A Hollywood-like proposal to explore the center of the Earth calls for exploding a crack in the planet's surface and dropping a probe in behind tons of molten iron, which would sink and forge a path to the core. [...]

Stevenson figures that a nuclear device would likely be the best way to blast the necessary gap, as long and deep as several football fields and about 1 foot wide. The event would be commensurate with an Earthquake measuring 7 on the Richter Scale.

At least 100,000 tons of hot iron would be poured instantly into the crack, along with a well-protected probe the size of a grapefruit.

"Once you set that condition up, the crack is self-perpetuating," Stevenson explains. The weight of the iron, which is much denser than Earth's outer regions, would open a gap all the way to the outer portion planet's core, about 1,860 miles below. The probe would fall at about 10 mph as the crack closes up behind it.

The weeks-long mission would seek to measure the temperature, electrical conductivity and chemical composition of the core. Stevenson said the amount of iron needed is equal to what's produced on Earth in a week or less. [...] "Think of the probe throbbing like a heart," Stevenson said. "It will set the neighboring material in motion and that causes a sound wave to travel away from the probe all the way to Earth's surface."