Sunset

Before the age of electricity and fire, when the Sun went down, there wasn’t any light. The Moon was only bright enough a few days a month to provide much illumination. Ancient people believed that everything – including the Sun – went around the Earth. But we now know that it’s the Earth that’s orbiting the Sun. The Sun appears to move through the sky because it’s the Earth that’s rotating on its axis. And when the Sun dips down below the horizon, we call this sunset.

Astronomers call sunset the instant when the Sun’s trailing edge completely disappears below the horizon in the West. Because the Sun is actually circle in the sky, it can take a couple of minutes from when its leading begins going beneath the horizon to when its trailing edge follows.

The time and place of the sunset depends on several factors: your place on the planet and the time of the year. In fact, every single place on Earth will have a slightly different sunset. You’ll need to find a tool that helps you calculate your local time.

And because the Earth’s axis is tilted, the time and place of the sunset changes over the course of the year. The winter solstice occurs around December 21st, and that’s the point at which the day is shortest and the night is longest for the northern hemisphere. And then around June 21st is the summer solstice, when the day is longest and the night is shortest. The spring and autumn equinoxes occur when the length of day and night are both exactly 12 hours. Day and night are equal.

Why are sunsets so beautiful? When the Sun is almost down to the horizon, we see it at a low angle, where its light passes through more atmosphere. The sunlight has more chance to scatter off dust particles and soot particles, and so we see the more easily scattered red and orange colors. This effect is even more spectacular when there has been a recent fire or volcanic eruption.