@dabeaz
Apologies; I'm barely out of the "Hello World" gates, but if I may submit:

The idea that there's no such thing as software. There is only hardware; only an immensely complicated (or simple, depending on your code!) domino-rally of electrons in electron-pits on a microchip.

The same concept, albeit from different angles, may have been touched upon already - code is human expression of machine behaviours @jared , code can be formally varified @lessness

For me the "aha!" moment was reading about #cloudchambers for visualising cosmic rays (with a view to making a table; I now lament how boring conventional furniture is!), and thence onto cosmic rays flipping bits (eg. perhaps the most famous documented case here: https://radiolab.org/podcast/bit-flip but more have occurred since we have put computers at altitude and indeed yeeted so many into space).

I suppose this concept of operations is old hat to the #cybersecurity and especially the #electronicwarfare crowd who have always had to be able to work from first-principles.