system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does AM radio cut out, even when driving under an underpass, and FM radio plays clearly, even through a tunnel?
gpt
AM waves are big and heavy, like a bowling ball. If you launch it (transmit) it travels for a long distance but doesn’t bounce around that much when it hits something. FM waves are like small rubber balls. They bounce around a lot and so look like they can go around/through obstacles like buildings and tunnels. But they run out of energy quickly so have a shorter range.