On 5/30/14, 2:41 AM, Dr. David Kirkby wrote: > On 28 May 2014 14:06, "Tom Holmes" <tholmes@woh.rr.com> wrote: >> >> Which begs the question: just where the heck, exactly, is the center of > the >> Earth given that it is in the 'middle' of a molten and dynamic core. > > I always thought that the centre was molten. There was something on the TV > in the UK a couple of weeks ago which seemed to indicate that the centre is > actually solid, although around that it is molten. Molten, but it's a composite material under a lot of pressure, so the transition between "liquid" and "solid" isn't like between ice and water. Think cold peanut butter. > > I did not see it all and was only watching bits of it, but it would appear > some female researcher had proven this. The proof appeared to be based on > the time of travel of shock wases from earthquakes and the different speed > they travel through solid and liquid. Seismic evidence is how they knew it was liquid in the first place. As you get better at doing the models, and getting better time measurements of the seismic propagation with higher performance seismometers, you can get a better model. Combine that with precise orbit determination (using accurate measurements of time and frequency from orbits) which allows accurate gravity models (e.g. GRACE and GRACE-Follow-On) > > Dave. > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. >