James Stewart

And so by the early 20th century, you had a theory that the Earth had an iron core and apparent proof that some sort of core did in fact exist.

We were finally beginning to crack the inner structure of our planet.

And yet, despite these great strides, these pioneers missed something.

Sometimes I get so focused on all the awesome stuff happening below our feet, I forget that the stuff on land also needs a bit of love too, perhaps now more than ever.

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As seismographs continued to spread around the world and more and more data was gathered for scientists to pour over, they noticed that S-waves didn't register on some seismographs.

Something was stopping them.

Now, remember I said that S-waves don't transmit through liquids?

Well, it was a small leap, therefore, to go from that fact to the idea that Earth's core must therefore be liquid iron.

It wasn't completely wrong, but there was something they had all missed, and it took a Danish scientist to find it.