Jeff Morris wrote:

OK, Nav, its clear you're not going to get this without some help. You keep
claiming the centrifugal force varies across the Earth. However, that is not
the case. Your assumption is that the Earth is rotating around the E-M
barycenter, and that because that is offset from the Earth center, the
centrifugal force is unbalanced. (Or more precisely, you claim the "r" in the
centrifugal force equation is different on the near and far sides of the Earth.)


I think it's you that does not understand that the rotation force is
based on the lunar cycle -28 days!

However, if we remove the daily rotation,

Great idea -not based in reality of course.

the Earth does not move around the
barycenter quite like you think.

Like I think?

Only the center of the Earth describes a
circle around the barycenter.

So the Earth does wobble (now you are getting really close to the whole
story -where harmonics of all the orbital periods give a complete
answer). Now, don't all points on the surface move similarly around the
barycenter and if they do, what is the difference in their orbital path
to that of a circle? Now as I see it, from the math, the differential
gravity model takes no account of this, exploiting the idea that the
orbital motion of every point on the surface is perfectly circular
around the moon (thereby allowing a cancellation of the centrigal
component), a point that you seem to be having a bit of trouble grasping.

By the way, the differential gravity idea first came from Newton. It's
correct as far as it goes but the orbital mechanics of the Earth-Moon
pair are more complicated (as far as I've been able to read, Newton only
saw the free falling body aspect in his tidal proposal). The Devil _is_
in the details and you can't ignore the system rotation. This really is
my last post on this. If you still haven't got the idea then I really
can't make it any clearer and you'll just have to ponder why University
Departments of Oceanographics (and NOAA etc.) all say that THE TIDES ON
EARTH are due to the difference between centrifugal and gravity forces.

Cheers

"Nav" wrote in message
...


Jeff Morris wrote:

OK, Nav, its clear you're not going to get this without some help. You keep
claiming the centrifugal force varies across the Earth. However, that is
not
the case. Your assumption is that the Earth is rotating around the E-M
barycenter, and that because that is offset from the Earth center, the
centrifugal force is unbalanced. (Or more precisely, you claim the "r" in
the
centrifugal force equation is different on the near and far sides of the
Earth.)


I think it's you that does not understand that the rotation force is
based on the lunar cycle -28 days!

However, if we remove the daily rotation,

Great idea -not based in reality of course.

We are looking for the dominant effect - the daily rotation is not a contributor
to that. There are a variety of effects we're ignoring.


the Earth does not move around the
barycenter quite like you think.

Like I think?

OK, as you claim.


Only the center of the Earth describes a
circle around the barycenter.

So the Earth does wobble (now you are getting really close to the whole
story -where harmonics of all the orbital periods give a complete
answer). Now, don't all points on the surface move similarly around the
barycenter

No. Only the center of the Earth revolves around the barycenter. Other points
on the Earth revolve around other points nearby. Stop arguing and just work it
out with a model. If you "wobble" a disk, all points wobble the same way.
You're claiming that some points describe small circles, and some point describe
large circles, but that clearly can't happen unless you rotate the disk.

and if they do, what is the difference in their orbital path
to that of a circle?

All paths are the same. That's my point - stop talking and wobble a plate on
the table without rotating it. All points on it trace the same circle. Hold a
pencil on each side and look at the circles they trace. They all have the same
radius, and therefore the same centrifugal force.

Now as I see it, from the math, the differential
gravity model takes no account of this, exploiting the idea that the
orbital motion of every point on the surface is perfectly circular
around the moon (thereby allowing a cancellation of the centrigal
component), a point that you seem to be having a bit of trouble grasping.


There is no need to grasp it. You entire argument is different points feel
different rotation. But they don't - all points on the Earth feel the same
centrifugal force.

But your argument fails another test: The centrifugal force is "fictional" -
it is just a convenience to simplify some problems. The only real force at play
here is gravity, so any alternate approach must yield the same answer as a
"gravity only" solution.

