Did You Know (Sunset)

Paintings of three sunsets and unique atmospheric conditions they create

Paintings by E.J. Lefavour

That Sunset or sundown is the daily disappearance of the Sun below the horizon as a result of Earth’s rotation.

The time of sunset is defined in astronomy as the moment the trailing edge of the Sun’s disk disappears below the horizon in the west. The ray path of light from the setting Sun is highly distorted near the horizon because of atmospheric refraction, making astronomical sunset occur when the Sun’s disk is already about one diameter below the horizon. Sunset is distinct from dusk, which is the moment at which darkness falls, which occurs when the Sun is approximately eighteen degrees below the horizon. The period between the astronomical sunset and dusk is called twilight.

Sunset creates unique atmospheric conditions such as the often intense orange and red colors of the Sun and the surrounding sky. (From Wikipedia). 

These are a few captures of disappearances of the sun below the horizon, and the resulting unique atmospheric conditions, as viewed from Annisquam.

E.J. Lefavour

www.khanstudiointernational.com

3 comments

  • “making astronomical sunset occur when the Sun’s disk is already about one diameter below the horizon.” Sometimes wikipedia is wrong. Astronomical sunset occurs much later than one sun diameter below the horizon.

    Fun Facts:
    Astronomical dawn: sun is 18 degrees below horizon. (When it gets really dark)
    Nautical Dawn: sun is 12 degrees below horizon. (When the horizon is no longer visible.)
    Civil Sunset: the sun is 6 degrees below horizon (When civil activities like throwing a football have to cease.) All you have to memorize is 6,12,18 and you win your Astronomy merit badge.

    I know the wiki statement is wrong because of “the rule of thumb”. Extend hand out with palm facing you and cover setting sun with thumb. If the four fingers rest on the horizon the rule of thumb says five more Minutes until sunset. I can look up in Weatherunderground that today:
    Sunset: 4:54 PM
    Civil: 5:24 PM
    Nautical 5:58 PM
    Astronomical 6:31 PM
    Astronomical sunset is going to occur 37 minutes after sunset tonight and that is many many solar disc diameters. Had to look that up. The solar disk is about a half degree across. So 18 degrees at astronomical twilight is around 36 solar disks below the horizon. (This may seem too many but that is only because the disk looks really big at the horizon, a completely other phenomena.)

    ps. I am such a geek I can make a sunset really boring. Ignore me while I go fix the sunset wiki page. I love your paintings.

  • Thanks Paul. And yes, we know you are a scientist and can be a little geeky, but that’s why we love you. I should know better than to venture into your areas of expertise. But no matter what you say or how scientifically you explain it, you can’t make a sunset boring. I really like the civil sunset thing – it just sounds so . . . civil (which doesn’t connect in my mind with football – maybe tea with the ladies, or a game of cribbage). Go set Wiki straight!

  • These are wonderful, sunset is my absolutely favorite time of the day!!

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