xkcd #3251: Time Machine Conversation
Title text:
It's possible to do sea navigation without a compass, but you'll have to get some spoilers from the Polynesians.
Transcript:
Transcript will show once it’s been added to explainxkcd.com
Source: https://xkcd.com/3251/
You make an excellent point about how information couldn't propagate before the information age.
I think we can give Randall credit for knowing this but making an editorial choice for brevity, particularly due to the scope of the rest of their work … on the other hand, that makes the 'um, actually' more fun and satisfying.
(Honestly, mostly just spelling this out in case others who aren't as familiar with XKCD (hi user from 'all') have context)