Cuddling my child on Shabbat morning, watching a spider walk across the wall, trying not to think about a friend's recent experiences (no, you *really* don't want to know) and instead pondering the thousands of years humans have spent quietly watching spiders walk across their walls and the thousands of years humans have spent wondering, how do they do that--? 

when it tripped and fell off.

Not just fell off, but fell with an audible "thud" upon landing.

Eventually it tried again, and fell again, twice-- this time it had the sense to trail a safety cord as it went so the recovery was fasting (spider learning curve!) but still, this was a really clumsy spider.