Why isn't the night sky white?
Everything we see seems obvious to us, like being glued to the ground of a round planet, that the Sun rises and sets every day and that the night is dark.
But why is it dark?
I am not referring to the trivial matter of half the Earth's back to the Sun, but to a much, much more seductive and puzzling enigma.
The first to bite into it was one of the great creative brains of all time, Johannes Kepler, who realized as early as 1610 that if the universe is infinite, as many scholars held and continue to hold, its infinite stars should swamp our view of the sky. in a white color as dazzling as the Sun itself is during the day.
Kepler used this argument in an attempt to disprove that the cosmos was infinite.
Brilliant, but inaccurate.
In its modern form, the mystery of why the night is dark is called the Olbers paradox, after the German astronomer Wilhelm Olbers, who worked between the 18th and 19th centuries.
His resume was impeccable, with the discovery of five comets and the asteroids Pallas and Vesta, and not content with this, he rescued the old enigma posed by Kepler.
If the universe is infinite, all our lines of sight should end at the surface of a star.
So the night sky should not be dark, but bright as a desert sunrise.
This is Olbers' paradox, which seems to have only one solution: that the universe is finite.
New bug.
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Where are the objects that the 'James Webb' has photographed?
Many contemporary cosmologists, I would say the majority, believe that the universe is infinite.
It is what the dominant
big bang
hypotheses in the field predict, grouped in the concept of cosmic inflation (I am not going to make the obvious joke).
According to these empirically untested ideas, the
big bang
it consisted of a quantum phenomenon, that unknown territory where our intuition begins to slip, and it generated an accelerated expansion of space at a speed much, much higher than the speed of light.
This seems to violate Einstein, whose theory of relativity is based on the fact that nothing can travel faster than light.
But it doesn't violate it, because Einstein is referring to objects moving through space, and here we are talking about the rate of expansion of space itself.
The mathematics says that cosmic inflation can quite naturally generate not just an infinite universe, but an infinite number of them.
What then of Olbers paradox?
The images that we have seen this week from the James Webb
Space
Telescope, Hubble's evolved heir, reveal with crystal clarity that the dark areas of the night sky that Hubble showed us are actually infested with galaxies of all kinds and sizes.
Its light has been traveling towards us for about 10,000 million years.
But there may well be another infinity of galaxies even further away whose light will never reach us, due to the accelerated expansion of the cosmos.
If those photos don't blow your mind, you're about to synthesize chlorophyll.
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