2007-08-13 08:27:01 · 4 answers · asked by gigi_sunflower 1 in Science & Mathematics ➔ Astronomy & Space
At the distance of astronomical objects, you can no longer perceive depth (or distance). All the stars "appear" to be at the same distance from us.
A sphere is a body where all the points are at the same distance from a centre. That is the mathematical definition.
Put the two together and you get that your brain perceives the sky as a sphere.
Our brain perceives distance through the parallax that 2-eyed vision gives us. This gives an impression of distance up to about 20 m or 60 ft. Beyond that, our brain has to rely on other clues: for example, seeing a house as a malll object, our brain will interpret it as being distant. If a car is partly hidden by the house, then our brain assumes (correctly) that the car is further away than the house.
No such clues in the sky (especially if there are no clouds).
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This would be true even if the Earth were flat. In fact, the ancient astronomers (3000 to 4000 years ago) "knew" that the sky was a sphere well before they were convinced that the earth was a ball.
The concept of declination and Right Ascension on the celestial sphere came before that of latitude and longitude on Earth.
2007-08-13 08:34:50 · answer #1 · answered by Raymond 7 · 1⤊ 0⤋
Human depth perseption doesn't extend that far. We can't tell if something is 240,000 miles away or 2.93 million light years away just by looking at it.
2007-08-13 16:51:11 · answer #2 · answered by Dan C 2 · 0⤊ 0⤋
Because the earth's round.
2007-08-13 15:41:43 · answer #3 · answered by Samalamlam 4 · 0⤊ 1⤋
Well, I didn't realize we did, but if so, I imagine it's an optical illusion due to the 'circular' horizon.
2007-08-13 15:32:03 · answer #4 · answered by Anonymous · 2⤊ 0⤋