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Low-Hanging Moon Explained
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."
I heard on various shows that it's because it's closer to things that our mind knows are big when it's close to teh horizon, trees buildings towers etc. When it's high in the sky there is nothing around it.
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
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I've heard however that the illusion even occurs while flying high in an airplane. A horizon of clouds really doesn't give much of a landmark to compare to.
The way I've heard it, humans subconsciously model the sky as a flattened dome. Thus, when presented with two objects of equal apparent size, one on the horizon and one at the zenith, the one on the horizon looks bigger (i.e. is perceived as having a larger actual size) because it's "farther away" than, yet appears to be just as big as, the object that is directly overhead (and thus "closer").
The Moon doesn't change sizes (that the human eye can ascertain at least) and it is not magnified by the atmosphere on the horizon. It is merely an optical illusion.
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!
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.
Please only do this with the moon, not the sun.
My guess is that if you tried to do this safely (welding goggles or eclipse glasses) the off-center darkness would probably disrupt the optical illusion to some degree.
The effect hasn't been captured on photo, hence the mystery. The size of the moon in a photo is the same regardless of pointing up or across.
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."
m o/astro/demo/8c2040.htm
No one agrees? What? It's a natural lense effect created by the gravitational field produced by the earth. It's called the "Gravitational Lens Effect"
http://www.physics.brown.edu/physics/demopages/De
The Straight Dope answered this one 10 years ago: Why does the moon appear bigger near the horizon?
I am an astronomer... and you appear to be mostly right. Which of course means that I'm about to nitpick.
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.
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 light, not focus it. Not to mention that this gravitational field is too weak to make a noticeable difference. That's why the experimental confirmation of the bending of light (after Einstein's prediction) had to wait for a solar eclipse, and couldn't be confirmed with Earth's gravity.
3) The angular diameter of the image of the moon (the light rays reflected from it) is equal when the moon is low and when it is high. It's an optical illusion, not a concrete fact. It also works with the Sun, which may be easier to measure. Take a picture of a sunrise or sunset, when the Sun appears large. Take a picture of the Sun in the sky, when it seems smaller. The disc of the Sun will have the same size in both pictures.
4) What the heck does the linked article have to do with the moon?