At the very centre of the earth, scientists have just discovered a new, previously unknown geological layer inside our world’s dense inner core. What is this strange new fifth layer composed of? How could we not know what’s beneath our feet, albeit very far down? And could we use it somehow? Professor Hrvoje Tkalčić tells Luke Turner how his research group made this discovery and how the inner inner core may be small, but it plays a mighty mighty role in all our lives. Every Monday and Thursday WHY? takes you on an adventure to the edge of knowledge, asking the questions that puzzle and perplex us, from the inner workings of the universe to the far reaches of our dreams. Follow us on your favourite app so you never miss an episode. WHY? is written and presented by Luke Turner. Audio production by Jade Bailey. Artwork by James Parrett. Music by DJ Food. Exec Producer: Jacob Jarvis. Lead Producer: Anne-Marie Luff. Group Editor: Andrew Harrison. WHY? is a Podmasters Production. Instagram | Twitter Learn more about your ad choices. Visit podcastchoices.com/adchoices