although, as I've pointed out, by refering both back to the origin of this universe, which we have good reason to believe was a mathematical and physical point where this universe began, we could in principle at least have a master datum for all four dimensions, providing a form of absolutism). The puzzle is why we perceive the spatial dimensions so differently from the temporal dimension. It is a fascinating question, but may not be fundamentally a question of the physics of spacetime. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
Charles, That's a very good description of the situation. The real dilemma has to do with why some people require absolutes, as perfect, complete, or pure, when nature doesn't offer any. The need originates in the brain, where perceptions are adjusted to find absolutes. Absolute zero is merely the theoretical bottom of the temperature scale, where atoms and molecules no longer collide with each other. Ah, acceleration isn't a force. It's a measure of the relative change in velocity per unit of time. Velocity is a measure of the relative change in distance per unit of time. F=MA, and all that. Bill Hawkins -Original Message- From: Charles P. Steinmetz Sent: Sunday, December 13, 2009 12:52 PM Nigel wrote: I use absolute in the sense that is commonly implied in the term absolute quantity, where an absolute quantity is the measure of the absolute occurence of a variable, as in so many volts, yards, kilos, etc. Volts and yards, at least, are also not absolute measurements in the same sense that measurements of time are not absolute. Volts express the difference in electrical potential, and yards the physical separation, between two spatial points. But two points in space just define a spatial interval, precisely analogously to two points in time specifying a temporal interval (more below). Whether or not one accepts that everything in the universe was initially collapsed into a singularity, even if we still haven't observed large parts of that everything, it would seem that everything physical in that universe, including space, fits my definition of absolute. No matter how large or small, in one way or another, and in theory at least, it can be measured and quantified. The properties of what we call time, however, are unique and lie outside of that categorisation. Time as such, unlike everything else, is not a physical entity that would have been collapsed into that singularity but can only have come about as a consequence of the ongoing expansion of material out of it that followed the Big-Bang. I know I've laboured to death the point about measuring time intervals but that's because it's really all we have. But that is no different than the other three dimensions of spacetime -- measuring intervals is all we have there, too. One kilometer is no different from one second in this regard -- in both cases, it is one unit *between* two places (we usually call places in time events, but it's the same thing). If general relativity (GR) is correct (and we have every reason to believe that it is), time is no different than space, although we perceive it quite differently. For example, in order to move about in the space dimensions we think we need to do something, while we need to do nothing to move about in the usual way in the time dimension (and, indeed, have not figured out how to move differently in time or to stay in one place). But note that we are really hurtling through space at a good clip, without it being apparent to our natural senses -- and in comparison to this, we really haven't much power to move about in space, either. So, we could say that we have an initial velocity through both space and time when we are born, and our initial velocity through time is more apparent to our natural senses than our initial velocity through space -- but in reality, there is no difference between them. When considering whether or not time exists, perhaps we should first ask exactly what we mean when we refer to time, do events occur within time, for example, or is time merely a consequence of events occuring? If the latter then does time have any real existence other than as a convenience to describe sequentiality, is spacetime really an entity or just a mathematical convenience, etc etc? In my view, these are all questions, not about time, but rather about our perception of time. At the end of the day, we have every reason to believe that GR is correct and, consequently, that spacetime is the fabric of the universe. Space and time are both altered, in complementary ways, by the great forces of the universe (gravity and acceleration -- time will tell whether the nuclear forces do so, as well, and there is some evidence to date that they may), implying that there is a conservation relationship that applies to the four dimensions collectively. But there is no difference in terms of the spatial dimensions being absolute and the temporal dimension not being absolute -- all of our measurements of the four spacetime dimensions are relative and not absolute in the sense you mean (although, as I've pointed out, by refering both back to the origin of this universe, which we have good reason to believe was a mathematical and physical point where this universe began, we could in principle at least have a master datum for all four dimensions, providing a form of absolutism). The puzzle is why we perceive the spatial
Re: [time-nuts] Beginner's time reference
You guys obviously missed Hermann Weyl's writings, specifically his Space-Time-Matter and Philosophy of Mathematics both of which I have read exhaustively in my early 20's. That is well over 40 years ago, yet I still feel the impact of some of his statements. That was mainly why earlier I expressed my opinion simply as bullshit - Regards - Mike Mike B. Feher, N4FS 89 Arnold Blvd. Howell, NJ 07731 732-886-5960 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
Perhaps because we may move about in the three spatial dimensions as we move unidirectionally in the temporal dimension? Charles P. Steinmetz wrote: The puzzle is why we perceive the spatial dimensions so differently from the temporal dimension. It is a fascinating question, but may not be fundamentally a question of the physics of spacetime. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
At 01:51 PM 12/13/2009, Charles P. Steinmetz wrote... In my view, these are all questions, not about time, but rather about our perception of time. Yes, he seems to have discovered Eddington's arrow of time. There also seems to be some confusion over the difference between the spacetime dimensions, and matter-energy. In a particular way, we don't _measure_ time or space, but express measurements in units of spacetime, such as the period between defined events or the distance between defined spatial points. But this is a pedantry - it's well understood what is meant by measuring time and distance. Likewise, we don't measure volts, but express the measurement of a difference in electrical potential in the unit volts. So, there's nothing unique about time in this regard. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
Mike wrote: You guys obviously missed Hermann Weyl's writings, specifically his Space-Time-Matter and Philosophy of Mathematics * * * That was mainly why earlier I expressed my opinion simply as bullshit Not at all. It's just that for all of Weyl's brilliant contributions to mathematics, philosophers generally hold an opinion similar to the one you expressed of his unfortunate forays into philosophy (as well as for the phenomenology of Husserl and Cassirer, upon which Weyl's views were based). Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
Well, one thing for sure, my mind was a lot more impressionable in my early 20's than it is now at 65 :). Regardless, I found Weyl's writings to coincide a lot more with my way of thinking than any of the other philosophers whom I read at the time. Coincidentally, your middle name would not be Proteus by any chance :). Regards - Mike -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Charles P. Steinmetz Sent: Sunday, December 13, 2009 11:28 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Beginner's time reference Mike wrote: You guys obviously missed Hermann Weyl's writings, specifically his Space-Time-Matter and Philosophy of Mathematics * * * That was mainly why earlier I expressed my opinion simply as bullshit Not at all. It's just that for all of Weyl's brilliant contributions to mathematics, philosophers generally hold an opinion similar to the one you expressed of his unfortunate forays into philosophy (as well as for the phenomenology of Husserl and Cassirer, upon which Weyl's views were based). Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
