The Whole Hole?
According to the Extraordinary Info of the Day, the deepest hole ever made by humans was in Russia's Kola Peninsula (near Finland). Started in 1970 and completed in 1989, the hole was 12,262 meters (7.6 miles) deep.
Though the goal was to dig a hole 15,000 meters deep, the project halted due to the intense temperatures. At the depth of 12,262 meters, the crew encounter rocks at 180°C (356°F). Plus, the rocks began to "act more like a plastic than a solid," and whenever a drill bit was pulled up for replacement, the existing hole tended to close as if the rock "flowed." Researchers predicted that at 15,000 meters, the rock temperature would have neared 300°C (572°F).
Your Task: The hole's length was what percentage of the distance from the earth's surface to its core?
Note: The hole is responsible for the rumored "Well to Hell," a claim that Russian scientists sent a heat-tolerant microphone down to the bottom of the hole, where it picked up "the screams of the damned."