By the way, the differential gravity idea first came from Newton. It's
correct as far as it goes but the orbital mechanics of the Earth-Moon
pair are more complicated (as far as I've been able to read, Newton only
saw the free falling body aspect in his tidal proposal). The Devil _is_
in the details and you can't ignore the system rotation. This really is
my last post on this. If you still haven't got the idea then I really
can't make it any clearer and you'll just have to ponder why University
Departments of Oceanographics (and NOAA etc.) all say that THE TIDES ON
EARTH are due to the difference between centrifugal and gravity forces.

As I've said, it's very easy to find numerous sites that scoff at the NOAA site
you've mentioned, its regularly cited as "bad science." And I don't deny that
there are a handful of sites that "handwave" that centrifugal force is the cause
of the second bulge, but there are dozens that refute that in great detail.
And virtually every published text supports my view.

And you still haven't responded to the obvious flaws in the formula you
proposed. If the centrifugal force from the Moon is as you claim, why does your
math show that the Sun's contribution is only 1% of the Moon's? You when to
great pains to show the math, but when I showed it was bogus you got very quiet
on that front.

"Nav" wrote in message
...
....
If you still haven't got the idea then I really
can't make it any clearer and you'll just have to ponder why University
Departments of Oceanographics (and NOAA etc.) all say that THE TIDES ON
EARTH are due to the difference between centrifugal and gravity forces.

I have never claimed that you can't derive the tides by computing the difference
between gravitational pull and the centrifugal force. My point has been that
centrifugal force is constant across the Earth, and thus does not explain why
the bulges are in opposite directions. The centrifugal force is exactly
canceled by the average gravitational pull, and what is left over is the
differential force. Your claim has been that the centrifugal force varies
across the Earth, and that's what I've taken exception to.

You keep citing the NOAA page,
http://www.co-ops.nos.noaa.gov/restles3.html
So I went back and read that in detail. In it is the "disclaimer":

"While space does not permit here, it may be graphically demonstrated that, for
such a case of revolution without rotation as above enumerated, any point on the
earth will describe a circle which will have the same radius as the radius of
revolution of the center-of-mass of the earth around the barycenter. Thus, in
Fig. 1, the magnitude of the centrifugal force produced by the revolution of the
earth and moon around their common center of mass (G) is the same at point A or
B or any other point on or beneath the earth's surface. Any of these values is
also equal to the centrifugal force produced at the center-of-mass (C) by its
revolution around the barycenter."

it goes on to develop differential gravity:

"While the effect of this centrifugal force is constant for all positions on the
earth, the effect of the external gravitational force produced by another
astronomical body may be different at different positions on the earth because
the magnitude of the gravitational force exerted varies with the distance of the
attracting body."

In other words, this site actually agrees with what I have been saying.
Frankly I owe an apology to the site's author, since I maligned it without
reading carefully. In fact, although it leads with a provocative line about a
"little known aspect of the moon's orbital motion," and has a rather confusing
diagram, its basic approach is correct and in full agreement with my claim.
Apparently the site was actually changed at some point about two years ago
because of complaints on another board.

Jeff Morris wrote:



In other words, this site actually agrees with what I have been saying.
Frankly I owe an apology to the site's author, since I maligned it without
reading carefully. In fact, although it leads with a provocative line about a
"little known aspect of the moon's orbital motion," and has a rather confusing
diagram, its basic approach is correct and in full agreement with my claim.
Apparently the site was actually changed at some point about two years ago
because of complaints on another board.


The site certainly agrees with me. Don't confuse rotation of the earth
with rotation about the system center. Here is the exact quote and it's
concurrance with my view is as clear as day:

"1. The Effect of Centrifugal Force. It is this little known aspect of
the moon's orbital motion which is responsible for one of the two force
components creating the tides. As the earth and moon whirl around this
common center-of-mass, the centrifugal force produced is always directed
away from the center of revolution. All points in or on the surface of
the earth acting as a coherent body acquire this component of
centrifugal force. And, since the center-of-mass of the earth is always
on the opposite side of this common center of revolution from the
position of the moon, the centrifugal force produced at any point in or
on the earth will always be directed away from the moon. This fact is
indicated by the common direction of the arrows (representing the
centrifugal force Fc) at points A, C, and B in Fig. 1, and the thin
arrows at these same points in Fig. 2."