In a message dated 12/12/2009 05:08:39 GMT Standard Time, john.fo...@gmail.com writes: Time does not just exist. That is correct. It is a human construct, like all other things. We define it, as all other things, and then make useful empirical comparative observations with it. --- It isn't quite as straightforward as that, in the sense that is of time being just a human construct, and not all other things are human constructs either. It's not too unreasonable to accept that events, in conventional physics at least, do generally occur in a sequential fashion, hence the intervals between them that we strive to measure, and that would occur without any human intervention or existence. It's when one attempts to quantify time itself as a measurable quantity in itself that problems arise. There are measurable quantities such as mass, length, potential difference etc, that again aren't human constructs but exist anyway, and would continue to do so even if we and our definitions all disappeared tomorrow. But with time there is no absolute quantity, just those intervals again, so when you say we define it, just how would you attempt to define it as an absolute quantity? Although it's reasonable to accept that we live in a universe where things occur sequentially, even if not necessarilly causually related, and hence the existence of intervals between events can be accepted also, and can be measured in terms of whatever units we choose to define, that still does not demonstrate that time itself actually exists. regards Nigel GM8PZR ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
In a message dated 12/12/2009 08:13:04 GMT Standard Time, charles_steinm...@lavabit.com writes: Time nuts do not and cannot measure time itself because time as an absolute entity just doesn't exist. I suppose specifying the interval since the big bang could qualify as an absolute measure of time (at least in our universe), but in practice it must elude us because everything in the universe is in motion and there is no practical way to relate our frame of reference to any frame with the location of the big bang at the origin. Note that assigning conventional units to measurements does not detract from the ontological existence (or not) of the measured things. Most would agree that physical extent (vector distance) exists, notwithstanding that the units we use to measure it are conventional. -- Again though, it's the interval that we measure. We tend to talk in terms of the passage or flow of time, which gives substance to the concept of time in some way existing as an independent entity, whilst sometimes losing sight of such terms again being only defined in terms of intervals. Assigning conventional units to measurement is not a problem, it's just that the units we assign to time measurement are always a measure of the intervals. There's no problem with this either until one starts to believe, as many seem to do without due consideration, that time itself is an absolute quantity. -- nobody has ever demonstrated the existence of time itself as a measurable quantity. Without intending to expreess a view regarding the ontological status of time, I would point out that one must be careful to distinguish between the ontological question and any practical/empirical questions such as the frame-of-reference issue noted above. The ontological question is murky because it appears that time is an orthogonal component of spacetime, and it can always be disputed under what conditions (if any) the constituent parts of ontological entities are themselves ontological entities. [And, the question presumes that one accepts the ontological existence of spacetime.] But this may be more philosophy than most time nuts want to contend with! - It's interesting though to note that the Ontological Argument, as a more specific term, generally seeks to find a logical basis for the existence of yet another mythical entity:-) I agree it becomes more of a philosophical argument than is sometimes comfortable, and more often than not perhaps a question of etymology rather than ontology as we debate the meanings and definitions of the words we use to describe things, but I do think it's important to stop and consider sometimes just what we do mean, or what is implied, when we talk about time. regards Nigel GM8PZR ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
At 06:47 PM 12/11/2009, gandal...@aol.com wrote... Unfortunately, that's not really the way it is. That's opinion, stated as fact. Time nuts do not and cannot measure time itself because time as an absolute entity just doesn't exist. That depends upon how one defines time. Also, how one defines reality, and where they sit on the philosophical/pragmatic scale. The OED's first definition is the indefinite continued progress of existence and events in the past, present, and future, regarded as a whole, and that's exactly what time nuts measure. Time exists in the same way any other dimension does. It is measured by comparision (how many cycles of Cs resonance between two other events, etc.). Zeno's paradox tells us that distance and motion don't exist, either. But, there they are. No sense trying to respond, since it is impossible for your fingers to travel the distance required to make a response. And just in case anyone wishes to shout me down on this, as happened when I dared to suggest the same some time ago, It's easy to be right, when you define terms to your own liking. Just what do you mean by some time ago, given your claim that time itself [isn't a] measurable quantity? :-) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
In a message dated 12/12/2009 11:35:49 GMT Standard Time, mi...@flatsurface.com writes: At 06:47 PM 12/11/2009, gandal...@aol.com wrote... Unfortunately, that's not really the way it is. That's opinion, stated as fact. -- Is it? Can you show me any definition of time which demonstrates it to be an absolute quantity other than those which relate only to intervals? Time nuts do not and cannot measure time itself because time as an absolute entity just doesn't exist. That depends upon how one defines time. Also, how one defines reality, and where they sit on the philosophical/pragmatic scale. The OED's first definition is the indefinite continued progress of existence and events in the past, present, and future, regarded as a whole, and that's exactly what time nuts measure. Time exists in the same way any other dimension does. It is measured by comparision (how many cycles of Cs resonance between two other events, etc.). Zeno's paradox tells us that distance and motion don't exist, either. But, there they are. No sense trying to respond, since it is impossible for your fingers to travel the distance required to make a response. --- I think you might be missing the point, the OED definition that you quote does not define time itself as an absolute measurable entity, and what time nuts measure are, yet again, the intervals between events. Dimensions, if you like, are properties rather than absolute entities but generally of something that has physical existence, so a rock, for an example, might be said to have mass, length, height, etc. It doesn't matter how you choose to define the properties, the rock con tinues to exist regardless. Similarly, less tangible items such as perhaps potential difference will exist anyway regardless of our definitions or the dimensions we apply to them. Frequency of course, as in how many cycles, is inversely proprtional to time intervals so back to square one:-) - And just in case anyone wishes to shout me down on this, as happened when I dared to suggest the same some time ago, It's easy to be right, when you define terms to your own liking. Just what do you mean by some time ago, given your claim that time itself [isn't a] measurable quantity? :-) Who said I was defining it to my own liking?, I did say it wasn't always a very comfortable contemplation. Some time ago is easily defined in terms of time intervals, albeit perhaps not to the usual time nuts' standards of precision:-), but that's the whole point, we know that the intervals exist that separate sequential events, and we know we can measure them with significant acuracy, but where does that leave us in terms of time itself. Considering time as a dimension isn't quite so bad but the point I was attempting to make, perhaps not very well, was that many folks choose to, or want to, treat time itself as something that exists in a physical form, such as a river for example, and hence, again just by way of example, something that we might consider travelling backwards and forwards along if only we could find the right boat. And continuing that analogy, if it's the flow of water that creates a river, what is it that flows to create time:-) ? regards Nigel GM8PZR ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
