system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Whem pouring liquid from one container to another (bowl, cup), why is it that sometimes it pours gloriously without any spills but sometimes the liquid decides to fucking run down the side of the container im pouring from and make a mess all around the surface?

Might not have articulated it best, but I'm sure everyone has experienced this enough to know what I'm trying to describe.
gpt
Surface tension.  Water wants to stick to hard surfaces.  This is what causes a meniscus in a test tube, for example.  That "u" shape at the top of the water.  The attraction between the surface and the water molecules is stronger than the attraction of the water molecules to each other.

So, when pouring, the force of the gravity on the water needs to overcome this surface tension to pull the water away from the container.  When the angle between glass wall and vertical direction is small, the component of gravity perpendicular to container wall is small and surface tension is stronger, causing the water to stick to the container and run down the outside.