Note the "one of the two forces".

Cheers

Jeff Morris wrote:

"Nav" wrote in message
...
...

If you still haven't got the idea then I really
can't make it any clearer and you'll just have to ponder why University
Departments of Oceanographics (and NOAA etc.) all say that THE TIDES ON
EARTH are due to the difference between centrifugal and gravity forces.


I have never claimed that you can't derive the tides by computing the difference
between gravitational pull and the centrifugal force. My point has been that
centrifugal force is constant across the Earth, and thus does not explain why
the bulges are in opposite directions. The centrifugal force is exactly
canceled by the average gravitational pull, and what is left over is the
differential force. Your claim has been that the centrifugal force varies
across the Earth, and that's what I've taken exception to.


F= mr omega^2. The distance from the barycenter to all points on earth
is NOT the same. Anyway, the site clearly shows in Fig. 2 that it is the
_DIFFERENCE_ between gravity and centrifugal force that makes the tides,
not gravity alone. There really is no point going on any more is there?
For myself, I'm sick of repeating the same point over and over.

EOT

Cheers


You keep citing the NOAA page,
http://www.co-ops.nos.noaa.gov/restles3.html
So I went back and read that in detail. In it is the "disclaimer":

"While space does not permit here, it may be graphically demonstrated that, for
such a case of revolution without rotation as above enumerated, any point on the
earth will describe a circle which will have the same radius as the radius of
revolution of the center-of-mass of the earth around the barycenter. Thus, in
Fig. 1, the magnitude of the centrifugal force produced by the revolution of the
earth and moon around their common center of mass (G) is the same at point A or
B or any other point on or beneath the earth's surface. Any of these values is
also equal to the centrifugal force produced at the center-of-mass (C) by its
revolution around the barycenter."

it goes on to develop differential gravity:

"While the effect of this centrifugal force is constant for all positions on the
earth, the effect of the external gravitational force produced by another
astronomical body may be different at different positions on the earth because
the magnitude of the gravitational force exerted varies with the distance of the
attracting body."

In other words, this site actually agrees with what I have been saying.
Frankly I owe an apology to the site's author, since I maligned it without
reading carefully. In fact, although it leads with a provocative line about a
"little known aspect of the moon's orbital motion," and has a rather confusing
diagram, its basic approach is correct and in full agreement with my claim.
Apparently the site was actually changed at some point about two years ago
because of complaints on another board.

Holy Back Pedal!!! Now you're claiming you agreed with me all along??? Just
22 hours ago we had this exchange:

Actually, applying it in this context is your problem. Centrifugal
acceleration
is constant, it doesn't vary across the surface of the Earth as you claim.
Remember, it doesn't even exist, its actually a reference frame shift.

It is a much larger force than differential gravity but you want to
ignore it? You are wrong Jeff, it does vary across the surface of the
earth Jeff -the Barycenter is at ~3/4 r! On the moon side it's ~1/7 as
large. Finally, (repeating yet again) it is the ____DIFFERENCE______
between inertial and gravity forces that make the tides. To say it's
only "differential gravity" (I shudder at that term) is clearly wrong -
this was a simple proof.


You actually provided the math that "proves" centrifugal force varies, and thus
causes tides much larger predicted by the accepted formula. Now you're
claiming you never meant that at all?


Right, Navie. Its the Constellation all over again.



"Nav" wrote in message
...


Jeff Morris wrote:



In other words, this site actually agrees with what I have been saying.
Frankly I owe an apology to the site's author, since I maligned it without
reading carefully. In fact, although it leads with a provocative line
about a
"little known aspect of the moon's orbital motion," and has a rather
confusing
diagram, its basic approach is correct and in full agreement with my claim.
Apparently the site was actually changed at some point about two years ago
because of complaints on another board.


