system
Given the following post, respond as if you're commenting on Reddit:
human
[Physics] Why is it that raindrops on a window seem to prefer following the trails of their fallen comrades?
gpt
It's to do with the molecules on the droplets' edges wanting to reduce their energies. A molecule in the middle of the droplet gets pulled on by all of the molecules around it with an equal force as they're all the same, whereas on the droplet edge a moleculesis also getting pulled on by the surface molecules, who will exert a force of a different magnitude. This creates an imbalance and causes those molecules to sit in a higher energy state. As such, the droplet will follow the path that surrounds these molecules with water instead of exposing them to the surface, therefore reducing the energy of the molecules at the edge, and as a consequence the energy of the droplet as a whole.