3 ms·
When I first learned about this, especially the "Because your brain recognizes it's moving and adjusts what you see to make sure it sees the 'right' thing" part
by MauranKilom 6y ago
When I first learned about this, especially the "Because your brain recognizes it's moving and adjusts what you see to make sure it sees the 'right' thing" part, it explained a phenomenon that really confused me as a child:
I would sometimes "catch" our bathroom clock (analog, with second hand) going backwards for a second. But no matter how long I stared at it, it wouldn't happen again. Only when I turned my attention to it would it sometimes seem to go backwards for the first second.
With the "your brain extrapolates the movement backwards" this makes perfect sense if the second hand will vibrate a bit on each tick. Apparently, if I focused on the clock while the second hand was vibrating for a fraction of a second after moving, it might be moving ever so slightly backwards at that moment, which is extrapolated to a full second of backward movement. In the end it's just another optical illusion.
- jniedrauer 6y ago> I would sometimes "catch" our bathroom clock going backwards for a second. Woah, I remember this too. It's a memory I had long forgotten. Every once in a while if you glance at an analogue clock that doesn't have a smooth second hand, it looks like the first time the second hand moves is backwards.
- ksaj 6y agoIf you have a clock with a smoothly sweeping second hand, and try to trace it's path ahead by 5 or so seconds (in other words, when it's at 0, you're looking at 5, at 1 second you are looking at 6, etc) the time will speed up and slow down in bizarre ways, and sometimes even look like the second hand completely stops occasionally. It's a combined effect of saccades and your brain drifting in and out of focus.
- labawi 6y agoWhile it could be vibration, it doesn't seem very likely you could see the vibration and motion-estimate it backwards. I seem to recall a similar confusion a couple of times. It's more likely just a bad coverup and/or a timestamp confusion in asynchronous processing.
- Digit-Al 6y agoHave you ever noticed car wheels looking as if they are spinning backwards instead of forwards?
- malingo 6y agoThis is due to the rotation rate of the structural elements of the wheels being just above the flicker fusion threshold frequency, around 60 Hz [1]. As the wheels spin faster, they just look like a blur. [1] https://en.m.wikipedia.org/wiki/Flicker_fusion_threshold https://en.m.wikipedia.org/wiki/Flicker_fusion_threshold
- Digit-Al 6y agoThanks. Very interesting.