When visible light travels through space without encountering any objects, it continues to propagate in a straight line until it interacts with something or is absorbed by particles in space. In the vast expanse of space, light can travel enormous distances without obstruction.
In the absence of any objects or particles to scatter or absorb the light, it will simply continue to travel indefinitely until it reaches something that interacts with it. This could be a planet, star, dust cloud, or other celestial objects. When light encounters such objects, several things can happen depending on the nature of the interaction:
Reflection: Light can bounce off the surface of an object, similar to how a mirror reflects light. This reflection allows us to see objects that do not emit their own light, like the moon or other planets. The reflected light carries information about the object's color, texture, and other properties.
Refraction: When light passes through a transparent or translucent object, such as a glass prism or Earth's atmosphere, it can change direction due to the change in the medium's refractive index. This phenomenon is responsible for the dispersion of light into its constituent colors in a prism and for various atmospheric optical effects like rainbows.
Absorption: Some objects or materials can absorb certain wavelengths of light, converting the light's energy into other forms, such as heat. The absorbed light is no longer available for transmission or reflection, as it is converted into a different type of energy within the object.
Scattering: When light encounters particles or molecules in the atmosphere or interstellar medium, it can scatter in various directions. This scattering contributes to phenomena like Rayleigh scattering, which explains the blue color of the sky, or the reddening of light passing through interstellar dust clouds.
If light continues to travel through empty space without interacting with any objects, it essentially remains unchanged, maintaining its properties of wavelength, frequency, and polarization.