Night sky is dark because light from distant stars has yet not reached our earth. Light emitted by stars formed after the instant of creation i.e. 13.7 billion light years ago is on the way to reach us. As light from these distant stars reach us, night sky must keep getting brighter.
How true is this? And to what extent? Can one day night sky become as bright as a day?
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4$\begingroup$ Have you looked up "Oblers paradox"? There are some issues with your question, that may distract from it. Stars were not formed "at the moment of creation". They started forming some 100 million years later, and have continued to form since then. $\endgroup$– James KCommented May 15, 2017 at 20:21
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1$\begingroup$ Yes, the issue regarding instant of creation is now edited. Olbers paradox does gives an insight into this. $\endgroup$– pooja somaniCommented May 16, 2017 at 6:24
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1$\begingroup$ One solution to the paradox is the redshifting of light as it travels through expanding space. Unless you are gifted/cursed with the ability to see microwaves, your view of the nightsky should not be brighter. $\endgroup$– user15317Commented May 16, 2017 at 10:21
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$\begingroup$ It's a great question! $\endgroup$– FattieCommented May 16, 2017 at 20:18
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1 Answer
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The rate of star formation in the universe peaked about 3.5 billion years after the Big Bang, or 2.7 billion years after it, according to a different study—in any case, for most of the universe's lifetime fewer and fewer stars have been forming each year. Though I don't have precise data on the death rate, on the whole the number of stars is decreasing as more old stars die than new ones form.
Meanwhile, the light from old stars is being redshifted out of existence by the expansion of the universe, which is itself accelerating.
I'm sure there's a mathematical model that can quantify this properly, but I think those two facts, combined, must be the answer to why the sky isn't getting brighter.
