system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does sperm know what to do?

How does it know to seek out an egg?

extra credit upvote for: How do atoms know to form a sperm in the first place (and particles know how to form those atoms)
gpt
It doesn't. It is a great and common misunderstanding that cells know to do things, or that atoms have intention. They do not. A cell is a machine. A complicated machine, but a machine nonetheless. It reacts to stimuli because those stimuli trigger changes throughout the cell, which often form chain reactions to induce, say, movement, or a difference in cell transcription, or death. In the specific case of sperm, they respond to chemical signals produced by the egg, which cause them to move towards the egg. When they reach the egg they bind to it, which triggers further changes and causes the sperm to start attacking the outer layer of the egg by producing chemicals called proteases.

An atom also doesn't know anything. Every atom obeys physical laws. Those physical laws sometimes cause atoms to stick to each other, for a variety of reasons in a variety of ways. As they stick to each other to form molecules, further reactions occur, which then trigger yet more reactions and so on. This explains everything that is in the universe, just atoms obeying the most fundamental laws there are.