The CMB is relic radiation that fills the entire Universe and is regarded as the most conclusive evidence for the Big Bang.

Although this microwave background is mostly smooth, the Cobe satellite in 1992 discovered small fluctuations that were believed to be the seeds from which the galaxy clusters we see in today's Universe grew.

Dr Adrienne Erickcek, and colleagues from the California Institute for Technology (Caltech), now believes these fluctuations contain hints that our Universe "bubbled off" from a previous one.

Their data comes from Nasa's Wilkinson Microwave Anisotropy Probe (WMAP), which has been studying the CMB since its launch in 2001.
Their model suggests that new universes could be created spontaneously from apparently empty space. From inside the parent universe, the event would be surprisingly unspectacular.

Arrow of time

Describing the team's work at a meeting of the American Astronomical Society (AAS) in St Louis, Missouri, co-author Professor Sean Carroll explained that "a universe could form inside this room and weÕd never know".