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Posted on 01/07/2009 9:20:26 AM PST by BGHater
It's a classic image from every youngster's science textbook: a cutaway image of Earth's interior. The brown crust is paper-thin; the warm mantle orange, the seething liquid of the outer core yellow, and at the center the core, a ball of solid, red-hot iron.
Now a new theory aims to rewrite it all by proposing the seemingly impossible: Earth has not one but two inner cores.
The idea stems from an ancient, cataclysmic collision that scientists believe occurred when a Mars-sized object hit Earth about 4.45 billion years ago. The young Earth was still so hot that it was mostly molten, and debris flung from the impact is thought to have formed the moon.
Haluk Cetin and Fugen Ozkirim of Murray State University think the core of the Mars-sized object may have been left behind inside Earth, and that it sank down near the original inner core. There the two may still remain, either separate or as conjoined twins, locked in a tight orbit.
Their case is largely circumstantial and speculative, Cetin admitted.
"We have no solid evidence yet, and we're not saying 100 percent that it still exists," he said. "The interior of Earth is a very hard place to study."
The ancient collision is a widely accepted phenomenon. But most scientists believe the incredible pressure at the center of the planet would've long since pushed the two cores into each other.
Still, the inner core is a mysterious place. Recently, scientists discovered that it rotates faster than the rest of the planet. And a study last year of how seismic waves propagate through the iron showed that the core is split into two distinct regions.
Beyond that, little is known. But Cetin and Ozkirim think a dual inner core can explain the rise of plate tectonics, and help explain why the planet remains hotter today than it should be, given its size.
"If this is true, it would change all Earth models as we know them," Cetin said. "If not, and these two cores coalesced early on, we would have less to say, but it could still be how plate tectonics got started."
Based on models of Earth's interior, Cetin thinks the two cores rotate in opposite directions, like the wheels of a pasta maker. Their motion would suck in magma from behind and spit it out in front. If this motion persisted for long enough, it could set up a giant current of circulation that would push plates of crust apart in front, and suck them down into the mantle in back.
Friction generated by the motion would keep the planet hot.
Scientists asked to comment on this hypothesis were extremely skeptical. Some asked not to be quoted, citing insufficient evidence to make a well-reasoned critique of the study, which the authors presented last month at the fall meeting of the American Geophysical Union in San Francisco.
"In terms of its volume, and even its mass, the Earth's inner core is quite small relative to the whole planet, about 1 percent," Paul Richards of Columbia University said. "I seriously doubt that inner core dynamics could play a significant role in moving the tectonic plates."
ML/NJ
So, if I could curl up and occupy that ONE point at the exact center of mass, all of the forces surrounding me would be equal and opposite in all directions. Fair enough. Off by a micron or two, though, and I’m smushed!
Hardly. You would be surrounded by approximately 4000 miles of matter whose non uniform density complicates the problem quite a bit, but the field of unbalanced matter would be relatively small and quite distant. Even being several miles off wouldn't matter.
ML/NJ
They have to add up to zero.
So if we built a Dyson sphere with the mass of a black hole, at the diameter of an event horizon, would we still have a black hole? Would the sum of the gravity in the center of that artificial black hole be zero?
I don't know. Isn't Al "the Boob" Gore using his vast intellect to tackle that pesky continental drift problem? I'm almost sure I heard something about a "plate shift" credit program.
When the Days Were Shorter
Alaska Science Forum (Article #742) | November 11, 1985 | Larry Gedne
Posted on 10/04/2004 10:31:59 AM PDT by SunkenCiv
http://www.freerepublic.com/focus/f-chat/1234919/posts
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Hydrostatic vs shear stress.
A submarine that goes deeper than it’s rated depth shall implode, but not because of the difference in pressure between the upper and lower portions of the hull, but because the outside forces are greater than what the hull can resist.
For every force there is an equal and opposite force for systems in equilibrium, but nothing says the egg shaped earth has an equilibrium without dynamic changes in such a model. If the forces cancel each other at the center, this just means the center isn’t moving, but is in equilibrium.
If all the gravitational forces are acting upon each other, there might not be an acceleration, but the hydrostatic stress on that small volume still will be tremendous.
I thought the model of the interior core was one of a plasma.
If that’s true, then it’s another argument against the prevalence of extraterrestrial life. Without a molten core and magnetic field, the solar wind would rip Earth’s atmosphere away like it did on Mars and the planet would get bombarded with a lot more radiation. If it’s normal for planets to quickly cool down and lose their magnetic fields (like Mars, Venus, and the Moon), then extraterrestrial life, particularly intelligent extraterrestrial life, becomes a lot less likely. In various ways, the Moon has been credited for life on Mars but one of it’s biggest contributions may be the collision that formed it.
