Um grande buraco
“Let us ignore friction, the rotation of the earth and other complications. Just picture a hole or tunnel that enters the earth at one point, goes straight through the center and comes back to the surface at the opposite side of the planet […] assuming that he [traveler] simply dropped into the hole […] the total trip would be about 42 minutes. If there were no friction […] our traveler could oscillate through the tunnel repeatedly”.
Scientific American (August 2003)