At 07:13 AM 12/12/2009, gandal...@aol.com wrote... I think you might be missing the point, the OED definition that you quote does not define time itself as an absolute measurable entity, and what time nuts measure are, yet again, the intervals between events. Define absolute measurable quantity, and give an example of something (not countable, like fingers on a hand) which is. What units do you measure in? Certainly not most SI units, which vary by reference frame (time, length, mass, current, luminous intensity), and/or are simple counts (mass effectively, mole) - which leaves temperature. How do you measure temperature without using any of the other SI units? How does one measure, if not by comparison? Is pi measurable? Can I measure the circumference of a circle of diameter 1? How? Or are you focused on absolute? If so, how is time any different than distance? You measure between the points you want to measure. I can measure the length of a bar of platinum-iridium, and call that 1 meter, or I can measure the distance a photon travels in 1/299 792 458 of a second. Is one somehow less real than the other? Considering time as a dimension isn't quite so bad but the point I was attempting to make, perhaps not very well, was that many folks choose to, or want to, treat time itself as something that exists in a physical form, such as a river for example, and hence, again just by way of example, something that we might consider travelling backwards and forwards along if only we could find the right boat. Einstein didn't claim time didn't exist - he linked it with space. Time and distance are both relative to the frame of reference. Einstein had no problem making frequent reference to the speed (distance/time) of light. When he said Time is an illusion, it was in reference to time separated from space. That doesn't mean it doesn't exist, or isn't physical. This is nothing new. The GPS system was designed with the understanding that the satellites exist in a different frame of reference than the receivers. Yet, it works, because we measure time and mathematically adjust for the different reference frames. Seems to me you're just being pedantic. It's like claiming Newtonian physics is wrong, even though it works perfectly well for 99.99% of what it's used for. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
Remember that saying from the Hitchhikers' Guide: Time is an illusion - lunchtime doubly so. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
In a message dated 12/12/2009 13:00:21 GMT Standard Time, mi...@flatsurface.com writes: At 07:13 AM 12/12/2009, gandal...@aol.com wrote... I think you might be missing the point, the OED definition that you quote does not define time itself as an absolute measurable entity, and what time nuts measure are, yet again, the intervals between events. Define absolute measurable quantity, and give an example of something (not countable, like fingers on a hand) which is. What units do you measure in? Certainly not most SI units, which vary by reference frame (time, length, mass, current, luminous intensity), and/or are simple counts (mass effectively, mole) - which leaves temperature. How do you measure temperature without using any of the other SI units? How does one measure, if not by comparison? Is pi measurable? Can I measure the circumference of a circle of diameter 1? How? Or are you focused on absolute? If so, how is time any different than distance? You measure between the points you want to measure. I can measure the length of a bar of platinum-iridium, and call that 1 meter, or I can measure the distance a photon travels in 1/299 792 458 of a second. Is one somehow less real than the other? Only focussed on absolute inasmuch as that was what I was referring to in the first place and you're still mising the point. Time, as a distance if you wish between two points, is measurable as the duration of the interval, no problem with that, but whereas your platinum-iridium bar continues to exist outside of your measurement of its properties the same cannot be said of any particular interval between events. Considering time as a dimension isn't quite so bad but the point I was attempting to make, perhaps not very well, was that many folks choose to, or want to, treat time itself as something that exists in a physical form, such as a river for example, and hence, again just by way of example, something that we might consider travelling backwards and forwards along if only we could find the right boat. Einstein didn't claim time didn't exist - he linked it with space. Time and distance are both relative to the frame of reference. Einstein had no problem making frequent reference to the speed (distance/time) of light. When he said Time is an illusion, it was in reference to time separated from space. That doesn't mean it doesn't exist, or isn't physical. -- Perhaps I should have been a bit more specific. One quote, which was actually attributed to Freeman Dyson when discussing the difference in approach between Poincare and Einstein commented His version of the theory was simpler and more elegant. There was no absolute space and time and there was no ether.. It was only an off the cuff comment anyway so not particularly relevant to my argument as such, but please do explain in what way time itself might be physical -- This is nothing new. The GPS system was designed with the understanding that the satellites exist in a different frame of reference than the receivers. Yet, it works, because we measure time and mathematically adjust for the different reference frames. Seems to me you're just being pedantic. It's like claiming Newtonian physics is wrong, even though it works perfectly well for 99.99% of what it's used for. -- Call me pedantic if you wish, but it has nothing at all to do with claiming that Newtonian physics is wrong, which I'm not, even though that it can have its limitations. I'm sorry you can't, or won't, understand but the ability to measure intervals between events does not in itself demonstrate the existence of time as any kind of physical entity. If we can only define time in terms of the interval between events then so be it, but isn't that just where we came in? Is it possible that flatsurface might be synonymous with flatearth?:-) regards Nigel GM8PZR ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
At 08:53 AM 12/12/2009, gandal...@aol.com wrote... I'm sorry you can't, or won't, understand but the ability to measure intervals between events does not in itself demonstrate the existence of time as any kind of physical entity. LOL. You're over your head here. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
Give it to them Nigel . . . . . Roy -- From: gandal...@aol.com Sent: Friday, December 11, 2009 11:47 PM To: time-nuts@febo.com Subject: Re: [time-nuts] Beginner's time reference In a message dated 11/12/2009 21:47:28 GMT Standard Time, michael.c...@wanadoo.fr writes: For me time just exists. What time nuts do is to try and measure and characterise it. Unfortunately, that's not really the way it is. Time nuts do not and cannot measure time itself because time as an absolute entity just doesn't exist. We can measure the length of the intervals between events, time intervals if you choose to call them that, but nobody has ever demonstrated the existence of time itself as a measurable quantity. And just in case anyone wishes to shout me down on this, as happened when I dared to suggest the same some time ago, I have since been heartened to read in Walter Isaacson's excellent biography that a certain Mr Einstein arrived at the same conclusion. We could of course both be wrong, but at least I'll be wrong in good company:-) regards Nigel GM8PZR ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
Here's another way to look at it: Time is what keeps things from happening all at once. Also, without time there can be no motion (velocity, acceleration x time). The units of distance are arbitrary - from the King's foot to a chosen number of atomic wavelengths. And so the units of time are arbitrary - fractions of the rotation of the Earth. Distance exists and time exists, but the measure of things is man - in the sense that without man, there would be no units of measurement. I may measure time with a clock, but I can't characterize time. I can only compare and characterize man's instruments for measuring time. Maybe it's like people's perception of Evolution. Some see it as a thing that causes things to be the way they are. Others know that evolution is a process that describes what happens to genes in changing environments. Oh, I am collapsing under the weight of these heavy thoughts . . . Bill Hawkins -Original Message- From: gandal...@aol.com Sent: Friday, December 11, 2009 11:47 PM To: time-nuts@febo.com Subject: Re: [time-nuts] Beginner's time reference In a message dated 11/12/2009 21:47:28 GMT Standard Time, michael.c...@wanadoo.fr writes: For me time just exists. What time nuts do is to try and measure and characterise it. Unfortunately, that's not really the way it is. Time nuts do not and cannot measure time itself because time as an absolute entity just doesn't exist. We can measure the length of the intervals between events, time intervals if you choose to call them that, but nobody has ever demonstrated the existence of time itself as a measurable quantity. And just in case anyone wishes to shout me down on this, as happened when I dared to suggest the same some time ago, I have since been heartened to read in Walter Isaacson's excellent biography that a certain Mr Einstein arrived at the same conclusion. We could of course both be wrong, but at least I'll be wrong in good company:-) regards Nigel GM8PZR ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
