system
Given the following post, respond as if you're commenting on Reddit:
human
When I take 2 hammers and hit the heads together, they appear as though they don't really touch each other. What's happening?
gpt
Hammer heads usually aren't flat, they're slightly convex.  You're seeing two points on those curves touch, then bounce away - but to your eye, it (correctly) looks like most of the hammer heads aren't coming into contact.  
  
Side note - be careful when you're doing this; sometimes tools shatter.