It is a question of mundane simplicity but one that has stumped history’s greatest geniuses: How big is the universe? This year a group of astrophysicists has deduced an answer: The visible universe stretches at least 24 gigaparsecs in all directions. That’s a radius of 78 billion light-years to the less versed.
Neil Cornish, an astrophysicist at Montana State University, and his colleagues got their result by mining data from the cosmic microwave background, ubiquitous radiation left over from the Big Bang. Using the Wilkinson Microwave Anisotropy Probe, Cornish earlier helped determine that the universe is 13.7 billion years old. That age tells how long light from the Big Bang has been traveling and so provides a clue to the size of the universe—but it’s not the whole story.
In some exotic theories, the universe could be smaller than it appears because space curves in on itself. As a result, ...
