Low-Hanging Moon Explained 381
gollum123 wrote to mention a BBC article which explains the low-hanging moon of the past few nights. From the article:"For the past few nights the moon has appeared larger than many people have seen it for almost 20 years. It is the world's largest optical illusion, and one of its most enduring mysteries. The mystery of the Moon Illusion, witnessed by millions of people this week, has puzzled great thinkers for centuries. There is still no agreed on explaination for why the moon appears bigger when it's on the horizon than when it's high in the night sky."
Mr President, Dr. Evil is on the line... (Score:5, Funny)
Good day, gentlemen. As you are no doubt aware, I have perfected a device capable of altering the orbital path of the moon. First of all, I must offer kudos on a most inspired cover story...'illusion' indeed...really, a first rate piece of propagan-da. Of course, you know it cannot last...
You see, gentlemen, things will only get worse...my device, which I've dubbed 'the Lunatrix', will continue destablizing the moon's orbit, drawing it ever closer to our fragile planet. First, abnormally high tidal waves will decimate all costal regions...then, as the tidal influence grows steadily stronger, geological disruptions will occur on a global scale, tearing apart the earth's crust like fresh bread, releasing the liquid-hot mag-ma within. No place on the planet will be safe...civilization as you know it will cease to exist...that is...unless you pay me...
One hundred billion kajillion fafillion dollaaars!!!
<DramaticMusic>
Gentlemen, you have my demands...peace out.
Re:Mr President, Dr. Evil is on the line... (Score:2)
Besides, I happen to know the Lunatrix was only the third-place prize in the last Pepsi contest.
Re:Mr President, Dr. Evil is on the line... (Score:2)
Reminds me of the time I was at the last Phish concert of the 1997 tour... just before the last set, the band annouced "This guy standing here in front has been at the front of every set all tour long... we don't know how he does it."
Obvious. (Score:3, Funny)
Actually... (Score:5, Interesting)
Additionally, I wrote a college term paper about this illusion and in my research I found the illusion to be less pronounced in denizens of mountainous areas who have less exposure to things like train tracks that extend straight into the horizon. Without that frame of reference, they are less likely to think of objects near the horizon as necessarily being very away.
Re:Actually... (Score:2)
Except your thesis seems to fail by inspection - because you are comparing apples to oranges. Denizens
Re:Actually... (Score:5, Informative)
Step 1: look at the moon near the horizon
Step 2: now, block out the horizon and all other objects with your hands, and look at the moon
The moon looks MUCH smaller whe you frame it with your hands and block out the extraneous stuff.
Also works with the sun, etc.
Re:Actually... (Score:5, Funny)
Hey you batard I jus ttried this and no wIc an't seewhatIm typing....
Re:Actually... (Score:4, Funny)
Iris: "Oh... tomhudson posted instructions on Slashdot that were crafted to get less intelligent people to look at the sun. You're smelling their smoking eye sockets".
Blanche: "Oh. I thought that's what was going on, but I wanted to be sure".
Sound FX: [audience laughter from I Love Lucy]
Re:Actually... (Score:4, Funny)
The other way to make the moon smaller is to turn around, bend over, and look at it between your legs.
Yes, it sounds like a prank but it's not. We actually studied this illusion as part of a course dealing with optics and perception in college.
Re:Actually... (Score:4, Funny)
Re:Actually... (Score:5, Funny)
I don't know much about this whole telescope thing your talking about but the magnifying glass is a great idea. Of course you have to make sure that it's in focus or you wont see the fascinating details involved with the flares. Make sure that you hold the magnifying glass at the correct position so that the focal point of the magnifying glass is directly on your cornea. And ignore the smell.
Re:Actually... (Score:2)
You can show them the train tracks illusion on a piece of paper and they will be less receptive to it than a flatlander would be.
