You know that illusion when you look at something spinning really fast..?
488848
Temporal aliasing\n\nTemporal aliasing is the term applied to a visual phenomenon also known as the "stroboscopic effect". It also accounts for the "wagon-wheel effect", so called because in video or motion pictures, spoked wheels on horse-drawn wagons sometimes appear to be turning backwards.\n\nTemporal aliasing is one example of a range of phenomena called aliasing that occur when continuous motion is represented by a series of short or instantaneous samples. It occurs when (a) the view of a moving object is represented by a series of short samples as distinct from a continuous view, and (b) the moving object is in rotational or other cyclic motion at a rate close to the sampling rate.\n\nExplanation\nConsider the stroboscope as used in mechanical analysis. This is a "strobe light" that is fired at an adjustable rate. Suppose you are looking at something rotating at 60 revolutions per second: if you view it with a series of short flashes at 60 times per second, each flash illuminates the object at the same position in its rotational cycle, so it appears that the object is stationary. Furthermore, at a frequency of 60 flashes per second, persistence of vision smooths out the sequence of flashes so that the perceived image is continuous.\n\nIf you view the same rotating object at 59 flashes per second, each flash will illuminate it at a slightly different part of its rotational cycle. Fifty-nine flashes will occur before you see the object in the same position again, and you will perceive the series of images as if it is rotating once per second.\n\nThe same effect occurs if you view the object at 61 flashes per second, except that each flash illuminates it a little earlier in its rotational cycle and so, it seems to be rotating backwards.\n\nIn the case of motion pictures, action is captured as a rapid series of still images and the same stroboscopic effect can occur.\n\nWagon-wheel effect\nSee main article: Wagon-wheel effect \nMotion-picture cameras conventionally film at 24 frames per second; however, the wheels of a vehicle are not likely to be turning at 24 revolutions per second, which would be extremely fast. However, suppose each wheel has twelve spokes and rotates at only two revolutions per second. Filmed at 24 frames per second, the spokes in each frame will appear in exactly the same position. Hence, the wheel will be perceived to be stationary. In fact, each photographically captured spoke in any one position will be a different actual spoke in each successive frame, but since the spokes are close to identical in shape and color, no difference will be perceived.\n\nIf the wheel rotates a little more slowly than two revolutions per second, the position of the spokes is seen to fall a little further behind in each successive frame and therefore the wheel will seem to be turning backwards.\n\nDerivation\nThe reason it is called "aliasing" is that in electrical engineering, when a continuous signal is replaced by a series of samples — say, a 24.1 Hz signal is sampled 24 times per second — the result seems the same as if a 0.1 Hz signal were sampled 24 times per second, so 0.1 Hz is said to be an "alias" of 24.1 Hz.
368129
the wonder of seeing what actually happens rather than confirming you already know it.
393990
It's not a characteristic of the human eye, which does not have a "frame rate". The effect occurs with devices like TV and movie cameras which have frame rates of 16 to 60 Hz. Any data sampling system is prone to such aliasing. If spokes pass a given point at exactly the frame rate, or at exactly 2, 3, etc. times tha frame rate, the wheel appears to be stopped. A slight change in wheel speed plus or minus makes the apparent wheel speed that plus or minus amount.
990419
To look like it is flying.
162299
It´s because your eye doesn´t receive light in a continuos way. Our eyes are "taking pictures" several times a second, and we have the perception of movement. When a wheel turns fast, suddenly the speed sinchronizes with your eye so first it looks as it is stopping, then it goes backwards, and then again seems to turn forwards.\nThis happens when the speed is changing.
239445
This is due to relative velocity. It's a great concept...it's the same concept which applies to you sitting at your desk..believe it or not...the earth you are situated on is revolving at the rate of once everyday..but do you feel it?? Nope...that is because you are revolving with it at the same speed. The formula for relative velocity is Vu-Vo where Vu is your speed and Vo is the speed of the other car..since they are the same, you subtract and voila..you get zero..therefore the car appears to be moving at zero speed in your vision. Check out relative velocity on GOogle..its a fun topic and your question is the fundamental base to relativity...Wow huh??\n\nGood luck.\n\nAyerhs\n\nPS: it is most definitely not because they have it on cruise control..I mean they could if they wanted but thats not the reason that they seen stationary to you.
1128742
It definitely seems like that....never thought about it until today but I can definitely see it NOW.\n\nIt's too bad that someone would be so incredibly blind AND dense as to enjoy such a thing.
