Why is the Sky Dark at Night?

The only question that has bowled me ever since childhood is why does it get dark at night? Does the sun take away all of its light only to make the sky pitch black? The answer may seem simple, but is it really so?

Moonlight is nothing but...

...sunlight reflected from its surface rendering the moon powerless to illumine the night sky.

One look into the night sky is enough to tell you that there are countless stars that are emitting light. Well, if all these stars are emitting light, why do we see only a faint glow around the stars.

Why isn't this light, lighting up the sky as it really should be doing? That way, we would have fewer dark nights and more nights flooded with day-like light.

It is true then, that the universe, with its unfathomable hands, has stretched and wrapped us in dark history.

To a small child, the answer is pretty obvious, the night is dark because we are facing away from the sun.

But then, would that mean the other stars are not as powerful as the sun? Or are they just too far away to brighten up the darkened and so-called night sky? Let's explore the different reasons.

Explaining the Darkness

The sun is the main source of light for our planet and galaxy, and with planets rotating on their axes, it makes sense to assume that the side of Earth facing the sun is lit up.

This interplay of light causes the other half of the Earth to be in darkness, as it's shadowed by the Earth itself.

This shadow extends for thousands of kilometers, due to which we get to experience a lunar eclipse once a while.

Contribution of Science

Considering that the sky is dotted with numerous stars that emit their own light, the night sky should be far from being dark.

Other than lending a dim glow to the otherwise dark sky, the light from the stars hardly does anything much.

Ever wondered where all the light is going and what is it that is hindering the light from being visible? Alternatively known as Olbers' Paradox, the dark night sky is a popular and debatable cosmological problem.

Debatable because there's not just one theory to explain why the light emitted from the stars does not reach far and wide to lighten up the sky at night.

Olbers' Paradox stated that if the universe is infinite and static, then the line of sight from any given angle would end at a star.

Which would mean that every part of the sky would be filled with stars so aligned that their light would merge so as to give out a bright light.

According to the Big Bang Theory, the universe is continually expanding, indicating that galaxy clusters are merely moving away from each other.

The theory contradicts the assumption of an infinite and static universe, which obviously meant being able to see innumerable stars that overlapped each other to create a solid wall of light.

Astronomers believed that the universe is around 12 to 15 billion years old, implying that we can only observe a portion of it approximately 15 billion light-years away from our vantage point.

According to astronomers, the light of the stars beyond this mark may not have reached us as yet, which is why our sky is not as illuminated as it should be.

The Role of Atmosphere and One Bright Star

According to scientists, the cycle of day and night is created by Earth's rotation and daylight occurs when sunlight reflects off air molecules.

This means that a part of the earth is thrown into darkness merely because it is not facing the sun.

With the sun being the only bright star in our galaxy, it's the sole source of light for the dark side of Earth.

The vast distances between planets prevent sunlight from bouncing off them, causing sunlight to be absorbed into space. This leads to dark nights and bright days for us.

So Says the Moon...

Ever wondered why the moon doesn't illuminate the night sky? It's because the moon, a satellite, simply reflects sunlight back from its sunlit side.

The moon can't emit its own light. The reflected sunlight from its surface isn't strong enough to fully light up the sky, resulting in the faint glow we call moonlight.

You must have heard of a dying star. Well, to say the least, the light that you see and believe to be that of a breaking star, or falling star, has in reality occurred several billion years ago and has reached you only at that moment.

So, in reality, the light of the thousands of twinkling stars that we see are only the facade of the light as it was million of years ago. Which means that the speed of light is finite and is not sufficient to light up space.

And with the expansion theory to support the saying, it won't be wrong at all to say that the amount of light reaching us from these far thrown stars and galaxies is dwindling all the time.

Well, if these stars are so far from us, and if this distance is increasing, it makes sense why we see the stars as emitting a faint light. This further explains why we see a sky filled with darkness rather than light.