# Moon Illusion **URL:** \ **Category:** Cecil's Columns/Staff Reports\ **Created:** [June 24, 2005, 10:15am UTC](https://boards.straightdope.com/t/moon-illusion/309652 "2005-06-24T10:15:46Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Wallenstein](https://avatars.discourse-cdn.com/v4/letter/w/b5a626/32.png) [@Wallenstein](https://boards.straightdope.com/u/Wallenstein)\ **Post date:** [June 24, 2005, 10:15am UTC](https://boards.straightdope.com/t/moon-illusion/309652/1 "2005-06-24T10:15:46Z")
[Why does the moon always look bigger at the horizon?](http://www.straightdope.com/classics/a2_110.html) This topic has been in the UK press over the last couple of days, as the angle of the moon this week made it appear vast on the horizon. Nice to see that the physics behind this is seeping into mainstream press: > **[Patrick Moore explains the phenomenon of the moon illusion](https://www.theguardian.com/science/2005/jun/24/spaceexploration.g2)** > > This week, the moon seems spectacularly big in the sky. What's going on? Renowned astronomer Patrick Moore explains the phenomenon of the moon illusion. Article is by Patrick Moore, famous sky-watcher in the UK. ---
**Author:** ![flodnak](https://avatars.discourse-cdn.com/v4/letter/f/838e76/32.png) [@flodnak](https://boards.straightdope.com/u/flodnak)\ **Post date:** [June 24, 2005, 10:49am UTC](https://boards.straightdope.com/t/moon-illusion/309652/2 "2005-06-24T10:49:50Z")
Also, yesterday’s Astronomy Picture of the Day included [a link to an earlier APotD](http://antwrp.gsfc.nasa.gov/apod/ap031011.html) using multiple exposures to prove the Moon Illusion is, indeed, only an illusion. Cool stuff. ---
**Author:** ![Pleonast](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pleonast/32/1183_2.png) [@Pleonast](https://boards.straightdope.com/u/Pleonast)\ **Post date:** [June 24, 2005, 9:26pm UTC](https://boards.straightdope.com/t/moon-illusion/309652/3 "2005-06-24T21:26:38Z")
Even the [BBC](http://news.bbc.co.uk/2/hi/uk_news/magazine/4619063.stm) has something to say about it. ---
**Author:** ![kasarul](https://avatars.discourse-cdn.com/v4/letter/k/f07891/32.png) [@kasarul](https://boards.straightdope.com/u/kasarul)\ **Post date:** [June 26, 2005, 12:53am UTC](https://boards.straightdope.com/t/moon-illusion/309652/4 "2005-06-26T00:53:22Z")
Has anyone here seen the moon in it’s huge state? Apparently the moon around 20 years ago in England (and the last couple of nights according to the BBC) took up nearly the entire horizon. My wife vehemently disagrees with the ponzo explanation as she claims the moon was far too large to measure accurately. Has anyone here seen the moon this large and also done the ‘arm length measurement’ experiment? ---
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [June 26, 2005, 4:26am UTC](https://boards.straightdope.com/t/moon-illusion/309652/5 "2005-06-26T04:26:16Z")
> [@kasarul](#): > > Has anyone here seen the moon in it’s huge state? Apparently the moon around 20 years ago in England (and the last couple of nights according to the BBC) took up nearly the entire horizon. > > Has anyone here seen the moon this large and also done the ‘arm length measurement’ experiment? Yes. It’s the same size. _Really._ Now, if it is actually touching the horizon, there’ll be some distortion in size (and shape, even) due to refraction. But otherwise, it’s the same size. Honest. ---
**Author:** ![Askance](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/askance/32/8281_2.png) [@Askance](https://boards.straightdope.com/u/Askance)\ **Post date:** [June 27, 2005, 4:07am UTC](https://boards.straightdope.com/t/moon-illusion/309652/6 "2005-06-27T04:07:19Z")
> [@kasarul](#): > > Apparently the moon around 20 years ago in England (and the last couple of nights according to the BBC) took up nearly the entire horizon. What does this mean? 359 degrees? ---
**Author:** ![McCranie](https://avatars.discourse-cdn.com/v4/letter/m/ecccb3/32.png) [@McCranie](https://boards.straightdope.com/u/McCranie)\ **Post date:** [June 28, 2005, 2:00am UTC](https://boards.straightdope.com/t/moon-illusion/309652/7 "2005-06-28T02:00:34Z")
Measuring the moon by holding a ruler or paperclip at arm’s length is not accurate enough. I used a telescopic lens (500mm, to make the image of the moon as large as I could) on a 35mm SLR camera, and took photos, and printed them on 8x10 paper. I couldn’t measure any difference. ---
**Author:** ![Elendil\_s\_Heir](https://avatars.discourse-cdn.com/v4/letter/e/7cd45c/32.png) [@Elendil\_s\_Heir](https://boards.straightdope.com/u/Elendil_s_Heir)\ **Post date:** [August 31, 2012, 1:10am UTC](https://boards.straightdope.com/t/moon-illusion/309652/8 "2012-08-31T01:10:15Z")
Since that column is up again, I’m bumping this thread. And BTW, the fourth paragraph from the end, beginning “I know you’re not infallible…,” should be in _italics_.