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Citation Station: The length of a day only is only 23hours long

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    • CommentAuthorcompience
    • CommentTimeDec 21st 2006
     

    I recently read that the length of time it takes the earth to complete one full revolution is not 24hours but is actually 23 hours, 56 minutes and 4.09 seconds. We have a leap year every four years to make up for this shortfall.

    Can anyone confirm this?

    The only other info i have on it is a debate about how to calculate leapyears:-
    "his calculation is not complete! On century-years we don't have a leap year except when they are dividable by 400, such as 2000. There wasn't a leap year in 1700 nor in 1800 as in 1900."

    •  
      CommentAuthorMrFingers
    • CommentTimeDec 21st 2006
     

    there is a difference between a solar and a true day. a solar day is the time it takes for the sun to return to the same position in the sky. a true day takes into account that since the earth has changed position in 24 hours relative to the sun in its orbit, a solar day is not a full revolution of the earth.

    maybe that gives you a hint

    •  
      CommentAuthorUdoboy
    • CommentTimeDec 21st 2006
     

    I thought the leap day/leap century thing was because the year is actually 365.24 solar days long.

    • CommentAuthorcompience
    • CommentTimeDec 21st 2006
     

    no.. we're clearly not talking about how long it takes the sun to come up and go down.. cos they changes every day.

    its how long it take the earth to do one complete revolution.

    •  
      CommentAuthorMrFingers
    • CommentTimeDec 21st 2006
     

    well the sun's movement in the sky is directly related to earth's rotation so thats not really fair lol :)

    something interesting:
    * Monday - moon day (celestial)
    * Tuesday - Tyr's day (Old Norse god)
    * Wednesday - Woden's day (Old English god)
    * Thursday - Thor's day (Old Norse god)
    * Friday - Frigg's day (Old Norse goddess) (Friday is often erroneously associated with Freyja)
    * Saturday - Saturn's day (Roman god)
    * Sunday - sun day (celestial)

    •  
      CommentAuthorUdoboy
    • CommentTimeDec 22nd 2006
     

    Yah, I've always said things will get annoying when the Judeo-Christian days of the week roll along:

    Father Day
    Son Day
    Holy Ghostday
    Fatherday2
    Sonday2
    Holyghostday2
    Sunnotsonday

    ?
    :bigsmile:

    •  
      CommentAuthorlegatissimo
    • CommentTimeDec 22nd 2006 edited
     

    I think those have a nice ring to them. "Thank goodness it's Holyghostday2," and "sounds like someone's got a case of the "Son Days"

    •  
      CommentAuthorTrance
    • CommentTimeDec 22nd 2006
     

    A day name with numbers in? Sounds too mathematical for my liking!

    •  
      CommentAuthorTaed
    • CommentTimeDec 22nd 2006
     

    "I don't think he's heard of second breakfast, Pip."

    • CommentAuthorcompience
    • CommentTimeDec 23rd 2006
     

    I surpose this is actualy fairly easy to work out..

    all i need is the speed the earth spins at, and the circumference of the earth, then if i was any good at maths i could work out long it takes to spin round once.

    • CommentAuthorcompience
    • CommentTimeDec 23rd 2006
     

    or i could just find a webpage thats more or less done that for me

    The Earth rotates once in a few minutes under a day (23 hours 56 minutes 04. 09053 seconds). This is called the sidereal period (which means the period relative to stars). The sidereal period is not exactly equal to a day because by the time the Earth has rotated once, it has also moved a little in its orbit around the Sun, so it has to keep rotating for about another 4 minutes before the Sun seems to be back in the same place in the sky that it was in exactly a day before.

    http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970401c.html

    •  
      CommentAuthorTaed
    • CommentTimeDec 23rd 2006
     

    It's kinda like the question, "What is the chance that the next person you will meet will have MORE than the average number of hands?"

    (The answer is around 99.9999%, since almost no one has more than 2, and a not-insignificant number have 0 or 1, the average is something around 1.99999, and hence the chance of meeting someone with 2 hands (or more) is pretty high.)

    • CommentAuthorcompience
    • CommentTimeDec 24th 2006
     

    what? its nothing like that the hell are you talking about..

    •  
      CommentAuthorMrFingers
    • CommentTimeDec 24th 2006 edited
     

    it's exactly what i told you :) and now you know which direction the earth travels in its orbit.

    •  
      CommentAuthorUdoboy
    • CommentTimeDec 24th 2006
     
    Posted By: Taed

    It's kinda like the question, "What is the chance that the next person you will meet will have MORE than the average number of hands?"

    (The answer is around 99.9999%, since almost no one has more than 2, and a not-insignificant number have 0 or 1, the average is something around 1.99999, and hence the chance of meeting someone with 2 hands (or more) is pretty high.)

    There are three kinds of untruth: Lies, Damned Lies, and Statistics.

  16.  

    Whoever said that we only have leapyears on centuries divisible by 400 is insanely wrong! 100 years is divisible by 4, and a leap-year is every 4 years.

    •  
      CommentAuthorTaed
    • CommentTimeJan 11th 2007
     

    The years 1700, 1800, and 1900 were NOT leap years. The year 2000 was. 2100 will not be.

    •  
      CommentAuthorUdoboy
    • CommentTimeJan 11th 2007
     
    Posted By: papertrail89

    Whoever said that we only have leapyears on centuries divisible by 400 is insanely wrong! 100 years is divisible by 4, and a leap-year is every 4 years.

    Taed is right; you are not.

    • CommentAuthorAsmadeus
    • CommentTimeJan 14th 2007
     

    Google is your friend, and everything you want to know (about leapyears) is there :
    http://www.spaceref.com/news/viewpr.html?pid=995

    You'll learn that a year is 365.2422 long, which is 11 minutes shorter than 365.25, and that's why there are no leap year once every 400 years (since 1582).
    You'll also learn that there were already leapyears in the Julian Calendar, and that the error accumulated to ten days, untill some pope dropped eleven days of a year - going from October 4 1582 to October 15.

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