Why the moon looks bigger at the horizon

[DaveC426913]

My guess it that you took it about 50 feet away from the building, with no zoom lens...but does it matter?...the moon in that pic looks like the full darn moon I see month after month after month, when not near the horizon...that's what i mean by normal looking...the average run of the mill variety I see with my own eyes while standing on terra firma.. In fact, even when the moon is at perigee, I never noticed it being any bigger, maybe I never looked up, i don't know, or if I did, the increase of 12 % diameter was probably not noticeable anyway...and in fact, when I saw the moon near the horizon last night, I could only notice it's apparent size increase by looking through my curled thumb and forefinger through one eye, and looking normally through the other eye (if i may use that term 'normally)..the moon's apparent size was pathetic...but all i know is this: see that nice pic you took of the moon...thanks...there is a halo of sorts around it...about three times the diameter of the moon...now place a dot on the midpoint between the circumfernce of the moon and the circumference of the halo...do that in all 4 quadrants, and connect the dots to form a circle with a diameter of about 1.5 times the diameter of that moon...now that circle you just drew..THAT's the apparent diameter of the moon I have seen on occasions in the past...over twice the projected surface area of an 'average' sized moon in appearance when overhead...and come by gee or by golly, I'm someday going to find and see that huge moon again...whether due to illusion, perigee, location, subjectivity, mood, or circumstances...or combination thereof... I hope you get a chance to see it someday also...but don't take any pictures...I don't want any tricks...just watch, and marvel at its apparent size: HUGE!

:facepalm:
PJ, don't go into the sciences or engineering. Bridges don't get built or atoms smashed by "eyeballing" measurements.

 

[PhanthomJay]

Well now that you know it is an illusion it never will look quite as big as it did before you knew that.

I guess you're saying that the moon looked not as big to me last night because I knew it was an illusion, and if I didn't know, it would have appeared larger? Hmm, I never thought of that...I'll find out next year at the vernal equinox.

It's a bit like how Christmas changes once you know that Santa isn't real.

But even the broken bell will toll for those who still Believe (Credit: 'The Polar Express', "...to the North Pole, of course!" (Hanks).)

 

[D H]

Even though I know it is an illusion, the Moon can still at times appear to be quite large near the horizon. I think color has something to do with it. We had some rain as of late, so on the few days when we could see the Moon near the horizon it was only off-white and not all that large-looking. Tonight, after a couple of dry days, the Moon was a bit orangish and appeared to be bigger as well.

That could explain why the harvest Moon looks so big. Late summer / early fall tends to be dry, resulting in increased particulates. Farmers harvesting crops adds even more particulates. These particulates will increase the atmospheric effects that reduce the angular size of objects near the horizon. These are small effects, however, and are overwhelmed by whatever is happening in our minds that makes objects near the horizon appear to be larger -- big red rubber ball type objects in particular.

 

[DaveC426913]

These particulates will increase the atmospheric effects that reduce the angular size of objects near the horizon.

Can you elaborate? Never heard of such a thing.

 

[PhanthomJay]

:facepalm:
PJ, don't go into the sciences or engineering. Bridges don't get built or atoms smashed by "eyeballing" measurements.

Eeeeeeks I've been an engineer for 40 years, and no one has caught on yet! But you seem to be good at eyeballing measurements, as per your quote from post #5 in two-double-ought-seven

use a tube over one eye to eliminate the foreground (close the other eye); note how small the moon suddenly appears. Now open the other eye. The eye with the unobstructed view sees a larger moon, and you have the slightly unnerving experience of seeing two different-sized moons at once.

That's pretty good double eye-balling,there, Dave.

 

[DaveC426913]

Eeeeeeks I've been an engineer for 40 years, and no one has caught on yet!

Don't believe you. No engineer would make such a mistake.

That's pretty good double eye-balling,there, Dave.

Yes. Awesome. I could not have shown you a better example of what you're doing wrong. Thank you.

Notice how I am talking about comparing two things side-by-side and simultaneously? That's a comparison.

 

[PhanthomJay]

Don't believe you. No engineer would make such a mistake.



Yes. Awesome. I could not have shown you a better example of what you're doing wrong. Thank you.

Notice how I am talking about comparing two things side-by-side and simultaneously? That's a comparison.

