Why Does the Sky Glow Even After Sunset? The Enigmatic Afterglow Explained

Why Does the Sky Glow Even After Sunset? The Enigmatic Afterglow Explained

Even after the sun has dipped below the horizon, the sky often retains a beautiful glow. This phenomenon occurs because the sun hasn't actually set from the perspective of the upper atmosphere. At this altitude, sunlight still reaches the atmosphere, although it does so at a sharp angle, just below the horizon.

During this time, we observe the glowing sky due to the scattering of sunlight by molecules in the air. These molecules scatter the light in various directions, including down towards us. This scattering process is known as Rayleigh scattering, named after the scientist who first described it. It's the same reason why the sky appears blue during the daytime. When the sun is high in the sky, shorter blue wavelengths of light are scattered in all directions, giving us a blue sky.

As the sun continues to move lower below the horizon, less and less sunlight reaches the upper atmosphere. The glow gradually fades, and night truly begins when the sun is about 18 degrees below the horizon. This marks the end of astronomical twilight and the beginning of night, when the sky becomes fully dark.

Understanding this process not only explains the enchanting colors of dusk but also highlights the intricate interactions between sunlight and our atmosphere, enriching our appreciation of these everyday natural phenomena.

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