If you’re not a morning person, then you probably love living on the moon or out in space! The whole “lack of oxygen” thing aside, a round-the-clock night sky sounds pretty tempting! But that got me wondering… - Why is there so much light on earth, but almost none once you leave our planet? You might think that it’s light during the day and dark at night because the earth spins on its axis, and the sun illuminates either hemisphere. That’s part of the reason, but it’s more complicated than that. I mean, our star shines on the moon too, but the sky above it is always black! It all comes down to the unique.

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Atmosphere surrounding our earth, it’s full of dust, dirt, gases, and waterdroplets – which all act like tiny mirrors and reflect the sunlight. When sunlight bumps into these small particles, it diffuses and creates different colors. That’s why we see a blue sky and all those spectacular shades during sunrise and sunset. It’s a whole different story elsewhere… If you find yourself on the moon, where there’s no atmosphere, the sky will be black. You’ll be able to see the stars even when the sun is blazing on the surface during the lunar day. The same is true of space, it’s filled with lots of different gases, but it has no atmosphere with molecules to reflect light. In other words, space is empty, that’s why even when the sun is shining, space looks like a black void. If one day the earth’s atmosphere disappeared, it would be just as dark as it is in space or on the moon. 

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That one’s clear, but the sun isn’t the only star (or source of light) in the universe. So… - Why don’t other stars shine with blazing light at night? You’re not the first to wonder about that. An astronomer named Thomas Digges researched this question back in the 16th century. Digges was sure that the universe had no end, and the stars in it could not be counted. He tried to answer why all these innumerable stars don’t blind us with glaring light… but failed. His questions were just way far a head of his time, and he didn’t have the tools to find the answer. In the early 19th century, German astronomer Wilhelm Olbers suggested that the reason the sky is dark at night was a dusty veil that hid most of the stars from us. This idea also proved to be wrong later, the stars shed not only light but huge energy that could heat dust particles so that they would start shining themselves. 

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In that case, the night sky would still belight because of shining dust, and yet the sky gets dark every evening after sunset. What’s bad about this theory then? Digges, Olbers, and other astronomers of the past believed the universe was infinite, but modern astronomy knows better. The number of stars, as countless as they may seem, is simply not enough to illuminate the sky at night. The sky gets dark because the stars, just as the universe itself, don’t last forever. They are finite. You see, the universe has its own bordersand isn’t as ancient as scientists used to think. Sure, just shy of 14 billion years is no whipper snapper to us humans, but it’s still surprisingly young in cosmic terms and it’s not much for all the light from the most distant stars to be able to reach the earth. In other words, thanks to our fancy powerful telescopes, we now know that it takes light billions of years to get to us from the farthest stars. This means, when we look at the sky, we glance into a very distant past. Modern telescopes can show us that the light started its journey to the earth about 10 billion years ago.