system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does lightning strike from ground up but appears to be from sky to ground?
gpt
It’s actually both. Lightning first strikes from the cloud to the ground, but this isn’t bright enough for us to normally see. These branching pathways keep going until one touches the ground, at which point the intense lightning we see follows that same path back upwards.

This all happens so quickly that we can’t see it without taking a video and slowing it down. And because we don’t really see the ground shooting lightning out into the sky when there isn’t a storm, it naturally appears that the lightning is coming from the cloud.