Where do antipodes live? Map of Opposite Points of the Earth
From Moscow, for example, the tunnel leads to the South Atlantic, and the exit will be quite far from the coast of Antarctica - the nearest mainland. From the territory of Russia it makes sense to dig only in the Ulan-Ude region - such a tunnel leads to the very south of Chile, and from Taimyr - then the journey will end in Antarctica. The exact antipodes map will help to accurately calculate the points of departure and arrival.
Of course, such travel is possible only in the imagination. Until the 2010s, the record for the depth of immersion under the earth belonged to Soviet geologists who had drilled (exclusively for scientific interest) the Kola superdeep well with a depth of 12, 262 meters; in the 21st century, oilmen from different countries broke a record, having drilled three wells deeper than Kola. None of them reached a psychological mark of 13 km depth.
If you nevertheless imagine that the tunnel passing through the center of the earth is drilled, its walls are strengthened, withstand the pressure of magma and do not melt in it, then we can fantasize about the fate of the person who jumped down. It is unenviable: already at a depth of 48 kilometers, atmospheric pressure will equal the pressure at the bottom of the ocean with the corresponding consequences. In addition, the daredevil is sure to seal to the wall of the tunnel by centrifugal force.
If we ignore these arguments, then we can calculate that the flight from one end of the planet to the other will take 38 minutes. When the traveler reaches the opposite edge, he will begin to fall down - that is, in that direction, which was just called "up"; and so the body of the poor traveler will fall back and forth several times until it is finally attracted to the center of the earth.