Smokey is the biggest. (2nd is how a large island can not be seen in a world of Google Earth, which found my grandma sunbathing in her yard)

we know from the writers that all of this can (supposedly) be explained scientifically, so I really want to know what the hell it is.

A couple of things about the smoke-dude:

1. Did you notice that he really didn't make an appearance in s2, and if he did, it was a guise or just not picked up.... but who else wasn't there.. Walt. Maybe the otheres had Walt control him during that time.

2. He tears the pilot from the cockpit before he tells more about the trip, kills Eko for not 'repenting' his sins, yet he just wanted to bring Locke down the vents with him for god knows what.. to play?
(I doubt the dinasour theory, Locke would have found tracks by now!)

3. the others don't mention it, or him or what, unless, he is their Jacob. Smoke-loc obviously studied the Losties, esp that first night when they were staring into the jungle after he was ripping up trees.

So I guess that is my theory, jacob is smokey, or vice versa. Maybe patchy is Jacob, controls smokey, the others are scared of patchy because he is gone insane, and wanted Walt to take over control of their beloved Cerberus.