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."

Comments

Mr President, Dr. Evil is on the line...

[TripMaster Monkey]

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.

old news...

[deft]

some guy who got gods powers is trying to get laid... apparently its taking longer than the last guy i saw try this one.

Wait a minute....

[Joe Random]

That's no moon!

As Robin Williams said:

[mcSey921]

The moon, like a testicle, hangs low in the night sky.

There goes the karma.

Re:Bruce Almighty flashback

[toddbu]

There's a similar illusion with mountains. When I look at Mount Rainier between some large trees, it looks huge. When I look at it while driving down the highway, it doesn't look all that big. I actually find it disappointing to stand at the foot of the mountain. From that vantage point, it doesn't look all that impressive. Having climbed Mount St. Helens, looking down on a mountain from the top, it looks huge. It's really weird.

Actually...

[objekt]

Assuming a perfect non-eliptical orbit, the moon on the horizon is farther away than the moon directly overhead by almost half the diameter of the Earth.

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...

[gardyloo]

Also works with the sun, etc.

Hey you batard I jus ttried this and no wIc an't seewhatIm typing....

"Low-hanging" moon?

[Kelson]

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?

[eskwayrd]

They left out the key word:
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!

No mystery,

[Maljin Jolt]

it's bug in Matrix. A 2D transform/rendering artefact. Ever noticed a simple static texture for moon, with a black circle occlusion blended, no animation at all?

Re:Bruce Almighty flashback

[DavidTC]

You pegged it. The 'comparing to other stuff' is a red herring, it's that out brain treats up and down distance completely wrong.

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.)