Anyone who can tilt their head up enough to glance at the night sky would be able to tell you that outer space looks black. Images captured by space telescopes and even by astronauts working on the International Space Station only corroborate this fact. But have you ever pondered about why outer space appears black?
Perhaps the most common answer to this seemingly simple question is that there’s a lack of light. Long exposure images captured by the Hubble Space Telescope, however, reveal that this isn’t the case at all. In fact, there are so many light-emanating stars residing in countless galaxies as far as the best telescopes can see, and with all these sources of light existing in every crevice of outer space, lack of light couldn’t possibly be the answer… right?
Well… yes and no. But the true answer is a bit more complicated than that.
Firstly, it should be noted that the universe is finite, and this means that the number of stars in outer space is limited despite how plentiful they appear in images. The fact remains, however, that the universe is vast and that extensive distances exist between said stars. This distance impacts the intensity of the light emanating from stars and makes them appear dimmer as a result.
To make matters worse, light originating from the universe’s furthest galaxies struggles to reach Earth because of a phenomenon called redshift. As light from the most distant galaxies attempts to reach us, some of it eventually arrives in the form of infrared light, which the human eye can’t really see. The lack of visibility in this situation masks some of the light that would otherwise make the universe appear brighter than it does.
If the universe were actually infinite, then outer space wouldn’t appear black, but instead filled with light from an unlimited number of stars. An interesting concept to try to grasp, indeed.
