Title text:
The inflection point was probably in late 1966 or 1967, so when Neil Armstrong flew to space on Gemini 8, plate tectonics was not widely accepted, but when he landed on the Moon three years later it was the mainstream consensus.
Transcript:
Transcript will show once it’s been added to explainxkcd.com
Source: https://xkcd.com/3159/
No, I'm wrong. It's the Mid-Atlantic ridge.