Radar Motion Tracking through Walls — Science Fiction or Science Fact?

Radar tracking systems have been around for about 80 years now. Typically, when someone mentions radar it evokes images of giant antennas used to track clouds or planes miles and miles away. Close range radar that works through walls seems to be something exclusive to the realm of science fiction. Perhaps the most iconic example of this is the motion tracker from the 1986 movie Aliens. Its ominous pulsing and shrieking tracking tone made it a fantastic plot device for building tension in the movie.