Curosity Geek Science

Curiosity: Why is Space Black?

Curiosity: Why is Space Black?
Have you ever wondered: Why is the space black in colour?

Take for example you’re floating in Space and you decide to take a look at the Sun, it would be so bright that your eyes might burn out then you decide to look away to the rest of the sky and all you see is total darkness decorated with spots of tiny little lights that can’t hurt you.

If you’re always on your seat during science class in high school, you would know the universe is pretty large, even infinite. So shouldn’t the universe be super bright with the billions of stars it’s home to? Have you ever asked yourself that question, if you’ve, you probably won’t be surprised to know you’re not the first? With our experience on Earth we know with the absence of light in the atmosphere it becomes dark i.e black. But we also know that in space are billions of stars like our Sun that serves as light sources across the universe, but in spite of all the stars in the universe space still look very dark and scary at times.

This question was famously asked by the German astronomer called Heinrich Wilhelm Olber and is now been referred to as Olbers’ Paradox after him. The paradox says:

If the Universe is infinite, static and has existed forever, then everywhere you look should eventually hit a star.

Why the Earth is different.

The same can’t be said of our Planet Earth, cause we have Day and Night and not absolute darkness like space. Daylight is the period between when our Sunrise and Sunset and is the condition of brightness created by the rays. The atmosphere on Earth is full of a plethora of gases, dust particles and water moisture. When the sun rays hit these obstacles it causes it to reflect and refract. The reflection & refraction caused due to the obstacles it faced in the atmosphere brightens up our Planet in its splendid colours and makes it a suitable environment to live in.

Why Space is dark.

With numerous light sources residing in space, the universe still looks dark from  Earth. This most especially due to the constituent of Space (hydrogen, helium atoms, dust e.t.c). This makes the density so low that it seems nonexistent as light in space would travel in a straight line without any disturbance like on Earth (reflect and refract), just like what you experience with laser lights- They move in a straight line to where the pointer is pointing to without disturbance and distribution like a torch light.

With that illustration, it proves that we can only see lights in space from the source, not by the illumination the surrounding gets from the light source. The atmosphere on earth is responsible for the illumination of the sun on the Planet, unlike Space that is just an empty space with no obstruction for it to bounce on.

Reflection on Olbers’ Paradox.

After years, scientist found out that Olbers paradox couldn’t be all right, even Olbers know the universe can’t be infinite, static and timeless at the same time, the best it can be is two of those three factors.

Fast forward to 1920, Edwin Hubble discovered that the Universe isn’t static and that the universe is even running away from us in different angles and directions. This amazing discovery led to the BIG BANG THEORY! The theory proved that the universe was all at a point of space and time intially until it started to expand at a rapid pace. That said, it proved that our universe is no ay static and timeless and so the paradox was solved.

In a layman understanding: The reason why we don’t see the stars in different directions and angles is that many of these stars in the universe haven’t been around for a long time enough for us to get their rays of light. That definitely sparked a current in your brain, like it did for me too, cause that explains a lot on the extreme size of our universe.

In relation to Olbers’ instinct, we should still receive light rays of the stars but we don’t. This is simply because as the universe continued to expand around us it became so large that the wavelengths of that initially visible light became stretched out in space out and out and dragged to the wide end of the electromagnetic spectrum until they became microwaves and there is no light that we can see.

A similar situation happens to sound too. When you hear a siren the noise becomes higher when it gets nearer then it begins to go lower when the siren distance starts to increase again. This is known as the ‘Doppler Effect’.

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Also published on Medium.

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