The questions that we all have regarding space and the Universe are answered to a greater extent now. Thanks to the hard work of all the Scientists around the world. One of such questions is: why is the outer Space black in colour? Why do the Moon, the planets and the Sun have different colours?
Has your curious mind ever compelled you to think on it? Well, I’ve always had such questions. I wanted to become an astronaut when I was a kid. Yes, you heard that. A lot of us, at least once in our lives have thought about it, right? This is one of the reasons why I have so many ‘Universe’ and ‘Solar System’ books in my collection.
Before deviating on to some other topic, let us delve into this question and see why the outer Space is black in colour.
The first thing is that the Space is empty. Unlike Earth, there is no atmosphere. Neither any dust nor any particles. Also, you might be wondering that there are so many stars out there. Millions and billions of them. And they are really bright! How can the space be considered empty and on top of that, black and dark? The thing is, it is empty because it is really huge compared to the number of celestial bodies it has. Also, it appears black to the human eyes more than it actually is.
Let Us See Why The Outer Space Is Black In Colour!
The colours that we see depend on the Sun’s interaction with the atmosphere and how our eyes perceive that particular colour. We can understand this by knowing why the sky appears blue in the daytime. The thing is, during the day, the Sun’s light reaches the atmosphere and hits the tiny molecules of air, which scatter off the light. The blue colour, in the visible spectrum (VIBGYOR: violet has smallest wavelength and red has the longest) has a small wavelength and hence is scattered the most. This is the reason why the sky appears blue when Earth is facing the Sun. But when that part faces away from the Sun, we see a black sky because there is no light to scatter molecules.
Coming back to the Universe, as we discussed earlier, there are billions of stars. But for them to be able to light up the sky, first, they should be nearer enough. Which they aren’t. Also, these stars are so many light years away from us. That particular light photon that took off from the surface of the star will take years to reach the Earth. Do you know? The images we get to see in our telescopes are of the time when that photon took off from the star. Which might be hundreds of years ago. And that particular star might not be the same right now. It may be dead too. Hence, when we look at the sky, we are really seeing the past!
Therefore, it is true that there is light. The stars do emit light. But it does not reach us completely due to their distance from us, especially because the Universe is expanding and that they are moving away from us. And then there aren’t much particles between us to scatter that light too. In addition to it, this available light is not huge enough to light up the entire sky. Also, black is not a colour. It is just absence of light!
I hope you find this information useful. Do let me know if I missed out any important part!