On Sat, Dec 12, 2009 at 6:33 AM, Mike S mi...@flatsurface.com wrote: At 06:47 PM 12/11/2009, gandal...@aol.com wrote... Unfortunately, that's not really the way it is. That's opinion, stated as fact. That all depends on what your definition of is is :-) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
In a message dated 12/12/2009 15:17:23 GMT Standard Time, mi...@flatsurface.com writes: At 08:53 AM 12/12/2009, gandal...@aol.com wrote... I'm sorry you can't, or won't, understand but the ability to measure intervals between events does not in itself demonstrate the existence of time as any kind of physical entity. LOL. You're over your head here. -- If you say so. Closed minds are always difficult to communicate with so I think I'll just give up on this one. regards Nigel GM8PZR ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
Whoah I can imagine this kind of debate over a soccer/hockey/insert your sport here/ team, but on the nature of time? unless I am missing some irony? - Original Message - From: gandal...@aol.com To: time-nuts@febo.com Sent: Saturday, December 12, 2009 5:17 PM Subject: Re: [time-nuts] Beginner's time reference In a message dated 12/12/2009 15:17:23 GMT Standard Time, mi...@flatsurface.com writes: At 08:53 AM 12/12/2009, gandal...@aol.com wrote... I'm sorry you can't, or won't, understand but the ability to measure intervals between events does not in itself demonstrate the existence of time as any kind of physical entity. LOL. You're over your head here. -- If you say so. Closed minds are always difficult to communicate with so I think I'll just give up on this one. regards Nigel GM8PZR ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.427 / Virus Database: 270.14.104/2560 - Release Date: 12/12/09 07:38:00 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
Well, here's another statement that reveals the nature of time: Time flies like an arrow. Fruit flies like a banana. Bill Hawkins ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
At 12:41 PM 12/12/2009, Ian Sheffield wrote... I can imagine this kind of debate over a soccer/hockey/insert your sport here/ team, but on the nature of time? unless I am missing some irony? He's either having a very hard time stating something very obvious (and behaving as if it's insightful), or incorrectly parroting something he doesn't understand. He claims Time nuts do not and cannot measure time itself because time as an absolute entity just doesn't exist. That's the same as saying one can't measure distance, because space doesn't exist. Bollocks. Alternately, he simply means there is no universal epoch for time, so just as a spacial coordinate requires a defined reference, so too does a time measurement. So, there's nothing unique about time, or our measurement of it, in that regard, and no insight. Since we live in spacetime, that's entirely expected. He's refused to define his terms, and can't give an example of something which _is_ measurable (in units other than spacetime), so he seems simply to be arguing about angels on pinheads. Of course spacetime exists. It's where we (and all other energymatter) live. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
Some (Penrose, Nottale) suggest that time may be discrete rather than continuous. 10E-43 second might be your basic tick. Mike S wrote: Alternately, he simply means there is no universal epoch for time, so just as a spacial coordinate requires a defined reference, so too does a time measurement. So, there's nothing unique about time, or our measurement of it, in that regard, and no insight. Since we live in spacetime, that's entirely expected. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
I can not see how time is any different to any other quantity in Maxwell's equations, so time must be just as measurable, real and physical. cheers, Neville Michie ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
At 05:02 PM 12/12/2009, Mike Naruta AA8K wrote... Some (Penrose, Nottale) suggest that time may be discrete rather than continuous. 10E-43 second might be your basic tick. Yes, Planck time. Closer to 5.4e-44 s. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
There is at least one thing that you cannot do with time, which you can do with pretty much everything else: you cannot go back and recheck your measurement. ... I'll let the thinkers think about that one, while I will have another scoop of ice-cream before it melts (time, time) Didier -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Neville Michie Sent: Saturday, December 12, 2009 4:03 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Beginner's time reference I can not see how time is any different to any other quantity in Maxwell's equations, so time must be just as measurable, real and physical. cheers, Neville Michie ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
Nigel wrote: Again though, it's the interval that we measure. [In response to my suggestion that, in theory, we could specify the interval since the big bang and it would be absolute in a fairly robust sense, at least in this universe.] Assigning conventional units to measurement is not a problem, it's just that the units we assign to time measurement are always a measure of the intervals. There's no problem with this either until one starts to believe, as many seem to do without due consideration, that time itself is an absolute quantity. I agree it becomes more of a philosophical argument than is sometimes comfortable, and more often than not perhaps a question of etymology rather than ontology as we debate the meanings and definitions of the words we use to describe things, but I do think it's important to stop and consider sometimes just what we do mean, or what is implied, when we talk about time. This is getting old, but I'll give it one more try. What you allude to in the last paragraph above -- taking care to separate all semantic issues from genuine philosophical issues -- is, as I see it, the heart of this discussion. And it appears to me that you are conflating semantic issues with genuine philosophical issues. I think we all agree that intervals are what we measure. The question is whether this has any bearing on whether time is an absolute quantity, and if so, whether time being or not being an absolute quantity is philosophically interesting. A number of us have been trying, without success, to get you to be more precise about what you mean by time being [or not being] an absolute quantity, and how that might be important. As it stands, you have not done so, so we are left to guess what meaning and import this phrase has in your view. The two possibilities I see are that you mean (i) time has no ontological status -- that is, that it doesn't really exist, but is merely an imaginary construct that we impose on the universe; or (ii) even if time does have ontological status, it is not philosophically interesting unless it is absolute (whatever that means). What a number of us have been saying is that the way we measure time is purely conventional (and therefore, I suppose, imaginary), but that accepting this says nothing about either of these two issues -- i.e., whether time really exists or whether it is philosophically interesting. I take no position on the ontological status of time, but not because we measure it only in intervals or because it is not absolute (whatever that means). Rather, for me, it is an issue whether time -- as one dimension of spacetime -- can be a separate ontological entity. In my view, when Einstein, Dirac, Bohr, Lorentz, Schroedinger, and other founding fathers of modern physics spoke or wrote regarding the existence of time, this is the issue they were addressing. However, if we accept that spacetime exists, nothing is really riding on whether time is a separate ontological entity -- it has ontological status as a constituent of spacetime. So, the remaining question is whether the claim that time is not absolute (whatever that means) -- if true -- somehow renders the issue of time a merely semantic matter, or otherwise philosophically uninteresting. I don't see how this could be, but then I cannot imagine what you mean by time not being absolute, other than it can only be measured by intervals, and you have not explained what you mean in any but the most vague and circular terms. If you are able to articulate what it would be for time to be an absolute quantity, and how this would make a difference with respect to its ontological status or philosophical interest, I'll be happy to listen -- but I won't hold my breath. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
