Passive radar

Passive radar is like listening to a conversation between two people without actually talking to them yourself.

You know how when you play hide and seek, you can hear your friends laughing or footsteps even though you can't see them? That's kind of how passive radar works.

Instead of using your ears like in hide and seek, passive radar uses special antennas to listen for signals bouncing off of things in the air, like airplanes or birds.

These signals, called radio waves, are sent out by things like TV or radio stations, and bounce off of airplanes or birds in the sky. The antennas pick up these bounced signals and use them to determine where the object is and how fast it's moving.

So without making any noise of their own, passive radar can still "hear" where things are without them even knowing it's being listened to. It's like being a spy, but with radio waves instead of secret messages.