Too much time on his hands

Alexander Klotz a student from McGill university has recalculated how long it would take to fall tight through the earth, old estimates claim 42 minutes, Alexander now claims it's closer to 38 minutes due to the earths changing density.
A few points Alexander.  One there isn't a hole right through the earth, and there never will be!  And two, you couldn't fall right through even if there was, something called gravity will stop you around the middle, otherwise all the people on the opposite side of the earth would have fallen off a long time ago.
Now Alex is obviously a clever chap, so maybe if he sets his mind to curing cancer, or predicting earthquakes it might be time well spent, but working out how long something impossible might take is a bit pointless.
He even worked out what speed you'd reach 18.000 mph, but again thats not taking into account wind resistance, so thats wrong as well.  Unless he knows of an airless gravity free tube through earth........