A star is like a giant lamp that emits light in all directions. At a point on the Earth it is night if it is not facing the Sun, at that moment we do not see the light of our star because the body of the Earth hides it. Now, if there are millions and millions of stars and each one of them is like a lamp, then why don’t they fill the night sky with their light? Where is the light?
This question was posed by the astronomer Heinrich Olbers (1758-1840) in the 19th century, which is why it is currently known as ‘Olbers’ paradox’.
In the distant future the night will be even darker
Throughout history, various explanations have been proposed to resolve this paradox, from the fact that the universe is not infinite until it does not stop expanding, through the non-uniform distribution of stars, its finite life or the effect of slow gravitational.
At first it was all darkness, the first appeared about 13.7 billion years ago and it is very fast but not instantaneous. It has a speed of almost 300,000 kilometers per second, so when an object emits light, it does not illuminate its surroundings immediately. Light from the Sun, for example, takes about eight minutes to reach Earth. Thus, although the universe is very populated with stars, there are many whose light has not had time to reach us from the very beginning.
Since the Big Bang, the universe has expanded at an accelerated rate. This expansion ‘stretches’ the light from the most distant galaxies, shifting it towards the red spectrum and making it less energetic. Eventually, this light travels so far that it becomes invisible to our eyes, contributing to the darkness of the night sky. In Román paladino, the night is dark because we are not able to see the light.
Another important aspect to keep in mind is that stars are not uniformly distributed in the universe, there are large gaps between galaxies and galaxy clusters. This explains, for example, why when we look at one side of the sky we see many stars and yet when we look at another we see none.
Stars do not have an infinite life, they are born, evolve and die. As they age, many turn off, ceasing to emit visible light. Stars like the Sun only live approximately 10 billion years, so some astronomers hypothesize that in about 1,000 billion years the universe will become darker and will be inhabited by stellar remains such as white dwarfs and black holes.
Finally, there is what is known as the gravitational lensing effect: massive objects – such as galaxies and galaxy clusters – can bend light from more distant stars, making it appear to come from another direction.
The fossil light of the Big Bang
The resolution of Olbers’ paradox has had a profound impact on our understanding of the universe. It has led to the development of more accurate cosmological models and has allowed scientists to study the formation and evolution of galaxies.
Additionally, recent discoveries such as microwave background radiation have provided additional evidence for the expansion of the universe and the Big Bang. This cosmic background radiation is a weak glow that fills the entire universe and is considered the ‘fossil light’ of the Big Bang.
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