“Even having Leap Year doesn\u2019t get our calendars exactly right. So periodically the International Earth Rotation and Reference Systems Service adds leap seconds to our daily lives we don\u2019t notice.”<\/p><\/blockquote>\n
Every four years we add a day \u2014 except not quite every four years because we have that divisible-by-400 rule. So even having Leap Year doesn\u2019t get our calendars exactly right. So periodically the International Earth Rotation and Reference Systems Service\u00a0adds leap seconds to our daily lives we don\u2019t notice, especially now that most people\u2019s clocks are updated automatically on their cell phones. We add a leap second less than once a year. There have only been 27 leap seconds since 1972. They are based on very precise measurements of the rotation of the Earth, which isn\u2019t perfectly constant, to bring things into alignment.<\/p>\n
Ultimately these things are tied to the motion of the Earth around the sun and the exact rotation of the Earth and little tiny things adjust that interaction between the Earth and the moon that causes little slow downs and speed ups. All of these things are little adjustments so that our written calendar, which we use to organize our daily lives, lines up as closely as possible to the astronomical calendar, which for us is important because of seasons.<\/p>\n
If we lived on any other planet besides Earth, we\u2019d still need to observe Leap Year.<\/h3>\n On some planets, like Venus, it rotates so slowly, that the difference between the time it takes to rotate and the time from noon to noon is very extreme. The longest solar day of any of the planets in the solar system is on Mercury. Its day is about 176 Earth-days long. Venus\u2019 day is 117 Earth days long and it rotates backwards compared to the direction it goes around the sun. Uranus is tipped almost exactly on its side so for its northern summer, the sun is directly over the north pole. And for its northern winter it would be complete darkness in the northern hemisphere for years because it takes it 84 years to go around the sun. So the seasons can be quite extreme on other planets. We\u2019re set up well here on Earth.<\/p>\n","protected":false},"excerpt":{"rendered":"
UCF Physics Professor Josh Colwell explains the science behind the need for Leap Year and other facts you may not know about the bonus day.<\/p>\n","protected":false},"author":98,"featured_media":106714,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"lazy_load_responsive_images_disabled":false,"footnotes":"","_links_to":"","_links_to_target":"","_wp_rev_ctl_limit":""},"categories":[24],"tags":[364,2557,4361],"tu_author":[],"class_list":["post-106713","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-science-technology","tag-astronomy","tag-joshua-colwell","tag-space"],"yoast_head":"\n
Why Do We Need Leap Year?<\/title>\n \n \n \n \n \n \n \n \n \n \n \n \n \n\t \n\t \n\t \n \n \n \n \n \n\t \n\t \n\t \n