From: nguyenpd@ntmtv.UUCP (Phat Nguyen)
Subject: WHY THE SUN LOOKSMALLER AT ITS TOP
Originator: nguyenpd@nmtvs315
Reply-To: nguyenpd@ntmtv.UUCP (Phat Nguyen)
Organization: Northern Telecom Inc, Mountain View, CA
Date: Fri, 28 Aug 1992 01:14:55 GMT

> Wow, a good explanation but ... sorry I have to disagree by what
> you said.  If it is our brain's perception that the Sun is bigger
> when it is closer to the horizon then it should not fool the camera's
> lens, right??  The fact is I can set up my 35mm camera in one spot,
> shoot the Sun when it comes up in the morning then again when the
> Sun is over our head then compare the pictures, the Sun should be
> the same size, right???   BZZZZZZ!!!   Wrong!!! 

Have you tried to shoot the sun at one spot yet??????


> I have taken many sunsets/sunrises and in other daytimes and the fact
> is the Sun during sunsets/sunrises is STILL bigger than during 
> daytimes ... the magnifying effect of the moisture in the air IS the
> phenomenon that makes the Sun appear to be bigger to both the naked
> eyes and artificial ones ... line of sight to the horizon is ~25-30 
> miles and the asmostphere is ~2-mile thick, so in the morning/evening
> when the air is cooler and the Sun is closer to the horizon, you are
> looking thru ~30 mile thick "magnifier glass" as compared to ~2-mile
> thick one at high noon with less moisture in the air ...

> I don't know about the trees or buildings that are closer to us that
> fool our brain into thinking that the Sun is bigger ...  with the same
> logics, I can also lie down on the ground and look at the Sun behind 
> the trees and buildings when the Sun is over our head, our brain should
> also trick us into thinking that the Sun is closer to us thus it should 
> also appear bigger at anytime, right??  How come I don't see the Sun as
> bigger then??  Just some thoughts ... :))


I have to agree with you that the 'magnifier glass' effect may make
the sun look bigger.  However, the increasement in the diameter is
so negligible that can only be detected by an excellent naked eye.  Your
explanation about the magnifying effect still doesn't explain why
the moon looks bigger when it is at the horizon than when it is at
the top.  I am sure that the moisture in the air at night is more than
in other daytimes for sure.  Besides, are you sure that each time
you photograph the sun you use the same lense and photograph it from
the same position and the same angle?  If you are willing, you can
try to photograph the sun in just one day by using the same lense
and set the camera in just one place.  You will be surprised.  There
already exists an experiment that kind of sort performed by a famous
perception psychologist at McGill University.   His photograph is
published in the PERCEPTION -- a psychology textbook that I believe
is available at all universities -- When I studied it, my professor
asked the classes to measures the diameters of the moon taken at
the horizon and the moon at its top.  Initially, the moon at the
horizon tended to look bigger.  However, when we actually did the
measurement.  The diamter came out exactly the same.  There is
also another experiment that was performed by my professor at the
University of California at Davis.  Two slides of the moon was taken --
one is taken when the moon is at its top and the other one is when
the moon is at the horizon.   The students were placed into a dark
room where the slides were projected.  The students didn't know
what slide was shown first.  It came out that all the students said
that the first slide was bigger (even though this was the one that
was photograph when the moon at its top.)  The professor cleverly
placed the moon slide behind another slide that had some landscape
-- some mountain top, trees, and houses --   It was done with such
detail that the students didn't know that they was fooled.  Then
the second slide was shown, this time my professor only extracted
the image of the moon at the horizon and projected it onto the screen
that looked like a sky at night.  Everyone agreed that this moon was
much smaller than the first.  Then he placed the two slides side by
side.  The result was the same.  The moon with the landscape foreground
still looked much more bigger.  Then he asked us to measure the diamters
of the two moons.  Surprisingly, the two diamters were exactly the same.
If you don't believe it (as do most engineers who tend to look at
things according to physics theories), you can try it yourself and you
can even check out the book on Perception (I highly recommend it -- it
showed how to fool the eyes so one could see colors while watching
a virtually black and white cardboard placing on a turnable).  If you
think that the images of the suns or moon that are projected into your
eyes are bigger at sunrise than at noon, you are in for a big surprise.
The sizes of the image is exactly the same.  It is your brain that 
interprets that one is bigger than another based on the foreground.  Can
you change the way you view things?  The answer is NO,NO,NO!  The
interpretation of the brain is done unconsciously.  Anyway!  I highly
recommend the book because it gives us engineers a different perspective
on the true nature of the universe.  I still remember my professor told
me that in the 1960's, everyone in the scientific community assumed that
mimicking the eyes was extremely easy (They believed that the eyes were
nothing more than a camera).  So there was a group of computer science
graduates at MIT tried to program the computer so it could act like
a camera and they projected that since the concept was so easy, they could
achieve that in just 3 years.  Now, almost thirty years have passed and
thousand of the so-called computer scientists working on the project.  They
still haven't able achieved the ARTIFICIAL EYE.  That shows the eyes
are extremely complicated.  The eyes and brain can be fooled very easily.
Anyway, check out the book and go through it carefully.  Hey!  what
I said came straight from the psychology textbook that is taught at
all world-wide universities.  Just remember that if there are theories
in mathematics and physics, there are also theories in psychology and
sometimes the theories in psychology can explain whatever the phenomenon
that physics cannot explain.

I just passed along what I have had a chance to learn.  Since most netters 
are "computer-oriented" folks who care more about computers than psychology
or neurology; so they are in for a BIG SURPRISE!!!!


Nguye^~n Doa~n Pha't
Northern Telecom
Mountain View