{"id":30,"date":"2011-01-09T00:00:22","date_gmt":"2011-01-09T00:00:22","guid":{"rendered":"http:\/\/www.skycaramba.com\/blog\/?p=30"},"modified":"2011-02-22T04:23:44","modified_gmt":"2011-02-22T04:23:44","slug":"big-moon-rising","status":"publish","type":"post","link":"https:\/\/www.skycaramba.com\/blog\/2011\/01\/09\/big-moon-rising\/","title":{"rendered":"Big moon rising"},"content":{"rendered":"

For the week ending January 15, 2011<\/em><\/p>\n

Most people say the full moon looks bigger when it\u2019s rising and setting. It looks bigger, but it\u2019s not. I\u2019m not talking about its physical size staying the same no matter where the moon is. I\u2019m saying the moon takes up the same amount of sky in either place.<\/p>\n

We\u2019ve all heard about atmospheric effects that alter images. When the moon or sun appears to be just above the horizon, it is actually below it. You see it because the earth\u2019s atmosphere bends the light.<\/p>\n

However, it doesn\u2019t magnify the image of either the full moon or the sun. That\u2019s an illusion that happens entirely in the brain. If you can measure how much of the sky the full moon takes up when it rises or sets and compare that to its overhead \u201cfootprint\u201d, you\u2019ll get the same measurement.<\/p>\n

I don\u2019t have the equipment to take a proper measurement, and you probably don\u2019t either. But I do know a few things you can do to make comparisons that will reveal any changes in apparent size from position to position.<\/p>\n

You can take an object like a coin or a tiny rock. Hold it at arm\u2019s length in front of the full moon when it rises on January 19th<\/sup>. How much of the object covers the moon? Remember that and make the comparison again an hour or two later. Do it again an hour or two after that. It\u2019ll be the same.<\/p>\n

You can look at the moon through a telescope at various times of the evening. Make a mental note of how much of the moon you can see with any one eyepiece. Use the same eyepiece to look later. You\u2019ll see just as much of the moon. Or, if the moon took up only part of the viewing field, it will take up the same amount.<\/p>\n

The easiest and fastest way to prove that the magnified moon is just an illusion is to look at the rising or setting moon upside down. While upright, look at how big the moon looks just above the horizon. Then, turn around, bend over, and look at the moon between your legs. It\u2019s instantly smaller!<\/p>\n

Nobody\u2019s sure why this illusion happens. The most popular idea is that it\u2019s important for humans to have a better view of things on the horizon than of things overhead, so the brain magnifies the images from over yonder.<\/p>\n

Now that I\u2019ve given you that fact about the moon\u2019s apparent size, here\u2019s another one. The moon\u2019s distance changes during its orbit, so sometimes it actually does take up just a little more space in the sky. But the difference isn\u2019t enough that you can tell by casually looking up at it.<\/p>\n

At any given time, the moon is about a half degree wide in our sky. How convenient that the sun also takes up almost the exact same amount of space. That\u2019s why the moon can neatly cover it during a solar eclipse.<\/p>\n","protected":false},"excerpt":{"rendered":"

Most people say the full moon looks bigger when it’s rising and setting. It looks bigger, but it’s not.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[60,59],"_links":{"self":[{"href":"https:\/\/www.skycaramba.com\/blog\/wp-json\/wp\/v2\/posts\/30"}],"collection":[{"href":"https:\/\/www.skycaramba.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.skycaramba.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.skycaramba.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.skycaramba.com\/blog\/wp-json\/wp\/v2\/comments?post=30"}],"version-history":[{"count":7,"href":"https:\/\/www.skycaramba.com\/blog\/wp-json\/wp\/v2\/posts\/30\/revisions"}],"predecessor-version":[{"id":35,"href":"https:\/\/www.skycaramba.com\/blog\/wp-json\/wp\/v2\/posts\/30\/revisions\/35"}],"wp:attachment":[{"href":"https:\/\/www.skycaramba.com\/blog\/wp-json\/wp\/v2\/media?parent=30"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.skycaramba.com\/blog\/wp-json\/wp\/v2\/categories?post=30"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.skycaramba.com\/blog\/wp-json\/wp\/v2\/tags?post=30"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}