When I was a kid, I liked to dig holes in my backyard in Cincinnati. My grandfather joked that if I kept digging, I would end up in China.
In fact, if I had been able to dig straight through the planet, I would have come out in the Indian Ocean, about 1,100 miles (1,800 kilometers) west of Australia. That’s the antipode, or opposite point on Earth’s surface, from my town.
But I only had a garden spade to move the earth. When I hit rock, less than 3 feet (1 meter) below the surface, I couldn’t go deeper.
