The sun sets in the west because of the Earth's rotation around its west-east axis. This movement creates the impression that the sun is moving across the sky from east to west, and when it reaches the horizon to the west, it appears to set.
The Earth rotates on its axis, completing a full rotation from west to east in nearly 24 hours. This rotation explains why the sun appears to move from east to west in the sky: it's like watching a backdrop pass by the window of a train while in reality, it's you who is moving. Here on the surface, we do not directly feel this rapid rotation, but it is this phenomenon that causes the sunset in the west every day. Wherever you are on Earth, when your position gradually turns towards the area opposite the sun, you simply witness the sunset.
The sun seems to move across our sky every day, gradually rising in the east in the morning, reaching its highest point around noon, and then slowly descending towards the west at the end of the day. However, this is merely an impression: this movement is said to be apparent, as it is not the sun, but rather the Earth itself, through its rotation from west to east, that causes this daily path to appear to us. It's a bit like when you are driving in a car and you see the landscape passing by around you: the landscape itself remains fixed, it is us who are moving. Each day, this regular cycle gives rise to the familiar day-night rhythm, defined by this constant rotation of our planet on itself.
The Earth rotates on its axis, but its axis is tilted about 23.5 degrees relative to its orbit around the Sun. This tilt is what causes the seasons, of course, but it also influences the exact spot where the Sun sets throughout the year. Depending on the time of year, this tilted axis causes the Sun to appear to shift gradually towards the north or south on the horizon. As a result, in winter, you may notice that the Sun sets more in the southwest, while in summer, it tends to set more in the northwest.
When it is near the horizon, the sun appears flattened and sometimes distorted due to atmospheric refraction. In simple terms, its light passes through a layer of thicker air at that moment, slows down slightly, and changes direction. As a result, we can still see it for a few moments after it has actually gone below the horizon. This phenomenon explains why sunsets seem to last longer than expected and provides those famous sunsets with intense reddish-orange hues.
Depending on the seasons and where you are located on Earth, you will notice that the sun does not set in exactly the same place. In winter, at our latitudes, the sun sets more towards the southwest. In summer, it sets more towards the northwest. The closer you get to the equator, the less these differences become visible, with the sunset remaining almost stable throughout the year. In contrast, near the poles, the seasonal changes are much more spectacular: you can even have days with sunlight all night long (midnight sun) or entire days without light, depending on the season.
Atmospheric refraction allows us to see the sun even when it is already below the horizon. In fact, when you watch a sunset, what you see in the last minute no longer exists on the horizon; it is simply the light refracted by the Earth's atmosphere.
The phenomenon of twilight, where the sky displays various shades of color, is largely due to the scattering of sunlight as it passes through the atmosphere. The blue wavelengths are scattered (a phenomenon known as Rayleigh scattering), allowing for red and orange colors to emerge at sunset.
Near the Earth's poles, the sun can remain visible for several consecutive days: this is called the 'midnight sun.' This phenomenon is due to the tilt of the Earth's axis combined with our planet's orbital position around the Sun.
The duration of sunset depends on your latitude: the closer you are to the equator, the faster the sunset (about just 2 minutes!), while the closer you are to the poles, the longer the process can take.
Yes, the tilt of the Earth's axis at 23.5° directly affects the apparent position of the sun in the sky. It is responsible for the seasons and explains why the sun does not set exactly in the west throughout the year but oscillates towards the northwest or southwest depending on the season.
Yes, it is possible under certain specific circumstances. For example, from a high altitude such as a mountain peak or a tall tower, one can observe the sunset and then see it again while descending quickly to a lower location, as the visual horizon changes depending on the altitude.
The warm colors of the sunset come from a phenomenon called 'Rayleigh scattering.' As the sun approaches the horizon, its light passes through a greater thickness of the Earth's atmosphere. Thus, shorter wavelengths (blue and violet) are scattered more, allowing longer wavelengths like red and orange to reach our eyes.
The duration during which the sun appears to approach the horizon and disappear depends on the angle at which its trajectory meets the horizon. This angle varies based on your latitude and the seasons, making some sunsets longer or shorter depending on the time of year.
The sun generally sets in the west, but its exact position varies slightly depending on the seasons and the latitude where one is located. At the equinoxes, it sets almost precisely in the west, but at the solstices, it can set more to the northwest or southwest depending on the season.
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