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How exactly would you treat the cause of poor eyesight? Laser eye surgery is an option, but it is recent, more costly than glasses, and has various risks associated.


At night you can actually see further than during the day. At night you can see stars that are many light years away, but during the day the furthest thing you can see is probably the sun, which is 8 light minutes away. There's probably no definite answer because the brighter and bigger the object (and the darker the surrounding and the clearer the air), the ...


With clear, dark skies (no urban light pollution), about 2.5 million light years. That's the distance to the Andromeda galaxy, which is visible (in the northern hemisphere) with ordinary visual acuity: Vision does not depend on distance, but on the brightness of the things being viewed, and ...

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