Michael Caine, age 9, of Charleston, West Virginia, for his question:

Is it possible to dig a hole from the North to the South?

Lots of people imagine a hole through the earth, from one side of the globe to the other. A tunnel from pole to pole is the same idea. However, such a thing is downright impossible    at least at present. For one thing, the tunnel would get hotter and hotter as we dug deeper and deeper. Long before we got to the center, things would be hot enough to melt metal machinery. Any person down there would be fried to a frazzle.

But dust let's suppose we had some sturdy new metals and machines did not melt in the middle of the earth. If we start to dig down at the North Pole, the entrance to the tunnel would have to be more than a mile below the surface of the Arctic Ocean. But let's plan to overcome this impossible problem and keep digging. Let's also plan to keep digging through the impossible heat. Suppose we did these impossible things and a few others. If we dug in the right direction, when our tunnel grew to be almost 7,900 miles long it should open up    right at the South Pole.