User Tools

    To create and edit articles, please register and log-in

Main Menu : categories & index etc.

Main menu
Click categories to expand

A-Z listingplugin-autotooltip__plain plugin-autotooltip_bigA-Z listing

This is an alphabetical index of all content pages.

Other categories



Also see

Importance Ratings
Curator's rationale
AI Policy

Twitter feed 𝕏

Feeds + s.e.o. etc.
rss / xml feed
sitemap file
A-Z listing (archived)

Indexed under : Psychology / General

Wikenigma - an Encyclopedia of Unknowns Wikenigma - an Encyclopedia of the Unknown

The 'Moon Illusion'

The Moon illusion is an optical illusion which causes the Moon to appear larger near the horizon than it does higher up in the sky. It has been known since ancient times and recorded by various cultures. The explanation of this illusion is still debated.

Source : Wikipedia

What is known is that it's a purely psychological illusion rather than an optical one. The same phenomenon causes distant hills to look far more steeply inclined than they actually are.

Further reading: Helen Ross; Cornelis Plug (2002) The Mystery of The Moon Illusion.[ paywalled ] USA: Oxford University Press.

Editor's Note:

For those not convinced that it's a purely psychological illusion, try the the following experiment : When the Moon is low, and looks particularly large, find a very small coin (or other disc) that is exactly the right size to obscure the Moon when held at arm's length. On a subsequent evening, when the Moon is high, and appears small, take the same coin, at the same arm's length, and it will perfectly fit the Moon, as before.

For a 'live' demonstration of the peculiarity of the illusion, hold up a small coin as in the example above, and then focus your eye on the coin itself - whilst paying close attention to the apparent 'size' of the Moon. You should see the Moon appear to 'shrink' as you do so. Focus on the Moon again, and it will 'grow' back to its enlarged size.

    Please share this page to help promote Wikenigma !

Dear reader : Do you have any suggestions for the site's content?

Ideas for new topics, and suggested additions / corrections for older ones, are always welcome.

If you have skills or interests in a particular field, and have suggestions for Wikenigma, get in touch !

Or, if you'd like to become a regular contributor . . . request a login password. Registered users can edit the entire content of the site, and also create new pages.

( The 'Notes for contributors' section in the main menu has further information and guidelines etc.)

Automatic Translation

You are currently viewing an auto-translated version of Wikenigma

Please be aware that no automatic translation engines are 100% accurate, and so the auto-translated content will very probably feature errors and omissions.

Nevertheless, Wikenigma hopes that the translated content will help to attract a wider global audience.

Show another (random) article

Further resources :