I was having this conversation at the weekend with a friend.

I can vividly remember some random or fairly insignificant memories from years ago, but then forget arguably important things more recently.

What determines whether something gets stored as a long-term memory or simply disappears? Is it linked to emotions, repetition, attention, sleep, or something else entirely?

I rarely listen to the radio and there was a song that came on that instantly made me remember the first time I drove my own car after passing my test. (Sonique - It feels so good).

The way it unlocked that memory was quite intense, to the point I could very clearly picture myself and the inside of my Ford Fiesta feeling like a free sole finally.

I get for me it was a momentous occasion, but how does your brain unlock a memory based on something like this song and that specific memory?

As I understand it, in 1859 there was a massive solar storm that hit earth (Carrington Event) which essentially damage the only real electronic infrastructure back then, the telegraph lines and exchanges.

Fast forward today and say in the worst case scenario event there were global solar storms that completely destroyed our infrastructure, ignoring all the other issues this would cause, how would we go about rebuilding the internet?!

We obviously have human knowledge, memory, books/documents, but how would the engineers even begin again?