I'm hoping to build my own circuit around the device, which might cut down the costs somewhat. Some rubidium sources on eBay go for less than $100, but I'm not sure what quality to expect. Any advice or suggestions are appreciated! Short answer: Sure, get one of the $100 rubidium boxes and see what you can do with it. Long answer: You just stuck you toe into a huge tar pit. Pick a corner that seems like fun and dive in. How are you planning to measure if whatever you build is any good? -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
Dear Hal and others, Thank you for your suggestions. I suppose I should have emphasised that I was looking to have my own reference, i.e. something not dependent on GPS, LORAN, or other signals from the aether. Indeed I might get better accuracy for less money by tapping the GPS time signal, but to me that's not as much fun as building my own atomic reference. Hal, is there much difference in quality for these rubidium tubes? Will I get what I pay for? In any case, you make a good point about measuring the accuracy. I'm a university student, so perhaps I can pay the physics department a visit. Otherwise, maybe I could compare it to the GPS signal? Kind regards, Charl On Fri, Dec 11, 2009 at 9:30 AM, Hal Murray hmur...@megapathdsl.net wrote: I'm hoping to build my own circuit around the device, which might cut down the costs somewhat. Some rubidium sources on eBay go for less than $100, but I'm not sure what quality to expect. Any advice or suggestions are appreciated! Short answer: Sure, get one of the $100 rubidium boxes and see what you can do with it. Long answer: You just stuck you toe into a huge tar pit. Pick a corner that seems like fun and dive in. How are you planning to measure if whatever you build is any good? -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
Hi Simple answers: Will you have fun - yes indeed. Will a $100 rubidium deliver more accurate time long term than a GPS - no. To get close to what the GPS delivers you will need to go at least to a Cesium standard. Getting one with a working tube is not going to be cheap. Once you do, the tube has a finite lifetime. They are an expensive thing to replace when they wear out. Most manufacturers rate the tube life in the 5 to 10 year range. The rubidium also has wear out mechanisms. Most people seem to get 10+ years out of them in continuos use. Lots to play with. Bob On Dec 11, 2009, at 7:00 AM, Charl wrote: Dear Hal and others, Thank you for your suggestions. I suppose I should have emphasised that I was looking to have my own reference, i.e. something not dependent on GPS, LORAN, or other signals from the aether. Indeed I might get better accuracy for less money by tapping the GPS time signal, but to me that's not as much fun as building my own atomic reference. Hal, is there much difference in quality for these rubidium tubes? Will I get what I pay for? In any case, you make a good point about measuring the accuracy. I'm a university student, so perhaps I can pay the physics department a visit. Otherwise, maybe I could compare it to the GPS signal? Kind regards, Charl On Fri, Dec 11, 2009 at 9:30 AM, Hal Murray hmur...@megapathdsl.net wrote: I'm hoping to build my own circuit around the device, which might cut down the costs somewhat. Some rubidium sources on eBay go for less than $100, but I'm not sure what quality to expect. Any advice or suggestions are appreciated! Short answer: Sure, get one of the $100 rubidium boxes and see what you can do with it. Long answer: You just stuck you toe into a huge tar pit. Pick a corner that seems like fun and dive in. How are you planning to measure if whatever you build is any good? -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
If you want a _Time_ reference, somewhat you need a way to compare/synchronize your time reference with others, event if it's the best cesium or maser available. If you only need a _Frequency_ reference, a rubidium will probably get you happy, even without exterior comparison... Best regards, Jean-Louis - Original Message - From: Charl ch...@turingbirds.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Friday, December 11, 2009 12:00 PM Subject: Re: [time-nuts] Beginner's time reference Dear Hal and others, Thank you for your suggestions. I suppose I should have emphasised that I was looking to have my own reference, i.e. something not dependent on GPS, LORAN, or other signals from the aether. Indeed I might get better accuracy for less money by tapping the GPS time signal, but to me that's not as much fun as building my own atomic reference. Hal, is there much difference in quality for these rubidium tubes? Will I get what I pay for? In any case, you make a good point about measuring the accuracy. I'm a university student, so perhaps I can pay the physics department a visit. Otherwise, maybe I could compare it to the GPS signal? Kind regards, Charl On Fri, Dec 11, 2009 at 9:30 AM, Hal Murray hmur...@megapathdsl.net wrote: I'm hoping to build my own circuit around the device, which might cut down the costs somewhat. Some rubidium sources on eBay go for less than $100, but I'm not sure what quality to expect. Any advice or suggestions are appreciated! Short answer: Sure, get one of the $100 rubidium boxes and see what you can do with it. Long answer: You just stuck you toe into a huge tar pit. Pick a corner that seems like fun and dive in. How are you planning to measure if whatever you build is any good? -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
Charl, If it is autonomous operation you want, then your only choice is a Cesium Beam frequency reference. By definition it is absolute ! But that does not address resolution. For instance, if the Cs is old tube and noisy, while it may be accurate, due to the noise you may not be able to resolve any better then, say, 1 part in 10-9 (not good). If you need more absolute resolution, then your only choice would be to have a new tube put in or buy another one. However, all this says nothing about accurate time, because there is no such thing ! Accurate time only means something with respect to a recognized reference point. In this case USNO for the USA or another countys primary lab. So, if you mean you want accurate time in addition to frequency you will need to have a method of comparing or setting your time device to a selected external time reference. This is where the GPS comes into the picture. It is the medium by which you can track and adjust your local time device to an external reference, USNO (for GPS), within a given time resolution (down to nanoseconds or better). Because time and frequency are related, having a time reference also gives you a frequency reference. Having a very good local oscillator for the short term controlled by the GPS for the long term tracking is a good choice and relatively inexpensive compromise between having nothing and spending a lot of money for Cesium standard that may only last between 5 and 10 years if new. Purchasing a used Cs is a crap shot, may be good, but could be bad. While a Rubidium oscillator looks good at first, you need to consider they are not a primary reference because they drift, albeit generally slower then a Quartz oscillator. A really good Quartz oscillator will outperform the eBay run of the mill Rubidium for short term measurements. A good Rubidium will prevail for medium term measurements and of course provide a much slower drift when in an out of lock condition (called holdover) with the GPS tracking. Another point to consider is the Rubidium has a short lifetime compared to a Quartz oscillator. Things do fail, but the Quartz oscillator likes to have continuous operation and, actually, generally improves because of it. There are many Quartz oscillators that are still ticking after 30-40-50 years ! The Rubidium, on the other hand, wears out faster when it is turned on with a life span of 5 to 10 years if new. So I would suggest doing some research like reading through the Timenut archives, reading various publications available from NIST off the web, perusing TVBs web site at www.leapsecond.com and KO4BBs site www.ko4bb.com under the timing and manuals subpages. There are a variety of manuals on frequency and time equipment. You should be able to find some hp app-notes on the subject as well. There are other worthwhile sites too. It doesnt hurt to have a mix of items. For instance a good oscillator (or two or three) tracked by GPS, a Rubidium (or two) for good measure and after you get your feet wet then decide if you really want to spend the money necessary to own, operate and maintain a Cesium. Oh, by the way, unless you are damn rich, the wife will never agree to the Cesium when she hears the price. BillWB6BNQ Charl wrote: Dear Hal and others, Thank you for your suggestions. I suppose I should have emphasised that I was looking to have my own reference, i.e. something not dependent on GPS, LORAN, or other signals from the aether. Indeed I might get better accuracy for less money by tapping the GPS time signal, but to me that's not as much fun as building my own atomic reference. Hal, is there much difference in quality for these rubidium tubes? Will I get what I pay for? In any case, you make a good point about measuring the accuracy. I'm a university student, so perhaps I can pay the physics department a visit. Otherwise, maybe I could compare it to the GPS signal? Kind regards, Charl On Fri, Dec 11, 2009 at 9:30 AM, Hal Murray hmur...@megapathdsl.net wrote: I'm hoping to build my own circuit around the device, which might cut down the costs somewhat. Some rubidium sources on eBay go for less than $100, but I'm not sure what quality to expect. Any advice or suggestions are appreciated! Short answer: Sure, get one of the $100 rubidium boxes and see what you can do with it. Long answer: You just stuck you toe into a huge tar pit. Pick a corner that seems like fun and dive in. How are you planning to measure if whatever you build is any good? -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To
