Humanity is forever moving. Sometimes, somewhere it moves very fast. Other times, other places, it moves slowly.
The space between two solid objects is finite. No two objects can occupy the exact same space at the same time. My prevalent thoughts are about the changing space that happens between each of us. When in motion, we avoid occupying the same space with others at the same time--we're all adjusting to those changing spaces surrounding us. We do this independently of each other, but in coordination with each other. While walking, running, dancing, driving, etc. Adjusting our own personal space to our liking--given the circumstances surrounding us at any given time. Most of the time, humans are successful in avoiding collisions with others. But, humanity is not perfect so things happen even when well prepared.
Another intriguing aspect of the human condition, unconscious processes of human societies learned over time.
-Personal space -Conversational space -Emotional distance -Emotional closeness -Introverted personalities -Extroverted personalities -Public speaking/talking -Mob mentality (loss of personal control in public) -Eye contact/Eye averting