system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are snowflakes symmetrical?

How does one side of the snowflake know what what the other side looks like? How do they grow six identical segments? Shouldn't the shape of each segment be random?
gpt
The formation of ice crystals is dependent on the precise atmospheric conditions. Because each arm is experiencing the same atmospheric conditions, each arm forms the same way.

This is also why no two snowflakes are alike: each one follows a different path to the ground and experiences different minute fluctuations in temperature, humidity and airflow, all of which impact the crystal formation.