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Guru
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The 'Moon Illusion' Again!

06/28/2007 1:24 AM

According to NASA, the full moon of Saturday night, June 30th, will be particularly suitably situated to view the 'moon illusion'. NASA even offers their apparently 'most favored' explanation, referred to as the 'flattened sky'[1], as pictured below.

Fig. 1

I like this one, because it's my own pet theory as well!

However, there may be more to it. Professor Don McCready of the Psychology Department, University of Wisconsin-Whitewater[2] says it has to do with the 'Oculomotor Micropsia' of the human eye. It is described in exhausting detail in an article on the university's website.[2]

Whatever the case, look on Saturday night and decide for yourself.

-J

[1] Summer Moon Illusion (NASA)

[2] THE MOON ILLUSION EXPLAINED (UWW)

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#1

Re: The 'Moon Illusion' Again!

06/29/2007 2:06 AM

Wow - the posting date is cutting it fine Jorrie ! I only just noticed this while checking who was on-line. Probably not much use to me , the UK is clouded with rain at present . If I can't see the moon I'll read the links.

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#2

Re: The 'Moon Illusion' Again!

06/29/2007 2:39 AM

Hi Jorrie...

What is this "flattened sky"???... What is this mean???...I can't understand it at all...

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#3
In reply to #2

Re: The 'Moon Illusion' Again!

06/29/2007 2:48 AM

Hi George.

The term "flattened sky" simply means that things on the horizon appear to be much farther from you than things above you, although they may have the same actual distance.

We have no real way of perceiving the distances of things high above the horizon due to lack of reference points along the way, so we perceive them as not too far away...

Jorrie

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#4
In reply to #3

Re: The 'Moon Illusion' Again!

06/29/2007 5:02 AM

It is usually explained by that the brain assessing the size of an object, by comparison to adjacent objects in-sight.

Since the moon is optically (to the human eye mechanism) at distance , it appears as the same size, in absolute measurement, wherever you may see it.

So, when compared to a nearby man's head, it may appear the size of a melon. When compared to a remote bridge, it may appear the size of a car, etc.

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#5

Re: The 'Moon Illusion' Again!

06/29/2007 5:29 AM

Jorrie , I hope you wont mind me me illustrating differing views by this CR4 link . Many people will not have seen.

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#8
In reply to #5

Re: The 'Moon Illusion' Again!

06/29/2007 8:03 AM

In this link that you (Kris) refer to I have a comment where I describe a similar (but not the same) optical illusion...

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#13
In reply to #8

Re: The 'Moon Illusion' Again!

06/29/2007 1:14 PM

Just to make reference easier , hear is your post George.

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#6

Re: The 'Moon Illusion' Again!

06/29/2007 6:41 AM

Ah, but depending on the timing and where the Moon is in its orbit there is a difference in size that the camera can and dose show.

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#7
In reply to #6

Re: The 'Moon Illusion' Again!

06/29/2007 7:02 AM

Hey , that's cool ! I just had to go check how long you stood still for.

It's interseting how much confusion and debate goes on about the moon. Patrick Moore's explanations seem to be the best I have come accross. I haven't explored this site , but I would guess it is very good : The Sky at Night.

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#9

Re: The 'Moon Illusion' Again!

06/29/2007 8:16 AM

Let's be honest . . . How many times have you sat in a car with a girlfriend when a giant moon appears just above the horizon and it didn't cause romance to shift into a higher gear?

My theory is that an occurrance such as that makes everything bigger.

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#10
In reply to #9

Re: The 'Moon Illusion' Again!

06/29/2007 10:06 AM

The last time we had this discussion I told people a neat way to trick your brain. When the moon is large on the horizon, turn around, bend over and look at it between your legs. Now the moon will be the small actual size it is supposed to be. Without having the correct horizon your brain does not make the change to have it appear larger.

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#11
In reply to #10

Re: The 'Moon Illusion' Again!

06/29/2007 10:50 AM

HA! That was a nice trick. It didn't work. Everything looked the same, just upside down.

I believe the thrust of this experiment is to make normally intelligent, dignified people look silly!

Trying to explain it to onlookers only makes it worse.

Now, if a had a DeLorean, some industrial cable and a clock tower and I were to tell people it was a "scientific experiment" then they could believe that.

Finally I just said, "I'm a human 'croquet wicket'". They all wandered away. I'm not sure if it's because they thought I was a nut, or because they didn't know from which direction the huge wooden ball was coming from!

Yeah I felt silly. The next thing you'll tell us is that you can balance a coin on your nose!

But in a way your experiment worked! I tricked my brain all right!

FYI, during the crucial "bend over" part, a flick of the trousers and there will be not one, but two full moons! And that's no illusion!

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#12

Re: The 'Moon Illusion' Again!

06/29/2007 11:27 AM

It didnt work? Hmm it wasnt a joke actualy, I have tried it and others I have showed tried it and it did work. Weird. Tonight I will give it another try if the conditions are right.

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