You know the whole ‘digging a hole to China*’ thing? So let’s say you did manage to dig a hole straight through the earth (kudo’s to your non-gravity digging skills and amazing heat resistance!), and then promptly decided to jump down it. How long would it take to reach the other side? You can put your slide rule away, because the answer is 42 minutes, apparently.
Of course, then you’d have to worry about the fact that gravity would immediately suck you back down into the hole, keeping you in a perpetual 84 minute round-trip.
*the American usage comes from Henry David Thoreau, who was complaining about his neighbor’s incessant digging.