Re: Pull of the Moon

[Phil Bigelow <bigelowp@juno.com>]

The umbra in the Mesozoic also would have been a lot larger.

In the early Precambrian, the effect would have been even more
pronounced, and there would have been MANY more eclipses per year than
there are today.  This phenomenon may have had a significant cooling
effect over the globe, to the extent that any future computer models that
address Precambrian climates may have to include that data into their
dataset.

A suggestion for the artists on the list:  Paint a Precambrian scene
where the comparatively tiny Sun is starting to reappear from behind the
huge Moon after an eclipse.  What an other-worldly painting that would
make!  The Earthglow that illuminates the New Moon would be a haunting
sight, alone.

Or paint a scene from the perspective of orbit, where the Precambrian
Moon casts an umbral shadow across 1/4 of the Earth's surface at once!

Too many ideas, absolutely no artistic talent,

<pb>
--
"We recognize, however dimly, that greater efficiency, ease, and security
may come at a substantial price in freedom, that law and order can be a
doublethink version of oppression, that individual liberties surrendered,
for whatever good reason, are freedoms lost." - Walter Cronkite, preface
to the 1984 edition of George Orwell's _1984_.


On Tue, 18 Apr 2006 14:03:19 -0600 frank bliss <frank@blissnet.com>
writes:
>   This discussion brought an image of a Cretaceous Lunar Eclipse into 
>  
> my minds eye.  Since the moon may have been 1/4 larger (ie. 1.25  
> minutes of angle), it would have periodically covered the suns disc  
> 
> much more completely and for a somewhat longer period of time (maybe 
>  
> the same length though because it was moving faster across the sky)  
> 
> for each eclipse. No annular eclipses in the Meso.  It would have  
> been quite a scene (and a good one to paint for one of you artists)  
> 
> of a Mesozoic eclipse putting all thee huge browsers of the day  
> asleep for an hour in the middle of the day.
> Frank (Rooster) Bliss
> MS Biostratigraphy
> Weston, Wyoming
> 
> 
> On Apr 18, 2006, at 6:02 AM, Phil Bigelow wrote:
> 
> >
> > On Tue, 18 Apr 2006 11:48:55 +0100 Steve White
> > <steve_d_white@hotmail.com> writes:
> >> I have a question. I read sometime back that the moon has been 
> slowly
> >> moving
> >> further out of orbit and that during the Mesozoic
> >
> >
> > Indeed it was. The Moon is constantly "stealing" rotational energy 
>  
> > from
> > the Earth (by causing tidal drag on the Earth's angular 
> momentum).
> > Earth's days are getting longer.  This "stolen" energy is then 
> used to
> > push the moon into a higher orbit.   Voila, conservation of 
> energy.
> >
> >
> >
> >> it was actually
> >> something
> >> like a quarter closer to Earth (but don't quote me on that).
> >
> >
> > I asked a similar question a while ago on the vrtpaleo list, the 
> only
> > difference was that I was seeking an algorithm to calculate a rate 
> of
> > separation vs. time curve.  I didn't get any answers then, but I 
> have
> > since learned that such an algorithm cannot be created, because 
> the
> > "true" curve probably doesn't follow a strict mathematical  
> > formula.  To
> > be sure, in a "perfect" 2-body system, the curve of the changing  
> 
> > rate of
> > separation (in cm/year) would start out high near the Y-axis (the  
> 
> > moon is
> > hypothesized to have formed at a distance of only 14,000 miles 
> from  
> > Earth
> > when it was formed ~4.4 Gya) and then the rate of separation 
> decreases
> > with geologic time (today: at 238,000 miles, with a rate of  
> > separation of
> > 1.5 inches per year).  But the E-M system isn't a perfect system, 
> and
> > that real curve is probably bumpy and jagged.
> >
> > So, failing to find a nice smooth curve to explain everything, the 
>  
> > only
> > fall-back methodology is to rely solely on the empirical data.   
> > This data
> > is obtained primarily from two sources:  1) rythmites and 2) 
> growth
> > layers on certain corals.  These data will give you the length of 
> a  
> > day
> > and the length of a lunar month.  From that information, you can
> > calculate the E-M separation at that point in time.
> >
> > I believe there are both rythmite and coral data from the 
> Mesozoic.
> >
> >
> >> I was
> >> interested in this from an artistic view (should we make the 
> moon
> >> larger in
> >> our Mesozoic skies?)
> >
> >
> > By all means.   The Mesozoic moon would only be modestly larger in 
> the
> > sky than it is today. (If you *really* want to shock your viewers, 
>  
> > paint
> > a scene from 4 Gya, when the moon was only 14,000 miles away!).  
> So if
> > you already know the E-M distance for a point in time, and if you  
> 
> > are a
> > stickler for scientific accuracy in your artwork, you can 
> calculate  
> > the
> > "angular" size of the Moon in the Mesozoic sky from its diameter 
> (2160
> > miles).  It's just simple trigonometry.
> >
> > As an aside, I recently saw a piece of paleo artwork (the 
> painter's  
> > name
> > escapes me, but it isn't anyone on this mailing list).  It was of 
> a
> > Precambrian shoreline scene at dusk, with stromatolite mats  
> > sticking out
> > of a tidal pool.  The author had drawn the moon at today's angular 
>  
> > size!
> > Worse, he also had the Big Dipper in the scene!
> >
> > He demonstrated good artistic technique (the painting was  
> > beautiful), but
> > his contextual knowledge was in desperate need of improvement.  
> :-(
> >
> >
> >> but was also curious to the effects a closer
> >> moon would
> >> have had on Earth - would the gravitational pull have been 
> stronger,
> >>
> >> affecting tides more radically in the likes of the Tethys Ocean 
> and
> >>
> >> Cretaceous Inland Seaway?
> >
> >
> > Tethys yes.  WIS not as much.
> >
> > Tidal magnitude not only depends on the E-M distance, it also  
> > depends on
> > the geometry of the land masses and the size of the body of water
> > involved.  Scattered land masses block global tidal movement.  
> N-S
> > trending land masses also block global tidal movement.   At points 
> in
> > time when there was only one huge landmass and mostly ocean, the 
> ocean
> > tides would be freer to move, unhindered by N-S trending 
> continents.
> > This would cause huge tides like nothing currently seen (larger 
> single
> > bodies of water = larger tides).
> >
> > Tethys shorelines, being E-W trending and bordering a huge sea, 
> would
> > have had large tidal currents, whereas WIS shorelines, being N-S  
> 
> > trending
> > and bordering a smaller sea, would have had considerably lower 
> tidal
> > currents. [Although ironically, the WIS shorelines, being  
> > perpendicular
> > to the tidal movements, may have experienced higher tidal 
> *amplitudes*
> > than did the Tethys shorelines which were parallel to the tidal
> > movements].
> >
> > Gondwana and Pangea, being huge lumpy land masses surrounded by a  
> 
> > single
> > Megasea (I coined a new term), probably gave the ocean a lot of  
> > room to
> > slosh around unhindered.  In contrast, some of the late Mesozoic 
> land
> > masses, like N. and S. America and Africa (post break-up), were
> > dominantly N-S trending.
> >
> > <pb>
> > --
> > "We recognize, however dimly, that greater efficiency, ease, and  
> 
> > security
> > may come at a substantial price in freedom, that law and order can 
>  
> > be a
> > doublethink version of oppression, that individual liberties  
> > surrendered,
> > for whatever good reason, are freedoms lost." - Walter Cronkite,  
> 
> > preface
> > to the 1984 edition of George Orwell's _1984_.
> >
> 
> 
>