Well sir, I sure hope you noticed Jupiter to the right of the moon. Neat, huh? And by side by side comparison, I'm willing to bet (although i know you are not willing) that the moon appeared larger than Jupiter to you. Even though we know that Jupiter is bigger, it appeared smaller. Not due to any illusion of course, but simply because it's pretty far away compared to the moon from us.

Now, look at the full moon again some time, when Jupiter is not hanging around simultaneously next to it. Then, a year or 2 later, look at Jupiter when the moon is not around. Then tell me if you think Jupiter still appears smaller than the moon you saw a year or 2 ago. I know I could tell that it still would appear smaller. Most people could. Can you?

 

[DaveC426913]

Well sir, I sure hope you noticed Jupiter to the right of the moon. Neat, huh? And by side by side comparison, I'm willing to bet (although i know you are not willing) that the moon appeared larger than Jupiter to you. Even though we know that Jupiter is bigger, it appeared smaller. Not due to any illusion of course, but simply because it's pretty far away compared to the moon from us.

Now, look at the full moon again some time, when Jupiter is not hanging around simultaneously next to it. Then, a year or 2 later, look at Jupiter when the moon is not around. Then tell me if you think Jupiter still appears smaller than the moon you saw a year or 2 ago. I know I could tell that it still would appear smaller. Most people could. Can you?

That is a silly analogy. You should know this too. This is not helping your cause to convince anyone that you understand the effects involved.

It's been a blast PJ.

 

[PhanthomJay]

That is a silly analogy. You should know this too. This is not helping your cause to convince anyone that you understand the effects involved.

It's been a blast PJ.

I think you are losing your sense of humor, but I can't tell for sure. That's why I don't like April Fool's day.

Anyway, OK, if you don't like the Jupiter analogy, try this :

Have someone place two oranges on a table that is 25 feet in front of you. That someone has measured the orange on the left to be 3.5 inches in diameter, and the one on the right to be 3.0 inches in diameter. You don't know those measurements. Now you are asked, "Which one appears bigger to you"?. I assume, by your Instantaneous Side by Side Comparison Theory, (which I think is a good one, by the way), that you will pick the one on the left . At least I would. I couldn't say how much bigger, but I could only say, by eyeballing it, that the one on the left is 'somewhat bigger'.

Now, a month or so later, again standing 25 feet in front of the table, have that same someone place just one of those oranges on the table (asuming it hasn't wilted). Either the big one or the smaller one, it doesn't matter. Now you are asked, " Is this the big orange you saw last month, or the smaller one?". I don't know what your answer would be, but mine would likely be "I have no idea; without a side by side comparison, since the size difference was small, I really can't tell which one it is!".

Now, a month or so later, the experiment is repeated, with the following difference: one orange is 3.5 inches in diameter, and the other is 2.5 inches in diameter. They are again placed side by side, the 3.5 inch one on the left; and again I would say, 'the one on the left surely appears bigger, that other one is puny looking'. I couldn't say how much bigger, but only say 'noticeably bigger'.

Now, a month after that, again just one of those oranges, say the 3.5 inch one , is placed on the table. And then the question is posed, " Is this the big orange you saw last month, or the small one?". My answer would likely be " Oh my, that's the big one for sure, that other one was puny looking" . In other words, since the apparent size difference was so large to begin with, I think I can make that subjective statement. The greater the difference, the more likely I can make that subjective call (I bet the Earth looks bigger when viewed from the moon, than the moon looks bigger when viewed from earth, and there's no way to make a side by side comparison of the 2 from your location). And it doesn't matter whether it is apparently bigger, or actually bigger, or whether by illusion or too much alcohol that day...it still looks 'bigger'.

I hope this clears up for you my take on this. But I'm ready for you to find yet another flaw in this argument. Unless, by that statement "It's been a blast", you are implying that you will not respond further.

 

[DaveC426913]

I think you are losing your sense of humor, but I can't tell for sure.

I am, yes.

Have someone place two oranges on a table that is 25 feet in front of you.

All your orange examples are not comparable to observing the Moon. There are myriad clues to the size of a known object such as an orange that is sitting on a table, a mere 25 feet away, with your binocular vision.