Re: [time-nuts] Beginner's time reference
Bill, he was planning to spend 100 USD on a used Rubidium, I think a Cs is way over his budget ;-) But I agree that a Rubidium has a shorter life span and if you get one for 100 USD on eBay, I would expect it to be worn out already. I would not spend 100 USD on a used oscillator, Rubidium or not, if you expect to get a -stable- (not -accurate-, full ack) reference. Regards, Heiko WB6BNQ schrieb: Charl, If it is autonomous operation you want, then your only choice is a Cesium Beam frequency reference. By definition it is absolute ! But that does not address resolution. For instance, if the Cs is old tube and noisy, while it may be accurate, due to the noise you may not be able to resolve any better then, say, 1 part in 10-9 (not good). If you need more absolute resolution, then your only choice would be to have a new tube put in or buy another one. However, all this says nothing about accurate time, because there is no such thing ! Accurate time only means something with respect to a recognized reference point. In this case USNO for the USA or another county’s primary lab. So, if you mean you want accurate time in addition to frequency you will need to have a method of comparing or setting your time device to a selected external time reference. This is where the GPS comes into the picture. It is the medium by which you can track and adjust your local time device to an external reference, USNO (for GPS), within a given time resolution (down to nanoseconds or better). Because time and frequency are related, having a time reference also gives you a frequency reference. Having a very good local oscillator for the short term controlled by the GPS for the long term tracking is a good choice and relatively inexpensive compromise between having nothing and spending a lot of money for Cesium standard that may only last between 5 and 10 years if new. Purchasing a used Cs is a crap shot, may be good, but could be bad. While a Rubidium oscillator looks good at first, you need to consider they are not a primary reference because they drift, albeit generally slower then a Quartz oscillator. A really good Quartz oscillator will outperform the eBay run of the mill Rubidium for short term measurements. A good Rubidium will prevail for medium term measurements and of course provide a much slower drift when in an out of lock condition (called holdover) with the GPS tracking. Another point to consider is the Rubidium has a short lifetime compared to a Quartz oscillator. Things do fail, but the Quartz oscillator likes to have continuous operation and, actually, generally improves because of it. There are many Quartz oscillators that are still ticking after 30-40-50 years ! The Rubidium, on the other hand, wears out faster when it is turned on with a life span of 5 to 10 years if new. So I would suggest doing some research like reading through the Timenut archives, reading various publications available from NIST off the web, perusing TVB’s web site at www.leapsecond.com and KO4BB’s site www.ko4bb.com under the timing and manuals subpages. There are a variety of manuals on frequency and time equipment. You should be able to find some hp app-notes on the subject as well. There are other worthwhile sites too. It doesn’t hurt to have a mix of items. For instance a good oscillator (or two or three) tracked by GPS, a Rubidium (or two) for good measure and after you get your feet wet then decide if you really want to spend the money necessary to own, operate and maintain a Cesium. Oh, by the way, unless you are damn rich, the wife will never agree to the Cesium when she hears the price. BillWB6BNQ Charl wrote: Dear Hal and others, Thank you for your suggestions. I suppose I should have emphasised that I was looking to have my own reference, i.e. something not dependent on GPS, LORAN, or other signals from the aether. Indeed I might get better accuracy for less money by tapping the GPS time signal, but to me that's not as much fun as building my own atomic reference. Hal, is there much difference in quality for these rubidium tubes? Will I get what I pay for? In any case, you make a good point about measuring the accuracy. I'm a university student, so perhaps I can pay the physics department a visit. Otherwise, maybe I could compare it to the GPS signal? Kind regards, Charl On Fri, Dec 11, 2009 at 9:30 AM, Hal Murray hmur...@megapathdsl.net wrote: I'm hoping to build my own circuit around the device, which might cut down the costs somewhat. Some rubidium sources on eBay go for less than $100, but I'm not sure what quality to expect. Any advice or suggestions are appreciated! Short answer: Sure, get one of the $100 rubidium boxes and see what you can do with it. Long answer: You just stuck you toe into a huge tar pit. Pick a corner that seems like fun and dive in. How are you planning to measure if whatever you build is any good? -- These are my
Re: [time-nuts] Beginner's time reference
Bill, he was planning to spend 100 USD on a used Rubidium, I think a Cs is way over his budget ;-) Luck has more to do with that than money. My cheapest cesium standard, at $500, also turned out to be the only one out of three with a healthy tube. You have to plan on buying a few turkeys. If you're shopping for a cesium standard on eBay especially, where the sellers don't tend to know what they're selling or how to test it, it makes sense to bid low and wait until you get lucky. But I agree that a Rubidium has a shorter life span and if you get one for 100 USD on eBay, I would expect it to be worn out already. The LPRO-101 I bought from China recently for ~$100 is in good shape (it's the dotted blue trace in the plot I posted earlier, measured against the aforementioned $500 Cs.) It locks up quickly, and its lamp voltage is right in the middle of the normal range. Others have had good results from the same seller, so I think they're actually pretty safe. -- john, KE5FX ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
I'm hearing a lot of recommendations for types of oscillators, but noone has asked the question - what is the desired performance? For me, I wanted a clock that stays within a second of UTC for a year. I'm pretty sure the LPRO I bought will exceed that, (though I guess I won't know for another 12 months). Of course, I needed a way to evaluate what I built, so I also picked up a Thunderbolt. What was that about a tar pit? :-) I built my own clock/counter circuit, but it was a lot of work. I see a lot of Datum 9100s for sale on eBay for under $50. Has anyone tried out one of those? I still need to write up my circuit, but it is similar to (but not based on) this: http://www.qsl.net/zl1bpu/MICRO/CLOCK/ Thanks, -JP On Fri, Dec 11, 2009 at 8:42 AM, John Miles jmi...@pop.net wrote: Bill, he was planning to spend 100 USD on a used Rubidium, I think a Cs is way over his budget ;-) Luck has more to do with that than money. My cheapest cesium standard, at $500, also turned out to be the only one out of three with a healthy tube. You have to plan on buying a few turkeys. If you're shopping for a cesium standard on eBay especially, where the sellers don't tend to know what they're selling or how to test it, it makes sense to bid low and wait until you get lucky. But I agree that a Rubidium has a shorter life span and if you get one for 100 USD on eBay, I would expect it to be worn out already. The LPRO-101 I bought from China recently for ~$100 is in good shape (it's the dotted blue trace in the plot I posted earlier, measured against the aforementioned $500 Cs.) It locks up quickly, and its lamp voltage is right in the middle of the normal range. Others have had good results from the same seller, so I think they're actually pretty safe. -- john, KE5FX ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's Time Reference
