[time-nuts] New tide gauge uses GPS signals to measure sea level change
hmurray at megapathdsl.net
Fri May 30 18:00:41 EDT 2014
[Structure of Earth's core]
jimlux at earthlink.net said:
> 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.
> 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.
There was an article in Scientific American back in the early 1970s
discussing the structure of the Earth and all the tricks the seismologists
used to figure things out. I remember a diagram of the cross section of the
Earth with a blizzard of seismic paths, bending and bouncing at each boundary.
In that time frame, there was a lot of money for seismic research. It was a
key part of the test ban treaties.
What did seismologists use for timing back then?
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