system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: It makes sense that high power cell towers can reach cell phones. How do cell phones send signals back to towers?
gpt
If you have a flashlight, it will illuminate a few feet in front of you. Not very bright, definitely not as bright as a high-powered lamp. But, if you move quite far away from a person holding a flashlight, you can still see the flashlight, even if you can't see anything it's illuminating.

Same with cell phones. The signal may be weak, but it can still be "seen" by the tower from very far away.