No GUESSES! No Maybe This, Maybe That, NO FIP ANSWERS!?

Question

What is the EXACT reason the moon sometimes looks HUGE (like a silver dollar) in the sky and sometimes looks tiny (smaller than a dime).

Forget PONZO! That's a "maybe".

This photo is good, but would be better if taken on the same skyline.
http://news.bbc.co.uk/2/hi/uk_news/magazine/4619063.stm

I have seen this appear on the same skyline and I can't explain to my 10 year old wizard what is happenig. Can you?

Please provide links to support your answers. So

This guy says No to the lens theory.
http://www2.abc.net.au/science/k2/stn-archive1/posts/topic2105.shtm

He/she says "Optical Illusion" but now I am going to start photographing this because I cannot believe this does not have a definitive answer. AMAZING! I will post findings here , in the future search BIG MOON to follow this stellar investigation. I also happen to live 60 min. from NASA so I may just have to jump in the car and take a drive.

HOW CAN THERE BE NO ANSWER! The moon in the closest astronomical body and this has been going on for eons. We have landed there, walked there, shoot lasers there almost every day, but CANNOT ANSWER THIS? WOW! This is getting very interesting.

Oh yea, FIP ... ooops meant no FLIP answers such as "Who Knows?:" Once an question gets to many answers it seems to get skipped over by people thinking that it has been taken care of already.

I can't choose a best answer yet, but I am trying. Looks like some things are in agreement. 1) the moon does not change in size, 2) atmosphere lens theory is out. 3) It's not becuase the moon comes closer or farther from the earth.

The optical illusion seems to the best answer but my daughter and I are going to test it before I can agree it is correct. The size differences we have experienced just seem to enormous to give in without further proof.

I thank all of you for your time and effort resonding to this question

Answer 1

Look, this is an optical illusion, and it's hard to pinpoint a single reason because human perception is incredibly complex ... there is more than one process in effect. I've studied human perception for years, and there are things like size constancy, the Ponzo illusion, oculomotor micropsia, etc. So the EXACT answer you are looking for is a complex answer.

... This is the best link I've found on the topic, and the answer is not simple:
http://facstaff.uww.edu/mccreadd/

One thing to watch out for, whenever you see two photographs side-by-side like in that link you provided (BBC should be ashamed), they are meaningless unless they are of the same scene on the same night, using the same camera settings.

The two photographs in your link are terribly exaggerated versions caused by the focal length of the *camera* used to take the photos. I guarantee you that if you look at a cityscape like the picture on the left, the moon will *not* look like the moon in that photo.

Answer 2

The moon is always the same size in the sky. It is actually a psychological trick in our minds that makes the moon look bigger. When the moon is high in the sky, we don't have any reference points near it to compare its size to, so it doesn't look all that big. But when the moon is on the horizon, (especially behind some kind of land features, such as a mountain range), the moon looks much larger to us, only because we are comparing the size of the moon to something familiar in the distance. Behind a mountain range, we can compare the moons size to something that we know is already large, and so we think that the moon is actually larger at the horizon. All this talk about atmospheric lensing is a myth. It really makes very little difference in the moons apparent size. If you don't believe me, you can do a very simple experiment for yourself to prove it. Next time you see a full moon on the horizon, hold your arm out in front of you, fully extended, and try to cover up the moon with your pinkie finger. It should be roughly the same width, (unless you have a fat pinkie finger), then wait till the moon is high in the sky and try the same thing again. You will be surprised that the moon is still the same size even though it looked so much bigger at the horizon.

Answer 3

Bottom line is that no one really knows what causes this illusion. It's not so much a question of physical science as question of psychology. That is, the image isn't really any bigger but we THINK it's bigger.

Source has more details with links to several other websites.

So I have no real answer for except that this might make a great topic for a research project.

Answer 4

The moon is not really bigger near the horizon than it is high in the sky, it just seems that way to your eye. If you take careful measurements, or carefully calibrated photographs, just as it rises and just as it passes overhead, the size will be unchanged.

BTW, you can make the illusion vanish by looking at it upside down. When it is near the horizon, bend over and look at it between your legs and it will look just as small as when it is overhead. This works for normal objects too. Look at any distant object this way and it looks smaller. I am not kidding and this is not a trick to make you look silly. I have tried it and it really works. You don't really have to look between your legs, you can look to one side a little past your legs, the important thing is to be looking at it upside down.

Answer 5

The atmosphere acts sort of like a lens making the moon appear larger.

Answer 6

Because our atmosphere is ball-shaped. When the moon is above you, you are looking theough comparitively little gas, so it looks smaller. When the moon is on the horizon, you are looking through a lot of gas, which refracts the light and enlarges the image.

Answer 7

Same reason the Sun at Sun rise or sunset looks bigger than it does at noon. Like others have said, air acts like a magnifying glass. The line of sight looking to the horizon goes through more and thicker/denser air (remember air gets thinner at higher altitudes) than your line of sight does when looking straight up.

Answer 8

atmosphric interference. the more dust and particulates in the air, the smaller amount of light actually gets to the earthwithout bouncing off something. the more it bounces, the more it sperads out, making the moon look bigger.

Answer 9

That is not the moon, it's the sun at different places on Earth!

Answer 10

sometimes the orbit of the moon brings it closer to the earth