Today is the Equinox, so I figured that there would be less than 12 hours sunlight tomorrow in the northern hemisphere, but when I check the web, I find that almost every place in the northern hemisphere has slightly more than 12 hours sunlight. Why?
http://www.sunrisesunset.com/calendar.asp
2007-09-23 02:29:43 · 5 answers · asked by Hein H 1 in Science & Mathematics ➔ Astronomy & Space
1. The sun is not a point source of light but is in fact about one-half degree of arc across as seen from Earth.
2. The atmosphere causes light to refract because it is denser than a vacuum. This allows to the sun to be seen slightly longer that it would if we had no atmosphere.
2007-09-23 05:44:06 · answer #1 · answered by Jim E 4 · 1⤊ 0⤋
Hi Hein!
There's nothing mysterious about this question!
The sunrise/sunset tables measure the sunrise and sunset as the moments the upper edge of the sun touches the horizon, not when the center of the solar disc does.
If the tables measured the times from the moment the center of sun's disc breaks the plane of the horizon, it would measure 12 hours exactly at the equinoxes. But it doesn't. The rising sun takes an extra few minutes between when the first gleam of sunlight appears over the horizon and the time the center of the disc crosses the plane of the horizon, and another few minutes at sunset until the last flicker of the sun's upper limb dips beneath the edge of the earth.
That's why the day when the sunrise and sunset are most closely equal will be September 26th.
2007-09-23 05:34:45 · answer #2 · answered by Anne Marie 6 · 1⤊ 1⤋
Because of atmospheric refraction, the image of the Sun on the horzion is about 1 degree higher than its actual position. So even when the sun is geometrically below the horizon, it is still visible for a few minutes.
2007-09-23 02:35:17 · answer #3 · answered by ZikZak 6 · 4⤊ 1⤋
flowers strengthen fit roots in the event that they have atleast 8 hours of dark. So fit roots = extra effective flowers to respond to your question they might strengthen extra effective below 12 hour sunlight. in case you prefer them to strengthen quicker you ought to use 24 hour sunlight yet they arent going to be the superb flowers they may well be.
2016-11-06 04:00:33 · answer #4 · answered by Anonymous · 0⤊ 0⤋
The exact date of the equinox is traditional.
Doug
2007-09-23 03:14:48 · answer #5 · answered by doug_donaghue 7 · 0⤊ 5⤋