Practical astronomy

It is common among empiricists to attribute a variation in the Earth's
rotation to so-called tidal friction -

http://bowie.gsfc.nasa.gov/ggfc/tides/intro.html

Notwithstanding the silly reasoning behind variations in axial
rotation using the return of a star to a location using the
calendrically based 23 hour 56 min value,would anyone here care to put
the depth of the ocean (average depth 2 miles) in context with the
Earth's diameter (6 900 miles) using the size of a bowling ball as a
gauge (12 inches/215 mm).

The idea is to appreciate the power of geodynamics rather than have it
subservient to the surface ocean.So,in terms of millimeters or
fractions of an inch,how thin is the ocean with respect to planetary
diameter in terms of the veneer on a bowling ball ?

On Fri, 4 Jul 2008 09:06:50 -0700 (PDT), oriel36
wrote:

The idea is to appreciate the power of geodynamics rather than have it
subservient to the surface ocean.So,in terms of millimeters or
fractions of an inch,how thin is the ocean with respect to planetary
diameter in terms of the veneer on a bowling ball ?

Do you think that dragging a 50um film of fluid over the surface of a
bowling ball wouldn't have any effect on its rotation? Nonsense. There
are good mathematical models of Earth's rotation that demonstrate how
both solid-Earth tides and ocean tides contribute to the observed long
and short term rotational rate variation.

The actual forces that the ocean is able to exert on the Earth are very
small, but so is the net effect of those forces.
_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

On Jul 4, 10:06*am, oriel36 wrote:
would anyone here care to put
the depth of the ocean (average depth 2 miles) in context with the
Earth's diameter (6 900 miles) using the size of a bowling ball as a
gauge (12 inches/215 mm).

It is well known that the mountains and oceans of the Earth are
extremely tiny compared to the Earth.

But then, the variations in the period of the Earth's rotation are
also very tiny, only able to be detected now that atomic clocks are
available.

So it is unclear to me where the contradiction lies.

The Earth's diameter is 7,923 miles, so we're talking about .003
inches being the equivalent of 2 miles.

(Incidentally, 12 inches is just over 30 centimeters: about 305 mm. It
is entirely possible that a "12 inch" bowling ball might actually be
exactly 300 mm in diameter, since slide rules and phonograph records,
for example, are in such metric sizes.)

John Savard

In article ,
Chris L Peterson wrote:
On Fri, 4 Jul 2008 09:06:50 -0700 (PDT), oriel36
wrote:

The idea is to appreciate the power of geodynamics rather than have it
subservient to the surface ocean.So,in terms of millimeters or
fractions of an inch,how thin is the ocean with respect to planetary
diameter in terms of the veneer on a bowling ball ?

Do you think that dragging a 50um film of fluid over the surface of a
bowling ball wouldn't have any effect on its rotation? Nonsense.

If the bowling ball was floating freely in space, and if its rotation
rate was monitored to millisecond accuracy over several centuries,
it could have a noticeable effect. Because I think you agree with me
than however small that effect may be, it must still be somewhat
larger than zero...

There
are good mathematical models of Earth's rotation that demonstrate how
both solid-Earth tides and ocean tides contribute to the observed long
and short term rotational rate variation.

The actual forces that the ocean is able to exert on the Earth are very
small, but so is the net effect of those forces.
_______________________________________________ __

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com


--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stjarnhimlen dot se
WWW: http://stjarnhimlen.se/

On Fri, 04 Jul 2008 18:15:02 GMT, (Paul Schlyter) wrote:

If the bowling ball was floating freely in space, and if its rotation
rate was monitored to millisecond accuracy over several centuries,
it could have a noticeable effect. Because I think you agree with me
than however small that effect may be, it must still be somewhat
larger than zero...

Yes, that's exactly my point. Gerald apparently thinks that because the
ocean is only a tiny component of the Earth, it can't have any effect.
He overlooks the fact that the effect is itself very small, only
detectable with extremely precise instrumentation (or very long
observation), just like the variation in rotation of a bowling ball
would be tiny- but likely detectable- if you applied some viscous force
to a thin film of fluid on its surface.
_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

On Jul 4, 11:13 am, Quadibloc wrote:
[...]
(Incidentally, 12 inches is just over 30 centimeters: about 305 mm. It
is entirely possible that a "12 inch" bowling ball might actually be
exactly 300 mm in diameter, since slide rules and phonograph records,
for example, are in such metric sizes.)

Hmmm, my bowling ball is at home (I'm away at a BBQ) so I can't
measure it; Wikipedia to the rescue:

http://en.wikipedia.org/wiki/Bowling_ball

" Regulation ten-pin bowling balls must weigh no more than
" 16 pounds (7.2 kg) (governing bodies do not regulate how
" light a bowling ball may be) and have a diameter of 8.5
" inches (21.6 cm).