As someone relatively new to the precision time/frequency game my viewpoint is a little different to the more seasoned folk. Your statement that you wanted to build your own atomic standard leads me to believe that this is more of a learning experience for you. Even if you want to build it yourself, at some point you will wonder Just how good is this thing? Is it better than the last one I built? The cheap and easy way to answer that, unless whatever you build is very good indeed, is with some kind of GPSDO. Probably not as good as a cesium but much cheaper. If I did not have a Z3801, I would still be just guessing about those OCXOs and eBay rubidiums. I suggest that you visit James Miller's website. You can build a simple divider/comparator that will let you either lock whatever source you have to GPS or compare its frequency to GPS. The last LPRO I got off eBay was $59 including shipping. The last Tbolt was just over a hundred. HP 10811 OCXOs are good but pricey. There are all kinds of rubidiums and quartz oscillators out there to experiment with and learn from. If a learning experience is what you want, read every post here for several months while exploring the archives. Watch eBay closely for a month or so to see what things sell for. Decide on what is achievable and affordable and start having fun. You will find that it is highly addictive. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's Time Reference
On Fri, Dec 11, 2009 at 9:50 AM, John Green wpxs...@gmail.com wrote: As someone relatively new to the precision time/frequency game my viewpoint is a little different to the more seasoned folk. Your statement that you wanted to build your own atomic standard leads me to believe that this is more of a learning experience for you. Even if you want to build it yourself, at some point you will wonder Just how good is this thing? Is it better than the last one I built? The cheap and easy way to answer that, unless whatever you build is very good indeed, is with some kind of GPSDO. Probably not as good as a cesium but much cheaper. If I did not have a Z3801, I would still be just guessing about those OCXOs and eBay rubidiums. I suggest that you visit James Miller's website. You can build a simple divider/comparator that will let you either lock whatever source you have to GPS or compare its frequency to GPS. The last LPRO I got off eBay was $59 including shipping. The last Tbolt was just over a hundred. HP 10811 OCXOs are good but pricey. There are all kinds of rubidiums and quartz oscillators out there to experiment with and learn from. If a learning experience is what you want, read every post here for several months while exploring the archives. Watch eBay closely for a month or so to see what things sell for. Decide on what is achievable and affordable and start having fun. You will find that it is highly addictive. +1 [another time-n00b] -aps ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
Hi 1 second in a year is 3.2x10-8. There are OCXO's that will do that with some tender loving care. Unless your Rubidium breaks it should do that easily. In both cases you will want to get it set on frequency and time at the start of the year. Back to GPS Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Justin Pinnix Sent: Friday, December 11, 2009 9:50 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Beginner's time reference I'm hearing a lot of recommendations for types of oscillators, but noone has asked the question - what is the desired performance? For me, I wanted a clock that stays within a second of UTC for a year. I'm pretty sure the LPRO I bought will exceed that, (though I guess I won't know for another 12 months). Of course, I needed a way to evaluate what I built, so I also picked up a Thunderbolt. What was that about a tar pit? :-) I built my own clock/counter circuit, but it was a lot of work. I see a lot of Datum 9100s for sale on eBay for under $50. Has anyone tried out one of those? I still need to write up my circuit, but it is similar to (but not based on) this: http://www.qsl.net/zl1bpu/MICRO/CLOCK/ Thanks, -JP On Fri, Dec 11, 2009 at 8:42 AM, John Miles jmi...@pop.net wrote: Bill, he was planning to spend 100 USD on a used Rubidium, I think a Cs is way over his budget ;-) Luck has more to do with that than money. My cheapest cesium standard, at $500, also turned out to be the only one out of three with a healthy tube. You have to plan on buying a few turkeys. If you're shopping for a cesium standard on eBay especially, where the sellers don't tend to know what they're selling or how to test it, it makes sense to bid low and wait until you get lucky. But I agree that a Rubidium has a shorter life span and if you get one for 100 USD on eBay, I would expect it to be worn out already. The LPRO-101 I bought from China recently for ~$100 is in good shape (it's the dotted blue trace in the plot I posted earlier, measured against the aforementioned $500 Cs.) It locks up quickly, and its lamp voltage is right in the middle of the normal range. Others have had good results from the same seller, so I think they're actually pretty safe. -- john, KE5FX ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
Charl, I am very new to this as well and I had similar goals you to yours. In the end, all of these standards use a crystal oscillator. It is just a matter of what is doing the disciplining. The Cesium Beam, Rubidium, and GPS signals all discipline a crystal oscillator. The quality of the signal and the quality of the crystal oscillator ultimately determine the quality of your 'standard'. I agree with the comments about the lifespan of the Cesium and Rubidium references and the 'crap shoot' of buying Cesium Beam standards from eBay. However, it is fun to play with these and I have had good luck finding 'resuscitatable' equipment. The only option for a primary, independent, stand alone reference is a Cesium Beam or higher. The rest are secondary standards and must be calibrated against something else. If you have a Cesium Beam and run it in the 'CS OFF' position, pumping the tube down and leaving the crystal oscillator on continuously, you get pretty amazing stability from just the crystal oscillator after it has been on for a couple of months. You can compare it to a GPSDO or you can turn on the Cesium Beam (only when you need it) and be 'independent of the grid', so to speak. A GPSDO such as the TBolt gives you NIST linked accuracy and a clock that you can set to GPS time or UTC time with adjustments for the time delay in your antenna coax, etc., to get you as close as possible. If your Cesium Beam also has a clock, you can set it to match the GPSDO and watch the two to see if it stays within a second per year with the 'CS OFF'. However, running a Cesium or Rubidium continuously will likely be expensive in the long term. In any event, this is a very addicting activity and has been the source of great satisfaction except for my wife who thinks I have 'too much stuff'. Good luck. Joe ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
Building oscillators, restoring old frequency standards, interfacing to a clock or time display, and tracking your successes and failures is the lure. For independent checking of time and to some extent frequency, I play with several radio related approaches: WWV, WWVB, CHU, GPS, and Russian Tsikada/Parus satellites. LORAN may or may not be going away. You will often hear that time is the inverse of frequency, but the inverse of frequency is period or time interval. Time is set by governments. Have fun, explore, John WA4WDL ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
- Original Message - From: jmfranke jmfra...@cox.net snipped You will often hear that time is the inverse of frequency, but the inverse of frequency is period or time interval. Time is set by governments. I agree with the the sentment, but not the last phrase. For me time just exists. What time nuts do is to try and measure and characterise it. International organisations decide on some basic definitions and standards, such as how many ticks make a toc, when to start counting etc, not governements. Governements just decide on when to start the day in their patch, and when to add or subract a bit to keep the farmers and industrialists happy. Mike NN4ACS ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
Excellent comments! John WA4WDL -- From: mike cook michael.c...@wanadoo.fr Sent: Friday, December 11, 2009 4:46 PM To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Beginner's time reference - Original Message - From: jmfranke jmfra...@cox.net snipped You will often hear that time is the inverse of frequency, but the inverse of frequency is period or time interval. Time is set by governments. I agree with the the sentment, but not the last phrase. For me time just exists. What time nuts do is to try and measure and characterise it. International organisations decide on some basic definitions and standards, such as how many ticks make a toc, when to start counting etc, not governements. Governements just decide on when to start the day in their patch, and when to add or subract a bit to keep the farmers and industrialists happy. Mike NN4ACS ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
