What cause the light streaks that we sometime sees when driving or closing the eye half way on lights? Why?
148010
There are many possible physical causes for the diffraction.  Eyes half shut: your eyelashes.  Driving: windshield wiper streaks (visible streaks are at right angles to wiping streaks).  Possibly cataracts or scarring from laser eye surgery.
418568
You need to adjust your headlights, they are likely pointing too high and you are setting off the light sensors on the light poles that turn the lights on and off.
265516
A few months ago, my mother suddenly started seeing "floaters". When she called the optometrist, she was asked whether she also sees bright flashes of light at the edges of her field of view, and/or when her eyes are closed. (Go into a room without any light source to test this.) If you do, you probably are experiencing "posterior vitreous detachment", which in itself is not a bad thing--I did some poking around on the web at that time and it appears that a large percentage of people experience this. The concern, however, is that in some cases, the retina also detaches.\n\nI'd urge you to go to your optometrist. The optometrist may refer you to an ophthalmologist to examine your eyes. In my mother's case, the ophthalmologist dilated her eyes, examined them, did not detect retinal detachment, but scheduled her for a follow up examination saying that if retinal detachment were going to occur, it would probably happen within about six to eight weeks. \n\nAs other respondents have suggested, retinal detachment is a serious thing, and requires surgery.\n\nBest of luck...
485148
Yes!  This happens to me all of the time.  Almost every time I drive. I like to think it is a loved one watching over me (lights kept flickering at the funeral).  It is wierd, I know!
384345
photoreceptors. they allow us to be able to see in low light such as moonlight but also in very bright lights. the photoreceptors are devided in to two groups rods and cones.\nrods are for low light\ncones for bright light. \nolder people can damage photo receptors and thats one reason for legal blidness. if you have damage you can not legally drive.
691655
these particles are not really present in the light that you see. They are actually the nerves in your eye which are illuminated by the intensity of light. the same effects are not noticed when you look directly at a low intensity light(eg. Tubelight, zero watt bulb etc.)
904924
I see the exact same thing.  And I thought it was only me that saw these !  You can see them outside in bright daylight if you look up at a bright sky for long enough.  They look like myriads of little white flashes moving around in all directions.  I don't think they are caused by an electrical overload in your retinas or optical nerves because I can also see them at normal light levels and even in a completely dark room.  If you stare at one spot for long enough (about 5 to 10 seconds) they will start to appear.   It even works when staring at a white computer screen (it doesn't have to be particularly bright), or even a blank sheet of paper !\n\nI have to say I don't see them unless I look for them, but when I do they are always there.  And, contrary to previous answers, they don't go away after a time, in fact they get stronger if anything.  If I don't blink and stay staring at the same spot for 1 to 2 minutes, eventually my entire field of vision is covered with these lights - they are all I can see until I move my eyes at which point they disappear completely !\n\nThey remind me of the 'static' noise that you see on a TV set that isn't tuned to any station, so they could be due to electrical noise in your optic nerves, or even in the brain itself.  I'm glad it's not only me that sees them, I thought I was starting to lose my eyesight !\n\nIncidentally, there is another phenomena that is similar to this, when you stare at a bright light in a dark room.  This effect looks like a myriad of bright streaks emanating out in straight lines in all directions away from the light source.  More like a halo than worms or static noise.  I think this is definitely something to do with the way your eye functions, but I have never seen any explanation for it.  Has anyone else experienced this ?
289936
your eyes when you blink
513231
I'm not real clear on your question, but you might be referring to star "trails" that are seen in unguided long exposure photos of the night sky.  The "trails" or "streaks" become more obviously circular the closer the stars are to the north or south celestial poles, and are caused by the earth's rotation on its axis over an extended period of time.\n\nA good example with a nice caption can be found here: http://www.aao.gov.au/images/captions/misc014.html
938852
The driver cannot see the lighting of the lights on the road as teh car will be travelling at the same speed of light. The car will be on the same point of the road where the light is falling. Because the car will travel that distance along with light which is about to hit the road. let me explain. Let us assume that car is "c" lights are "l" and the lighting is "r". So their positions will be some thing like this\n     c   lr\nAs lights will be before car.\nNow lights have released the light and the light is hits the ground and at teh same time car reaches that point.\n           cr   lr1\nr1 is the light that is released at that point of instant.\nI had explained a lot and in that effort I had missed the point that this cannot be explained like this. LOL.
559526
Most of the time, those are brief after-images; it's a reflection of the processing of images by the retina.\n\nOn occasion, it can reflect retinal pathology--retinal detachment, occlusion of a blood vessel, etc--and it can be the prodrome of a migraine.\n\nIf it only occurs briefly and with closed eyes, it is generally nothing; the disease states usually will cause the little dots whether your eyes are open or closed.
322469
Light triggers a reaction to you brain thinking that there is dust in the air.
848680
I have had that problem.  I asked my optometrist about it once.  They told me that it is normal.  It's a combination of a couple of factors:\n1.  Your eyes are trying to accomodate for the lack of light by adjusting to the dark.  This causes your pupils to dialate, which causes blood to flow more rapidly through your eyes, which over-stimulates the optic nerves.\n\n2.  Minor visual hallucination:  Your brain is trying to fill the void with images, trying to make sense of the newly-limited input filtering in.
527159
It's due to the way in which your eyes percieve light. Focus is determined by a point of reference. If your friend that you are looking at is the point of reference, they will appear as if they are not moving.\n\nThis is similar to when it looks, in a car, as if you are going backwards when the truck next to you starts moving forward.
719819
This question comes up very regularly. If you do a search you will find it has been answered dozens of times in the past few months.\n\nThe thing you need to relaise is that the speed of light is an absolute constant. It doesn't matter what speed you are travelling at, the light will always be travelling away from you at the same speed: the speed of light.\n\nThe freaky part is that the light from your headlights would seem to be travelling away form you at the speed of light (C), but to an observer who was sitting still the light would also appears to be travelling away from them at the speed of light. How can that happen? Well it's one of the tricky bits of relativity, but part of the solution lies in understanding that although light never slows down or speeds up relative to any observer it does change frequency.\n\nSo to you the light from your headlights will look quite normal, but to someone sitting still your headlights will appear to be emitting x-rays. The light would be invisible to them.\n\nThe corrolary of that is that any light approaching your windshield will be equally shifted into the x-ray part of the spectrum. Although the headlights will be emitting visible light, any time they strike an object and reflect back they will reflect back extremely low frequency light that is invisible to the human eye.\n\n\nSo yes, you most ceratinly owuld need headlights if a car is travelling at the speed of light. Unfortunately it won't do a damn bit o good to turn on your headlights. That's not because the light won't travel, it will travel just fine. The problem will be that any light that reflects back off the road will be invisible to the human eye.
1110465
Those are usually called "floaters", and they're basically bits of undissolved organic material literally "floating" in the gel part of your eye. They aren't a big deal unless they start impeding with vision, which can be a sign of a tear somewhere in your eye. If you've seen an optomitrist and they can't find any tear then it's just floaters (which unfortunately do get worse with age).
273966
We do not know exactly why this happens, but it might reflect a "crossing" of pathways in the brain, between the normal reflex of the eye in response to light and the sneezing reflex.\n\nClick below for a FULL explination