Falling/Tripping

Why is it so funny to see people fall? I know I have a sick sense of humor, but I fucking LOVE when I see someone wipe out. It makes me giggle. It brightens my day. That's all it takes. Of course, I wouldn't laugh (out loud) if someone got really hurt by falling. But, most of the time, it's innocent and brilliantly funny! So, take a spill, America. I'll laugh violently at you!