This fellow won’t be getting out to play for awhile, but most of his friends are under the weather, too. See the nearest set of tracks crossing right to left? Snowshoe rabbits.
What is your length of day, today? Today is three minutes shorter in Dallas than it is in Fort Yukon. In a practical sense, our days have been longer for some time. It all depends on how you measure daylight, and believe it or not, there is more than one way to do that.
There is sunrise and sunset, measured at the moment the sun drops below the horizon. Meteorologists refer to the time between sunrise and sunset as the “length of day.”
Too easy? Don’t be disappointed, there is always civil twilight to complicate your day. Civil twilight is defined as “the time period when the sun is no more than 6 degrees below the horizon at either sunrise or sunset. The horizon should be clearly defined and the brightest stars should be visible under good atmospheric conditions (i.e. no moonlight, or other lights). One still should be able to carry on ordinary outdoor activities.” See how easy it is to complicate things? Scientists refer to the time between civil sunrise and civil sunset as the “length of visible light.”
Still too easy? There’s always nautical twilight, “the time period when the sun is between 6 and 12 degrees below the horizon at either sunrise or sunset. The horizon is not defined and the outline of objects might be visible without artificial light. Ordinary outdoor activities are not possible at this time without extra illumination.”
And for the really hard to please, there is always astronomical twilight, “the time period when the sun is between 12 and 18 degrees below the horizon at either sunrise or sunset. The sun does not contribute to the illumination of the sky before this time in the morning, or after this time in the evening. In the beginning of morning astronomical twilight and at the end of astronomical twilight in the evening, sky illumination is very faint, and might be undetectable.”
So how do I measure the length of a day? I look out the window. If I see light in the sky, then it’s day. I like simple.
Here is how today stacks up in Fort Yukon and around the world:
length of day
|Fort Yukon||12 h 7 m||13 h 51 m||16 h 0 m||18 h 30 m|
|Dallas||12 h 4 m||12 h 54 m||13 h 52 m||14 h 49 m|
|Copenhagen||12 h 3 m||13 h 17 m||14 h 45 m||16 h 16 m|
|Istanbul||12 h 3 m||12 h 58 m||14 h 3 m||15 h 7 m|
|Christchurch NZ||12 h 15 m||13 h 12 m||14 h 20 m||15 h 29 m|
How does your city stack up?
All definitions and times based on information found at WeatherUnderground.