Dr. David Stevenson is a planeteary scientist at Cal Tech University. Dr. Stevenson works on many different research projects at Caltech which deal with studying the interiors of planets throughout our solar system--from Earth-Moon formation, to giant planet formation (including atmospheric zonal flows on Jupiter and the composition of its moons). As interesting as the compositions of other planets may be, perhaps the most relevant (and most overlooked) research David does is developing--at least in theory--a way to send a probe deep into the interior of our own planet Earth, in order to understand more about its composition--particularly that of the outer core. Understanding the composition of the Earth's core could help answer many scientific questions, such as the origin of Earth's magnetic field. David Stevenson was born in New Zealand in 1948. Growing up there, he started developing his love for science by reading the works of science fiction authors like Isaac Asimov, Robert Forward, and Fred Hoyle. After finishing university in New Zealand, David came to Cornell University where he took classes with famous science fiction writer Carl Sagan. Studying the interior of Jupiter at Cornell, David fell in love with the idea of using physics to understand Earth and other planets. "It's a playground for the application of physics, " he says. David wrote a paper describing his unusual idea about how to probe the Earth's core in the prestigious scientific journal Nature. In his paper, David describes the process as beginning with pouring a massive quantity of liquid iron down a crack in Earth's surface, which due to its massive weight would continue to tunnel downward until it reached the molten core. A probe placed in the liquid iron on the surface would then be carried along with the iron (getting to the core in about a week) where it could measure the core's temperature, pressure, and chemical composition and report them using tiny artificial earthquakes that could be detected from the surface. In spite of seeing the benefits of being able to probe the Earth's core, David maintains a sense of humor about the difficulty of realizing such a plan. "Before, people thought this was a ridiculous idea, " he said. "I hope that I've shifted the viewpoint from ridiculous to merely unlikely."