Thank you for your suggestions. I suppose I should have emphasised that I was looking to have my own reference, i.e. something not dependent on GPS, LORAN, or other signals from the aether. Indeed I might get better accuracy for less money by tapping the GPS time signal, but to me that's not as much fun as building my own atomic reference. What do you mean by building my own atomic reference? Do you want to build one from scratch? Or buy something and make it do something? Building one from scratch is going to be a lot of work. It will take a good shop. If that's what you want to do, I'd suggest buying a dead one (hopefully cheap) so you can take it apart and get an idea of what you are getting into. Hal, is there much difference in quality for these rubidium tubes? Will I get what I pay for? In any case, you make a good point about measuring the accuracy. I'm a university student, so perhaps I can pay the physics department a visit. Otherwise, maybe I could compare it to the GPS signal? Most of the low cost rubidiums are recycled telco gear. I don't know how long they have been used. If they last a few more years that's ballpark of $50 per year so budget for something like that. If you want to know how good your setup is, GPS has almost cornered that market. It's low cost and very very good over the long term. The big boys use GPS to compare their clocks. Search for common view. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
snip The big boys use GPS to compare their clocks. Search for common view. common view time transfer Stanley ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
In a message dated 11/12/2009 21:47:28 GMT Standard Time, michael.c...@wanadoo.fr writes: For me time just exists. What time nuts do is to try and measure and characterise it. Unfortunately, that's not really the way it is. Time nuts do not and cannot measure time itself because time as an absolute entity just doesn't exist. We can measure the length of the intervals between events, time intervals if you choose to call them that, but nobody has ever demonstrated the existence of time itself as a measurable quantity. And just in case anyone wishes to shout me down on this, as happened when I dared to suggest the same some time ago, I have since been heartened to read in Walter Isaacson's excellent biography that a certain Mr Einstein arrived at the same conclusion. We could of course both be wrong, but at least I'll be wrong in good company:-) regards Nigel GM8PZR ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
Hi We ran one of the NIST common view gizmos for a number of years. After watching what they were doing off of published data, I think a time nut could do the same thing. The only gotcha being that you have a good clock to compare to. Bob On Dec 11, 2009, at 6:44 PM, Stanley Reynolds wrote: snip The big boys use GPS to compare their clocks. Search for common view. common view time transfer Stanley ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
Time does not just exist. That is correct. It is a human construct, like all other things. We define it, as all other things, and then make useful empirical comparative observations with it. It sure is a handy, and sometimes addicting, construct however! John Foege KB1FSX Sent via BlackBerry by ATT -Original Message- From: gandal...@aol.com Date: Fri, 11 Dec 2009 18:47:02 To: time-nuts@febo.com Subject: Re: [time-nuts] Beginner's time reference In a message dated 11/12/2009 21:47:28 GMT Standard Time, michael.c...@wanadoo.fr writes: For me time just exists. What time nuts do is to try and measure and characterise it. Unfortunately, that's not really the way it is. Time nuts do not and cannot measure time itself because time as an absolute entity just doesn't exist. We can measure the length of the intervals between events, time intervals if you choose to call them that, but nobody has ever demonstrated the existence of time itself as a measurable quantity. And just in case anyone wishes to shout me down on this, as happened when I dared to suggest the same some time ago, I have since been heartened to read in Walter Isaacson's excellent biography that a certain Mr Einstein arrived at the same conclusion. We could of course both be wrong, but at least I'll be wrong in good company:-) regards Nigel GM8PZR ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
As a newbie to the field of timekeeping, I'm a bit uncertain what would make a good first system. The price tag of the high end masers unfortunately puts them outside my range, based on what I could see on eBay. I'll be happy to pay for good equipment, but once it gets to 4 digits it starts putting some serious dents in my bank account. I'm hoping to build my own circuit around the device, which might cut down the costs somewhat. Some rubidium sources on eBay go for less than $100, but I'm not sure what quality to expect. Any advice or suggestions are appreciated! It's interesting to consider how well a GPS clock can perform relative to a local cesium. I took a plot (attached) of a Thunderbolt with a 10811-60109 (t=850s) and one of the sub-$100 LPRO-101 rubidiums, then drew some lines on it to indicate the spec limits of one of the better cesium standards (the HP 5071A). I also tried to copy the traces from Tom's Z3801a at http://www.leapsecond.com/pages/gpsdo/ onto the plot. It seems that the *unlocked* OCXO in Tom's Z3801A is turning in a performance better than the specs of a 5071A with the high-performance tube option, all the way out to tau ~= 400 seconds. It's better than a standard 5071A until about 2000 seconds. If the Z3801A had a much longer lock bandwidth -- say if there were a rubidium standard between the GPS receiver and OCXO that could be locked at tc 2000s -- then the GPS receiver might be pretty competitive with the standard 5071A model, at 1/20 the price. -- john, KE5FX attachment: gps_vs_5071_specs.gif___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
Hi John, but you may not be comparing apples to apples. Tom's plots are actual performance of probably a very good sample unit. The 5071A spec lines you drew are worst-case specs. In reality, the 5071A probably performs much better than it's spec limits? Also, I think the 5071A just has a good 10811 OCXO in it as well, so the short term performance of the 5071A is probably limited by that OCXO. bye, Said In a message dated 12/10/2009 17:48:57 Pacific Standard Time, jmi...@pop.net writes: It's interesting to consider how well a GPS clock can perform relative to a local cesium. I took a plot (attached) of a Thunderbolt with a 10811-60109 (t=850s) and one of the sub-$100 LPRO-101 rubidiums, then drew some lines on it to indicate the spec limits of one of the better cesium standards (the HP 5071A). I also tried to copy the traces from Tom's Z3801a at http://www.leapsecond.com/pages/gpsdo/ onto the plot. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
but you may not be comparing apples to apples. Tom's plots are actual performance of probably a very good sample unit. The 5071A spec lines you drew are worst-case specs. In reality, the 5071A probably performs much better than it's spec limits? Also, I think the 5071A just has a good 10811 OCXO in it as well, so the short term performance of the 5071A is probably limited by that OCXO. All very true, but meeting the minimum specs is what it takes to earn the bragging rights. :) -- john, KE5FX ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
John Miles wrote: but you may not be comparing apples to apples. Tom's plots are actual performance of probably a very good sample unit. The 5071A spec lines you drew are worst-case specs. In reality, the 5071A probably performs much better than it's spec limits? Also, I think the 5071A just has a good 10811 OCXO in it as well, so the short term performance of the 5071A is probably limited by that OCXO. All very true, but meeting the minimum specs is what it takes to earn the bragging rights. :) -- john, KE5FX Unless one uses a 3 cornered hat technique or equivalnet one can only measure the relative stability of a pair of sources. What source was used as the reference in your measurements? Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Beginner's time reference
Unless one uses a 3 cornered hat technique or equivalnet one can only measure the relative stability of a pair of sources. What source was used as the reference in your measurements? The measurements were made with an upgraded 5061A (Datum tube and 10811-60109). I have used it to measure my GPS clock at 2.0E-12 at t=100s before, so it's actually inside the 5071A limit there. I don't know where its floor really is but it appears to be much better than spec (as are most 5071As, presumably). -- john, KE5FX ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