Re:Actually... (Score:2)
old news... (Score:5, Funny)
Re:old news... (Score:4, Funny)
Bruce Almighty flashback (Score:5, Insightful)
I was thinking the same thing a few nights ago, watching the moon rise
over LA. Then I considered, "Near the ground, I consider it in proportion to the objects around it. In the sky, I have no reference"
Great thinkers? Centuries? Bah.
Now what they need to figure out is how to fix the pollution in LA. The
moon is red until it gets above the smog. Well, that is if you're not
*IN* the smog.
Re:Bruce Almighty flashback (Score:2)
Guaranteed to make you look foolish, but it works.
Re:Bruce Almighty flashback (Score:5, Interesting)
-kaplanfx
Re:Bruce Almighty flashback (Score:3, Interesting)
And the perception of depth goes away if you close one eye. And the appearance of continuous motion vanishes if you blink your eyes rapidly. In other words, if you literally change the way you are looking at the world, you will change the way your nervous system processes the light that enters your eye. Your example is intriguing, but not all that revealing.
I won't hypothesize why what you said works (since I haven't tested it), but I will point out that
Head standing optional (Score:3, Interesting)
The moon subtends about 2 solid degrees. By fortunate coincidence, this is more or less the same angle subtended by by most adult's fingers when their hand is held at arms length -- very rought it's true, but close enough.
So, just hold your index finger at arms length. It will be wide enough, approximately, to just cover the moon. Remember how it looked. Then look for the moon later when it's higher in
Re:Bruce Almighty flashback (Score:4, Informative)
Internal representation of the sky. (Score:3, Informative)
Re:Bruce Almighty flashback (Score:5, Interesting)
Re:Bruce Almighty flashback (Score:2)
Re:Bruce Almighty flashback (Score:2)
Near the ground you compare it to objects on the horizon. Some of those objects are things you have experience with up close (like buildings, trees, and mountains). So you get a sense of scale. The moon appears to be just behind the horizon, making it gigantic (though nowhere as big as it really is).
Far from the ground you compare it to other flying objects that you also occasionally see on the ground
Re:Bruce Almighty flashback (Score:4, Interesting)
I actually figured the whole thing out after visiting both a Planetarium and a Bucky-Dome [bfi.org].
The first clue came at the planetarium. At the top of the dome was a small circle. If you visually estimated the size of the circle, you would assume it is 1-2 feet across. However, according to the planetarium guy, it is actually 6 feet across.
The second clue came at the Cinerama Dome. The dome, like all geodesics, is made up of identical hexagonal pieces. However, inside the dome, all the pieces look distorted and irregularly shaped.
The key here is that while both domes are semi-spherical, when you are in them, they both look like they are much wider than they are tall (sort of a squashed sphere shape). Your brain, for some reason, assumes that things directly above you are closer, and that things near the horizon are further, so the dome looks misshapen. With an improper mental image of distance, the tiles look distorted due to perspective, and the circle looks smaller because it is further than it appears.
Basically, what this means is that the moon is the correct size on the horizon, and this "bug" causes it to look too small when it is high in the sky.
And, if you think about it, this bug makes perfect sense. Most things your brain would see (think primitive man on the savanah here) that are straight ahead are going to be far away, or at least 10 meters or so away, so your brain adjusts accordingly. Similarly, most things you see when looking down are close, on the scale of a couple of meters, so your brain also adjusts from that. Most things you see looking up are the sky, and with no frame of reference, your brain assumes that looking up is just like looking down (after all, looking forwards is the same as looking backwards). Therefore, your brain associated things on the horizon as far, and therefore bigger than they appear, and things up or down as close, and smaller than they appear.
Re:Bruce Almighty flashback (Score:5, Interesting)
We are completely incapable of estimating them, at all.
I don't know if it has anything to do with looking down, but that's an interesting theory.
But I have to point out that everything we can see up is either very close, maybe three hundred feet max, with most of it within ten, or was, for the vast majority of human existence, infinitely far away, like clouds and stars. So it's not just because downward is so close. Up is basically the same way, being very close, with a few weird exceptions for mountains. (Of course, down has the same exceptions.)
