system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are there still radar dead spots over the oceans, despite all of the modern technology?
gpt
Radar needs a direct line of sight connecting the tower and the object.  The earth is curved so if you go far enough away from a tower you can't see any radar towers. 

The ocean is just too big to have a line of sight to from a tower to every part of it.