how far can a human see ?
404864
Infinite, look at the stars. Through the earth's atmosphere one can only see approx 60 miles on a clear day.
894597
Nearsighted people can't see things that are far away.\nFarsighted people can't see things that are near.\nKind of confusing, but there you go.
538925
Also depends on conditions where the watcher is.  In 1995 I was backpacking in the mountians of northern New Mexico and we could clearly see the headlights on the interstate over 15 miles away.  At the same location in 1982 we were able to see a handheld flashlight aimed down from the top of a mountain at over 3 miles distance.
896517
See one point of view at
246225
Currently, the accepted view is that the universe is approximately 78 billion light-years in size. A light-year is the distance light travels in one year (a large number since light travels about 186,000 miles each second). To determine this, astronomers used the WMAP project. See the links to determine how this was accomplished, but only if you don't mind being confused (it is quite lengthy and quite confusing - even for an astronomer such as myself!).
2845
3 ft if it is the person who needs to see the complete image, because however distant the mirror, the virtual image will always be twice the distance of the mirror from the observer, and the mirror will work like an aperture.\n\nIf someone else wants to see an object in the mirror, the size does not matter as long as the distance of the observer to the observed person relates to the mirror "aperture".
42704
20 cm unless you are near-sighted, in which case it is closer
1001818
see a minor distance creat such a difrnc, 10/10
908785
very close to 2 meters.
810612
Actually the Hubble Space Telescope has an unlimited range. It can actually see ALMOST to the edge of the observable universe (..about 13.7-billion light years). For about the first 100,000 years of its existence, the universe was opaque.  Hubble can see no farther than this 100,000 year limit because there's nothing for it to see.
1186503
No one can ever know what another person is seeing. Can you see auras? Then great.
610977
You need to have two eyes to determine distance.  Basically, if you close one eye, you can still see, but when light hits your retina, it's all in a single plane, so even though your brain tries to add depth, it's basically getting a flat image.  But with two eyes next to each other, you can tell how far away something is based on how much is location relative to other objects changes in the information you're getting from each eye.  If something is further away, the distance between your eyes isn't going to make much of a difference to it's location on the retina, but if it's closer up, it's going to make a lot more difference.  The brain uses the information it gets about these differences to determine how far away an object is.  If you only had one eye, you'd be able to see objects, but you wouldn't know where they were, so you'd bump into walls all the time!
602746
It doesn't exist, vision is based on a 20 foot system, so 20/20 is the best. 30/20 would be vision in which a person sees something clearly at 20 feet that a person with 20/20 vision could see at 30 feet.
278667
I got this!!\n\nDon't even look at them, I don't mean purposely look 15ft in the other direction everytime they are around.\nI mean look at their shoulder area if you have to look that way, you can adjust your eyes on what you are really looking at this way with never having to worry about making eye contact.\nI have very good vision and scope people out while they are far away and then I can walk right past everyone and yet see nobody.\n:o)
646082
It means that to see something a 'normal' person can see from twenty feet away...you also have to be only twenty feet away...so your eyesight is 'normal' If you are 20/100 then you have to be twenty feet away to see something a 'normal' person can see from 100 feet away.
1169146
At least 12 feet.\nI could be wrong though.
511294
It indicates the person is near sighted.