On Jul 4, 11:42*am, Chris L Peterson wrote:
On Fri, 04 Jul 2008 18:15:02 GMT, (Paul Schlyter) wrote:
If the bowling ball was floating freely in space, and if its rotation
rate was monitored to millisecond accuracy over several centuries,
it could have a noticeable effect. *Because I think you agree with me
than however small that effect may be, it must still be somewhat
larger than zero...

Yes, that's exactly my point. Gerald apparently thinks that because the
ocean is only a tiny component of the Earth, it can't have any effect.
He overlooks the fact that the effect is itself very small, only
detectable with extremely precise instrumentation (or very long
observation), *just like the variation in rotation of a bowling ball
would be tiny- but likely detectable- if you applied some viscous force
to a thin film of fluid on its surface.
_________________________________________________

Chris L Peterson
Cloudbait Observatoryhttp://www.cloudbait.com

I do not overlook facts,I enjoy working with rotational dynamics in a
way you can't even imagine,at least not just yet.The idea is to get
familiar with rotational dynamics and its effects such as the how
rotational geodynamics of the molten/flexible interior causes the
Earth to deviate from a perfect sphere and is involved in the motion
of the fractured crust.This requires a good appreciation between the
relative layers such as crust is to oceanic depth and from there to
the enormous rotating interior,an interior which in itself is in a
flexible and molten state.

In short,you are perfectly entitled to believe that the ocean slows
the Earth's rotation down 1 second over a short period but that means
you have little appreciation of rotational dynamics and how it
generates the planetary profile and subsequently how the geodynamics
affects the motion of the thin surface crust.

This is how an astronomer thinks in this wonderful era where you mesh
evolutionary geology and crustal dynamics with rotational dynamics.The
last time I looked,you lot were still working with a geostationary
convection cells mechanism for crustal motion whereas I find it
easier to work with rotational geodynamics influencing crustal
geodynamics.

Rather than kill the conversation,consider the relationship of oceanic
depth to planetary crustal depth and then look at the rotating molten/
flexible interior,if you stil think the ocean,which is moving with the
rotating Earth,slows the planet down then so be it .This is practical
astronomy that is closer to home and people can enjoy in the ;long
run.

Why do you even bother with that nutbar? It's obvious he has the mentality
of a flat earth type.!


Yes, that's exactly my point. Gerald apparently thinks that because the
ocean is only a tiny component of the Earth, it can't have any effect.
He overlooks the fact that the effect is itself very small, only
detectable with extremely precise instrumentation (or very long
observation), just like the variation in rotation of a bowling ball
would be tiny- but likely detectable- if you applied some viscous force
to a thin film of fluid on its surface.
_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

On Jul 4, 1:18 pm, " wrote:
On Jul 4, 11:13 am, Quadibloc wrote:

[...]
(Incidentally, 12 inches is just over 30 centimeters: about 305 mm. It
is entirely possible that a "12 inch" bowling ball might actually be
exactly 300 mm in diameter, since slide rules and phonograph records,
for example, are in such metric sizes.)

Hmmm, my bowling ball is at home (I'm away at a BBQ) so I can't
measure it; Wikipedia to the rescue:

http://en.wikipedia.org/wiki/Bowling_ball

" Regulation ten-pin bowling balls must weigh no more than
" 16 pounds (7.2 kg) (governing bodies do not regulate how
" light a bowling ball may be) and have a diameter of 8.5
" inches (21.6 cm).

Then he was right about how big a bowling ball was in millimeters,
even if he had its size in inches wrong.

John Savard

On Jul 4, 11:43*am, Chris L Peterson wrote:
On Fri, 4 Jul 2008 09:06:50 -0700 (PDT), oriel36

wrote:
The idea is to appreciate the power of geodynamics rather than have it
subservient to the surface ocean.So,in terms of millimeters or
fractions of an inch,how thin is the ocean with respect to planetary
diameter in terms of the veneer on a bowling ball ?

Do you think that dragging a 50um film of fluid over the surface of a
bowling ball wouldn't have any effect on its rotation? Nonsense. There
are good mathematical models of Earth's rotation that demonstrate how
both solid-Earth tides and ocean tides contribute to the observed long
and short term rotational rate variation.

The actual forces that the ocean is able to exert on the Earth are very
small, but so is the net effect of those forces.
_________________________________________________

Chris L Peterson
Cloudbait Observatoryhttp://www.cloudbait.com

True, but...

Trying to talk sense to Oriel?

Not unlike teaching a pig to dance. It just annoys the pig and gets
you dirty.

My apologies to pigs, most of whom I've met display better manners and
more wisdom than Gerald Oriole does.

LOL.

\