system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5 why does wet sand stick together?
gpt
Damp sand sticks together because water forms little grain-to-grain bridges. Surface tension--the same force that lets some insects walk on the surface of a pond--acts like rubberbands between the grains. Adding water to damp sand fills spaces between the grains. The bridges vanish and the sand begins to flow more easily.