https://www.livescience.com/technology/communications/science-history-first-computer-to-computer-message-lays-the-foundation-for-the-internet-but-it-crashes-halfway-through-oct-29-1969
This is a time I wish I could have been a part of. It started out as 4 nodes. Had I been a bit older I would have been a part of the beginning. It was 6 years later that I did become a part of implementing the ARPANET which would become the internet. It's likely most on this board weren't even born yet.
Fortran is a computer language that is for the most part ridiculed (unjustly) now, however it was used to get us to the moon and back, and was used to implement the first packet switching.
"From there, the military agency funded a project to create such a network. For the system to work, it needed a way to break up messages from a sender into smaller portions that were then reassembled at the destination. Boehm and Baran simulated this process, which would eventually become known as packet switching, using a program written in the computer language Fortran."
Those were exciting times never to be had again.