Yep. I remember reading about that . . . somewhere. I read something else to the effect that if you could fall through the Earth (or another body) without resistance, you would never actually reach the far side, since gravity would reverse it's pull along the way. Essentially, you'd bobble back and forth and back and forth and back and forth, until you eventually came to rest in the center. [I think the second bit was on here, just after that remake of Total Recall came out and it's train through the center of the planet was under discussion.]