We’ve all sat and admired the stunning blue sky after dawn and the gorgeous orange hues at dusk at least once in life. What if I told you that outer space doesn’t have any light.
It begs the question: how is the Earth’s sky blue then, and why is space dark? Find out the answer in this thorough guide on everything you need to know about light in space.
Does Colour Exist in Space?
Outer space, as we know it, is a pitch-black surface. However, it is livened up with the glitter of billions of stars and galaxies that project a suffused light into the dark field.
Because most of them are light years away from Earth, the naked eye can’t focus.
If we consider the dim starlight as a prism, the rainbow of colors will amount to a faint white. So, yes, color does exist in space — you’d need a telescope to capture it.
Why is Space Dark, but the Earth’s Sky is Blue?
To understand why space is dark, we’d first need to break down how we perceive light.
Our Visual Perception of the World
We know the sky is illuminated by the Sun’s projection of bright light. But how does it cover one entire half of the Earth?
When ultraviolet radiations hit the Earth’s atmosphere, they are quickly reflected and re-radiated in multiple directions. This is known as the ‘scattering effect’.
The Sun projects all colors of visible light, which combine to make white. The human eye perceives blue and green light best. Hence the re-radiation of light throughout the day gives us the illusion of a ‘blue sky.
As the sun starts to set and prepares to shed light on the other half of the world, the distance for the ultraviolet radiation to travel increases. Upon reaching most of the blue light scatters, leaving behind stunning orange and red hues seen during dusk.
The Scattering Effect in Space
Space is essentially a vacuum and has no ‘obstacles’ like dust, molecules, and water vapors. This makes it impossible for light to scatter. Different wavelengths from the sun travel in a straight line until they collide with the Earth’s atmosphere.
The visible light of the Sun in space looks completely white because it isn’t reflected. Hence, the human eye cannot comprehend it, and the Universe appears pitch black.
How Does Olbers’ Paradox Explain the Darkness in Space?
One might ask – if the Sun, a star, can brighten up the entire Earth. Why can’t a billion stars in the Universe combine to add light to space?
Well, one might expect that to happen if the Universe was infinite in nature. If the size and evolution of space were limitless, we’d see stars in every direction. They’d reflect light all around and brighten up the massive dark field. Our experience, however, believes that space is void of visible color.
This is known as the Olbers’ Paradox, where the expectation of a bright Universe doesn’t meet the experience of outer space.
Due to cosmic expansion, stars and galaxies continue to fade away. Also, due to the distance in light years, some haven’t had time to actually reach the Universe. This makes the systemic contribution of light almost impossible, which is why space appears pitch black.
Alternative Reasons Why Space Is Dark
Although the Scattering Effect is the most widely understood concept for the existence of light in space. Some scientists have offered a different perspective of reason, and four of them are listed below:
When a star moves away, the wavelength of all visible light increases and particularly shifts towards red. The further it moves, the longer the wavelength until it can no longer be sighted. Even beyond the sight of a laser pointer telescope like the Hubble. Thus, making space appear dark.
This is known as the Doppler Effect. The frequencies of light change due to the relative motion between the observer and the light source.
Age of the Universe
Recently, the Hubble Space Telescope discovered the very edge of the observable universe at 13.4 billion light years. It depicts when the Universe, supposedly, came into existence and so denotes the age of space.
The measure also shows that we cannot see any stars surviving past the 15-billion light-year distance until they reach this timeframe. It compromises the visibility of light in space.
Finite Number of Stars
Despite the millions and billions of stars, galaxies, and dark energies in space, there’s still hardly any light in space. One of the reasons is that every star is finite and comes with an expiry date.
Besides surviving in an ever-expanding cosmic field, every massive star explodes into an incredible supernova and leaves behind flecks of energy that do not contribute much in terms of visible light.
With the advancements in technology, we can identify colossal explosions of stars, but they still appear in a wide, deep space void of all color.
Human Eye Coordination
Besides the Universe’s own physical aspects that affect the color variance in space, there’s also the fact that humans can only see so much.
The human eye can detect a narrow spectrum of light. This doesn’t include ultraviolet radiations typically found in the Sun, gamma ray radiations often projected in the explosion of a galaxy, and wavelengths like infrared and microwaves.
So, we employ the help of special telescopes, cameras, light detectors, and sensors to help us see the light we miss. This severely limits our visual perception of the Universe. It increases the blackness of outer space manifolds.
Frequently Asked Questions
What is the actual color of space?
Knowing that the prism of every color that exists equals white, we can easily assume the actual color of space. It combines with stars emanating different wavelengths and galaxies. It is perfectly white or at least beige, bursting with hot flashes of energy..
Why can’t you see the sun in space?
It’s almost impossible to see the sun in space because light waves travel in a straight direction without scattering. This is why when you look away from the sun. You’d notice a dark blank space and incredibly bright light when looking towards it.
Is space completely dark?
Although it is seen as pitch black, space isn’t considered to be completely dark. Light does exist in outer space, but it keeps dimming the farther the distance. Given the cosmic expansion, stars and planets also continue to fade and lose their light, turning space dark.
Knowing the reasons why space is dark helps us acknowledge just how vast the Universe is, and how old it is. Also helps to understand the cosmos better. It’s time to appreciate the blue skies and starry nights of Earth — that’s one thing you will miss up above the atmosphere!