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On Earth, the sky is bright during the day because air molecules reflect sunlight, like a small mirror. But on the moon there is no atmosphere, so the sky is pitch black, and even the stars are gone. By the same token, the universe itself is empty, with little matter that can reflect light into our eyes, so the space we see is dark – even around the sun.
But there are still doubts about the darkness of the universe: why can’t the light from all the celestial bodies in the universe combine to form a bright light? Why does the sky turn dark at night?
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Thomas Ditches was a 16th-century astronomer who also studied these questions at the time. He believed that the universe is infinite, the universe is expanding in all directions, and in this endless space, there are countless stars. But according to his reasoning, if the universe is full of stars and the sky is shrouded in starlight, the night sky will be as bright as the day. However, this is not the case. Ditches failed to solve this puzzle all his life.
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Wilhelm Oberth (a 19th-century astronomer) also spent many years thinking about the same question, and the question of why the sky is dark is called “Oberth feint”. Oberth considered many possibilities and finally concluded that the reason was dust in space: maybe we can’t see the light from distant stars because the dust in the universe absorbs it.
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But after Oberth’s death, astronomers calculated the sum of all the stars’ luminescence, and found that this energy was enough to heat up all the dust that stood in the way. In other words, the night sky also became bright under the shining dust. So the problem goes back to the starting point.
Edward Harrison of the University of Massachusetts wrote in his book “The Darkness of Night: The Mystery of the Universe”: There are not enough stars in the universe to cover the entire sky, so the night sky is black.
With the help of powerful space telescopes, we can see stars far away from us. It takes millions of years for light to travel from distant stars to Earth, so when we look deep into the night sky, we are looking back in history. The most powerful telescopes can help us see a certain star that emitted light 10 billion years ago.
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The history of the universe is only 15 billion years, and the more advanced the telescope, the farther stars we can see. Edgar Allan Poe was inspired by this theory and wrote many novels and poems with horror and supernatural colors, including “The Raven”, “The Whistleblower’s Heart”, etc. In 1848, Allan Poe wrote in “I Got It: A Prose Poem”: In the depths of the dark night sky, we see the nothingness before the birth of the universe.
According to Harrison’s theory, Poe’s poems depict a real universe. As his poem wrote, “Through the stars we see the source of the universe”.