I believe that I got the first external cassette drive for the PET on the west coast. Only used it a very few times. The big boost was when I got the floppy disk drive. I could do anything!
For a nice introduction to relativity, look at The Einstein Theory of Relativity: A Trip to the Fourth Dimension by Lillian R. Lieber. $15 on Amazon. Written in 1945 and still quite good.
Looks interesting. Should start with a definition of the Hyperbolic Tangent. It is only about 2/3 of the way that the definition occurs in a discussion of computing exp(x).
In the mid 70's, I was a graduate CS student at USC's Information Sciences Institute. I remember my feeling of awe when I used Arpanet (or was it Darpanet) to log into London and do stuff there. Wow!