system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If there are billions of stars in the space and very few obstacles, why the sky is not full of light?
gpt
For many of the stars, their light has not reached Earth yet.

Also, light intensity decreases with distance, which make many of the visible stars very faint; on a moonless night without light pollution the sky is very densely packed with points of light.