From: chris.s@comcast.net   
      
   Noah's Dove wrote:   
      
   >   
   >  I also decided that seismology is a *MUST* to go and have a look at.   
   > And that's what I did. I read up about seismology to see if there was   
   > anything which might have been misinterpretted and which might disclose   
   > that the earth was hollow. I then discovered why it is they say the   
   > Earth's core is a LIQUID. The reason is because certain waves can ONLY   
   > travel through SOLID material. These waves can not travel through:   
   > liquids, gases or a vaccum. However, scientists simply "assume" that   
   > the core is a liquid - they do not explore the possibility that the   
   > core is a gas or even a vaccuum.   
      
   Apparently you didn't read all that much about seismology.   
   Here's what you have right:   
   	S-waves (that is Secondary waves or shear waves, -back and forth   
   		waves like the cracking of a whip) can only travel   
   		through solids.   
   	P-waves (that is, primary waves, pressure waves, compression   
   		waves or longitudinal waves - bunching together and   
   		spreading apart waves like sound) can travel through   
   		solids, liquids and gas.   
      
   Here's what you missed:   
   	P-waves can't travel through vacuum.   
   	P-waves change their speed, direction, and intensity when they   
   		travel from solid to liquid or to gas.   
      
   	Our seismic data is consistent with P-waves hitting a liquid   
   		outer core at around a depth of 2900 km of a density   
   		around 10 g/cm^3   
      
   	Somewhat more recently, but by much, we found that our seismic   
   		data is consistent with the P-waves hitting a solid   
   		inner core at around a depth of 5150 km, i.e. the   
   		center 1200 km radius sphere, with a density around 12.8   
   		g/cm^3.   
      
   	There are earthquakes all the time.  We have copious data that   
   	fit with these models.  At the same time they could not fit with   
   	a hollow Earth.  They rule it out.  Jules Verne and Edgar Rice   
   	Burroughs notwithstanding.   
      
   > I also discovered that approximately   
   > 7,000 miles from an earthquake you will find a "shadow" area where   
   > certain types of waves never appear. Could the core/hollow be blocking   
   > out these waves? Then at about 10,000 miles or so these waves reappear.   
   > I also realised the complexity of such waves and how they are reflected   
   > and saw that it is quite easy to misinterpret them.   
      
   	The hollow doesn't block the waves, rather, the changing density   
   	of the Earth, bends the seismic waves in a similar way to which   
   	different densities of fluid - say a layered water, oil, alcohol   
   	drink - bends light waves to a different degree.  The Earth acts   
   	like a lens to the seismic waves.   
      
   Later I acquired a   
   > very good seismic modelling program which runs under windows (and which   
   > I'll upload if anyone wants). It is a most excellent program which   
   > shows how the waves move through the earth PLUS, what the various   
   > monitoring stations will actually see on their print outs. As you look   
   > at this you will see that our methods of watching seismic waves leaves   
   > much to be desired. When waves come up we have no idea where they were   
   > - we really can't tell much.   
      
   	Actually, we can tell a great deal, especially when we compare   
   	data from the thousands of seismic stations world wide.  It   
   	does, however, take a bit of training to interpret the data,   
   	including learning about the physics of waves in general, and   
   	mathematics including Fourier transforms.  But it's the same   
   	basic science that lets us get high quality ultrasound pictures   
   	of a developing fetus.   
      
   > But look too and you will see a great many   
   > waves bouncing off the "mantle" - we are told this is due to a change   
   > in density. Keep in mind that a Hollow object makes the wave movements   
   > many many times more complex because waves bounce back and forth   
   > between the two thin crusts and this will complicate the hell out of   
   > the whole thing. And when you look at the seismic model you will see   
   > that waves are reflected, re-reflected, re-re-reflected and so on. The   
   > earth sometimes "vibrates" for an hour or two after a big quake.   
      
   	Ya... but that happens at the interfaces between two different   
   	media as well, when density changes, regardless of whether that   
   	change is to zero or not.  You'd be well served by taking a   
   	physics class on vibrations and waves.   
      
   >  Probably the BIGGEST argument against the hollow earth is a   
   > PSYCHOLOGICAL one. Most people, including myself, just can not believe   
   > that it could possibly have been missed - or was it?   
      
    >stuff about early 20th century explorers omitted.   
      
   Of course, now we have satellites and a global positioning system which   
   easily confirm that our permanent stations on the poles actually are at   
   90 degrees north and south latitude respectively, not to mention that   
   the earlier explorers could easily confirm this by the positions of the   
   stars, regardless of the local topography.   
      
      
      
   >  Also, during that initial exercise of mine, I studied geomagnetism. I   
   > had never felt comfortable with the "dynamo-in-the-core" theory. The   
   > idea that currents in the core could create a magnetic field. I have   
   > many reasons for rejecting this idea. For example, in order for there   
   > to be convection currents in the first place, there have to be   
   > temperature differentials of a big enough degree. IOW, some magma in   
   > the core must be a lot hotter than the other. This must also imply some   
   > sort of cooling process or some process which keeps one part warmer   
   > than the other.   
      
   	That would be the surface of the Earth being in contact with   
   	the atmosphere, which is in contact with space... we radiate   
   	heat out into the -270 degree void of outer space.  The heat   
   	is supplied by radioactive decay of a variety of isotopes   
   	within the Earth.  The core, in turn loses heat to the mantle,   
   	which loses heat to the crust.  Each layer has a larger surface   
   	area than the other, further aiding in its cooling, yet energy   
   	continues to be supplied by radioactive decay.   
      
   > Without an adequate temperature differential currents   
   > won't arise in the first place. We can rule out cooling, because some   
   > scientists have found that the earth is not cooling.   
      
   um.. no.   
      
   > But even if we do   
   > have these currents, I still don't see how magnetism is generated. Heat   
   > is not a friend of magnetism. As a substance is heated, so it loses its   
   > magnetism - of course that's not quite an appropriate argument here.   
      
   	What you have right:   
   		as a magnetic material is heated past a certain   
   		temperature - the Curie point - it loses its magnetic   
   		alignment.   
   	What you're missing:   
      
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