A comment on Reddit really caught my eye, which referred to the spinning ceiling fan as having the 'Ballerina Effect'. Upon clicking the link, I saw this GIF (loving the renaissance of GIF's!).
If you stare at the female humanoid shape in the middle, you will perceive 'her' moving in one direction, clockwise or counter-clockwise. If you then look at the image to the right or left of 'her', which is moving in the opposite direction - it seems to shift the perception of direction 'she' is moving in. Totally weird!
I've never heard of the 'Ballerina Effect' before, but find it quite extraordinary that your brain can perceive that kind of movement in two completely different ways.
To continue the Blade Runner theme this weekend, there was a gorgeous video of London uploaded to Vimeo containing amazing aerial views of London. The first part of the video, with the night shots, just look incredible and very 'Blade Runner' indeed. Interesting to see aswell how London is becoming much 'taller' and built up as a city in recent years. One of my first short films, 'Practice Makes Perfect' includes a time-lapse of London, without any Ghurkin or Shard - it looks quite naked!