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also, very importantly: shearing waves do not propagate in liquids (quakes create both pressure and shearing waves). you can tear a solid, such as a sheet of paper, but trying to do the same to a liquid doesn't make sense. whereas pressure waves, like sound, propagate in both solids and liquids

so it's very obvious that (at least an outer layer of) the core is liquid because it's "dark" when looked at using shearing waves

Thank you. I didn't know that.

Waves, when moving from one medium (material type) to another, will bend if they strike at an angle. They will bend one way if moving unto a less dense medium, the other way if entering a more dense medium. Earthquakes generate massive waves in the earth. By measuring how long those waves take to reach different seismographs (tools for measuring Earthquakes), scientists can determine how the wave moved through the earth, and through that path, the density of the materials the waves moved through.

Temperature data is hypothesized based on the material we know the upper mantle to be made of (from lava) and its density and then supported by deep holes we have dug, where thr Temperature increases in a fairly linear manner.

Thank you! Very detailed answer 🙂👍

If you think that's cool, look up how they use spectroscopy to determine the composition of other stars and planets millions of lightyears away.

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There is already a pretty detailed discussion of this in our FAQs.

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