Advertisement
If you have a new account but are having problems posting or verifying your account, please email us on hello@boards.ie for help. Thanks :)
Hello all! Please ensure that you are posting a new thread or question in the appropriate forum. The Feedback forum is overwhelmed with questions that are having to be moved elsewhere. If you need help to verify your account contact hello@boards.ie

Equinox date

Options
  • 29-02-2016 11:52pm
    #1
    ezra_pound
    Registered Users Posts: 2,497 ✭✭✭


    So as far as I knew the equinox was always the 20th or 21st march. It looks like march 17 has equal day and night though, not the other two dates, sunrise to sunset being 6:33 to 18:33. Surely that would make it the equinox.

    Where am I going wrong with this?


Comments

  • Options
    #2
    Rougies
    Registered Users Posts: 2,677 ✭✭✭Rougies


    ezra_pound wrote: »
    So as far as I knew the equinox was always the 20th or 21st march. It looks like march 17 has equal day and night though, not the other two dates, sunrise to sunset being 6:33 to 18:33. Surely that would make it the equinox.

    Where am I going wrong with this?

    The main reason is because sunrise time is measured when the top of the sun rises above the horizon and sunset is measured when the top of the sun lowers below the horizon, which adds a few minutes to the time the center point of the sun rises and sets. Simply put, the equinox is the day when the center point of the sun crosses above and below the horizon at exactly 12 hour intervals.


  • Options
    #3
    ezra_pound
    Registered Users Posts: 2,497 ✭✭✭ezra_pound


    Rougies wrote: »
    The main reason is because sunrise time is measured when the top of the sun rises above the horizon and sunset is measured when the top of the sun lowers below the horizon, which adds a few minutes to the time the center point of the sun rises and sets. Simply put, the equinox is the day when the center point of the sun crosses above and below the horizon at exactly 12 hour intervals.

    Thanks


Advertisement