Whereas we've always been able to see things miles away and verify they are, in fact, that far away.
People think Douglas Adams' idea of a race that can't conceive of 'up' is a bit silly, but we have a fairly serious blind spot there.
For example, we think mirrors flip you around left to right. Well...it's just as correct to think they've flipped you around up to down. If you flipped an image in the mirror up to down, the person would be correct, although standing on their head. (Or flipped them front to back, but that's understandable, as you can only see one side of that in a mirror, so how you'd 'flip' that is a bit abstract.)
Re:Bruce Almighty flashback (Score:3, Insightful)
Uh, no it's not. That would be silly. Look in a mirror, raise your hand, and try to conceive of the image of your hand going down. The reason mirrors flip left and right is because left and right are defined relative to which direction is forward, and mirrors
The question is WHY (Score:3, Interesting)
I would like to propose a hypothesis why this is actually not a "bug" but has a purpose: gravity and hand-to-eye-coordination.
Most of us may have noticed that when you throw things, the things won't keep going straight to that direction, but fall to ground. We are pretty good at throwing at things far away rather accurately. You don't need to calculate the
Re:Bruce Almighty flashback (Score:3, Informative)
Re:Bruce Almighty flashback (Score:3, Interesting)
The moon is actually rarely in the scenery when the moon is in the picure.
Re:Bruce Almighty flashback (Score:2)
Move. No, seriously - get everyone and leave. Plant some trees on the way out and I think the smog would be gone in no time.
I was going to say stop driving your cars, but I didn't want to seem like a smart ass
Re:Bruce Almighty flashback (Score:2)
> The red light isn't pollution. You're looking at a moonset. It's a sunset, but dimmer.
Hmmmm..
When I lived in the lands far away, where they sky was clear of impurities, the moon would rise white.
When I moved to the land of {{COUGH}}{{COUGH}} pollution, the moon rises many colors.
For the last few days, it's been a nasty sickly red. It's the pollution. I've watched it rise over the smog.
Unless, you're simply saying that the moon isn't really colored red, that it's my perspective through the atm
Re:Bruce Almighty flashback (Score:2)
Re:Bruce Almighty flashback (Score:3, Interesting)
Speaking of thumbnails, a really good trick for estimating distances if you can estimate object size:
Measure the width of your thumbnail. Measure the distance between your thumb and your eye (arm extended, hitchhiker). Divide the thumb-eye distance by the thumbnail width. You'll get a number around 30.
To e
Re:Bruce Almighty flashback (Score:2)
They mean a full moon, I believe. Something about it coinciding with sunset on the past couple of days. I'm not sure of the specifics though.
Re:Bruce Almighty flashback (Score:2)
(no not really... but that is what he's saying)
Re:Bruce Almighty flashback (Score:2)
Of course, those two categories also make (2) and (3) rather redundant...
I didn't think this was a big mystery. (Score:3, Informative)
Some one on some show said that if you bend over doubled and look through your legs at the moon, no matter where it is in the sky it will appear large as well for the same reason
you mean... (Score:5, Funny)
Re:I didn't think this was a big mystery. (Score:2)
That's just silly. It's an obvious ploy to get people to look stupid.
Now I have to try it. Damn youse!
Re:I didn't think this was a big mystery. (Score:2)
Re:I didn't think this was a big mystery. (Score:2, Funny)
Dude, you're just begging to have someone mention that you're comparing the moon to your crotch. But I'll let someone else handle that (as it were).
Re:I didn't think this was a big mystery. (Score:5, Funny)
That's no moon.
Re:I didn't think this was a big mystery. (Score:2)
Hold up your thumb and cover the image of the moon. Most nights, it's easy.
However, some nights, especially in summer, when the moon is just over the horizon, it will appear several thumbs wide.
