Hello, Russell Kane here.

I'm back for another season of character assassinating the nice guy

and binging up the baddies in evil genius.

Yep, even the biggest legends have their skeletons.

So join me and a panel of brilliant comedians to weigh in

on whether the biggest players in history are more evil or more genius.

I just think every celebrity, said with respect, Russell,

is out of their minds.

Evil genius with Russell Kane.

Listen first on BBC Sounds.

BBC Sounds, music, radio, podcasts.

On a mild summer day, just outside of Copenhagen, Denmark, a woman sits in her garden surrounded by oatmeal boxes, stored within hundreds of cards containing handwritten notes which would be incomprehensible to most.

But for the woman pouring over them, one card at a time, this is the key

to finding out what lies thousands of kilometres beneath her feet.

I'm Ella Hubber. And I'm Julia Ravy. We're both scientists turned radio presenters.

And these are the stories we wished we'd known when we were starting out as

scientists. This is unstoppable for discovery on the BBC World Service. Julia, today I'm going to

tell you the story of how one woman with a keen eye for detail and apparently magical mathematical

abilities challenged the theory of what is at the centre of the earth.

And she did it in her spare time. Her name was Inga Lehman.

Right, so where are we starting today, Ella? Let's start with a quote.

I may have been 15 or 16 years old when, on a Sunday morning, I was sitting at home together with my mother and sister, and the floor began to move under us.

...