Mulitregional vs Out of Africa

[Forum Monk]

I don't think the circumpolar current are affected much as I believe much of that is driven by the coriolis effect but I would have to look deeper into the mechanics of it.

Like you, I was immediately struck by the apparent "out of balance" appearance of the earth when pangea existed and it made me think about those questions. I wonder though, just how severe it really it was. We don't realize it, but the surface of the earth is moving at incredible velocity relative its center. But how "out of balance" was it?

[Digit]

I suspect that the imbalance Monk would be determined more by the depth of the continental mass than its area, but that of course multiplied by the velocity, which was greater in the past than now.
The present imbalance should be calculable by the dia of the precession circle, but in the past?
One way that might work would be if we could positively identify a given star of the ancients, and they gave us sufficient data, the dia of the precession should be calcuable from that star's rising, and from that whether the imbalance is changing, which it should be if the continents are moving towards a more balanced state.

[Forum Monk]

Presently, precession is caused by the oblatness of the earth, i.e. the bulge at the equater caused by rotational velocity. The suns gravitational pull causes a moment which determines the processional rate. It is also effected by the moon and the other planets but to a much, much lesser degree. Since precession is a long period cycle, the out of balance seen in a 24 hour rotation must be very, small and averages out. Seems to me it would only appear as a very slight nutational-like blip in the greater motion. The math for all of this is heavy and I have not seen it attempt to compensate for the distribution of mass on the surface of the earth. So I would conclude, mass distribution is not important for the precessional cycle.

Still, I wonder what the roational, centrifugal forces do to the mass distribution. It seems intuitive, it would affect the rotational velocity and introduce a wobble, which, if it was greate enough, could really shake things up. Again I have to wonder, how bad was it? Don't forget, though, the water itself also has mass. Let's see if I can find any studies of mass distribution.

[Digit]

Our post crossed Monk. Yes water has mass, but by being more evenly distributed at the time of Pangea its effect should have been minimal.
As you say, the measureable movements are small, but here we are dealing with enormous time scales.
The Earth is an oblate spheriod, more or less, it is actually more Pear shaped with lines of latitude in the north longer than there counterparts in the south, which of course demonstrates that continental mass X velocity can distort even a planet.
For this reason I have argued in the past that a black hole must be disc shaped, unless the laws of momentum don't apply in those extreme physics. This also why I tend to take statements of the nature that 'sea level has risen this year by 3 mm measured by satellite'. Satellites do not move in smooth, repeatable orbits, so how they achieve these figures I simply do not understand.

[Minimalist]

Before this gets too far into the mechanics of precession let me drag it back to archaeology for a moment.

Part of the Bauval-Hancock theory on the sphinx is that it was originally cut as an equinoctal marker in 10,500 BC...or thereabouts, when the sun rose in Leo. For that reason, it was carved as a lion. (Later on, after millenia of erosion it was re-carved with the face of the current megalomaniac pharoah.)

This theory requires that the sphinx be dated to much earlier than the 4th dynasty (which, as far as Schoch is concerned, he has done) but also that the concept of the zodiac existed AND one group of stars had been determined to resemble a lion. In 10,500 BC. At least 7,000 years prior to what we now consider the derivation of the idea.

7,000 years is a long time. Hard to imagine how the idea could ever be proven.

[Digit]

My point Min when I said about positive identification. Taking the constellation to be Leo the case stands up well. But how do we know that is the relevant constellation? The only constellations that trigger a response with me are The Dipper and Cygnus, all the others require a leap of imagination that I obviously lack.

[Minimalist]

You can't go by me....as far as I'm concerned none of them look like anything. I also do not do well on Rohrschact tests.

So an equinoctal marker in the shape of a lion during the Age of Leo requires that SOMEONE had already devised this system and that it was widespread enough at that early date so that it would be in general usage.

Hard to believe. Can't imagine ever being able to prove it.

[Forum Monk]

I didn't realize, but somehow we've got precession running in two threads now. Should we also move it to "Oh Christ" so I can sound like I know what I am talking about on that thread?

If I am not mistaken, the Egyptologists will proclaim in unison, that the AE did not hold Leo in particular regard. I don't even think it is mentioned in any of their texts. If the thing is 12000+ years old it would have to be the oldest man-made structure ever, predating anything else by about 4000 years. That alone should tell you something doesn't add up.

[Digit]

Constellations were thought up years a go, Marduk would know, I think they go back to at least Babylon, but even if we can identify the names they used how can we relate those names to a pattern of stars?
And don't ask me how we ended up on two threads Monk.

[ravenwing5910]

And don't ask me how we ended up on two threads Monk.

That's simple, it's all connected.

But since you have moved into the realm of mathematics, I am certainly out of this conversation. But keep it going I am very interested.

