As dark as night

If you look at a TV screen when it’s switched off, it looks a sort of dark grey. When you’re watching the latest sci-fi space movie blockbuster, the starfield background looks a deep dark black, so how is this possible? Does your TV suck light into the screen to make the grey screen look black? No, this effect is caused by the way your brain computes brightness in the world around us. The brain doesn’t simply measure the amount of light entering the eye; it does a comparison with other sources of light in the image. In fact it’s the bright stars that cause the space between to look darker, to look black rather than grey.

There's more to space than meets the eyes!