= The Core of the Earth =
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== Into The Heart of Our World ==
==== A Journey to the Center of the Earth: A Remarkable Voyage of Scientific Discovery ====
=== David  Whitehouse. Multco Hillsdale . 551.11 w593i 2016 ===

Also ... 
 . Journey to the Centre of the Earth / A Remarkable Voyage of Scientific Discovery into The Heart of Our World
 . Journey to the Centrer of the Earth / A Scientific  Exploration into the Heart of Our Planet

[[ https://tinyurl.com/DWihow | http://davidwhitehouse dot com/journey-centre-earth ]]
(sorry, my wiki software doesn't like the string wh---house.com
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 .p8 tunnel to center of the Earth, free fall in 21 minutes
  . er, no, unless you drop from the poles.  The Earth rotates, and you start out moving east with a velocity of cos(latitude)*465 m/s with a specific angular momentum of approximately 3e9 m2/s.  That angular momentum corresponds to a perigee radius of around 260 kilometers deep inside the "reduced gravity" core of the Earth.

Much of the book is about using sound waves from earthquakes and bomb tests to evaluate seismic propagation through the core,  Interesting, but the take-home lesson is that there is a lot of noise and not much accumulated signal, so far.

Diamond anvil cells can create some of the materials expected near tne outer core boundary, but the pressure and temperature is too high in the center, so we can only calculate and speculate about what is down there, and its acoustic velocity and impedance. 

I skimmed much of this; I wasn't engaged.