{"id":40448,"date":"2023-01-11T09:04:55","date_gmt":"2023-01-11T09:04:55","guid":{"rendered":"https:\/\/www.skyatnightmagazine.com\/?p=114977"},"modified":"2023-01-11T10:32:29","modified_gmt":"2023-01-11T10:32:29","slug":"calculate-the-speed-of-earths-rotation-by-observing-the-night-sky","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/rss_feed\/calculate-the-speed-of-earths-rotation-by-observing-the-night-sky\/","title":{"rendered":"Calculate the speed of Earth\u2019s rotation by observing the night sky"},"content":{"rendered":"

<\/p>

By Mary McIntyre\n \t\t<\/p>

Published: Wednesday, 11 January 2023 at 12:00 am<\/p>

\n\n

Earth takes 24 hours to complete one rotation, right?<\/span><\/p>\n

It actually takes slightly less than that.<\/span><\/p>\n

You can test out how much less by studying the movement of the stars to work out the length of time it takes Earth to spin once on its axis.<\/span><\/p>\n

Discover more astronomy experiments<\/a> and science projects<\/a>.<\/strong><\/em><\/p>\n

How to do it<\/strong><\/h2>\n

Observing a favourite star and a bit of maths will prove Earth\u2019s spin takes less than 24 hours.<\/p>\n

  1. Position yourself so you can see a bright star disappear behind a chimney pot.<\/span><\/li>\n
  2. Note the exact time it vanishes.<\/span><\/li>\n
  3. Repeat this with the same star, from the same position, over the next few nights, noting how many minutes difference there is.<\/span><\/li>\n
  4. After a week, you\u2019ll have six values.<\/span><\/li>\n
  5. Add them, divide the total by six to get the average, and convert them to seconds.<\/span><\/li>\n<\/ol>

    Watching Vega<\/a> we saw a difference of four minutes and five seconds (245 seconds).<\/span><\/p>\n

    The published figure is three minutes 56 seconds (236 seconds) short of 24 hours: that\u2019s one rotation every 23 hours, 56 minutes and four seconds.<\/span><\/p>\n

    Try it your self. What do you get?Let us know by emailing us at contactus@skyatnightmagazine.com<\/a>.<\/strong><\/em>\u00a0<\/span><\/p> <\/body><\/html>\n

    ","protected":false},"excerpt":{"rendered":"

    By Mary McIntyre Published: Wednesday, 11 January 2023 at 12:00 am Earth takes 24 hours to complete one rotation, right? It actually takes slightly less than that. You can test out how much less by studying the movement of the stars to work out the length of time it takes Earth to spin once on […]<\/p>\n","protected":false},"author":24,"featured_media":40449,"template":"","categories":[1],"acf":{"readingTimeMinutes":"< 1"},"uagb_featured_image_src":{"full":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2023\/01\/calculate-the-speed-of-earths-rotation-by-observing-the-night-sky.jpg",2121,1414,false],"thumbnail":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2023\/01\/calculate-the-speed-of-earths-rotation-by-observing-the-night-sky-150x150.jpg",150,150,true],"medium":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2023\/01\/calculate-the-speed-of-earths-rotation-by-observing-the-night-sky-300x200.jpg",300,200,true],"medium_large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2023\/01\/calculate-the-speed-of-earths-rotation-by-observing-the-night-sky-768x512.jpg",768,512,true],"large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2023\/01\/calculate-the-speed-of-earths-rotation-by-observing-the-night-sky-1024x683.jpg",800,534,true],"1536x1536":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2023\/01\/calculate-the-speed-of-earths-rotation-by-observing-the-night-sky-1536x1024.jpg",1536,1024,true],"2048x2048":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2023\/01\/calculate-the-speed-of-earths-rotation-by-observing-the-night-sky-2048x1365.jpg",2048,1365,true]},"uagb_author_info":{"display_name":"importmanagerhub@sprylab.com","author_link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/author\/importmanagerhubsprylab-com\/"},"uagb_comment_info":0,"uagb_excerpt":"By Mary McIntyre Published: Wednesday, 11 January 2023 at 12:00 am Earth takes 24 hours to complete one rotation, right? It actually takes slightly less than that. You can test out how much less by studying the movement of the stars to work out the length of time it takes Earth to spin once on…","_links":{"self":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/rss_feed\/40448"}],"collection":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/rss_feed"}],"about":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/types\/rss_feed"}],"author":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/users\/24"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media\/40449"}],"wp:attachment":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media?parent=40448"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/categories?post=40448"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}