THAT is the illusion being referred to.
Re:I didn't think this was a big mystery. (Score:2)
No it won't. You're crazy! Madness! [slashdot.org]
I tried this last week to prove it to some friends. The Moon will appear exactly the same size regardless of where it is in the sky. Try it tonight. Disbelieve the illusion!
Although, perhaps we should use something more objective, like a couple different coins.
If the moon really did look bigger in comparison to your thumb, it wouldn't really be an illusion or a perception problem. It would prove that something actually did increase
Re:I didn't think this was a big mystery. (Score:2)
Re:I didn't think this was a big mystery. (Score:2)
Re:I didn't think this was a big mystery. (Score:2)
Re:I didn't think this was a big mystery. (Score:2)
Re:I didn't think this was a big mystery. (Score:2)
Jack Stargazer (transcripts available on website, but I don't remember what show it was anymore) once mentioned on the show that the moon near the horizon will actually appear "normal"--by which I mean the same size it would appear anywhere else in the sky--if you double over and look at it. Perhaps you were thinking of this (?).
I tried, and it seems to "work." (I live in a rural area so could do it without looking like an idiot. In the city, it might be harder...)
Re:I didn't think this was a big mystery. (Score:2)
The moon has appeared larger? (Score:4, Funny)
That's some moon. (Score:2)
Re:That's some moon. (Score:2)
Re:That's some moon. (Score:2)
The more Star Wars allusions you make, the more moderation will slip through your fingers.
Re:That's some moon. (Score:4, Funny)
Any attack made by you against this post would be a useless gesture, no matter what technical data you have obtained. This post is now the ultimate power in the universe. I suggest we use it.
Re:That's some moon. (Score:2)
Here's another one:
^_^
Easy Fix (Score:5, Funny)
Re:Easy Fix (Score:3, Funny)
Re:Easy Fix (Score:2)
Re:Easy Fix (Score:5, Interesting)
For example, frightening movies totally lose their atmosphere if you tilt your head 90 degrees so the TV is sideways. You can see everything going on, but the images aren't alarming. At least, that's what I've found.
Read Mind Hacks [amazon.com] for some interesting stuff on visual processing. The rotating-during-scary-movie thing I first noticed as a little kid watching Jurassic Park, but in Mind Hacks I learned things about how we recognize rotated shapes -- we have to do a lot of processing to flip them over, and the time this takes is proportional to the angle. So I think we get the images with too much lag for the brain to do a lot of the post-post processing it usually does -- i.e. being frightened, comparing sizes properly, etc.
The visual parts of the brain are surprisingly dependent on orientation.
Perception of distance and perspective (Score:3, Insightful)
Wait a minute.... (Score:5, Funny)
Explained? RTFA? (Score:5, Insightful)
Who writes these titles? Do they even read the submission, let alone the article... (extra scorn if the submitter wrote the title)
Wacky. And I read the article too (before it got posted here). There's definitely no explanation... a couple theories, sure, but they debunk the theories right in the article.
- StaticLimit
Re:Explained? RTFA? (Score:2)
Idiots do. See also today's "SPF (anti-spam system) is approved by IETF". It is neither aniti-spam, nor approved.
You're not new here - you should know that!
As Robin Williams said: (Score:5, Funny)
There goes the karma.
Damn. (Score:2)
Umm... maybe because a thicker atmosphere? (Score:5, Interesting)
No? Well, it was just a shot-from-the-hip thought.
Re:Umm... maybe because a thicker atmosphere? (Score:2)
Nope, if you take a picture of the "large" moon at the horizon, and then take a picture of the "small" moon directly overhead with the same settings, they're exactly the same size on the image/photo.
Re:Umm... maybe because a thicker atmosphere? (Score:3, Funny)
When you hold the dime over your head, the thinner atmosphere (3 ft higher than your head) doesn't magnify it as much.
