What's the Deepest Hole Ever Dug?
How low can we go? That’s the challenge that has been taken up by scientists around the world over the last five decades, with each seeking to drill a hole that will go deeper than before. The goal: the Earth’s mantle. The mantle makes up 40 percent or more of the planet, which has a radius of 4,000 miles. The 1,800-mile-thick mantle sits—or more accurately, heaves up and down—just below the Earth’s crust and above the Earth’s core. The crust is just a tiny portion of the planet...