Sunset is the exact time the upper disk of the sun is at the horizon, whereas dusk is when the center of the sun is 18 degrees below the horizon, according to the National Institute of Standards and Technology. The hazy twilight in between sunset and dusk is caused by the scattering of sunlight in the upper atmosphere that gives the horizon a light blue appearance.Continue Reading
Sunset also refers to the end stages of any period, such as the sunset years of a life. Dusk is also the dark part of twilight or partial darkness of an area. Both words come from Middle English terms.
Dusk and twilight also occur in the morning before sunrise. Twilight also refers to the time of night when the western edge of the sky gets darker until the night sky is the same homogeneous color from one horizon to the other. Another definition for the word twilight is a later or terminal period, such as the twilight of the British Empire's power in the 1800s.
Astronomical twilight occurs when the sun is 12 to 18 degrees below the horizon. Nautical twilight is when the sun is 6 to 12 degrees below the horizon, and civil twilight is from sunset until the sun is six degrees below the edge of the earth.Learn more about Our Sun
The National Institute of Standards and Technology and the United States Naval Observatory are both responsible for keeping the official U.S. time. The two agencies coordinate their efforts to ensure that they are as synchronized as possible.Full Answer >
Once the sun touches the horizon, it takes approximately 2 to 3 minutes to go below the horizon. This is dependent on several factors, including latitude, time of year and atmospheric thickness.Full Answer >
The sun appears to set when it vanishes over the western horizon as the Earth rotates away from the sun. Depending on the Earth's tilt at a particular time of year, the sun sets either slightly north or south of due west.Full Answer >
Calculating the angle of the sun from the horizon requires measuring tools and some mathematical calculations. This experiment works best on a bright day, when the sun creates a distinct shadow.Full Answer >