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Why is the space very dark despite all the stars in the universe? – Najil, 15, New Delhi
People were asking about the darkness of space despite the stars for a long time so that this question has a special name – Ulber’s paradox.
Astronomers estimate that there is about 200 billion trillion star In the observed universe. Many of these stars are bright or even brighter than our sun. So why not fill the space with amazing light?
I am an astronomer Who studies stars and planets – including those outside our solar system – and their movement in space. The study of stars and distant planets helps Astronomers like me Understand why the space is very dark.
You can listen to more articles from the conversation, narrated by Noa, here.
You may guess because many stars in the universe are very far from Earth. Of course, it is true that the more the star is far, it looks less bright – Star 10 times away looks dull 100 times. But it turns out that this is not the whole answer.
Imagine
For a moment, the universe demonstrated that the light is so far that the farthest of the stars had time to reach the Earth. In this imaginary scenario, not all stars in the universe move at all.
Imagine a large bubble with the ground in the middle. If the bubble is about 10 Light years Via, it will contain about Dozens of stars. Of course, in several light years, many of these stars will look very dim from Earth.
If the bubble continues to expand to 1,000 light years over, then to a million light years, then a billion light years, then the farthest stars in the bubble will look more faint. But there will also be more and more stars inside the largest and largest bubble, and they all contribute to the light. Although the farthest stars look dim and Timur, there will be many of them, and the entire night sky should look very bright.
I seem to go back to where I started, but I am really a little closer to the answer.
Age matters
In fictional illustration, I asked you to imagine that the stars do not move and that the universe is very old. But the universe is only going on 13 billion years.
Although this is a human being surprisingly long, it is short of astronomical. It is short enough that the light of the stars is more far from about 13 billion light years old has not already reached Earth. Consequently, the actual bubble around the land that contains all the stars that we can see only extends to it 13 billion light years of land.
There is not enough stars in the bubble to fill every sight. Of course, if you look at some directions in the sky, you can see the stars. If you look at other parts of the sky, you cannot see any stars. This is because the stars that can prevent the vision line in these dark spots have not yet reached the ground. Over time, light from these distant stars will be time to get to us.
Doppler turned
You may ask if the night sky will eventually shine completely. But this brings me back to the other thing that I told you to imagine: that all stars do not move. The universe is already expanding, with distant galaxies Stay away from the Earth almost light at the light.
Since the galaxies move very quickly, the light from their stars is pushed to the colors that the human eye cannot see. This effect is called Doppler turned. So, even if he has enough time to get to you, You still cannot see Light from the distant stars with your eyes. The night sky will not be completely lit.
If you wait longer, the stars will be burned in the end – Stars like the sun last for about 10 billion years only. Astronomers assume that in the far future – a thousand trillion years from now – the universe will become dark, It is only inhabited by the remains of the star Like white dwarves and black holes.
Although our night sky is not full of stars, we live in a very special time in the life of the universe, when we are lucky enough to enjoy a rich and complex night sky, full of light and darkness.
Hello, curious children! Do you have a question you want an expert? I ask a very person to send your question to Uciouskidsus@theconversion.com. Please tell us your name, age, and city in which you live.
Since curiosity does not have the maximum age – adults, he told us what you also wonder. We will not be able to answer every question, but we will do our best.
This article has been republished from ConversationAn independent, non -profit news organization brings you facts and trusted analysis to help you understand our complex world. Written by: Brian Jacksonand Boys State University
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Brian Jackson receives NASA’s funds.
