 And now Inga Lehmann was one of the true pioneers of seismology in the early 20th century. And she was observing telecysmic waves from very distant earthquakes. So she was looking at these waves and she wasn't particularly looking for the Necor. But what she observed is that there are some additional arrivals of some waves that actually shouldn't be there if the Earth is as simple as just the mental and the core. So what she did, she didn't have computers at the time, but what she did is she basically created a model of the Earth by embedding another smaller shell within the outer core. She called it the inner nucleus. And by doing that, she was able to predict some of the arrivals that she was observing in her seismograms. And basically, those additional arrivals corresponded to the reflections from the inner core. And so there were waves that were reflecting and there were waves that were refracting through the inner core. So this is how she basically discovered the inner core. Of course, at that time, she couldn't know that the inner core was solid. She didn't have that evidence yet.