Light unto the end of the Universe...

Or, more simply put - Olbers's Paradox. If the sky is filled with stars - and it is - then why at night is it dark?

To quote the Wiki: 

Olbers' paradox, named after the German astronomer Heinrich Wilhelm Olbers (1758–1840), also known as the "dark night sky paradox", is the argument that the darkness of the night sky conflicts with the assumption of an infinite and eternal static universe. In the hypothetical case that the universe is static, homogeneous at a large scale, and populated by an infinite number of stars, any line of sight from Earth must end at the surface of a star and hence the night sky should be completely illuminated and very bright. This contradicts the observed darkness and non-uniformity of the night.

The theory that the night sky should be filled with light from the infinitude of stars that present themselves....

Arguments that explain it away: 

#1) Big Bang - time has not allowed the light to reach here.

Nope. I hate to say it but I don't buy the Big Bang theory. There are problems with it. Many, many problems, too many to lay out here. But before you second guess my skepticism let me remind you that it's losing it's cache even as we're talking now - 

#2) Gravity could deflect and concentrate those infinitude of tiny, distant stars into larger and larger stars, merging the wavelengths of a thousand distant stars into one - or black holes could deflect and suck the light in, creating black voids.

This is probably true. But true for many instances does not explain all the instances. Maybe it does? But while we're brainstorming here... 

#3) That as light travels, it shifts red or blue - coming towards us, heading away from us. And that shift takes it off the visible spectrum. So the night sky is in fact filled with light, but beyond the spectrums our eyes can see. 

So the night sky presents itself to us as black but is in fact filled with more colors than our eyes can perceive.

More below:

via Scientific American: https://www.scientificamerican.com/article/why-is-the-night-sky-dark/

via Emma Osborne: https://www.ogdentrust.com/assets/media/THS_Emma_Osborne_Physics_Essay_-_Olbers_paradox.pdf