I'm pretty sure that many of you have already participated in the discussion regarding "Is the UNIVERSE infinite?" Or atleast heard someone discussing about it. And these discussions are concluded with "Yes, it is!". Now let's give a thought to "Is it really infinite or we just assume it to be?"
In early ages, Universe was considered to be infinite and static. In this case they considered that the universe was, is and always will be infinite, this means that the age of the universe is infinite. They also considered all the stars to be uniformly spread in an infinite universe.
This clearly means that the size of the universe and number of stars which are evenly distributed in it are also "infinite". Now 'cause of this the NIGHT SKY should not be DARK but it should be BRIGHT instead. This is because, if the age of universe is infinite and if a star is very far away ( e.g. 100pc away) then the time required by the light to travel from surface of the star to Earth doesn't matter as the age of Universe is infinite, so this means that the light has already travelled that much distance and we must see all the stars which are present and the combined brightness of all stars should make the Nights Bright instead of Dark. But that's not the case, the Night Sky is DARK.
Let's take another approach to it. Consider our Sky divided in various planes according to the different distances. As, we consider our Universe to have uniform distribution of stars then, each plane will have number of stars to be square of the number of plane (For example: Plane 2 has 4 stars, Plane 4 has 16 stars). Now, we also know about the relationship between luminosity of the star and observed brightness of the star. Each plane will have same amount of observed brightness and so the combined brightness of each plane will lead to a Bright Night Sky.
One more approach is there. Let's consider a case in which the stellar dust is obstructing the light from the star and hence, dimming light received by the Earth results into a Dark Sky. But the thing is, the stellar dust obstructing the light will heat up eventually and start to glow. This again will result into a Bright Night Sky.
So, now the PARADOX is that considering the MODEL to be right, the night sky must be bright but we have a dark night sky.
Okay, so now we got a problem and we need to consider all possible solutions for it.
Solution 1:
We will consider our Universe to be finite and also all the stars present in it. As we all know that as the star burns up all of it's fuel it dies and so light is no longer emitted by it. Due to this, there will be few patches where there is no light and hence, the Night Sky is dark.
Solution 2:
Here, let's consider that our Universe is infinite in size but it has a finite age (which we have found out roughly to be 13.6 billion years). Due to this, there is a chance that the light from the most distant stars hasn't reached the Earth yet and 'cause of it there are patches where light is not received. And hence, we do have a dark Night Sky.
Solution 3:
HUBBLE'S LAW
Similarly to the Solution 2, here we will consider that our Universe is infinite in size but has a finite age. Our Universe is expanding at a rate faster than speed on light. It follows a "SPACELIKE INTERVAL". This mean that the space between the far away stars and the Earth is expanding at a velocity higher that the velocity of light. This is known as the " Hubble's Expansion". So, the light from the far away stars would never reach us. And hence, there are patches where the light is not received and the Night Sky is dark.
This is the most accurate and verified solution for the Olber's Paradox.
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