☀️ Why does the Sun change color throughout the day?

Every morning, it rises golden on the horizon, shines bright white at noon, then sets in a festival of reds and oranges. This great celestial actor, the Sun, changes color before our eyes throughout the day. Yet it's not the star itself that transforms, but rather how its light reaches us through Earth's atmosphere.


The Sun's light is primarily white, but in reality, it contains all the colors of the visible spectrum, from violet to red. These colors correspond to different wavelengths: violet and blue have short wavelengths, while red and orange have long wavelengths.

When a ray of light enters the atmosphere, it encounters air molecules, dust, water droplets... These particles scatter the light, and they do so more effectively for short wavelengths. This phenomenon has a name: Rayleigh scattering.

At midday, when the Sun is high in the sky, its light passes through a relatively thin layer of atmosphere before reaching our eyes. Blue and violet are scattered in all directions, giving the sky its blue color. Meanwhile, the sunlight that reaches us directly still contains a good portion of all colors, giving the Sun a slightly yellowish white appearance.


At sunrise and sunset, the situation changes dramatically. The light arrives grazing the Earth's surface and must travel through a greater thickness of air. This long journey through the atmosphere scatters almost all the short wavelengths like blue and green. What remains are mostly the warm colors: red, orange, and yellow. Result: a blazing Sun.

This color change can be amplified by the presence of additional particles in the air. After a volcanic eruption, for example, the dust ejected into the atmosphere can create intensely red sunsets for weeks. Similarly, in summer, heat, drought, or fires add fine particles that enhance the warm evening hues.

Conversely, certain conditions make sunrises and sunsets paler. Very humid or hazy air scatters more of all colors, sometimes giving a milky white Sun. And when at high altitudes, where the air is purer, color transitions may be less pronounced.

It's also important to know that our eyes play a role in this perception. In low light, like at sunrise or sunset, our color-sensitive receptors (cones) are less active than those detecting brightness (rods). This can slightly alter how we perceive the hues, making them softer or more saturated depending on conditions.