In 1973, 40 nodes connected 45 computers. This was the entire internet at the time

In 1973, 40 nodes connected 45 computers. This was the entire internet at the time. This chart was found in 2016 amongst some old papers.
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(TITLE FROM REDDIT r/coolguides)

Uhm, it says actually on the very picture this was the ARPAnet which is a precursor of what we call the internet. Though the network construct itself is very close, the main but not only difference is the accessibility and type of possible access. It's a wee bit like the difference between telegraph and telephone.