system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If I move a 1 lightyear long "stick", why wouldn't the other end move instantaneously?
gpt
Because there's no such thing as a perfectly rigid material.

The compression wave from you pushing one end would travel through the stick at the speed of sound, so even if you could push enough energy into your end of the stick, there'd be a huge lag before anything happened at the other end.