Now, while holding the dime directly above your head, and watching it carefully, release the dime. You will notice that the dime begins to appears very large as it drops into the thicker atmosphere. This phenomenon is much easier to observe if you use something larger - like, say, a brick
Explained? (Score:3, Interesting)
I'd really like to see a bit more attention paid to making Slashdot headlines accurate, both by submitters and editors.
Isn't it just because of the frame of reference? (Score:3, Interesting)
Bah... (Score:5, Funny)
not just the moon (Score:2)
Must be Friday (Score:2)
huh? (Score:2)
first, i did not read every post so excuse this if it has been addressed.
is the earth round? is the atmosphere also round? so if a nearly clear object is bent does it not act as a lense? so if the atmosphere is between the viewer and the moon, wouldn't it bend light the same as a lense? so now tilt the top of the lense towards the viewer just like the atmos
Re:huh? (Score:2)
Well, you could read TFA where it says "Then there are those who scoff that this is an illusion at all. They, at least, can be proved wrong. Hold a coin up to a low-lying moon to and compare differences in size. Any difference will remain exactly the same, as one traces the trajectory of the moon through the night."
It is not larger.
"There is still no agreed on explaination..." (Score:2)
The math (Score:4, Funny)
20 % alcohol = 20 Bigger moon 40 & alcohol = thats one BIG moon 90 & alcohol = the size of the moon is no longer a concern of yours. You're somewhere else.
a joke from my mother: (Score:2, Funny)
A blond newlywed was enjoying her honeymoon by staring at the night sky from a Hawaiian mountaintop with her newly betrothed. At one point he asked her which is closer, Texas or the moon.
She thought about it for a moment and then her eyes glittered with a knowing look.
She glanced around dramatically and replied, "Duuuh! Do you *see* Texas?"
-
This joke is intended as humor, no offense to any blondes out there, real or implied.
No blondes were harmed during the creation of this joke.
Mod me whatevever.. (Score:2)
But these past few nights I've just been sitting out watching the moon for a few hours at a time, and it really is something to look at if you haven't done so already. I know late night is prime geek computing time, but go outside for 5 minutes and check it out.
This is no mystery, its an optical illusion. (Score:3, Informative)
When the Moon is close to the horizon your brain compares its size with terrestrial objects. When its at its zenith, the brain does not. We only perceive it as being larger on the horizon, when in fact our brains are just misjudging its size.
NASA scientists don't know this? Bullshit alert!
A simple test of the moons size... (Score:2)
When the moon rises, extend your arm all the way, hold your thumb next to the moon and take an approximate measurement of the moon against your thumbnail. You just need an approximation.
A few hours later, when the moon is higher in the sky, do the same thing.
This seems to be enough to convince most people that the moon is about the same size.
Of course, then you have to deal wi
"Low-hanging" moon? (Score:5, Insightful)
Not since June 1987 has the moon been this low in the sky
Umm... how about twice a day, when it rises and sets?
Who writes this crap?
Re:"Low-hanging" moon? (Score:2)
Not since June 1987 has the full moon been this low in the sky
See this story [nasa.gov] for a bit more detail.
Re:"Low-hanging" moon? (Score:5, Interesting)
Not since June 1987 has the full moon been this low in the sky
Actually, they are not saying "this low in the sky". They are saying "hangs lower in the sky".
The difference is simple:
When the Moon is full (or nearly full depending on how long you have to wait for the Earth to rotate it into view), it can appear right on the horizon for any viewer (excepting those whose horizons block the Moon entirely). This happens roughly monthly, not every 20 years.
"Hangs lower in the sky" is referring to the arc that the Moon appears to travel as the Earth rotates. Since the summer solstice was a few days ago, the tilt of the Earth makes the Sun appear in its most northerly position. Consequently, the Moon appears in its most southerly position, and it appears to 'hang' lower in the sky than during winter months for viewers in the Northern hemisphere (this effect is reversed for Southern hemisphere viewers).
