[time-nuts] Q/noise of Earth as an oscillator
Michael Wouters
michaeljwouters at gmail.com
Wed Jul 27 08:43:04 EDT 2016
On Wed, Jul 27, 2016 at 8:08 AM, Attila Kinali <attila at kinali.ch> 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 <attila at kinali.ch> wrote:
> Hoi Tom,
>
> On Tue, 26 Jul 2016 12:36:37 -0700
> "Tom Van Baak" <tvb at LeapSecond.com> 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.
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