I'm not a radio guy, so discovery of how spread-spectrum (DSSS) and frequency-hopping (FHSS) work, literally below the radio noise levels was one of the "wow" moments a few years ago, when you literally discover a technology that is so clever that before you dig into it basically is close to magic.

How GPS navigation works was another one of these "wow" technologies and I strongly recommend reading/watching how it *actually* works, as it contains an impressive amount of human ingenuity.