What I saw on the web on 2021.10.15

1. Unsolved Math Problems
   by Randall Munroe
   https://xkcd.com/2529/
   this is accurate
   via rss
   
   
2. Where Newton meets Mandelbrot (Holomorphic dynamics)
   by Grant Sanderson
   https://www.youtube.com/watch?v=LqbZpur38nw
   some more funky pictures in the complex plane via iterated rational functions
   via rss
   
   
3. U.S. confirms it will accept Canadian travellers with mixed vaccines
   by Sophia Harris
   https://www.cbc.ca/news/business/u-s-canadian-travellers-mixed-vaccines-1.6213176
   a story i've been watching for some time, because of reasons
   via rss
   
   
4. Do you understand this viral (very good) math movie clip?
   by Mathologer
   https://www.youtube.com/watch?v=04x4ZdLpN-0
   i do now! the other problems referenced in the video seem fairly straightforward, though i haven't gone through all the details yet
   via rss