If I did the same experiment a very long (undetermined) distance away, using discs, which gave no indication of their actual size, you would have absolutely no clue which one I was showing you.

 

[PhanthomJay]

If I did the same experiment a very long (undetermined) distance away, using discs, which gave no indication of their actual size, you would have absolutely no clue which one I was showing you.

I'm sorry about your losing your sense of humor. If it was because of me, I apologize. I would have thought that years of dealing with my kind would have brought you patience.

Let me ask you this: Supposing you were a cave man on Planet X. There were 2 moons orbiting your planet of unknown size and at an unknown distance away. Moon A and Moon B. When orbiting side by side, you notice, by comparison, that one (Moon A) is much much much much larger than the other (Moon B). Now sometime later, Moon B has taken off to parts unknown, and it no longer appears in the sky. Only Moon A remains. Would you know that the remaining moon is Moon A, or would you not know? Assume that no other moon has come into existence, so that the remaining moon must be either moon A or Moon B. Could you tell, without having both moons present to make the call?

 

[DaveC426913]

Supposing you were a cave man on Planet X. There were 2 moons orbiting your planet

Do you think some warning flags should be going up if the scenarios have to get this contrived?

 

[PhanthomJay]

Do you think some warning flags should be going up if the scenarios have to get this contrived?

I did take an extreme example, but since we are at an impasse, let me compromise by saying this:

"Once upon a time, not too long ago, I saw a really really big moon. Or at least I thought I saw it...perhaps, instead, time has rewritten every line. But, whether real or imagined, it makes no difference, for one time, not too long ago, I saw a huge appearing moon, and its memory will stay with me forever."

 

[DaveC426913]

I did take an extreme example, but since we are at an impasse, let me compromise by saying this:

"Once upon a time, not too long ago, I saw a really really big moon. Or at least I thought I saw it...perhaps, instead, time has rewritten every line. But, whether real or imagined, it makes no difference, for one time, not too long ago, I saw a huge appearing moon, and its memory will stay with me forever."

I can live with that.

 

[PhanthomJay]

I can live with that.

Great, thanks, I'm glad this is over! So is my wife...she thinks I spend too much time on this forum, and looking at the moon, and not enough time helping around the house. And I'll have to admit, she's probably right.

Thanks for your valued input.

 

[DaveC426913]

Great, thanks, I'm glad this is over! So is my wife...she thinks I spend too much time on this forum, and looking at the moon, and not enough time helping around the house. And I'll have to admit, she's probably right.

Thanks for your valued input.

It is a calling for me too.


You keep watching those skies Phanthom.

Wherever you go, I'll be there.


I am.

Anti-PhanthomJay.

 

[PhanthomJay]

It is a calling for me too.


You keep watching those skies Phanthom.

Wherever you go, I'll be there.


I am.

Anti-PhanthomJay.

Looks like you'll be back in the running for the 2010 Best Humor Award!

 

[raylphscs]

I still think the illusion theory is wrong. It is aparently the optical lenz effect of the spherical atomsphere acted like a telescope. when the moon is near the horizon, it not only looks big, but you can see much details on its surface like the dark areas and dark spots. If a brain illusion caused the moon seem big, there should be no more details to be seen, only size bigger.
Illusion theory is wrong and is not scientific.

 

[D H]

Read the thread, raylphscs. There is a tiny atmospheric effect near the horizon. This tiny effect does not explain the Moon illusion for two reasons. (1) The effect is tiny. We perceive the Moon to be considerably bigger near the horizon compared to when it is overhead. (2) The atmospheric effect makes the apparent size of the Moon a tiny bit smaller when the Moon is near the horizon.

 

[Brin]

I still think the illusion theory is wrong. It is aparently the optical lenz effect of the spherical atomsphere acted like a telescope. when the moon is near the horizon, it not only looks big, but you can see much details on its surface like the dark areas and dark spots. If a brain illusion caused the moon seem big, there should be no more details to be seen, only size bigger.
Illusion theory is wrong and is not scientific.

Wow. I propose a new rule after reading this entire freakin' thread: Quantitative results. Go get your 'lenz effect of the spherical atmosphere acted like a telescope' equations and get to work. It's not that hard. I think it's like chapter 34 or something in Young and Freedman.

