Liked on YouTube: Why Is The Sky Dark At Night?

Why Is The Sky Dark At Night?
When you look at the night sky, or a photograph of space, what is it that strikes you more, what is it you see? The answer probably will be the stars, but in reality there is another thing that should hit you in the same way, which is the darkness of space, the darkness of the night sky. Subscribe for more videos:https://www.youtube.com/c/InsaneCuriosity?sub_confirmation=1? Have you ever wondered why the sky at night is dark? Why is space dark? It may seem a silly question but in reality the answer is not so obvious as it seems and tells us important things about the way it is in the universe. Let’s try to figure this out. As usual remember to subscribe to the channel if you have not done so and to activate notifications by activating the bell. Why should it surprise us that the space is dark and that there is so much darkness in the night sky? I’ll try explaining it to you: Imagine you are in a forest surrounded by trees , but also the empty space between trees. But now imagine that you’re increasing the number of trees, you will see less and less empty space between a tree and the other. If the trees become an infinite number you should not see empty space between one tree and the other, you should be completely surrounded by logs of trees in any direction. Of course the trees closest to you will seem bigger, while the far away ones may seem smaller, but the overall result is that all the look should be completely closed by trees and in all directions. Well, this example of an infinite forest and endless trees should help us understand what we should expect if the universe were infinite and contain an infinite number of stars. Well in this case all the space (and therefore also the night sky) should shine like the surface of a star. Let’s try to understand why. If there is an infinite number of stars and are distributed so uniform throughout the space, looking in any direction you should see a star. Clearly the nearest stars shine more and the stars farther away shine less but this fact is compensated by another fact or by that looking further away in the same space region fall more and more stars. The brightness of a light source and then a star decreases with the distance, but the number of stars grows with the distance. The same area is filling more and more stars, therefore the decrease of brightness and increasing the number of stars are perfectly balanced. The final result should be that the whole night sky should shine like the surface of a star. This fact was thought about when it was noticed and began to create some doubts to astronomers. This included Kepler in 1600 when he had accounted for this problem and then later the German astronomer Olbers spoke in one of his works and this is the reason why the question that the night sky is dark today comes often called Olbers paradox. Why is it a paradox? Well, because what we’re looking at isn’t a night sky as bright as a star but a dark sky, so we must actually explain why things are so. There are several possibilities, one possibility would simply be that there is no infinite number of stars in the universe. This is something that astronomers of the past took in and yet it seemed a bit strange because if you imagine that there be an infinite number of stars in the universe, this not only would say that there would be a point privileged within the universe or the centre of this distribution of stars which is a contrary thing to the idea of Nicolaus Copernicus (that there is a center in the distribution of matter of the universe). But there would also be another problem or the fact that one finite star distributes a number it wouldn’t be stable. Sooner or later this finite number of stars would end up collapsing into the midpoint. This is the reason why astronomers of the past, before Einstein and before knowing the theory of general relativity, preferred an infinite universe to an infinite space that contained an infinite number of stars. But this thing was in contradiction with the observation that the night sky is dark. Another possibility is that the universe does not exist always and this is a possibility that brings us a little closer to the answer that we think today is the right one. The idea is basically that if the universe has not always existed (so stars have not always existed also if there is an infinite number), some of these stars actually are so far away that the light has not yet reached us. If stars don't always exist but they lit up in a certain era, looking far enough we see areas of space where still the stars didn’t light. This as I said it brings us a little closer to the solution of the paradox of Olbers and the thing curious is that this idea is actually was exposed for the first time for written in a work not by a astrophysicist, but by a writer, by Edgar Allan Poe.. #InsaneCuriosity#RecentSpaceDiscoveries
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