how do scientists know the Earth’s core is liquid if no one has ever seen it or extracted a sample?

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how do scientists know the Earth’s core is liquid if no one has ever seen it or extracted a sample?

In: Earth Science
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Earthquakes generate different kinds of seismic waves that behave differently when passing through different materials. Notable, one of the types of waves (S waves) don’t pass through liquids. This creates a kind of “shadow” that tells us that part of the core is liquid. But the behavior of the other kind of waves (P waves) also tells us that there is something solid inside that liquid.

Here is a picture for reference:

[https://akm-img-a-in.tosshub.com/indiatoday/images/story/201602/seismic-waves-650_042715041742.jpg](https://akm-img-a-in.tosshub.com/indiatoday/images/story/201602/seismic-waves-650_042715041742.jpg)

Most of what we know about Earth’s core comes from earthquakes. When an earthquake happens, it sends sound waves through the ground so powerful that sensitive instruments can detect them from all the way on the other side of the planet. Just like how light refracts and lenses while going through materials of different densities, the core of the Earth works like a lens bending the sound waves that pass through it in a very specific way. By measuring these sound waves, it’s possible to work out a lot of very precise detail about Earth’s core including what state of matter it is.

They *don’t know* and no true scientist would claim so. It is a highly likely theory however because many phenomena and measurements that we actually can observe fit a theoretical liquid core much better than a theoretical solid one.

In the old days, 30 or 40 years ago, it was thought that the core was liquid. Now it’s believed that there is a solid core surrounded by liquid. I lost a bet over this with my son.