[time-nuts] Q/noise of Earth as an oscillator
Jim Palfreyman
jim77742 at gmail.com
Fri Jul 29 20:24:22 EDT 2016
> What about an ADEV/TDEV plot of the pulsar J0437-4715?
Very boring. It's a straight line from top left to bottom right. :-)
See page 5 of this: http://arxiv.org/pdf/1004.0115.pdf
Jim Palfreyman
On 29 July 2016 at 17:33, Azelio Boriani <azelio.boriani at gmail.com> wrote:
> What about an ADEV/TDEV plot of the pulsar J0437-4715?
>
> On Fri, Jul 29, 2016 at 12:39 AM, Jim Palfreyman <jim77742 at gmail.com>
> wrote:
> > Hi All,
> >
> > Tom gave me a nudge to look here - I hadn't been following this thread.
> >
> > For those that don't know, I study pulsars and so the way we measure what
> > pulsars do could be relevant to this discussion.
> >
> > First, I have never heard of a Q measure when referencing a pulsar. I
> think
> > the key here is that it's not resonating as such. Rotating yes,
> resonating
> > no.
> >
> > Pulsars spin and slow down due to giving off energy (magnetic dipole
> > radiation). So in the pulsar world we mainly refer to spin frequency (F0)
> > and frequency derivative (F1). With some of the younger and more
> "erratic"
> > pulsars, F2 (and further) can be modelled.
> >
> > Here's some data on the Vela pulsar (hot off the presses - measured just
> > now):
> >
> > F0 11.1867488542579
> > F1 -1.55859177352837e-11
> > F2 1.23776878287221e-21
> >
> > Vela is young and erratic. Millisecond pulsars are outstanding clocks.
> > Here's the data for J0437-4715 - one of the most stable pulsars we know
> > about:
> >
> > F0 173.6879458121843
> > F1 -1.728361E-15
> >
> > I'm sure the "Q" of Vela would be pretty decent - but I can tell you now,
> > as a time-keeper, she's useless.
> >
> >
> > Jim Palfreyman
> >
> >
> >
> > On 28 July 2016 at 20:50, Tony Finch <dot at dotat.at> wrote:
> >
> >> Neville Michie <namichie at gmail.com> wrote:
> >>
> >> > The conical pendulum has a simple form of a weight on a string,
> instead
> >> > of oscillating in one plane as a conventional pendulum, it swings
> around
> >> > in a circular orbit in the horizontal plane. It has a definite
> resonant
> >> > frequency.
> >>
> >> I don't think it does have a resonant frequency, any more than the Earth
> >> does: the angular velocity of the pendulum is sqrt(g/h) where h is the
> >> height of the pendulum; give it more energy, it swings higher, so h is
> >> smaller, so the frequency is higher.
> >>
> >> Tony.
> >> --
> >> f.anthony.n.finch <dot at dotat.at> http://dotat.at/ - I xn--zr8h
> >> punycode
> >> South Thames, Dover: Southwesterly 5 or 6. Slight or moderate. Rain or
> >> showers. Good, occasionally poor.
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