Moon By Spinoff

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>[John]: Presumably, the Earth would be molten to great depth.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

That's a very interesting argument. By my botec estimates, if we compare Jupiter's tidal force on Io with the early Moon's on Earth, Juputer is roughly 24,000 times more massive, the cube of distance is 8,000 times smaller for Earth-Moon, Io has about three times smaller diameter than Earth, and the spin period of Earth would have been about 10 times faster than Io's. The net of all these factors is that the early Moon-Earth tides would have been about 10 times stronger than Jupiter-Io tides are today. That's enough to do a lot of melting okay. But is ten times more heat on Io enough to melt those volcanoes and level its surface? My intuition doesn't tell me, and I don't see a simple way to compute that in botec fashion.

Bit I'm inclined to suspect that some evidence of the fission chasm survives this period because otherwise, we'd lose an elegant explanation for Earth's unusual continent-basin surface.

Approaching this problem with a backwards time arrow, geologists indicate that continental drift began about a quarter billion years ago from a single "Pangea" continent. That is when the Atlantic basin began forming. Prior to that, the Earth had just one small continent (25% or so of Earth's surface) and was 70-75% ocean basin. So the Moon had nothing to do with splitting the continents that formed the Atlantic, as Darwin had originally proposed.

But then apparently something took away 75% of the Earth's crust and upper mantle. Surely that was the Moon-forming event.

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>If the Earth were spinning at such a rate that Fg on the equator were zero, and the crust then failed, one might expect the crust to be violently blown off the surface.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

"Overspin" means the centrifugal force exceeds the force of gravity, which must happen because gravity plus cohesion hold the crust in place. When Fg = 0, as you say, if you held a baseball in your hand and opened your hand, the baseball would not fall to the ground but would remain in place orbiting the Earth. The whole crust on the prolate bulge would have orbital speed. So with a bit more spin, it would eventually crack and lift off, but hardly explosively. Then the Earth will spring back and reshape itself.

Note that whatever becomes the "equator" at this stage need bear no resemblence to today's equator. -|Tom|-

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>
"Overspin" means the centrifugal force exceeds the force of gravity, which must happen because gravity plus cohesion hold the crust in place.
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May I humbly ask of how exactly such an overspun body could've come to being? If the spin was so great, every little rock on it's surface would roll towards equator, forming a ring contiguous with the planet itself; and we'd have a nice system of rings or at least a few smaller sized moonlets by now. Much easier to imagine would be a huge "volcanic eruption" about when the main body got mostly molten and those nasty heavy radioactive metals first came together by the means of centrifuging and gravitational stratification...

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>[AB]: May I humbly ask of how exactly such an overspun body could've come to being?<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

Most of the discussion on this message board refers to the scientific papers posted on the web site itself. In this case, the discussion is about "The original solar system", [url] metaresearch.org/solar%20system/origins/...nal-solar-system.asp [/url]

The short answer to your question is that all planets start out huge, gaseous, and of very low density just after fissioning from the Sun. Then as they cool and contract, they are forced to spin up to conserve angular momentum (like an ice-skater pulling in her arms). They may spin up, reach overspin, and fission several times, each event producing either a singlet moon (for solid planets) or a twin pair (for gaseous planets).

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>If the spin was so great, every little rock on it's surface would roll towards equator, forming a ring contiguous with the planet itself; and we'd have a nice system of rings or at least a few smaller sized moonlets by now.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

Radiation pressure forces and micrometeoroids are too strong and numerous in the inner solar system for rings to be stable over billions of years. Even Saturn's rings have been argued to be less than 100 million years old.

I didn't understand your remark about about rocks rolling toward the equator. As Earth approaches overspin, it takes on a prolate shape, but surface rocks are stable and experience no north-south forces. In fact, the surface becomes an equilibrium shape, just as it is today. Rocks don't get pushed toward the poles because the equator bulges out, or toward the equator because of centrifugal force. The two forces balance. -|Tom|-

Another factor which would increase spin rate is the phase change iron undergoes under extreme pressure. Iron under normal conditions has a density of about 8 g/cc, but under extreme pressure it goes to 10 or 12 g/cc, with a coresponding reduction in volume (it colapses).
I would think this would happen rather suddenly, and cause a rather abrupt spin increase, perhaps enough to cause a spinoff.

John Duff

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>

The short answer to your question is that all planets start out huge, gaseous, and of very low density just after fissioning from the Sun. Then as they cool and contract, they are forced to spin up to conserve angular momentum (like an ice-skater pulling in her arms). They may spin up, reach overspin, and fission several times, each event producing either a singlet moon (for solid planets) or a twin pair (for gaseous planets).

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I hate to argue with a pro, still I shall.
Overspin is inherently non-stable, and also requires some bond other than gravity to keep the body together. In case of gas or liquid there's no such bond at all, so overspin is prevented by continuous casting out gas and liquid into dissipating rings. It must happen as outflow rather than spit-outs. As only the rocks are left after all the gas/liquid is shed, the overspin momentum is then shed by casting those rocks into the rings. Then the main body heats up by the means of friction and gravity, melts up, thus gets a new liquid fraction to cast out to kill the overspin, then it starts to cool down. The crust finally seems to provide a kind of the additional bond to contain the overspin, but it only seems so, as the equatorial area would get just as many volcanoes as necessary to cast the lava out into the same rings as before. Then it cools some more and becomes more like the Earth is now, but even now the Earth's crust is not solid enough to bond individual rocks, it's more like a blob of liquid mud, since no rigid chrystalline crust can stand the tides and a whole bunch of other effects that turn the crust into a construction of smaller rocks and rocky layers kept together only by friction and gravity. Please understand that the chrystalline bonds are too weak to sustain a large enough structure, a rock in space - yes, Earth crust - never.
Thus an overspun Earth (as a body kept together by gravity) is about as stable as an overspun orbit, which is totally nonsensical.
In a few words - a large enough body kept together by the gravitational bonds is different from a freely orbiting pile of rocks only by the friction inside that body; and friction is not a bond.

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>
Radiation pressure forces and micrometeoroids are too strong and numerous in the inner solar system for rings to be stable over billions of years. Even Saturn's rings have been argued to be less than 100 million years old.
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Thus we have no rings to enjoy in the nigths. What a shame!

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>
Rocks don't get pushed toward the poles because the equator bulges out, or toward the equator because of centrifugal force. The two forces balance. -|Tom|-
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They balance out only without the overspin. Overspin creates the outflow of matter from the equatorial area, the equator becomes a sharp edge extending into a dissipating ring-like structure around the body.

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>
John Duff - Another factor which would increase spin rate is the phase change iron undergoes under extreme pressure. Iron under normal conditions has a density of about 8 g/cc, but under extreme pressure it goes to 10 or 12 g/cc, with a coresponding reduction in volume (it colapses).
I would think this would happen rather suddenly, and cause a rather abrupt spin increase, perhaps enough to cause a spinoff.
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No way it could happen across all the planet body instantaneously. As the conditions fulfill in some area, the phase transition happens there; across the whole body it's a gradual process rather than avalanche one.

<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>I hate to argue with a pro, still I shall.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

If it is not asking too much, may I suggest reading the paper at the reference I gave before criticizing with a strawman argument? That way, I do not have to retype the paper's contents here. <img src=icon_smile.gif border=0 align=middle> Your points are not applicable to classical fission models, which have been around for more than a century now. -|Tom|-