17 replies to this topic

[the L]

Title says all. Why moon looks bigger when is rising then when is above us?

Edited by the L, 09 September 2012 - 10:40 PM.

[Darkwind]

You have things on the ground you can compare it to.  It is the same size, your brain just configures it as bigger.  The atmosphere can distort too.

[notoverrated]

idk does it? never noticed a difference.

[StarMountainKid]

I read a lot about this once. The theories I remember are: the atmosphere's refraction index is not great enough to create this phenomena.  We do not perceive the sky as a perfect sphere, the horizon seems closer to us than the zenith appears, so the moon on the horizon appears closer to us and therefore larger than the moon does at its zenith.

I like Darkwind's explanation about having something to compare the moon's size to. I wonder if this would apply to moonrise in a desert?

I don't know if I buy this theory (there are more of them). Sometimes the sun appears huge at sunset, and sometimes not. What's the explanation of this phenomenon?

[Hasina]

Coyote steals the moon when it's rising and setting and he replaces it, it's just to mess with us. Actually, I believe it's just an optical illusion due to it being closer to the horizon, if you hold a quarter out at arms length, I believe, you'll see it's the same size no matter what.

[Darkwind]

AHHhhhooooooooo...

[and then]

I'd always heard it was the air density due to pollutants such as smoke and haze that caused a magnification... oh well....like so many other things... IDK  

[orangepeaceful79]

the L, on 09 September 2012 - 10:37 PM, said:

Title says all. Why moon looks bigger when is rising then when is above us?

I'll corroborate what has been mentioned before.  It is an optical illusion perpetrated by our brain, which has the nifty talent of always wanting a frame of reference for visual information.  The moon looks larger on the horizon because there are relatively nearby things on the horizon to compare the moon with.  When it is at its high point in the sky, or azimuth, there is no frame of reference other than the stars, which our brain knows are far away - and so we get the sense that the moon is smaller and farther away.  Our senses are subjective rather than objective, which is generally a good thing for our survival.  we can adapt well to changing surroundings.  What it makes us bad at however is recording data in situations when objectivity is needed.  Objectivity in humans must be learned....its not standard equipment for us.

[the L]

Its called ponzo illusion. http://en.wikipedia..../Ponzo_illusion
But how come that pilots notice the same thing from air planes?

[QuiteContrary]

I read science does not know for sure why the moon or sun appear so huge sometimes. Yes, there are a couple theories that may not fit every situation, but basically they don't know for sure.

[the L]

QuiteContrary, on 10 September 2012 - 04:28 AM, said:

I read science does not know for sure why the moon or sun appear so huge sometimes. Yes, there are a couple theories that may not fit every situation, but basically they don't know for sure.

I also read that. I wanted to hear best guesses.

[QuiteContrary]

Gottcha.

Edited by QuiteContrary, 10 September 2012 - 04:31 AM.

[the L]

Today moon was high. And I tired to look it from the point where two building soround it. Doesnt seen bigger. Stayed small.

[Render]

It is a cognitive illusion, so "it's all in our heads". There still isn't a conclusive explanation, but the closest one appears to be the already mentioned Ponzi illusion.

Quote

When the moon is low, we judge it to be far away. Something far away must be really big to span half-a-degree across the sky, so our brain inflates the moon accordingly.

The Moon Horizon Illusion http://science.nasa....n_moonillusion/

Edited by Render, 11 September 2012 - 08:23 AM.

[tyrant lizard]

I saw Patrick Stewart talking about this once. He basically said it was an optical illusion. And he should know - he's the Games Master!

I was driving down the road once and I saw the moon cresting the roofs of some houses and thought it appeared giant - the biggest I'd ever seen it. But mere seconds later when I drove up over a high fly over and my view of the moon rose up so that its backdrop was away from the houses it didn't seem large at all.