From: Anders Sandberg (asa@nada.kth.se)
Date: Wed Oct 29 1997 - 12:50:58 MST
Geoff Smith <geoffs@unixg.ubc.ca> writes:
> I seem to remember reading an article that stated that the very centre of
> the core was a massive crystal(I think of iron) How was this determined?
> Well, don't quote me on this, but I think either someone shot some time of
> EM radiation through the earth and measured it's distortion on the other
> side (of course, the radiation would be altered differently depending on
> how it entered the grain of the crystal) Hmm... that doesn't sound like a
> very likely scenario now that I think about it.
No, no known EM radiation is strong enough to pass through the whole
earth. Neutrinos of course pass through it all the time, but they
don't reveal much. So this explanation sounds bogus, as you say.
> How about this: when an
> earthquake occurs on the other side of the planet, you measure how long it
> takes to go through the diameter of the earth. The time it takes should
> be influenced by the direction the shock wave passes through the crystal.
This sounds like a reasonable way of determining if it is there or
not; anisotropy should be easy to detect. I took a brief dive into the
web and found references to inner core anisotropy, and these pages:
http://earth.agu.org/revgeophys/tromp01/node2.html
http://www.sigmaxi.org/amsci/articles/95articles/Wysession-full.html
http://www.physics.georgetown.edu/~jkf/seminars/f96/cohen.html
which seems to support the crystal idea. It may not be a single
crystal, but a lot of them packed together.
> Apparently, the arrangement of the domains of this large iron crystal
> explain the earth's large magnet field. Also, one could explain pole
> shift(not the kind Danny was talking about!) by the inversion of this iron
> crystal, which might be induced by some external magnetic field... a large
> metallic asteroid? Sorry I'm being so vague... has anyone else read the
> article to which I am poorly alluding?
This sounds bogus, since the mass (and hence possible magnetic dipole
moment) of asteroids are orders of mangitude less than the earth.
The most popular current theory is that the magnetic field is produced
by dynamo currents in the liquid outer core, driven by the earth's
rotation. The shifts in the magnetic field are caused in this model by
chaotic shifts between two parts of the same attractor. No need for
ultra-magnetic asteroids.
-- ----------------------------------------------------------------------- Anders Sandberg Towards Ascension! asa@nada.kth.se http://www.nada.kth.se/~asa/ GCS/M/S/O d++ -p+ c++++ !l u+ e++ m++ s+/+ n--- h+/* f+ g+ w++ t+ r+ !y
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