That sounds reasonable. You should be debating ml/nj
Yes but to find the force acting on a point within the sphere you need to integrate the force vector field from the point to the surface. At the center of the sphere this will be a very large force.
ML/NJ
If a 2.2 kg cube stands on a scale, it imparts about a pound of force due to the acceleration of gravity on the mass. If another 2.2kg block sits on top of the first the combined force is 2 lbs. As more and more blocks with the same mass are stacked the force increases. When the stack gets up to several dozen miles each additional block adds less than 1 lbs force because its distance from the center of mass causes its acceleration to decrease. But the weight on the scale is the sum of all the individual forces.
Now start at the top of the crust. A 2.2 kg mass of dirt exerts about a pound of force on the column of earth beneath it. Move in. A 2.2 kg mass of dirt underneath the first exerts about a lb of force on the column of earth beneath it. The two combined exert about 2 lbs of force. Repeat this exercise all the way to the center of the earth’s mass. The force exerted by each mass will vary, near the center this force will approach zero, but the total force is the sum of each individual mass.
Repeat this in all directions and convert that force to pressure and that is the pressure at the center of mass. Certainly much more than zero.
Go to someplace where a highway has been cut through the rock. At the bottom of the cut there is stone there with tons of stone above it withstanding all this pressure you want me to envision. You will be standing on neighboring rock that used to be under the same pressure before the cut was made. Maybe you can find a small piece to take home or maybe you will have to use a tool to chip a small piece you can carry. Bring it home and put it a vise. Once you subject the rock to real pressure it will almost certainly fracture, but it had previously survived all that pressure you talk about. Solids are not fluids.
I don't pretend to understand this particularly well but I don't think anyone does. In your little mind experiment where you have me add all the forces of all those 2.2 kg blocks down to the center of mass, you conveniently (for your view) have me stop right there. But why shouldn't I just keep on going and start accumulating all those equal and opposite force vectors once I pass through the center?
ML/NJ
If we had a hollow earth then your cave analogy would be correct.
At the bottom of the road cut the stone is indeed withstanding the pressure of the rock above it. Why do you think they brace mine tunnels?
In my mind experiment I did not stop with the initial colunm summation.
“Repeat this in all directions and convert that force to pressure and that is the pressure at the center of mass. Certainly much more than zero.”
Start at the antipode of the point I began the first summation. Repeat the process. You have the same force bearing down from that direction too.
The scientists are talking about the temperature of the Earth’s interior not the surface temperature!
We all know about man-made global warming!
The scientists are talking about the temperature of the Earth’s interior not the surface temperature!
We all know about man-made global warming!
I didn’t think a sarcasm tag was necessary - I guess it was.
Exerpt:
...But becoming aware of plasma changes everything. Because gravity can distort atoms and because pressure can preferentially "squeeze" electrons out of lower layers, rock can become susceptible to electromagnetic forces. Because plasma cables and sheets (i.e., electrical currents) have been detected flowing between Earth's magnetosphere and the surface, the circuit must close by passing through the Earth. Because magma is a liquid plasma, it will preferentially carry currents. Because electrical currents in plasma pinch into filaments and tend to form "double layers" (capacitor-like formations), the distribution of currents inside the Earth will be highly inhomogeneous. Electrical heating will cause temperature discontinuities in "lines and lumps." Electromagnetic forces between current filaments and between the layers of double layers will cause enormous and sudden pressure variations.
Why doesn't this show up in seismographs of earthquakes? Or does it show up, then go unrecognized because researchers have no concept of plasma behavior? No one has ever investigated how seismic waves act in different plasma conditions. The seismograph scrawls a single wavy line, but the geologist must interpret it according to a choice among several competing theories. With the awareness of plasma, seismographs no longer provide reliable--or even understandable--information about conditions at depth.
Satellites will update the gravity map of Earth
By BBC News Online science editor Dr David Whitehouse
A new gravity map of the Earth suggests that if you want to lose weight you should go to India, where the pull of gravity is slightly less than it is elsewhere on the planet.
You would be slightly less than 1% lighter there.
The gravity map has been prepared to help scientists plan the forthcoming Grace (Gravity Recovery And Climatic Experiment) satellites, to be launched in a few weeks.
New gravity map released
Moon Has Iron Core, Lunar-Rock Study Says
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