Hazel Rymer has journeyed closer to the centre of the earth than most, regularly peering into the turbulent, fiery world than makes up the earth's core. By taking measurements of micro-gravity on, and inside, volcanoes all over the world, she hopes to better understand why they erupt and what happens when they do. Having lost a close colleague to a random volcanic eruption, she appreciates the risks involved and, at the same time, insists that they are no greater than driving on the M25. She talks to Jim Al-Khalili about learning to think like a geologist after studying physics; the joys and frustrations of doing fieldwork on volcanoes; and why she loves gravity meter, G513.

Producer: Anna Buckley.