Whenever you look at the night sky or at pictures of outer space, what's the first thing that catches your attention? Is it the bright stars, the beautiful planets, or the neverending blackness? For most people, it's the endless black.
A lot of people wonder why space isn't colorful like the Earth’s daytime sky. Some think it's due to the lack of light in space, but only a few try to reason it out. Tenley Hutchinson-Smith is one of them.
Recently, Tenley Hutchinson-Smith (student of astronomy and astrophysics at the University of California, Santa Cruz (UCSC)) emailed the reason behind the darkness in space to Live Science. In the mail, she talked about the beliefs of people and how theories can change them.
Why does space look black?
Hutchinson-Smith wrote in her email, that many people think since there are countless light-reflecting luminous stars in the universe, space should be bright. But instead, it's dark. Their assumption, which physicists and astronomers call the Olbers' paradox, can be explained with the space-time expansion theory.
According to the theory, since our universe is expanding faster than light, it's forcing objects to move apart from each other. That means light coming from distant galaxies might also be stretching and changing into radio waves, infrared waves, or microwaves that are not visible to human eyes. And since they aren’t visible to us, it’s very likely that they’d appear dark.
Miranda Apfel, who also studies the same topics at UCSC, supported Hutchinson-Smith's claims. She described that stars emit light in all colors, but not all of them are visible to humans. If we could see microwaves, then the whole space would look glowy. But since we can't, we have to settle with dark-colored outer space.
Apfel said the darkness was due to the cosmic microwave background which filled up the entire space. She continued that space's nearly perfect vacuum atmosphere could also be a reason behind the darkness. Citing an example, she said if you look back in time, you'll remember that the Earth's sky has molecules including Nitrogen and Oxygen. These molecules reflect the sun's rays in blue and violet wavelengths which are easily visible to our eyes. But in space, since matter is absent, this light travels in a straight line and doesn't get scattered. Therefore, we only see the color black.
It's not black; it's more like charcoal!
According to a study published in this year's The Astrophysical Journal, space isn't as black as most scientists perceive it to be. When NASA carried out the New Horizons mission to study the planet Pluto, along with its moons and several other objects in the Kuiper Belt, researchers got a chance to observe space without any light interference from the Sun or the Earth. After analyzing the pictures clicked by the spacecraft, they concluded that space is two times brighter than it was thought to be. That means it's not pitch black, it's rather charcoal in color!