Twelve hours of daylight on the third full day of Autumn
Wed, 25 Sep 2013 02:41:04 GMT —
The Fall Equinox occurred at 4:44pm on Sunday, September 22nd.
At this time, the sun's most direct rays passed directly over the equator and all points on the earth get almost exactly the same amount of daylight.
However, we don't see exactly 12 hours of daylight in Mid-Michigan on this date.
The sunrise and sunset in Flint, for example, are 7:22am and 7:32pm which gives us 12 hours, 10 minutes of daylight.
On September 25th, the sunrise and sunset are 7:26am and 7:26pm which gives us 12 hours of daylight tomorrow (image 1).
So why do we receive an extra 10 minutes of daylight on the Fall Equinox?
There are a couple of reasons for this.
First of all, the earth's atmosphere refracts -- or bends -- sunlight at a small angle toward the observer.
This makes the sun's disk visible on the horizon a few moments longer than it would be if we didn't have an atmosphere.
Secondly, sunrise is said to have occurred when the sun's disk first appears above the horizon, not when the geometric center appears above the horizon.
Similarly, sunset doesn't occur until the entire disk of the sun disappears.
This also "creates" a few extra moments of daylight for us.
For more information on this topic, click here.
We also lose daylight the quickest around this time of year and gain it most quickly around the Spring Equinox.
For example, we are currently losing between 3 and 4 minutes of daylight every day in Flint.
This quick loss of daylight will eventually lead to a quick loss in temperature as we progress through Autumn.
In the meantime, we're still expecting a slow warming trend here with highs in the upper 70s by Saturday.
A cold front will bring cooler weather by next week.