104076
An optical illusion is when your mind perceives and interprets visuals differently. Basically, people call it a flaw of the visual system but basically it means that you are just experiencing and sensing things that are clear to you in a different way. It happens to everyone, and usually happens when you are not looking closely... \n\nWanna try a really cool optical illusion? Try this one:\nhttp://www.brainteasercentral.com/riddle.php?riddleid=680&PHPSESSID=c0b73d7cde4995835be4fad0b5d3152b\n\nFollow the instructions on the page and see what happens. I bet you'll be shocked. =p\n\nMore info on optical illusion here: http://www.michaelbach.de/ot/
77099
it would be called superluminal.\n\nyou can read more about it here - \nhttp://en.wikipedia.org/wiki/Faster_than_light
39217
Usually referred to as the wagon-wheel effect, this is most often seen in movies and on TV. Movie cameras record 24 frames per second, NTSC TV at just under 60 fps, and PAL TV at 50 fps. If from one frame to the next, the repeated discernible features of a rotating object (e.g. spokes or blades) appear closer behind the previous positions than ahead, the brain will assume the object is rotating in that direction. In the case where the new position is superimposed on the old position, the object will appear stationary.\n\nThis effect can also be observed under fluorescent or gas discharge lights (such as those on the highway) because these turn off and on at 120 Hz.\n\nThe effect can also be created by the vision of the observer. This occurs at distinct frequencies that depend on the individual, roughly around 10 Hz and 30 Hz.
736274
Wow, that is wierd\n\n I definetly agree that it is moving\nit looks like gears rotating
859647
The speed of light is an illusion imposed upon us by the Almighty. He lets you see the light whenever He wants you to.
1046019
when a car speeds by you, you feel wind. it's the same way with the earth, as it spins very fast.
319497
Have you ever noticed that the sun appears to come up on one side of the horizon, and then several hours later it seems to sink down on the other side of the horizon?\n\nIf you ever noticed this phenomenon, you were aware of the Earth spinning.
855665
Ask yourself this, "why would I stare at something all the time?"
323003
For most people, they only look that way under certain conditions: in a movie or video recording, or at night under certain types of lights.\n   This effect is called aliasing, where one does not observe a continuous picture, but lots of snapshots at regular instances of time.  In movies or video, this occurs at the frame rate of the camera.  Under certain lights like Sodium lamps (and incandescents to a lesser degree), their brightness varies with the 50 or 60 HZ frequency of the AC power supplied to them.  This has the effect of also time-sampling the scene, to some degree, just like a strobe light freezes a moving scene. \n    Consider, for example, if the wheel has a regular pattern of spokes, and it is captured in a 30 frame per second movie.  If the speed of the wheel is just right so that the wheel rotates 1 spoke distance in the 1/30th of a second interval between frames, then in each frame the wheel will look the same.  Thus, in the movie, the wheel will appear to be still.  If the wheel speeds up just slightly from this rate, the spokes will appear in each frame just slightly ahead of the last (although you are really looking at a different spoke in each frame), and the wheel will appear to turn forward very slowly.  If the wheel slows down from this rate, the wheel will appear to turn backwards very slowly.\n   This effect is generally not observed in direct sunlight, but the wheel will appear as a continuous blur.  However, because it is a blur, the eye is quite sensititve to even very faint aliasing effects which allow the brain to perceive some stucture there.  Such faint aliasing can come from a variety of unexpected sources, such as the slight increase/decreases in ambient light level as a car drives beside a guardrail with a regular spacing of posts.  Near each post, the light will be slightly brighter or darker from the reflections or shadows of light off the post.  This will give a regular time varying brightness in the car's frame of reference, which may cause a faint aliasing pattern to become visible.
81872
Yes..I have seen a many number of things both day and night..A massive object perhaps the size of a football field..with a smooth surface squared on all corners it was very massive and overwhelming..too big to be in the sky!! \nI have have witnessed a silver disc object above me in mid afternoon while fishing on my boat in the middle of the lake..it shot straight up into the sky with instant speed. Speed that we dont have here.\nAn elongated diamond light at night that graduated to having the intensity of a very bright spotlight...then dimming again to oginal intensity ..and shot off up into the sky..with incredible speed again...speed we dont have here.\nOrange glowing spheres in early evening...\nbackwards "c" shaped object in the daylight...\nthe list goes on..but..Yeah..I have seen many...Each time something does happen..it is like a new concept..it seems to keep opening the mind more and more..there are lots of things happening..it is not slowing down.