I have had several experiences where I was on the bus or in a car and looking out the window.
Every once in a while I would notice that when the vehicle stopped the sidewalk would still appear to be moving. (always the sidewalk, never anything else)
This would happen for several seconds or until the vehicle was in motion again.
It happened during the summer and winter seasons, and I thought a mirage could only occur during a hot, sunny day. (correct me if I’m wrong)
Is there an explanation for this or do I need to get my eyes checked?
I think you experienced a visual fatigue phenomenon - our visual systems try to compensate for any mid to long term stimulus, and when that stimulus is removed, the compensation takes a little while to go away.
It’s not uncommon for drivers to experience a sensation that everything is receding away from them after sustained periods of motorway driving. Another (quite startling) demonstration of this phenomenon involves staring at a rotating spiral for a minute, then looking at anything else - after looking away from the spiral, things appear to be fluctuating and rippling quite wildly.
Note, BTW, that the above explanations (your visual system is mis-compensating in some way) is not the same as a true “mirage” (seeing pools of water on the ground off in the distance) which is caused by light reflecting on layers of air of differing temperatures – in that case, your eyes are actually seeing real patterns of light.
Thank you Mangetout and Senegoid for the explanation. I have also experienced the same sensations in the examples you have used. If it’s something to do with a ‘visual fatigue phenomenon’ then I think my vision is going to be alright
This is known as a motion aftereffect, and as Mangetout says, it is a form of visual fatigue, although whatever it is that is getting fatigued is probably in the brain rather than in the eye itself (as is the case with negative afterimages).
Another name for it is the waterfall illusion, because one way to experience it is by watching a waterfall for some time and then looking at the cliff down which it is falling. The cliff face will appear to be moving upward (although, somehow, also not moving). The illusion can be quite strong.
I also experienced a rotary version of this once as a teenager, when I was watching the reel on an old reel-to-reel closely for some time, waiting to stop it at the right moment. When I looked up from this task I saw the clock on the mantelpiece apparently rotating in the opposite direction. It quite scared me at the time. I though tit was some sort of acid afterflash.
It is best to keep your eyes a single, solid color.