Why is space black?

We have all been fascinated by space movies since we were kids.

All the movies show outer space as a dark expanse.

It is all black, with pops of colors and different celestial bodies that emit light here and there.

There is dark space and black holes that mark our universe.

The space that surrounds us is what we are so familiar with yet we do not know why it is all so dark.

Let us take a step in and find out why the space we live in is this pitch-black expanse. 

What is space? 

Science defines space as the boundless three-dimensional extent to which objects and events have relative position and direction. 

The concept of outer space is considered to be of fundamental importance to an understanding of the physical universe. 

Space is everything that surrounds our planet, solar system, and more. It has many implications on us and has extreme impacts on everything else in general.  

Floating in space

If we were to be floating in space and we chanced upon the sun it would be so bright that our retinas would crisp up. 

However, the rest of the sky would be an expanse of soothing black, decorated with thousands of tiny little fewer burning points of light.

We know for a fact that our space is huge. It can be even called infinite as looking out into space in any direction would just lead to us witnessing even more of itself.

Stars would be spread across the entire place. 

Every place that we look, there will be a shining spark of a celestial body that looks back at us.

By this logic, it would be fair to assume that since stars are all over the sky, space should be as bright as a star. 

However, the reality is slightly different from that and it was all uncovered when a famous scientist -put forward the question.

First possibility-Heinrich Wilhelm Olbers Paradox

German astronomer Heinrich Wilhelm Olbers brought forward this famously asked question in the year 1823.

It became so famous that people named a paradox called Olbers' Paradox after him. 

The paradox goes like this: if the Universe is infinite, static, and has existed forever, then everywhere you look should eventually hit a star.

As we know, there are stars and galaxies in all directions in space. If this is true, which is something that has been proven, then why does our star-filled space appear black.

Shouldn’t there be a star in every direction we look?

Our experiences tell us this isn't the case.

By proposing this fascinating paradox, Olbers said that the Universe couldn't be infinite, static, and timeless. 

According to his research, the universe could be a combination of any of the two but it is impossible that it would be a combination of all the three. 

In the 1920s, debonair man about town, Edwin Hubble discovered that the Universe isn't static. Galaxies are speeding away from us in all directions.

Formation of theories

This eventually led to the formation of the theory that we lovingly call the Big Bang Theory today.

We all know what the big bang theory suggests,

The universe was once gathered into a single point in time and space and then expanded rapidly. 

Our Universe has proven to not be static or timeless.

Hence the paradox was simplified and solved.

Here's the short version.

The reason we do not see stars in every direction is that many of these stars in the universe haven't been around long enough for their light to get to us. 

This fact makes us come to terms with the fact that our universe is incomprehensibly massive in size.

The scale of time we're talking about when we do these thought experiments is boggling.

However, this does not solve all the questions that come forth.

Shortly after the Big Bang, the entire Universe was hot and dense, like the core of a star. 

A few hundred thousand years after the Big Bang, when the first light was able to leap out into space, everything, in every direction was as bright as the surface of a star. 

The universe and its expansion

Hence we should somehow witness the brightness of a star in every direction yet we do not.

The light from stars can be said to be a source of light but it does not illuminate the entirety of space. 

As the Universe expanded, the wavelengths of that initially visible light were stretched out and out and dragged to the wide end of the electromagnetic spectrum until they became microwaves.

This is Cosmic Microwave Background Radiation, and we can detect it in every direction we can look in.

Our universe today is an infinite universe and this plays a key role in this phenomenon. 

Knowing these facts we can understand that Olbers' instinct was right. 

It is just that the expansion of the universe is so large that it stretches out the wavelengths so that this light becomes invisible to our naked eyes. 

If we could however see the Universe with microwave detecting eyes, we would see this: brightness in every direction.