From: jhbrown@ai.mit.edu (Jeremy H. Brown)
To: all-ai@ai.mit.edu
Subject: GSB: Tonight! 5:30pm, 7AI playroom
Date: 12 May 2000 14:51:57 -0400

Did you know that your "friends" could subscribe you to the "Concussion of the Month" club? I didn't, until somebody signed me up. But I'm having so much fun with it that as soon as I figure out who signed me up, I'm gonna return the favor with a lifetime subscription.

I'm not writing today to tell you about the free trial I got last June, the interaction with a tree that led to the photo you saw on the AI Olympics pages. Nor am I writing to tell you about the snowboarding impacts of December and January. Nor, indeed, to tell you of the volleyball headthumper of April. I'm not even writing to tell you of the waterbed that fell on my head yesterday. No, I'm writing to tell you a tale of the triple-whammy of March. Gather 'round now and listen...

I was running away from someone. It doesn't matter where or why; suffice it to say that it was all in fun. But there I was, running along, headed for a doorway, when I noticed a highly inconvenient table between me and the doorway. Having a good deal of momentum going, I simply jumped up onto the table and, from there, leapt through the doorway.

Freeze frame. Let us model the situation as a freshman physics problem. (Advance warning, folks: I don't do metric.) The upper edge of the doorway itself is an immovable vertical plane beginning 7'6" above the ground level. The table is an immovable, horizontal plane extending backward from a few feet in front of the door, about 3' above the ground. I am an idealized 6'2" rod weighing an evenly distributed 220 pounds. What the rod is about to discover is that the gravity isn't working well enough today.

Having just left the edge of the horizontal plane, the rod is moving forward with velocity X, and gravitational acceleration G is just beginning to give the rod downward velocity Y. In particular, while the top of our rod at the time it leaves the table is about 9'2" above ground level, it is now beginning a parabolic descent. If we plot the parabola, however, we discover that when the rod's horizontal position coincides with the doorway, the top of the rod is now 7'7" above the ground -- i.e. one inch of the rod overlaps the immovable plane of the doorway's upper edge. In short, the gravity is too weak for the rod's continued good health.

The resulting collision is highly elastic, and converts a great deal of the rod's forward momentum into angular momentum in the form of "backward" spin.

So now our rod is dropping like a rock while rotating backward. Indeed, examining only the rod and the floor, one would think that rotation would bring the top of the rod down such that it will be the first point of the rod to encounter the floor in what would no doubt be another highly painful, highly elastic colision. However, such an inspection omits one other important detail: the continued presence of the table.

Yes, while dropping like a stone and rotating backward, the top of our rod clips the immovable plane of the table in an elastic collision which more or less cancels out the rod's spin. This leaves the rod's orientation parallel to the plane of the floor, and thus the third impact is spread evenly over the length of the rod (although certain deviations from an ideal rod ensure that the top of the rod gets another good whack.)

Needless to say, the rod lies on the floor and groans for awhile, waiting for the room to stop spinning. The rod's pursuers are suitably impressed, and try valiantly not to laugh. The rod has significant difficulty finding spots on its head that do *not* hurt. For the first time, the suspicion is born in the rod's mind that someone has subscribed him to the Concussion of the Month Club, and that the extra-dramatic nature of this concussion is due to February's missed shipment. The rod begins to plot revenge. The rod begins to look for Tylenol. The rod decides that his new motto will be "Subdural hematomas are for wimps." The rod finds that stream-of-consciousness narrative comes more easily than structured storytelling. The rod realizes that the Concussion of the Month Club is much less painful than thesis. The rod realizes that GSB is even less painful than that. The rod will be at GSB. You should be too.

****************** G I R L S C O U T B E N E F I T ****************** ****************** 5:30pm 7AI Playroom ******************