Calculate precisely how large the moon should appear under each of the conditions being proposed. Post them here if they are significantly different (not the 12% we know about already).

 

[JDługosz]

I still think the illusion theory is wrong. It is aparently [sic] the optical lenz effect of the spherical atomsphere [sic] acted like a telescope. when the moon is near the horizon, it not only looks big, but you can see much details on its surface like the dark areas and dark spots. If a brain illusion caused the moon seem big, there should be no more details to be seen, only size bigger.
Illusion theory is wrong and is not scientific.

Wrong, wrong, and wrong. The illusion theory is scientific because the actual angular size can be measured with scientific instruments. It is actually a tiny bit smaller at the horizon, so appearing larger is an illusion. I for one don't see more details when it is low, other than the phycological effect of being able to look at it for a while rather than just glance at it. If you stare at the high moon for a bit, it will seem to "expand" in your attention to fill your gaze. A low red moon might have different contrast than a high white moon. If you calculate the effect you site, you'll find it does not match your assertions.

 

[raylphscs]

Same angular size behind different lenz, meaning different image size! This was what the illusion theory ignored.! The so called experiments forgot the fact that there are different lenz between the moon and the observer when the moon is at different altitude. ! Why people don't consider everything involved when doing experiment? So end up with erroneous conclusion?
when we see objects on the other side of a lenz, the image looks different size if the lenz change shape, this is scientific, it is not illusion, it is the light rays bent causing the image size change. It is not any illusion causing the horizontal moon looks big. The moon image size change is because the atomosperic lenz shape changed between the moon and observer when the moon change altitude. If there were no atomasphere on earth, the moon image would never change size no matter on the horizon or above our head!

 

[Brin]

I'm guessing you haven't heard of "spherical symmetry?"

Seriously. Get a pad of paper, and draw the LENS. Show us the difference!

 

[DaveC426913]

Same angular size behind different lenz, meaning different image size! This was what the illusion theory ignored.! The so called experiments forgot the fact that there are different lenz between the moon and the observer when the moon is at different altitude. ! Why people don't consider everything involved when doing experiment? So end up with erroneous conclusion?
when we see objects on the other side of a lenz, the image looks different size if the lenz change shape, this is scientific, it is not illusion, it is the light rays bent causing the image size change. It is not any illusion causing the horizontal moon looks big. The moon image size change is because the atomosperic lenz shape changed between the moon and observer when the moon change altitude. If there were no atomasphere on earth, the moon image would never change size no matter on the horizon or above our head!

raylphscs, you have not thought this through. As previously pointed out, the effect of atmospheric lensing will actually serve to decrease the apparent diameter of the Moon.

And please stop screaming about being scienitific. The only one not being scientific here is you. You've got an idea stuck in your head that you haven't examined and won't let go of.

 

[raylphscs]

I'm guessing you haven't heard of "spherical symmetry?"

the atomasphere is symetrical to the center of the earth, but you are on the surface of the earth, it is not spherically symetrical to you. you are too far away from the center of the earth.

 

[rustynail]

@raylphscs:

You know that the moon revolves around the earth, and does not actually "change altitude", right?

 

[Brin]

the atomasphere is symetrical to the center of the earth, but you are on the surface of the earth, it is not spherically symetrical to you. you are too far away from the center of the earth.

Draw a picture, do the numbers. Read the thread. I'm done here.

 

[raylphscs]

As previously pointed out, the effect of atmospheric lensing will actually serve to decrease the apparent diameter of the Moon.

This was wrong, you pointed out doesn't mean it be the truth. while the moon near the horizon, the atomsphere lenz serves to enlarge the image. while it is above head, the atomosphere lenz changed shape and causing different image size.

 

[raylphscs]

As previously pointed out, the effect of atmospheric lensing will actually serve to decrease the apparent diameter of the Moon.

This was wrong, you pointed out doesn't mean it be the truth. while the moon near the horizon, the atomsphere lenz serves to enlarge the image. while it is above head, the atomosphere lenz changed shape and will decrease the image size.C:\Users\owner\Documents\moon_earth_atomosphere.jpg

 

[raylphscs]

@raylphscs:

You know that the moon revolves around the earth, and does not actually "change altitude", right?

By "altitude" I mean how close to the horizon, don't go by the literal meaning please