The sky appears dark instead of blue to an astronaut because of the absence of Earth’s atmosphere in space. The blue colour of the sky on Earth is due to Rayleigh scattering, where molecules in the atmosphere scatter sunlight, especially the shorter blue wavelengths. In space, without an atmosphere to scatter sunlight, the sky lacks this blue coloration and appears dark, revealing the vast, unlit expanse of outer space.

Let’s discuss in detail

The Dark Sky in Space: An Astronaut’s Perspective

Earth’s Blue Sky: A Result of Atmospheric Scattering
On Earth, the sky appears blue due to a phenomenon called Rayleigh scattering. This occurs when molecules in the Earth’s atmosphere scatter sunlight. Shorter wavelengths of light, particularly blue, are scattered more efficiently, giving the sky its characteristic blue colour.

The Role of Earth’s Atmosphere

The atmosphere plays a crucial role in determining the colour of the sky. It acts as a medium through which sunlight is scattered, affecting how we perceive light and colour in the sky.

Absence of Atmosphere in Space

In space, where astronauts orbit, there is no atmosphere. The absence of an atmospheric layer means there are no air molecules to scatter sunlight.

Why the Sky Appears Dark in Space

Without atmospheric scattering, the sunlight does not get dispersed into its component colors. As a result, the sky does not exhibit the blue hue that is observed from Earth’s surface. Instead, it appears dark.

Visibility of Stars and Other Celestial Bodies

This darkness in space allows astronauts to see stars and other celestial bodies more clearly. Unlike on Earth, where the atmosphere can obscure or dim celestial objects, in space, these objects are more vivid against the dark backdrop.

Download App for Class 10

The Contrast between Earth and Space
Thus, the dark sky seen by astronauts is a direct consequence of the absence of an atmosphere in space. It starkly contrasts with the blue sky seen from Earth, highlighting the significant role our atmosphere plays in shaping our visual experience of the sky.

Discuss this question in detail or visit to Class 10 Science Chapter 10 for all questions.
Questions of 10th Science Chapter 10 in Detail

What is meant by power of accommodation of the eye?
A person with a myopic eye cannot see objects beyond 1.2 m distinctly. What should be the type of the corrective lens used to restore proper vision?
What is the far point and near point of the human eye with normal vision?
A student has difficulty reading the blackboard while sitting in the last row. What could be the defect the child is suffering from? How can it be corrected?
A person needs a lens of power –5.5 dioptres for correcting his distant vision. For correcting his near vision he needs a lens of power +1.5 dioptre. What is the focal length of the lens required for correcting (i) distant vision, and (ii) near vision?
The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem?
Make a diagram to show how hypermetropia is corrected. The near point of a hypermetropic eye is 1 m. What is the power of the lens required to correct this defect?
Why is a normal eye not able to see clearly the objects placed closer than 25 cm?
What happens to the image distance in the eye when we increase the distance of an object from the eye?
Why do stars twinkle?
Explain why the planets do not twinkle?
Why does the sky appear dark instead of blue to an astronaut?