I'm not sure if this has anything to do with physics, but I have wondered
for many years about one thing. How do they know how many people watch
certain TV shows? I heard that 137 million people worldwide watched the
recent Super Bowl. Where do these figures come from, and how is it figured
out? When your TV set is on, can someone tell what you're actually
watching by the frequency or something? Or are these just "estimates," and
if so what are they based on? Any physics here?