This question was first posed in 1823 by an astrophysicist named Heinrich Olbers, and the question has since been referred to as Olbers’ paradox. Olbers had two main points to his argument. The universe is endless, and it is uniformly populated by an infinite number of luminous stars, which would imply that every line of sight must eventually terminate at the surface of a star. Therefore, Olbers’ argument (unlike our observation at night time) suggested that the night sky should be bright with no dark spaces between the stars.
There were four explanations given at the time:
- There’s too much dust to see the distant stars.
- The Universe has only a finite number of stars.
- The distribution of stars is not uniform.
- The Universe is expanding, so distant stars are red-shifted into obscurity.
Surprisingly, in his essay on “the Physical, Metaphysical and Mathematical — of the Material and Spiritual Universe”, Eureka, Edgar Allan Poe came up with the correct explanation for this paradox. Even though his argument was not backed up by scientific methods and had a few flaws, the idea was correct and a first at the time. Olbers’ Paradox would be resolved in 1988 by a scientist named Johann Madler, about 140 years after Poe posed his correct answer to the paradox.
In this excerpt from Eureka, Poe comes up with the correct answer to the question:
“Were the succession of stars endless, then the background of the sky would present us a uniform luminosity, like that displayed by the Galaxy — since there could be absolutely no point, in all that background, at which would not exist a star. The only mode, therefore, in which, under such a state of affairs, we could comprehend the voids, which our telescopes find in innumerable directions, would be by supposing the distance of the invisible background so immense that no ray from it has yet been able to reach us at all.”
Olbers’s Paradox was first resolved correctly by a poet, and not a scientist.
So in essence, the reason that the night sky is not uniformly bright is because of the infinite and expanding universe. Since the universe is expanding, it is impossible for the light of all stars to reach Earth at the same time. If the night sky did in fact end up being uniformly bright at some point, well, we should be pretty scared. And definitely revise on the theories of relativity.
Eureka also contains some other successes in physics, among which is the idea that the universe was generated from the explosion of a single particle — Poe had predicted the Big Bang theory by almost a century.