When the Moon 'hangs' lower in the sky, the illusion lasts significantly longer because the Moon appears to be closer to the horizon for a much longer period. As a result, far more people notice the illusion, even those who don't normally watch the Moon on a regular basis.
This is the lowest hanging full Moon in 20 years mostly due to the timing of the full Moon relative to the solstice.
Note: there is some slight magnification of the Moon at the horizon due to observing it through much more atmosphere than when the Moon is overhead. However, this effect makes the Moon look very slightly taller. The illusion being discussed here typically makes the Moon appear to be wider on the horizon.
Note: IANAA (I am not an astronomer), but I'm fighting the urge to sleep in order to become one!
Re:"Low-hanging" moon? (Score:4, Informative)
First, "Consequently, the Moon appears in its most southerly position, and it appears to 'hang' lower in the sky than during winter months for viewers in the Northern hemisphere (this effect is reversed for Southern hemisphere viewers)."
It's true that the seasons move the location of the ecliptic (the Sun's annual path across the sky) and thus the Moon at night is further south when the Sun is further north. However, there's another effect at play here: the Moon has an inclined orbit (relative to the ecliptic). So depending on where you are in that cycle (it's 17.5 years long, if I recall right), the Moon's position above or below the ecliptic adds to or subtracts from the ecliptics north-south changes.
So it's not so much the timing relative to the solstice (the odds of the solstice being on a day with an effectively-full moon are at least about 1/9, after all), it's about the precession of the lunar nodes.
Also, the Moon is squashed near the horizon, not stretched tall. I have a great photo of this somewhere, but I seem to have lost it in my last move.
Huh? (Score:2)
From the article: "Experts have yet to agree on either or, indeed, any explanation."
So... which is it?
close to the equator (Score:2)
When it is round it's OK, but as soonas it is a C or a D it really faces in a different direction
creeped me a little the first time I saq it
bigger moon ?
sorry it is DAMN rainy season here, I haven't seen the moon for days
Answer (Score:2)
To test this, go outside at noon (when the sun is highest and 'smallest'), take a penny, close one eye, and hold the penny out towards the sun so that it perfectly blocks the sun. Note how far away the penny is from your eye.
Now go out at sunset when the sun is low on the horizon and seems huge. Again take the penny and hold it out to where it perfectly blocks the sun. You will notice that you are holding the penny
No mystery, (Score:5, Funny)
Lense Effect (Score:2)
Then wait a few hours until it's small again and if it's smaller you have your answer.
Course the naked eye also tells you the same thing. There are visible features of the moon that are identifiable and they're huge when it's low. When it's higher up in the sky they are smaller.
The answer is clear there is no mystery.
logic schmogic (Score:2)
No, that's the illogical conclusion
-kgj
"Logic is a bouquet of pretty flowers that smell bad."
- Spock
Occam Schmoccam (Score:2)
Yes. It says the exact opposite of my assertion -- and it's usually right.
But it's not always right. And where it's not right, that's where the interesting stuff happens.
In any case, the intent of my original post was irony, not epistemology.
-kgj
Re:PONZO (Score:2)
Damn, I was wrong. (Score:2, Interesting)
In the May 1999 issue of Sky and Telescope, there appeared a follow-up article which proved that Sky and Telescope had in fact created the current meaning by mistake
Re:Illusion (Score:2)
The amount of bend varies from zero for light that's already going straight downward (i.e., a star that appears to be overhead really is overhead) to about 0.54 degrees for light grazing the horizon. The moon also happens to be just about 0.54 deg
Re:Lense Effect (Score:3, Informative)
1) Nobody with even a passing knowledge of science spells "lense" with an "e" at the end.
2) The gravitational field of the Earth does not produce a lens effect. A gravitational lens occurs when light from behind an object is focused by the entire circumference of the object:
whereas any "natural lens effect" by the Earth for Earth-dwellers would only bend the l