The site certainly agrees with me. Don't confuse rotation of the earth
with rotation about the system center. Here is the exact quote and it's
concurrance with my view is as clear as day:

"1. The Effect of Centrifugal Force. It is this little known aspect of
the moon's orbital motion which is responsible for one of the two force
components creating the tides. As the earth and moon whirl around this
common center-of-mass, the centrifugal force produced is always directed
away from the center of revolution. All points in or on the surface of
the earth acting as a coherent body acquire this component of
centrifugal force. And, since the center-of-mass of the earth is always
on the opposite side of this common center of revolution from the
position of the moon, the centrifugal force produced at any point in or
on the earth will always be directed away from the moon. This fact is
indicated by the common direction of the arrows (representing the
centrifugal force Fc) at points A, C, and B in Fig. 1, and the thin
arrows at these same points in Fig. 2."

Note the "one of the two forces".

Cheers

"Nav" wrote in message ...


F= mr omega^2. The distance from the barycenter to all points on earth
is NOT the same.

As the site expalins in the next paragraph, only the center of the Earth rotates
around the barycenter. Other points rotate around neighboring points.

Anyway, the site clearly shows in Fig. 2 that it is the
_DIFFERENCE_ between gravity and centrifugal force that makes the tides,
not gravity alone.

We never disagreed on this point. My issue has always been that since Centrifugal
Force is constant, it doesn't directly explain the two bulges. It is useful for
people who would have trouble with the seeming "negative gravity" of the far side
bulge, but it is also possible to fully describe the tides quite simply without
Centrifugal Force at all.

There really is no point going on any more is there?
For myself, I'm sick of repeating the same point over and over.

But your point seems to change on each post. First you claim CF varies, then you
claim to be in complete agreement with a site that says its constant. Now you're
saying it varies again. You provide your formula and challange me to work it out,
then never explain why it give bogus answers.

Constitution Constitution CONSTITUTION!!!!! opps .... constellation


EOT

Cheers


You keep citing the NOAA page,
http://www.co-ops.nos.noaa.gov/restles3.html
So I went back and read that in detail. In it is the "disclaimer":

"While space does not permit here, it may be graphically demonstrated that, for
such a case of revolution without rotation as above enumerated, any point on the
earth will describe a circle which will have the same radius as the radius of
revolution of the center-of-mass of the earth around the barycenter. Thus, in
Fig. 1, the magnitude of the centrifugal force produced by the revolution of the
earth and moon around their common center of mass (G) is the same at point A or
B or any other point on or beneath the earth's surface. Any of these values is
also equal to the centrifugal force produced at the center-of-mass (C) by its
revolution around the barycenter."

it goes on to develop differential gravity:

"While the effect of this centrifugal force is constant for all positions on the
earth, the effect of the external gravitational force produced by another
astronomical body may be different at different positions on the earth because
the magnitude of the gravitational force exerted varies with the distance of the
attracting body."

In other words, this site actually agrees with what I have been saying.
Frankly I owe an apology to the site's author, since I maligned it without
reading carefully. In fact, although it leads with a provocative line about a
"little known aspect of the moon's orbital motion," and has a rather confusing
diagram, its basic approach is correct and in full agreement with my claim.
Apparently the site was actually changed at some point about two years ago
because of complaints on another board.

Jeff Morris wrote:

"Nav" wrote in message ...


F= mr omega^2. The distance from the barycenter to all points on earth
is NOT the same.


As the site expalins in the next paragraph, only the center of the Earth rotates
around the barycenter. Other points rotate around neighboring points.


Anyway, the site clearly shows in Fig. 2 that it is the
_DIFFERENCE_ between gravity and centrifugal force that makes the tides,
not gravity alone.


We never disagreed on this point.


HOLY BACKPEDAL!!!!!!

Cheers

"Nav" wrote in message ...
Jeff Morris wrote:
"Nav" wrote in message
...
F= mr omega^2. The distance from the barycenter to all points on earth
is NOT the same.

As the site expalins in the next paragraph, only the center of the Earth rotates
around the barycenter. Other points rotate around neighboring points.

Anyway, the site clearly shows in Fig. 2 that it is the
_DIFFERENCE_ between gravity and centrifugal force that makes the tides,
not gravity alone.

We never disagreed on this point.

HOLY BACKPEDAL!!!!!!

