The latest question in the What If series (previously at Neatorama) concerns digging a deep hole in the ground. Our parents told us if we dug deep enough, we would come out on the other side of the earth in China. However, if you started in the United States and dug straight down, you'd end up in the Indian Ocean, west of Australia. Be that as it may, you can't dig through the earth's core, because it's too hot. And it gets too hot way long before you get near the core.
But in this scenario, heat isn't the only factor working against you. Randall Munroe also explains the difficulty of trying to dig such a hole, such as the logistocs and energy expenditure of removing the dirt once you get too deep to throw it, and the air pressure underground. That doesn't mean that people haven't tried it. You might recall this somewhat disturbing video of the deepest holes humans have dug.