Tides must have made colonisation of land by marine life a lot
easier.. First adapt to drying out part of the time.

Richard Webb

on a related topic see-

Title: What if the Moon didn't exist? Earths that might have been.
http://www.atmos.ucla.edu/~fovell/AS19/index.html


--
regards,
david

(RJ Webb) wrote in message ...
Tides must have made colonisation of land by marine life a lot
easier.. First adapt to drying out part of the time.

Mind you at least they had the sense to develop eyes whilst still in
almost zero gravity. Imagine having to bump into each other until they
developed eye sockets whilst on dry land.

Mike Tullett wrote in message ...

Do you want to write to newsgroups and ask them to pull that
bafflement before you get blinded by science?

On 25 Sep 2003 18:41:24 -0700, Michael McNeil in
. com wrote:

Do you want to write to newsgroups and ask them to pull that
bafflement before you get blinded by science?

I'd answer that question if I had the the first idea what you meant. I'm
not baffled, as I taught *some* aspects of dynamic oceanography for over 20
years and thus claim some knowledge of the topic.

--
Mike posted to uk.sci.weather 26/09/2003 08:15:20 UTC
Coleraine
Seeking information about the Internet and the way it works? - Subscribe to
news:uk.net.beginners

Hi all,

(Michael McNeil) wrote in message . com...

Which of the three basic laws of motion defined by Newton in his intro
to the Pricipia.. does the bulge on the opposite side to the moon
obey?

Action and reaction are equal and opposite?


In his book on astronomy for kids, Patrick Moore has sketched the
positions of the sun and moon at Spring and Neap Tides. The earth is
shown with bulges on both sides. There is no representation of the
(presumably smaller) bulge under the sun. Or was he just kee[ing it
simple?

Whichever answer you get for the last question, you are running up
against a paradox.

A great start for a budding astronomer this book. The Sun's tide is
coincident with the lunar "low tide" in this situation. Hence the
reason why the "low tide" at neap tide is higher than one at spring
tide.

I fail to see why virtually everything has to have some kind of
"weird" or unexplained reason for occurring, although I must admit,
your posts always encourage a flurry of responses!

cheers,

Paul K.

"Mike Tullett" wrote in message
...
On 25 Sep 2003 18:41:24 -0700, Michael McNeil in
. com wrote:

Do you want to write to newsgroups and ask them to pull that
bafflement before you get blinded by science?

I'd answer that question if I had the the first idea what you meant. I'm
not baffled, as I taught *some* aspects of dynamic oceanography for over 20
years and thus claim some knowledge of the topic.


Well it made reasonable sense to me.....
Thanks.

Col
--
Bolton, Lancashire.
160m asl.
http://www.reddwarfer.btinternet.co.uk

Imagine having to bump into each other until they
developed eye sockets whilst on dry land.

You've just described the average current-day driver ;-)



~~~~~~~~~~
This is sent from a redundant email
Mail sent to it is dumped
My correct one can be gleaned from
h*$el***$$n*$d$ot$**s**i$$m*$m$**on**$s$@*$$a**$*o l*$*.*$$c$om*$
by getting rid of the overdependence on money and fame
~~~~~~~~~~

Mike Tullett wrote in message ...

I'm not baffled, as I taught *some* aspects of dynamic oceanography for over
20 years and thus claim some knowledge of the topic.


So you have been teaching it as long as I have been trying to
understand it? And this is not bull sh then:

To understand the second bulge in the lunar component, we have
to treat the earth and moon as one system with a common centre of
mass. This is known as the Barycentre and lies within the earth,
nearly 3000 miles from the earth's centre.

Not only is the moon rotating about this point once very 28 days, but
so is the earth's centre, i.e. it wobbles as it orbits the sun.

One can argue to keep the earth rotating around that point, requires
an inward acting force (on the opposite side to the moon - a
centripetal force) and this weakens the "gravity" there thus allowing
that second bulge to form. I am simplifying things a lot and diagrams
would be useful.

This site looks quite sound - "Why are there two high tides each day"

http://www.math.nus.edu.sg/aslaksen/teaching/tides.html

Mind you, this is very much the Newtonian approach and assumes very
deep water (much deeper than is really the case), and no land to
affect the
tidal bulges as the encircle the earth.

1.

First of all can we agree that due to the surrounding mass of the
earth there is virtually no gravity or rather almost zero
gravitational attraction at the centre of the earth? This being
similar to what would happen to the smaller mass in a Cavendish
gravity experiment if two equal weights were counterbalanced each side
of it. (The centre mass is "not attracted to either." As it were)

(And by extension showing that the tidal raising ability of the full
moon is much less than at any other phase or portion of a phase.)

2.

By further extension the barycentre is the centre of the sun, moon and
earth. Therefore they will have no "pull" on an object at point zero.

3.
The simplification of an inward acting force (if that were a
possibility) requires that it is uni- or bi- directional in order to
affect only one or two sides of the earth; yet we have shown that the
barycentre is by definition a centre of gravity.

As regards Newton, he did not resolve the problem of tidal action
except that he acknowledged the seas only obeyed the perception in the
Sea of Aethiope and nowhere else.

Today of course we know that there are numerous varieties of tides
from the one a day that follows the sun at Fiji, to the complex double
highs of the Solent and the extraordinary ranges such as at Bristol.
And that some tides, such as those at Seattle, have a mixed tropical
and whatever the name for our type is.

As it happens it appears that the tide around the British Islands seem
to work on a three phase pulse where the tides at Orkney, Liverpool
and Dover are nearly at high or low tide at the same time but those on
the west of Ireland, Hull and Bristol are on the opposite part of the
range.

As for the rest of the stuff on that site I just get past boredom
trying to put it all straight. You must choose to believe what you
wish. I know I can't convince you otherwise.

In article ,
says...
Which of the three basic laws of motion defined by Newton in his intro
to the Pricipia.. does the bulge on the opposite side to the moon
obey?


All of them.

--
Alan LeHun