Why do the sun and moon look bigger when rising and setting?

[dane502]

Hi all!

This is my first post here, so please correct me if I am doing anything wrong. Before I posted this thread here, I read some of the other threads in the subject "General Astronomy", and now I am not sure, that this thread blends in with the other articles, since my question is far more simple than questions in other threads, but anyway...

I have always wonderd why the sun and the moon looks bigger when rising and setting, than when they are highest on the sky. If anyone could give me a clue or answers the question, I will be very thankful.

Best regards
dane502

 

[Kurdt]

I think that's generally regarded as being an optical illusion. Other theories about atmospheric lensing have been rejected. Here is an enormous article about the whole phenomenon.

http://www.lhup.edu/~dsimanek/3d/moonillu.htm

 

[mubashirmansoor]

Welcome to PF Dane502,

Isn't it considered opposite?

 

[Kurdt]

Welcome to PF Dane502,

Isn't it considered opposite?

What do you mean by opposite? As in the moon would appear smaller at the horizon?

Atmospheric lensing would cause a slight decrease in the apparent size of the objects but it is well known that in actual fact they appear bigger to us despite this. Have a look at the link I provided. There is also a summary on bad astronomy with a couple more links about the moon illusion.

http://www.badastronomy.com/bad/misc/moonbig.html

 

[russ_watters]

Atmospheric lensing would cause a slight decrease in the apparent size of the objects...

You sure about that? When learning celestial navigation, we used an altitude correction that traced the "true" position of an object below where it was viewed to be. Translation: it stretches vertically (at the very least) as it approaches the horizon.

 

[Kurdt]

Quite sure russ. The first website I linked to has a good explanation. There are some photographs illustrating the effect here.

http://cseligman.com/text/sky/moonillusion.htm