The electronic gadgets that surround us inevitably have their roots in tangible physics, so projects like this that demonstrate that fact are enlightening and wonderous.
Radio was among the first means of long-distance, widespread wireless communication owing to its simplicity, and that simplicity means it's very hardy against adversity and unlikely to meet its practical demise any time soon.
See https://en.wikipedia.org/wiki/Crystal_radio and https://en.wikipedia.org/wiki/Foxhole_radio
Building a receiver out of whatever scrap you have around is a highly recommended exercise, and even more so if you have any kids (do it with them) --- the astonishment at seeing a pile of parts come together and make sounds, seemingly without any power source, is definitely an unforgettable experience.