Doug Lennox, age 11, of Rochester, New York, for his question:

Could a tunnel through the earth lead to China?

Nowadays, it is stylish to visit China and it seems that almost everybody wants to go there. However, there are easier routes than by taking a tunnel through the earth. Besides, at this stage of our engineering, such a tunneling project is not feasible on account of the earth's interior heat, pressure and density. But these impossible barriers certainly should not deter us from speculating on the possibilities. Who knows, someday they may build it.

In any case, let's suppose they do. In theory, the earth's gravity would pull a person to the center of the planet, from which point the route would be uphill. However, the downhill falling speed would carry him almost

 almost up to the opposite side of the globe. From there he would fall back, almost to the surface at the starting end of the tunnel. In theory, this unconventional travel would make shorter and shorter trips between the exit and the entrance. In theory, unless rescued, he would finally come to rest in the middle.