Why the moon appeared at least 5 times larger at the horizon?

Question

tonight i was at the beach, and the moon was a bright orange, it was beautiful, but besides that it was at least 5 times the size of it normally in the sky. i read an article saying that it was because of the objects around the moon and it was an optical illusion, but i dont see how that could be true, because it was HUGE. please help, thanks

Answer 1

It is an illusion. You can make it go away by looking at it upside down. Do that whatever way you find least embarrassing. Bend over and look at it between your legs, or stand on your head, or whatever. Do it when nobody is looking if necessary. When you do, it will look smaller. I have done this and it really works.

This is true of all kinds of things on the horizon; not just the Moon. Distant mountains and trees and such, seen far away on the horizon where there isn't anything in your way and you can see far, looks bigger than it really is. It is just hour our brain processes the information from our eyes.

Answer 2

It is indeed an optical illusion, called the Ponzo illusion.

A link included:

Answer 3

i saw same thing, and thought it was big because the moon had more mass

Answer 4

Yes, illusion.  Just to add my two penny worth, it just shows you how unreliable are most people regarding observation.  

Just the other day someone said they saw this object in the sky and said it looked about the size of a car.  Whoa!  If you have no idea of what the object is, and no idea how far away it is, how can you say how big it is.  

And yes the tube test is good, but anyone who has a small telescope will tell you there is no difference.  If you have the magnification set so the moon occupies the full field of view, you can see right away there is no difference between near the horizon and overhead.  

And how big do you think the moon looks?  People say all kinds of stupid things from inches to a couple of feet, when in fact it is a fraction of an inch – you can cover it up with your little finger held at arm’s length.  And you’ll do that even when the moon looks big on the horizon.  

Try it.  

______________________________________...

Yes, David A is quite correct.  The moon is further away from you when on the horizon – not further away from the Earth, just from the part of Earth you are on.  So it will appear a tiny bit smaller.  

That is what causes a gravitational imbalance, better known as the tides.

Answer 5

When it is on the horizon you have buildings and stuff like that to compare it to.  When it's in the sky you cant make the comparison.

It's just an optical illusion.

If you take a dime and hold it at arms length in front of the moon when it's both in the sky and on the horizon you will have a common reference point to use and you will find the moon is actually the same size.

Answer 6

well, like everyone else observed it's an optical illusion.

In fact it's actually a little larger when it is overhead (or as nearly as it gets at your latitude).  Why?  Well, when it is on the horizon it is about 6500 km further away, the radius of the earth.  You can confirm this by drawing a simple diagram.  So, it is about 1/60 larger when it is at your meridian than when it is on the horizon.

Answer 7

It IS an optical illusion, and it is caused - as you read - by the appearance in your field of view (when the moon is low) of other normal-sized objects. A simple experiment will prove this: next time you're out around the full moon, bring along a paper towel tube. Look at the moon through the tube when the moon is low, and again when it is overhead. The moon should occupy exactly the same portion of the tube's restricted field of view, therefore the moon is exactly the same size at both viewings.

Note that atmospheric refraction might cause the moon to appear a little oblong, but this doesn't last very long after the moon climbs above the horizon.

Hope that helps!

Answer 8

It's an illusion, but it is not caused by comparison with trees and houses and shite. You can confirm that it is an illusion by looking at it upside-down. You can confirm that it is not due to comparing it to familiar objects by looking at it over featureless ocean or prairie. the truth is that no one really knows where the illusion comes from, but it probably has to do with the way our brains model the sky and attempt to estimate distance when no distance information is available.