The Universe Has a Cold Spot No One Can Explain

Deep in the cosmic microwave background—the leftover radiation from the Big Bang—there’s a strange, frigid region called the Cold Spot, about 10 degrees across. It’s colder than it should be, and a normal random fluctuation would be unlikely to produce it (roughly a 1-in-100 chance). One wild theory? It could be evidence of a parallel universe that collided with ours long ago. A more down-to-earth idea is a vast “supervoid” where fewer galaxies exist, and one has been found in that direction, but it appears to explain only part of the effect. Either way, it’s one of the biggest cosmic mysteries out there.