Why is the Sky Not Blue When Seen from Space?

The sky appears blue when viewed from the surface of the Earth because the Earth's atmosphere scatters short-wavelength blue light more efficiently than other colors. This is known as Rayleigh scattering, and it occurs when light waves are absorbed and then re-emitted by particles in the atmosphere. The particles in the atmosphere are much smaller than the wavelengths of visible light, so they scatter light in all directions.

Blue light has shorter wavelengths than other colors of visible light, so it is scattered more efficiently by the particles in the atmosphere. This is why the sky appears blue during the day, when the sun's light is scattered by the atmosphere. At sunset, the sun's light has to pass through more of the Earth's atmosphere before it reaches our eyes, which causes the sky to appear red or orange due to the scattering of longer-wavelength light.

However, when viewed from space, the sky does not appear blue because there is no atmosphere to scatter the light. In the vacuum of space, there are no particles to scatter the light, so the sky appears black. This is why astronauts on the International Space Station (ISS) and other spacecraft see a black sky when they look out the window.

In conclusion, the sky appears blue when viewed from the surface of the Earth due to Rayleigh scattering, which occurs when light is absorbed and re-emitted by particles in the atmosphere. However, when viewed from space, the sky does not appear blue because there is no atmosphere to scatter the light, and it appears black instead.