WHAT YOU SEE ISN’T ALWAYS AS IT APPEARS.
Photo By: Dan Marker-Moore Follow him here on IG @Danorst (CLICK photo for full size and see below for all reference links and links to Dan’s work).
Cool video by ASAP Science:
The theme of this post is the Moon but it applies exactly the same to the Sun as well.
How many times have you been driving just to turn a corner and there like a monolith, the dark reddish, pink moon has just broken the horizon? As it continues to rise it appears huge, almost as if it’s closer than usual or the earth’s atmosphere is magnifying the image somehow. Well truth be told, the Earth’s atmosphere IS having an effect on the Moon; as it sits low on the horizon you are viewing the image through MUCH more atmosphere than you are when its overhead. That’s why the low Moon and Sun appear a different color, the Sun, in fact can almost be looked at directly when it’s on the horizon (Though I don’t recommend it) because the atmosphere acts as a massive light filter. The higher they get into the sky, the whiter and brighter they become.
There’s one piece of this puzzle still not addressed; why it is the Moon so much bigger on the horizon than when it is high in the sky. Well that’s the problem; it’s not. The Sun and Moon are the same size on the sky weather they’re on the horizon or high in the sky. That just goes to show you that you can’t even tryst your own eyes and mind to be accurate in many cases. I’m honestly no different, for years I used to think the moon was larger on the horizon, somehow magnified by the Earth’s atmosphere but as I got older and learned more I realized that it isn’t the case at all. In fact, any distortions by the atmosphere would actually make the Moon a little smaller.
It’s called the MOON ILLUSION (Sun illusion when talking about the Sun) and really what’s going on here is somewhat of a mystery but the foundation lies in what’s known as an angular size illusion and Ponzo Illusion. Think of it this way, when clouds are overhead they are much closer than when they are on the horizon. Depending on how open your horizon is they can be a hundred miles away! Same applies to the Moon; when it is overhead it is as close as it gets to you and when it is on the horizon it is much further away. Your mind subconsciously knows this (You don’t consciously think it) and to compensate for the increased distance it gets fooled into thinking that the Moon is huge. Try it sometime; use your thumb, binoculars, telescope or camera like the photo I used here. You will find that it’s literally all in your head.
Dan Marker-Moore Tumblr: http://danorst.tumblr.com/
Dan Marker-Moore Vimeo: http://vimeo.com/markermoore
Dan Marker-Moore Blog: http://dontcrybaby.org/blog/
Detailed article on the illusion: http://www.pnas.org/content/97/1/500.full
Great NASA article on the illusion: http://science.nasa.gov/science-news/science-at-nasa/2008/16jun_moonillusion/
University of Wisconsin-Whitewater page on the illusion: http://facstaff.uww.edu/mccreadd/