Great question! Space isn't really dark black, it's just that we can't see the energy that is there with our eyeballs! Billions of years ago, the universe was ORANGE! This could happen because at the very beginning of the universe temperatures were HOT - >4000K! As space expanded, the wavelengths of light lengthened (this is a process called cosmological red-shift) until they moved out of the part of the electromagnetic spectrum we can see (visible light), into the microwave spectrum, where they are now.

You CAN see space, if you have the right tools! Some instruments can 'see' this microwave radiation, and have used it to make a picture of the universe.

But, you can also see it on TV! If you can find an old analog TV with bunny ears, set it up & turn it on. That TV static? It's picking up the microwaves in the universe! Here's a really, REALLY great video PBS Space Time made about this topic: video. Cosmic microwave background radiation is some cool stuff, and can tell us a lot about our universe!

Hello Aditya, that’s a really great question. I think the first question to answer to get at your question is, “what makes something black?” Black is the absence of light emission. In the context of a black car, the reason that paint job is black is because the composition of the paint is capable of absorbing all ranges of visible light. As a result, no light is reflect back towards the viewer, making the paint appear black.

Now, when it comes to the deep black of space, the lack of something emitting light or reflecting it is to blame. The vast and empty expanses of space have no light sources except large astronomical entities like stars. Other things are also capable of reflecting light and are therefore visible in space (i.e. a moon). However, outside of these types of light emitters/reflectors, space is mostly void and void does not produce light, causing it to appear black. Because things in space are spread so far apart from one another, most of what we see in space is darkness with a few light spots coming from distant stars.

The sky on Earth looks blue (most of the time) because of the atmosphere. The molecules in the atmosphere reflect/scatter lights in all directions, and the blue light (with shorter wave length) experiences stronger scattering than red and orange light (with longer wave length). But in the outer space, there is no atmosphere to scatter light. The sun light will go straight to human eye without scattering in the air, hence the sky will look dark, even though the sun itself may look much brighter.

When there's no light, everything looks black. Here's an answer from NASA. “At night, when that part of Earth is facing away from the Sun, space looks black because there is no nearby bright source of light, like the Sun, to be scattered.”

Space is mostly empty, and with no light being emitted from the vacuum of space, it appears completely black.