Emission and Absorption: Stars, planets, and nebulas emit their own light. However, this light has to travel through interstellar space to reach our eyes. Along the way, it encounters dust, gas, and other particles that can absorb and scatter light. This process reduces the amount of light that actually reaches us, making the space between celestial objects appear dark.

The Hubble law: The universe is expanding and the further away an object is, the faster it is receding from us. This means that the light from distant stars and galaxies is redshifted towards the red end of the spectrum. As a result, much of the light from very distant objects shifts into the infrared range, which is invisible to the human eye.

Olbers' Paradox: If the universe were infinite and uniformly filled with stars, the night sky would be bright everywhere due to the cumulative effect of light from countless stars. However, the night sky is mostly dark and observations suggest that the universe has a finite age and may even have a limited size.

Therefore, the combination of light absorption and scattering through interstellar dust, the distance and Hubble shift of celestial objects, along with the finite nature of the universe contribute to the appearance of a black night sky despite the presence of numerous light-emitting objects in space.