I'm not sure you really want to go back over this thread - your record is rather
shaky. Mine, however, has been quite consistent. Remember, I started by posting
sites with differing approaches to show that this problem can be looked at in
different ways. I then made my first comment about Centrifugal force with:

"Remember that Centrifugal Force may be a handy explanation, but it is a
"fictional force" that only appears real to an observer in an accelerating frame
of reference. Therefore, whenever it is used to explain something, there must
be another explanation that works in a non-accelerating frame."

but then you started claiming that differential gravity wasn't needed, I responded
with:

"Before I thought you were just arguing philosophically how much we should credit
centrifugal force, but now it appears you haven't really looked at the math at
all. The reason why "differential gravity" is invoked is because it represents
the differing pull of the Moon on differing parts of the Earth. Although this
force is all obviously towards the Moon, when you subtract off the centrifugal
force this is what is left. It is this differing pull that causes the two
tides."

or, in other words, exactly what I just said above.

a few posts later:
"Given that, your argument falls apart. The centrifugal force is exactly the
same on all points of the Earth, and (not by coincidence) is exactly opposite
the net gravitational force. What is left over is the differential gravity."

The bottom line here is that the tides are properly described by the differential
gravity equation. Centrifugal force can be used to explain how an outward force can
be generated, but it is not needed, and it does not yield the equation that describes
the tides.

Frankly, your the one who started this by claiming that the traditional explanation of
tides is fundamentally flawed, and that the differential force normally cited is not
what causes the tides. You really haven't produced any coherent evidence to support
this claim.

Now why try to distort the truth Jeff? I never ever said differential
gravity was not needed. I always said that it's the difference between
gravity and centrifugal forces. You do understand the connotations of
the DIFFERENCE between forces don't you? It does not mean that either
component is zero and actually implies that both are important. Shesh!
Still it's nice to see that you now agree that centrifugal forces should
not be ignored (as they are in the gravity only model). As I've said so
many times, the key to understanding is that the system rotates about
the barycenter and it is not just a gravity field problem. The rotation
actually provides the energy needed to power the daily tides -think
about it OK?

Cheers

Jeff Morris wrote:

"Nav" wrote in message ...

Jeff Morris wrote:

"Nav" wrote in message

...

F= mr omega^2. The distance from the barycenter to all points on earth
is NOT the same.

As the site expalins in the next paragraph, only the center of the Earth rotates
around the barycenter. Other points rotate around neighboring points.


Anyway, the site clearly shows in Fig. 2 that it is the
_DIFFERENCE_ between gravity and centrifugal force that makes the tides,
not gravity alone.

We never disagreed on this point.

HOLY BACKPEDAL!!!!!!


I'm not sure you really want to go back over this thread - your record is rather
shaky. Mine, however, has been quite consistent. Remember, I started by posting
sites with differing approaches to show that this problem can be looked at in
different ways. I then made my first comment about Centrifugal force with:

"Remember that Centrifugal Force may be a handy explanation, but it is a
"fictional force" that only appears real to an observer in an accelerating frame
of reference. Therefore, whenever it is used to explain something, there must
be another explanation that works in a non-accelerating frame."

but then you started claiming that differential gravity wasn't needed, I responded
with:

"Before I thought you were just arguing philosophically how much we should credit
centrifugal force, but now it appears you haven't really looked at the math at
all. The reason why "differential gravity" is invoked is because it represents
the differing pull of the Moon on differing parts of the Earth. Although this
force is all obviously towards the Moon, when you subtract off the centrifugal
force this is what is left. It is this differing pull that causes the two
tides."



a few posts later:
"Given that, your argument falls apart. The centrifugal force is exactly the
same on all points of the Earth, and (not by coincidence) is exactly opposite
the net gravitational force. What is left over is the differential gravity."

The bottom line here is that the tides are properly described by the differential
gravity equation. Centrifugal force can be used to explain how an outward force can
be generated, but it is not needed, and it does not yield the equation that describes
the tides.

Frankly, your the one who started this by claiming that the traditional explanation of
tides is fundamentally flawed, and that the differential force normally cited is not
what causes the tides. You really haven't produced any coherent evidence to support
this claim.