A team of physicists has claimed that our view of the early Universe may contain the signature of a time before the Big Bang.
The discovery comes from studying the cosmic microwave background (CMB), light emitted when the Universe was just 400,000 years old.
Their model may help explain why we experience time moving in a straight line from yesterday into tomorrow.
Details of the work have been submitted to the journal Physical Review Letters.
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, from the California Institute of Technology (Caltech), and colleagues now believe 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( Collapse )