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Fraser
2005-Jul-21, 05:12 PM
SUMMARY: One of the most mysterious places in the Solar System is right underneath your feet: the interior workings of the Earth. Since it's impossible to drill down more than a few km under the surface of the Earth, scientists have study how sound waves from earthquakes travel throughout the planet and get reflected as they bump into things. These sound waves have always acted differently than predicted in simulation. Scientists now think that iron, crushed under tremendous pressure, can significantly alter the speed and direction of these sound waves.

View full article (http://www.universetoday.com/am/publish/revelations_about_center_of_earth.html)

What do you think about this story? Post your comments below.

antoniseb
2005-Jul-21, 05:47 PM
It is so easy to (incorrectly) imagine that somehow, below a certain depth, the Earth at any level is homogenous. I like reading about experimental research like this that connects to the seismic studies we are doing.

I'm not sure how we will build tools to study pressures and temperatures high enough to see how things behave even deeper than this, let alone the pressures expected in the cores of the larger planets. Some technical challenges await us.

lswinford
2005-Jul-21, 07:34 PM
When something is dropped from a distance in our atmosphere, while the acceleration potential grows, there is an equilibrium wherein air pressure resistance blunts the acceleration and a stable speed is reached.

We have the makings of some stability as we approach the core wherein the mass of materials about us are as pulling in other directions. Just as there are zones where such things as the correolis effect is maximized there are zones where it is minimized or inconsequential. Approaching, say, the north magnetic pole is not like approaching the north geodesic pole, as the magnetic pole is not a simple and discrete geometric point, but more a somewhat localized area or region.

Approaching the core of the earth we find almost as much mass pulling us from above us that, like standing on that Canadian island where the north magnetic pole was charted a while back, it does not much matter whether you stand at one place or several yards away.

Compounding the matter, we have a center of gravity between the earth and moon that we wobble about. In short, there comes a place as we explore toward the earth's core where overlaying pressure holds diminishing significance.

antoniseb
2005-Jul-21, 07:47 PM
Originally posted by lswinford@Jul 21 2005, 07:34 PM
there comes a place as we explore toward the earth's core where overlaying pressure holds diminishing significance.
That would be right at the center.

I'm not sure I folloed all of your other arguments. For example: The center of gravity for the Earth-Moon system has no significance in the amount of pressure on materials at a give depth.

lswinford
2005-Jul-21, 07:59 PM
Just like working a hula hoop, motion has action and action keeps things hot and stirred. If the center of gravity for the earth alone is a point A, but the center of gravity for the combined masses of earth and the moon is at point B, then as point B moves in its sweep about the geometric point A, well doesn't that little sort of swirl sort of stir the pot a bit?

Its like putting a glass of water in a drunk's hand and telling him to keep it level. It may be level but the drunk will not really be sure. ;)

Greg
2005-Jul-21, 09:42 PM
I imagine there will be a slight tug towards the moon, but it is not a static picture. The Earth rotates and the moon revolves around so that there is no long term effect in any single direction.
Basically the article states that we may soon be able to understand the seismic data we are getting back from the lower mantle. Like any reading, it is full of what looks like static which is interference from the distribution of various mineral layers which are not evenly distributed. Making sense of the interference pattern should help clear up the "static" yielding clearer pictures of the lower mantle. The authors indicated they hope to apply this knowledge to reinterpret seismic data which then may result in some new findings or conclusions. It is something like being able to lok at something with an electron microscope compared to a conventional microscope, or looking at Titan from the same distance from voyager's camera versus Magellan's.

Guest_James
2005-Jul-24, 07:04 AM
Here's a new revolation for you all!


Also...If you trace the big bang back to a singularity you get a major divide by zero. (ie How can something come from nothing?)

The older you claim the universe is, in the name of the big bang theory, the less matter there appears to be to support the this explosion theory.

Perhaps the universe is not expanding at the speed of light (as is impossible for mass to achieve such a speed anyway) but that the universe is infinite and therefore, it can not expand. What is being observed is light arriving at ever increasing distances from the earth. No wonder the ancients thought that the earth was the center of the universe. Why is it that when I compare ancient constellation maps to the night sky, I see a lot more stars than were mapped out by the ancients?

GOURDHEAD
2005-Jul-24, 02:26 PM
Perhaps the universe is not expanding at the speed of light (as is impossible for mass to achieve such a speed anyway) but that the universe is infinite and therefore,* it can not expand. I'm not aware of anyone claiming that the observable universe is expanding at the speed of light currently. During inflation it is claimed that it expanded faster than the speed of light but how the mass contained within the volume moved, if at all, is usually glossed over. Being of infinite spatial volume and time duration does not inhibit its expansion; infinity plus any number, however large, is still infinity even when those numbers represent volume and time duration.

In the unobservable (from here) portions of the universe, it is plausible that galaxies may be separating from us at greater than the speed of light based on extrapolations using the (variable) cosmological coefficient of expansion aka "Hubble's Constant".