Exciting the Earth with a new frequency (and an adeguate amount of energy) sets a new rotational speed: you cannot retune a (for example) quartz crystal in the same way...
On Wed, Jul 27, 2016 at 3:42 PM, Tom Van Baak <[email protected]> wrote: > Hi Michael, > > I sympathize with both your and Attila's comments and would like to dig > deeper for the truth on this. > > Clearly both the earth and a pendulum (and many other periodic systems) > exhibit a decay of energy, when you remove the periodic restoring force. And > if you take the classic definition Q = 2 pi * total energy / energy lost per > cycle then it would seem earth has a Q factor. > > In fact, if you use real energy numbers you get: > > - total rotational energy of earth is 2.14e29 J > - energy lost per cycle (day) is 2.7e17 J > - so Q = 2pi * 2.14e29 / 2.7e17 = 5e12, the same 5 trillion as my earlier > calculation. > > But your point about resonance is a good one and it has always intrigued me. > Is this one difference between a pendulum and the earth as timekeepers? > > On the other hand, if you swept the earth with an external powerful frequency > in the range well below to well above 1.16e-5 Hz (1/86164 s) would you not > see a resonance peak right at the center? Given the mass of the planet and > its pre-existing rotational energy, it seems like there is a "resonance", a > preference to remain at its current frequency. Plus it has a slow decay due > to internal friction. This sounds like any other timing system with Q to me. > > Or imagine a planet the same size as earth made from a Mylar balloon. Much > less mass. Give it the same rotational speed. Much easier to increase or > decrease its energy by applying external force. Far lower Q than earth, yes? > > It might also be useful at this point, to: > > read the history Q and its definition: > http://www.collinsaudio.com/Prosound_Workshop/The_story_of_Q.pdf > > and read the patent in which Q first appeared: > http://leapsecond.com/pages/Q/1927-US1628983.pdf > > or view the first paragraph in which Q appeared: > http://leapsecond.com/pages/Q/1927-Q-patent-600x300.gif > > /tvb > > ----- Original Message ----- > From: "Michael Wouters" <[email protected]> > To: "Discussion of precise time and frequency measurement" > <[email protected]>; <[email protected]> > Sent: Wednesday, July 27, 2016 5:43 AM > Subject: Re: [time-nuts] Q/noise of Earth as an oscillator > > >> On Wed, Jul 27, 2016 at 8:08 AM, Attila Kinali <[email protected]> wrote: >> >> "I am not sure you can apply this definition of Q onto earth." >> >> It doesn't make sense to me either. >> >> If you mark a point on the surface of a sphere then you can observe >> that point as the sphere >> rotates and count rotations to make a clock. If you think of just a >> circle, then a point on it viewed in a rectilinear coordinate system >> executes simple harmonic motion so the motion of that point looks like >> an oscillator, so that much is OK. >> >> But unlike the LCR circuit, the pendulum and quartz crystal, the >> sphere's rotational motion does not have a >> resonant frequency. Another way of characterizing the Q of an >> oscillator, the relative width of the resonance, makes >> no sense in this context. >> >> It seems to me that the model of the earth as an oscillator is >> misapplied and that the 'Q' is not a meaningful number. >> I think the confusion arises here because of a conflation of a >> rotation of the sphere (which marks out a time interval) with an >> oscillation. Both can be used to define an energy lost per unit time >> but the former doesn't have anything to do with the properties of an >> oscillator. >> >> Something else that indicates that the model is suspect is that the >> apparently high 'Q' implies a stability which the earth does not have, >> as Tom observes. Viewed another way, this suggests that the model is >> inappropriate because it leads to an incorrect conclusion. >> >> Time for bed. I'll probably lie awake thinking about this now :-) >> >> Cheers >> Michael >> >> On Wed, Jul 27, 2016 at 8:08 AM, Attila Kinali <[email protected]> wrote: >>> Hoi Tom, >>> >>> On Tue, 26 Jul 2016 12:36:37 -0700 >>> "Tom Van Baak" <[email protected]> wrote: >>> >>>> Among other things, the quality-factor, or Q is a measure of how slowly a >>>> free-running oscillator runs down. There are lots of examples of periodic >>>> or >>>> damped oscillatory motion that have Q -- RC or LC circuit, tuning fork, >>>> pendulum, vibrating quartz; yes, even a rotating planet in space. >>> >>> I am not sure you can apply this definition of Q onto earth. Q is defined >>> for harmonic oscillators (or oscillators that can be approximated by an >>> harmonic oscillator) but the earth isn't oscillating, it's rotating. >>> While, for time keeping purposes, similar in nature, the physical >>> description of both are different. >>> >>> Attila Kinali >>> >>> -- >>> Malek's Law: >>> Any simple idea will be worded in the most complicated way. >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
