>In fact, you guys got me thinking.
>
>Would it be absolutely futile to say that that 'sky' does not exist
>as such, as there is nothing there at all, really
>yet it plays a very important role in human value system
> (01)
Yes. This is an interesting example, in fact. I looked into this in
detail when I was doing 'naive physics'. If you look at drawings done
by kids in kindergarten, they will draw the sky as a band of blue
color at the top of the drawing. If you ask them why, they will say
that the sky is high up. They will resist any suggestion that the
entire area above the horizon should be colored blue, because that
would mean that the sky comes all the way down to the ground, which
is false. So 'the sky' is not the actual atmosphere; they know that
there is air down here and that we breathe it. A similar distinction
is made between cloud (up in the sky) and mist (same stuff, but down
at ground level). One is an object, the other is an environmental
condition, a 'state' of the world. You can be in mist, but (until
recently) never in a cloud. (02)
Another interesting datum is provided by the moon illusion. If you
look at a full moon near the horizon it looks much larger than when
it is high in the sky. This illusion vanishes if you look at the
horizon upside-down by bending over and looking between your legs, so
it is cognitive rather than optical. What is the source of this? I
think it happens because the horizon is intuitively judged to be much
further away than the sky 'is'. The horizon is about 8 miles away.
Our visual systems see the sky as a surface, and judging from the
apparent size ratio of the moon illusion, I think we 'see' the sky as
a surface about 2 miles up. If you have ever tried to judge distances
on a level plain, 2 miles is about as far as you can see a human
being or a large animal as a distinct object, a speck. Maybe these
distances and the associated perceptual judgements were wired into
our brains when we were still trying to avoid being eaten by lions in
the savannah. (03)
There are other data, all however anecdotal. One I love was told to
me by an anthropologist who visited a single Australian tribe on
several occasions and befriended them, arriving each time in a small
passenger plane. In an idle conversation one of the elders asked what
it felt like when one got smaller. It emerged that watching the plane
fly he had decided that it got smaller as it rose, until it was only
about a few inches long. That much technological magic he could
understand and respect: but he was worried about how the people
inside could be shrunk and then later restored without it hurting.
Again, the idea seems to arise from the perception that things 'in
the sky' are in fact much closer than they really are, because the
sky can't be as high as it really is. In this case, the elder seems
to have seen the sky as only about half a mile high. (04)
There is lots of evidence for a "fisheye lens" distortion in distance
perception: we tend to underestimate distances proportionately as
they are taken further from us. (Nicely illustrated by the famous
Steinberg New Yorker drawing of the world seen from 9th Avenue
http://www.thenewyorkerstore.com/assets/2/50326_l.jpg ) It may be
that direct visual perception of objects, such as the horizon line,
acts as a kind of corrective to this, but that there isn't anything
in the atmosphere to produce the same corrections as terrestrial
objects and landscapes do. (05)
Anyway, a fascinating topic. And you are right, there really isn't
any such thing as 'the sky' as a place or volume, and yet we talk and
think as though there was: any we also know that we cannot define it.
And yes, this is a real challenge to ontologists, if they set out to
capture intuitive meanings like this. (Not all of them do, of course.) (06)
Pat Hayes
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