For thousands of years, human being have been contemplating the Universe and seeking to determine its true extent. And whereas ancient philosophers believed that the world consisted of a disk, a ziggurat or a cube surrounded by celestial oceans or some kind of ether, the development of modern astronomy opened their eyes to new frontiers. By the 20th century, scientists began to understand just how vast (and maybe even unending) the Universe really is.
Scientists have long tried to explain the origin of a mysterious, large and anomalously cold region of the sky. In 2015, they came close to figuring it out as a study showed it to be a “supervoid” in which the density of galaxies is much lower than it is in the rest of the universe. However, other studies haven’t managed to replicate the result.
Since its discovery in 2008, astronomers have been puzzled by a cosmic mystery so vexing that it has even led some to question whether the general theory of relativity – Einstein’s masterpiece theory of gravity – is wrong on cosmic scales. The trouble is that light travelling through the universe does not seem to be affected by the gravity of large structures such as galaxy clusters in the way that Einstein had predicted.