What is the Large-Scale Structure of the Cosmos?
On the highest observable scales, corresponding to billions of light-years, the cosmos has a cellular appearance, consisting of massive “walls” and filaments of galaxy superclusters separated by vast voids, the largest of which (the Eridanus void) being a billion light-years wide. Although the observable cosmos as a whole appears to be about 14.7 billion light years wide, this is an illusion, because much of the light in the universe has taken billions of years to reach us. The actual diameter of the observable cosmos is 92-94 billion light-years. At scales larger than about 500 million light years, no large-scale structure is apparent, the cosmos being homogeneous and random in any direction, exemplifying the so-called Cosmological Principle. This phenomenon is sometimes referred to as the “End of Greatness.” As the actual universe may be many times larger than the observable universe, the notion of specific structure may only be applicable at the smallest scales. The largest known st
