Traveling between any 2 points on Earth through a gravity train through the center of the Earth would take just 42 minutes

A gravity train is a theoretical mode of transportation intended to go between two points on a sphere. It follows a straight line through the center of the sphere. If you've seen the remake of Total Recall, you might remember that a gravity train was a major plot point of the movie.

On earth, a gravity train would take 42 seconds to to go from any two points on the planet. This would be the case if it was a perfect sphere and of uniform density. There are a number of reasons why a gravity train is a practical impossibility.

For starters, the pressure that a train would be put under through the center of the Earth is extremely high. There is no known material that could withstand that kind of pressure. Extreme heat would also be a problem. Finally, there tunnel would have to be completely airless, because air friction would make the train unusable.