[Digit]

The principles involve no maths RW and are familiar to anybody interested in engineering or astronomy, and there are as many disparate views in astro physics as archaeology. My favourite is the accepted view that the planets condensed from the Sun's accretion disc, which if correct leaves an argument as to why the sun spins as slowly as it does, and is usually dodged by the experts. But that's another forum.

[Forum Monk]

The Sumerians had named constellations probably around 3000bce. Marduk had posted the info several times (search for "mul mul") as the name for the Pleaides), but again we against the limits for written records.

As for plate tectonics I found an interesting link but I not sure if it works. The quotations below are actually taken from google's cache:

What drives plate tectonics ?

One of the major objection to continental drift was that continents could not plough their way through the oceanic crust. Plate tectonics does not have that problem as the plates are comprised of both oceanic and continental material. We did briefly mention some of the objections to contracting and expanding Earth hypotheses which seek to avoid this problem also. In the light of the above discussion, another problem with the contracting Earth hypothesis is that the rate of cooling would be too slow to account for the observed plate velocities. The expanding Earth hypothesis also has problems in that the increase in the Earth's radius required to explain the present day positions of the continents is far greater (nearly double) than that inferred from palaeomagnetic measurements and also the moment of inertia can have differed by < 1% in terms of the present day moment of inertia, although the expanding Earth hypothesis requires about 6% reduction.

So, having discarded contraction and expansion, how do we drive plate tectonics ? We already know about heat flow in the Earth and how the heat flow at ocean ridges is higher than average, while subduction zones have low heat flow. We also discussed the possibility that the Earth loses much of its heat from the mantle by the efficient convection process. We will not go into the details of the convection process suffice to say that we need to consider the competition between forces which oppose convection and those which promote it within a layer. The former include the viscosity of the mantle (which is very viscous because it is solid rock) and the thermal conductivity (conduction is a competing way of losing heat) while the latter includes the temperature difference across the layer, the greater this difference the more likely convection will occur, and the density (light material is more likely to rise). The ratio of the forces promoting convection to those opposing it defines the Rayleigh number (Ra). The larger the Rayleigh number the more likely it is convection will occur.

The laboratory experiments and the rebound studies provide data required for theoretical calculations to simulate convection. These are very complex and beyond what we need to address here but the results show it is quite reasonable for the Earth's mantle to convect (in the solid state) and in doing so it moves at velocities similar to the plates (100-200 mm per year). The plates seem to be passive passengers travelling as part of the convection system although may actually be part of the convecting system, representing the cooling outer boundary. Plates may also contribute to their motion by the forces of gravity (e.g. pulling the lithosphere down a subduction zone - slab pull, sliding down from a mid-ocean ridge to the subduction zone - gravity sliding or some force related to the intrusion of new material at the ridge - ridge push). These processes may contribute to some extent but they all require plate tectonics to exist in the first place. Large scale convection is the most reasonable mechanism (we know the Earth is losing heat), but there are still many unresolved questions about the actual form of the convection, i.e. how big are the convection cells, how regular is the convection, does the mantle convect as one layer or is it stratified and what role the continents have in convection ? However, this is a major area of current research in Earth Sciences, and answers should be forthcoming in the near future.

Extracted from cache image of:
http://www.huxley.ic.ac.uk/Local/EarthS ... drift.html

Hmmmm. It was an unexpected explanation for me.

[Minimalist]

If I am not mistaken, the Egyptologists will proclaim in unison, that the AE did not hold Leo in particular regard

Of course not, because they are wedded to dynastic Egypt which matured during the Age of Taurus (the Bull) c 4000 to 2000 bc. And Egypt did worship the bull.....as did Crete among others.

[Digit]

Doh! I'm baffled Monk. I follow the idea once the upwelling and subduction zones exist, but I've never understood why the Earth should lose heat through a massive continent like Pangea when the crust would have been much more easily ruptured beneath the oceans.
If there was a weakness where the continents split it must have been somewhere near where they originally joined, as otherwise the crust seems to be fairly even in thickness in the absense of mountains, which in any case could have only been formed by a collision in the first place.
What did the Earth look like pre-Pangea?

[Forum Monk]

If there was a weakness where the continents split it must have been somewhere near where they originally joined, as otherwise the crust seems to be fairly even in thickness in the absense of mountains, which in any case could have only been formed by a collision in the first place.

True. The theory (operative word THEORY) is a plate tectonics theory so the continents are on plates which have edges, where they join, spread or subduct.

What did the Earth look like pre-Pangea?

This is the million dollar (or pounds sterling if you prefer) question, my friend. Obviously if the theory is true, what did the continents look like before they drifted together???

And by the way - there are other very interesting theories even for plate tectonics. For example, follow this link to "The Continental Drift Extracts"
http://www.earthmatrix.com/symmetry/con ... itique.htm