We’ve sent probes to the edge of space, but how far have we really dug beneath our own feet? The Kola Superdeep Borehole in Russia reached 12.2 km—just 0.2% of Earth’s crust—before heat and pressure ...

Scientific exploration fueled the attempt by Chinese engineers to drill into the core of the planet and study its features. The digging of China’s first borehole over 10,000 meters (32,808 feet) deep ...