The explanation uses Pythagorean geometry to relate sensor height, target altitude, and the radar horizon. Because the Earth curves away, a radar can detect a very distant target only if that target is high enough to remain above the horizon. Mounting the sensor higher moves the line of sight farther out, which is why an aircraft carrier's tall island gives its radar an advantage over lower ships. Faster jets make this geometric limit operationally dangerous because they consume the fleet's remaining reaction time.
Chapter · 1:46-2:53
How radar-horizon geometry limits fleet warning
Start here for the geometry that limits shipboard radar range and makes fast, low-flying threats difficult to detect in time.