Why is the sky dark at night if the universe has so many stars?

This is known as Olbers’ paradox. If the universe were static, eternal, and filled uniformly with stars in every direction, the night sky should be bright everywhere. Instead, the universe is about 13.8 billion years old, so light from the most distant objects has not had time to reach Earth. In addition, the universe is expanding, which stretches distant light toward longer, dimmer wavelengths. As a result, only a fraction of all stars and galaxies contribute visible light to our night sky.