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Sunrise, sunset

February 7, 2020
By JOYCE COMINGORE - Garden Club of Cape Coral (news@breezenewspapers.com) , Cape Coral Daily Breeze

Dawn, dusk and twilight blend into making a day for us. In Cape Coral the first day of February was 10 hours, 58 minutes long. The last day of the month is 11 hours, 38 minutes, making the length of the daylight grow by 40 minutes in February 2020. We have an extra day with Leap Year, also.

Dawn has been described as from the Old English verb dagian, "to become day," the time that marks the beginning of the twilight before sunrise. The categories of dawn are Astronomical dawn, Nautical dawn, Civil dawn. If the sky is clear, it is blue and there can be clouds or haze, bronze, orange and yellow colors with some bright stars and planets still be visible to the naked eye in daylight. Dawn is the first sight of light in the morning and continues until the sun breaks.

"Sunrise, sunset, sunrise, sunset swiftly flow the days, seedlings turn overnight to sunflowers blossoming even as we gaze. Sunrise, sunset sunrise, sunset swiftly fly the years laden with happiness and tears."

"Matchmaker" from "Fiddler on the Roof" is a very profound song in my mind.

Twilight is the time before sunrise and after sunset, when there is some amount of light visible in the sky. Twilight occurs twice every 24 hours at dusk or dawn. When there is some amount of daylight but no sun, something we call dawn and sunset. Even though we equate twilight with dusk, this is technically not correct. There is a difference between dusk and twilight. When there is no sun but there is light, we have dawn or dusk.

Civil twilight is when the sun is 6 degrees below the horizon. Nautical twilight, or Military Twilight, starts when the sun is 12 degrees below the horizon. Astronomical twilight starts or ends when the sun is 18 degrees below the horizon. The diffusion of light is because the sun is somewhere behind the horizon.

The reverse phenomenon happens at dawn. Twilight happens twice a day, once at dawn and again at dusk. Civil dusk, Nautical dusk and Astronomical dusk are the same distance below the horizon once again. Because we see the evening sunset, we mostly associate twilight with evening but it happens in the morning, too, at daybreak. Dusk indicates the beginning of night and of the day, indicating there will be no more light if it is dusk and the beginning of light if it is dawn.

The Northern Hemisphere dwellers, or most of the Earth's population, notice longer days and shorter nights in the summer and it is the opposite in the winter. This happens because our Earth's axis is not straight up and down at a 90 degree angle, we are a little bit tilted. Therefore, as we orbit the sun every 365 days, sometimes the Northern hemisphere is closer to the sun and we have summer, while other times our winter has the opposite effect because we are farther away and chilly.

The Earth always orbits the sun every 365 days in an elliptical circle, giving us summer and winter by our relationship. Every 24 hours the Earth spins as it circles giving us day and night as to whichever side faces the sun. If the Earth axis was straight up and down at 90 degrees, the length of time spent facing the sun would always equal the length of time facing away. But no -- instead we are tilted at 23.5 degrees, with this tilt always pointing in the same direction in space, toward the North Star as we travel the elliptical circle around the sun. So, when the Northern Hemisphere is closer to the sun, we have summer and winter when it's farther away. The difference in the length of day from season to season can be larger or smaller, depending on where you are on the planet.

Latitude is a distance measured by distance from the equator. Because the Earth is a sphere, the higher latitudes near the poles are curving away from the Sun, therefore receiving less sunlight making them colder than the rest of the planet. With the 23.5 degree tilt away from the Sun, a pole receives less light giving a short window to its lower part in line with the Sun's rays. In the middle of winter, the sun never fully rises above the horizon making 24 hours of night; in the summer the reverse is true.

Then we contend with the solstices and the equinoxes. The Earth's tilt and rotation around the Sun means one day a year, the North Pole tilts as far away as possible toward the Sun while the South Pole is tilted as far away as possible, giving us the longest day of the year, or summer solstice for the Northern Hemisphere and the shortest in the Southern Hemisphere called the winter solstice.

Halfway between the solstices are the equinoxes. This is the point where the planet's tilt switches either toward or away from the Sun, lengthening the days until the fall equinox, then reversing. Solstices and equinoxes have variable dates due to the accounting differences in the Earth's orbit because a year is slightly more than 365 days. This is the year we make up for that with Leap Year. In the Northern Hemisphere, the winter solstice occurs around Dec. 22; summer solstice, June 22; spring equinox, March 21; and fall equinox, Sept. 23.

By the way, Punxatawny Phil did not see his shadow meaning, an early spring up North.

Thus, the sun rises and the sun sets, swiftly fly the years.

Joyce Comingore is a Master Gardener, hibiscus enthusiast and member of the Garden Club of Cape Coral

 
 
 

 

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