2007-10-23 05:47:44 · 7 answers · asked by andy2210 2 in Science & Mathematics ➔ Astronomy & Space
You can't see much of anything that subtends less than about 1 minute of arc (1/60 of a degree) unless the object is, itself, radiating visible light.
Doug
2007-10-23 05:53:30 · answer #1 · answered by doug_donaghue 7 · 1⤊ 0⤋
Normally the naked eye can see stars with an apparent magnitude up to +6m; angular resolution of the naked eye is about 1′ however, some people have a sharper vision than that. There is anecdotal evidence that people had seen the Galilean moons of Jupiter before telescopes were invented. Of similar magnitude, Uranus and Vesta had most probably been seen but could not be recognised as planets because they appear so small even at maximum brightness that their motion could not be detected. Uranus, when discovered in 1781, was the first planet discovered using technology (a telescope) rather than being spotted by the naked eye.
2007-10-23 05:52:51 · answer #2 · answered by Steven R 1 · 1⤊ 0⤋
If two white objects were about 30 micrometers apart on a black background (or black on white), you could just bearably make out that it was two objects instead of one.
More exactly, you could tell the difference between the "C" on the standard eye chart and the "O", when the gap in the "C" is only 30 micrometers -- but you would have to be only 10 cm (4 inches) away, with good lighting.
The above is for normal vision, lots of people can see much smaller details, even half as small.
2007-10-23 07:56:26 · answer #3 · answered by morningfoxnorth 6 · 1⤊ 0⤋
Meters is the wrong unit to measure that. The correct unit is arc seconds. The limit is 15 or 20 arc seconds for a perfect eye. 20 arc seconds is about how big a 1 meter thing would look if it were 10 kilometers away.
2007-10-23 06:19:13 · answer #4 · answered by campbelp2002 7 · 2⤊ 0⤋
Apparently the human egg cell is the largest human cell and almost visible to the naked eye. It is about 160 micrometers (millionth of a meter). So perhaps 200-250 would be visible?
2007-10-23 06:38:29 · answer #5 · answered by Anonymous · 1⤊ 0⤋
The relevant thing is not size, it's angular size. Something that is a yard wide would be easily visible at 100 yards, but not visible at all at 100 miles away. The smallest angular size we can see is about one minute of arc, that is 1/60 of a degree.
2007-10-23 05:58:16 · answer #6 · answered by mathematician 7 · 2⤊ 0⤋
well the correct answer is 90 micrometers
2013-11-13 09:14:50 · answer #7 · answered by Marine 2 · 0⤊ 0⤋