Moon By Spinoff

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...it seems to me that any existing ocean would tend to "heap" up more because it adjusts to equilibrium faster than the crust can. At the moment of disruption wouldn't a tremendous amount of ocean water fly out into space along with the rubble and coorbit with the Moon
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"To heap" is too mild a word. The velocity on the equator would be exactly that of a freely orbiting body. The pressure at the equator plane inside the globe would be exactly zero in radial direction, while staying at its present value in direction to the poles. No liquid matter inside the globe can survive such conditions without being squeezed out through all the cracks and pores of the crust; and the crust itself would behave as if been made of sand, i.e. much like liquid. No atmosphere or surface water would survive such conditions.

Thus to get a Moon by spin-off, the Earth would better be molten and have its core spinning much faster than the surface. So the Moon must be considerably older than the crust we inhabit - that's for a spin-off model... Far easier to imagine would be a capture of the Moon when the Earth was a gaseous/liquid/mud shapeless blob quite able to slow down such a large body without disintegrating itself, being yet not quite "integrated"; then the accretion could continue to the two centres instead of one.

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The pressure at the equator plane inside the globe would be exactly zero in radial direction, while staying at its present value in direction to the poles.

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This takes me back to Duffdvll's comment amount the phase change of iron's density. Iron is not the only material deep inside the Earth that can experience a phase change. If the pressure is taken off in the radial direction it stands to reason that some of the material that is not metastable would suddenly expand outward along the equatorial plane and tend to bulge the equator more than if centripetal acceleration were at work alone. This stored energy should be quite substantial. If these events really happened it would make a hell of an IMAX movie.

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If the pressure is taken off in the radial direction it stands to reason that some of the material that is not metastable would suddenly expand outward along the equatorial plane and tend to bulge the equator more than if centripetal acceleration were at work alone.
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I'm afraid, the phase change from higher to lower density should be rather endothermic. Then the expanding matter would get kinetic energy from its own heat. The more I think of it, the crazier seems the idea that our Earth could even survive overspin altogether.

But my initial point was that an overspun planet could not form in the first place. A nebula with excessive angular momentum should form a disc consisting of a system of concentric rings, the angular velocity being constant within individual ring due to internal friction and quantized between the rings. Only as the excess of angular momentum was being lost, could the further accretion happen. Thus the loss of angular momentum and the accretion process must happen in a dynamic equilibrium. Hence no overspun bodies can come to being by gravity and centrifugal forces alone. No surface overspin is possible to form. At least one more agent is required to contain the overspin in the core. The obvious nature of such an agent is that being the pressure from the outer layers of the forming body; and even then the excessive spin should be cast out to the outer layers by friction. That friction might bring up secondary centres of rotation between the overspun core and outer layers, and those eddying currents would bring out matter. If those matter outbursts are large enough - the satellite bodies could be formed, if small or overspun themselves - spread out like protuberances or jets. And all of it must happen very early in the bodies' formation.
All that being said, the core overspin is a rather unlikely thing to happen, since getting into the core area requires being in slowest motion wrt the center of masses of the whole system - that's if at the starting point there was a nebula. But if the planets and the sun itself start as ejecta from some parent object, then the core overspin ejection mechanism seems more probable. Overspun matter could possibly be contained by radiation pressure in an object like an active galactic nucleus or a quasar.

I suspect that the phase change of "normal" Iron to high density Iron would be a self-accelorating reaction, with the rate of reaction increasing expotentially. Such a reaction might occur slowly for months or years, but the last doubling of rate might very well be catastrophically abrupt.

Dr.Van Flandern (formal address seems appropriate since I am new to this site), I understand that a test mass (your baseball) at the equator is in low orbit and would not go flying off to outer space unless propelled by some energetic power source. But the Earth's crust is sitting on a volume of high pressure and I expect this pressure is sufficient to propell large pieces of the crust into higher orbits. It might even be possible that this release of pressure might be sudden enough, and powerful enough, to provide a delta V or a mile/sec or two, and cause some on the ejected material to reach escape velocity ( when added to the original orbital velocity of 5 or so miles/sec)

John Duff

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I suspect that the phase change of "normal" Iron to high density Iron would be a self-accelorating reaction, with the rate of reaction increasing expotentially.
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Nope. This reaction contains a negative feedback built-in. Pressure triggers shrinkage - shrinkage drops the pressure in surroundings down. The reaction being exothermic doesn't help since the reverse process is endothermic by the same margin.

tvf] As you know, I have repeatedly had trouble understanding your models, not because of what you say downstream, but because I could not understand the starting point, the point to which all else was attached.

[ab] That's most likely because of the highly different models of education we've been through. Don't forget that I'm a Russian russian from Russia and in Russia.

Might this be the result of a difference of perspective? In listening to this exchange I get the distinct impression that ab is viewing over spin from observation points on (or below) the surface of the body in question while tvf is describing it from an observation point several dozen diameters away.

Suppose Earth were to over spin today (but unrealistically neglecting the impact of the energy input required to get there). Observers on the surface would indeed see massive earthquake and volcanic events. These events would begin well before the condition of "even" spin was reached (is there a term for this?). The biosphere (and the observers) would be devastated, but perhaps not totally destroyed.

But from far out in space these effects would be secondary at best. The (billions? trillions? of tons of) matter ejected into or beyond orbit by volcanic activity would be almost unnoticeable. In the end it could probably be totally neglected.

Most of the stuff that didn't reach escape speed would return to the surface on a subsequent orbit; unless the equatorial bulge had receded substantially in the meantime. But that would only happen after a significant fission event. Billions of trillions of tons of stuff. One percent or more of the parent body's mass.

A massive eruption could possibly serve as a trigger for such an event. ?? But such an event would also be likely to trigger many massive eruptions, including one at the beginning. ??

Regards,
LB