Hi, Here's an answer I just received regarding the bowling ball drop: ***** Hi Patrick, For what it's worth (maybe not much; success in finding meteorites this way _does_ seem unlikely): Your 20-cm sphere would have a volume of about 4.2 liters. A mass of 7.5 kilos would give a density of 1.8. Seems low to me. http://courses.washington.edu/hydclass/Cive474/fallex.pdf describes how you compute terminal velocity, giving an example for an 8.5-inch, 16-pound sphere (yuck! English units!). They get a terminal velocity of 480 feet/second at an altitude of 10,000 ft, dropping to 412 feet/second at sea level. This terminal velocity scales as sqrt( diameter * density), so a two-inch object would have about half the terminal velocity, and so forth. Still, taking 450 fps as a ballpark figure, you would reach that in (450/32) = 14 seconds in a vacuum, and would come close enough to it in Real Air, for practical purposes, in (pessimistically) 30 seconds. 30 seconds at an average speed of (roughly) 450/2 = 225 fps gives a needed altitude of 6750 feet. A lot of "ballparkisms" there, I realize, but that's probably all you really need anyway. ***** 6750 sounds a lot more realistic than 20,000. Patrick