Do We Live in a Special Part of the Universe?
According to a tenet scientists call the cosmological principle, our place in space is in no way exceptional. But recent observations could overturn this long-held assumption
An illustration of the cosmic web, the universe’s large-scale structure of composed of galaxy-rich clumps and filaments alongside giant intergalactic voids mostly bereft of matter. At even larger scales, cosmic structure seems to smooth out into near-featureless homogeneity.
Ever since humans started gazing at the heavens through telescopes, we have discovered, bit by bit, that in celestial terms we’re apparently not so special. Earth was not the center of the universe, it turned out. It wasn’t even the center of the solar system! The solar system, unfortunately, wasn’t the center of the universe either. In fact, there were many star systems fundamentally like it, together making up a galaxy. And, wouldn’t you know, the galaxy wasn’t special but one of many, which all had their own solar systems, which also had planets, some of which presumably host their own ensemble of egoistic creatures with an overinflated sense of cosmic importance.
This notion of mediocrity has been baked into cosmology, in the form of the “cosmological principle.” Its gist is that the universe is basically the same everywhere we look—homogenized like milk, made of common materials evenly distributed in every direction. At the top of the cosmic hierarchy, giant groups of galaxies clump into sprawling, matter-rich filaments and sheets around gaping intergalactic voids, but past that, structure seems to peter out. If you could zoom way out and look at the universe’s big picture, says Alexia Lopez of the University of Central Lancashire in England, “it would look really smooth.”
